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diff --git a/14664-h/14664-h.htm b/14664-h/14664-h.htm new file mode 100644 index 0000000..0785a1b --- /dev/null +++ b/14664-h/14664-h.htm @@ -0,0 +1,10540 @@ +<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" +"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> +<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"> +<head> +<meta http-equiv="Content-Type" content="text/html;charset=utf-8" /> +<meta http-equiv="Content-Style-Type" content="text/css" /> +<title>The Project Gutenberg eBook of Things To Make, by Archibald Williams</title> +<link rel="coverpage" href="images/cover.jpg" /> +<style type="text/css"> + +body { margin-left: 20%; + margin-right: 20%; + text-align: justify; } + +h1, h2, h3, h4, h5 {text-align: center; font-style: normal; font-weight: +normal; line-height: 1.5; margin-top: .5em; margin-bottom: .5em;} + +h1 {font-size: 300%; + margin-top: 0.6em; + margin-bottom: 0.6em; + letter-spacing: 0.12em; + word-spacing: 0.2em; + text-indent: 0em;} +h2 {font-size: 150%; margin-top: 2em; margin-bottom: 1em;} +h3 {font-size: 130%; margin-top: 1em;} +h4 {font-size: 120%;} +h5 {font-size: 110%;} + +.no-break {page-break-before: avoid;} /* for epubs */ + +div.chapter {page-break-before: always; margin-top: 4em;} + +hr {width: 80%; margin-top: 2em; margin-bottom: 2em;} + +p {text-indent: 1em; + margin-top: 0.25em; + margin-bottom: 0.25em; } + +.p2 {margin-top: 2em;} + +p.center {text-align: center; + text-indent: 0em; + margin-top: 1em; + margin-bottom: 1em; } + +div.fig { display:block; + margin:0 auto; + text-align:center; + margin-top: 1em; + margin-bottom: 1em;} + +a:link {color:blue; text-decoration:none} +a:visited {color:blue; text-decoration:none} +a:hover {color:red} + +</style> + +</head> + +<body> + +<div style='text-align:center; font-size:1.2em; font-weight:bold;'>The Project Gutenberg eBook of Things To Make, by Archibald Williams</div> +<div style='display:block; margin:1em 0'> +This eBook is for the use of anyone anywhere in the United States and +most other parts of the world at no cost and with almost no restrictions +whatsoever. You may copy it, give it away or re-use it under the terms +of the Project Gutenberg License included with this eBook or online +at <a href="https://www.gutenberg.org">www.gutenberg.org</a>. If you +are not located in the United States, you will have to check the laws of the +country where you are located before using this eBook. +</div> +<div style='display:block; margin-top:1em; margin-bottom:1em; margin-left:2em; text-indent:-2em'>Title: Things To Make</div> +<div style='display:block; margin-top:1em; margin-bottom:1em; margin-left:2em; text-indent:-2em'>Author: Archibald Williams</div> +<div style='display:block;margin:1em 0'>Release Date: January 11, 2005 [eBook #14664]<br /> +[Most recently updated: February 21, 2021]</div> +<div style='display:block;margin:1em 0'>Language: English</div> +<div style='display:block;margin:1em 0'>Character set encoding: UTF-8</div> +<div style='display:block; margin-left:2em; text-indent:-2em'>Produced by: Don Kostuch</div> +<div style='margin-top:2em;margin-bottom:4em'>*** START OF THE PROJECT GUTENBERG EBOOK THINGS TO MAKE ***</div> + +<div class="fig" style="width:60%;"> +<img src="images/cover.jpg" style="width:100%;" alt="[Illustration]" /> +</div> + +<h3>Transcriber’s Note:</h3> + +<p> +If the pdf version of the book is viewed using facing pages with even numbered +pages on the left, you will see a close approximation of the original book. +</p> + +<p> +Notations of the form “(1,650) 2” appear at the bottom of some +pages; they are probably printer’s references for assembling to book. +</p> + +<p> +The text only version is of limited use because of the many figures used. I +recommend the pdf or rtf versions. +</p> + +<p> +Some of the projects should be approached with care since they involve +corrosive or explosive chemicals, electricity and steam boilers. +</p> + +<p class="p2"> +<b>Do not use lead solder, particularly on cooking utensils.</b> +</p> + +<p class="p2"> +Whether you simply want to travel back into the mind of a young boy at the +beginning of the twentieth century, or want to try your hand at some +interesting projects in carpentry, machinery, kites and many other areas, have +fun. +</p> + +<p> +The following are definitions of unusual (to me) terms used frequently in the +text. +</p> + +<h4>Terms</h4> + +<p> +Batten - Narrow strip of wood. +</p> + +<p> +Bevel (Bevelling) - A cut that is not a right angle. +</p> + +<p> +Bradawl - Awl with a beveled tip to make holes in wood for brads or screws. +</p> + +<p> +Chamfer - Cut off the edge or corner; bevel. +</p> + +<p> +Boss - Enlarged part of a shaft where another shaft is coupled or a wheel or +gear is keyed. +</p> + +<p> +Broach - To shape a hole with a tapered tool. +</p> + +<p> +Carbide - Calcium carbide, used to produce acetylene (C2H2) gas for lighting +and welding. +</p> + +<p> +Compo - “Composition”, like plastic. +</p> + +<p> +Creosote - An oily liquid containing phenols and creosols, obtained from coal +tar. Used as a wood preservative and disinfectant. Can cause severe +neurological disturbances if inhaled. +</p> + +<p> +Deal - A fir or pine board of standard dimensions +</p> + +<p> +Fish-plate - A plate bolted to the sides of two abutting railroad tracks. +</p> + +<p> +Fretworking - Ornamental design, often in relief. +</p> + +<p> +Gasholder Gasometer - Storage container for fuel gas, especially a large, +telescoping, cylindrical tank. +</p> + +<p> +Gland - The outer sleeve of a stuffing box that prevents leakage past a moving +machine part. +</p> + +<p> +Glass paper - Paper faced with pulverized glass, like sandpaper. +</p> + +<p> +Gudgeon - A metal pivot or journal at the end of a shaft or an axle, around +which a wheel or other device turns. +</p> + +<p> +Joiner - A cabinetmaker. +</p> + +<p> +Linoleum - A floor covering made in sheets by pressing heated linseed oil, +rosin, powdered cork, and pigments onto a burlap or canvas backing. +</p> + +<p> +Lissom - Easily bent; supple +</p> + +<p> +Longitudinal - Relating to length. +</p> + +<p> +Mortice - Cavity in a piece of wood or other material, prepared to receive a +tenon and form a joint. +</p> + +<p> +Panel saw - Handsaw with fine teeth. +</p> + +<p> +Pinion - Gear with a small number of teeth designed to mesh with a larger gear. +</p> + +<p> +Plinth - Architectural support or base. +</p> + +<p> +Rasp - Coarse file with sharp, raised, pointed projections. +</p> + +<p> +Sleeper - Railroad crosstie. +</p> + +<p> +Spanner - Wrench +</p> + +<p> +Spirit Lamp - Alcohol lamp; see example on page 188. +</p> + +<p> +Spirit - Alcohol +</p> + +<p> +Strake - Ridge of thick planking on the side of a wooden ship. +</p> + +<p> +Strut - Any part designed to hold things apart or resist compressive stress; +</p> + +<p> +Tap - Cut screw threads +</p> + +<p> +Tenon - Projection on the end of a piece of wood shaped for insertion into a +mortise to make a joint. +</p> + +<p> +Tenon saw - Saw with a thin blade for cutting tenons. +</p> + +<p> +Tinning - Coating with soft solder. +</p> + +<p> +Turner - Person who operates a lathe or similar device. +</p> + +<p> +Tyre - Tire +</p> + +<p> +Vestas - Matches; Vestai is the Roman goddess of the hearth, worshiped in a +temple containing the sacred fire tended by the vestal virgins. +</p> + +<h4>Currency Conversion</h4> + +<p> +Prices are quoted in old English currency, pounds, shillings, pence. +</p> + +<p> +“12s. 6d.” is read as “12 Shillings and 6 Pence.” +</p> + +<p> +Pence/penny<br /> +Shilling—12 pence.<br /> +Crown—5 shillings.<br /> +Pound—20 shillings.<br /> +Guinea—21 shillings.<br /> +</p> + +<p class="center"> +The approximate value of 1900 prices in 2002 is: +</p> + +<table summary="" border="1"> + +<tr> +<td>1900 Unit</td><td>Value in 2002 Currency</td><td></td> +</tr> + +<tr> +<td></td><td>English Pound</td><td>US Dollars</td> +</tr> + +<tr> +<td>Pence</td><td>.26</td><td>.48</td> +</tr> + +<tr> +<td>Shilling</td><td>3.10</td><td>5.80</td> +</tr> + +<tr> +<td>Crown</td><td>15.50</td><td>29.00</td> +</tr> + +<tr> +<td>Pound</td><td>62.00</td><td>116.00</td> +</tr> + +</table> + +<p> +[End Transcriber’s note.] +</p> + +<p> +[Illustration: Large model locomotive] +</p> + +<p> +Photo: Daily Mirror. Large model locomotive built for one of the royal princes +of Siam by Messrs. Bassett-Lowke, Limited. It is one-quarter the size of a +modern express engine; weighs two tons, with tender; is fifteen feet long; will +pull seventy persons; and has a highest speed of about thirty miles an hour. +</p> + +<hr /> + +<div class="chapter"> + +<h1>THINGS TO MAKE</h1> + +<h4>BY</h4> + +<h2 class="no-break">ARCHIBALD WILLIAMS</h2> + +<h3>AUTHOR OF<br /> +“VICTORIES OF THE ENGINEER,”<br /> +“HOW IT WORKS,”<br /> +“HOW IT IS MADE,”<br /> +ETC., ETC.</h3> + +<h4>THOMAS NELSON AND SONS, LTD.</h4> + +<h5>LONDON, EDINBURGH, AND NEW YORK</h5> + +<hr /> + +</div><!--end chapter--> + +<div class="chapter"> + +<h2>PREFACE.</h2> + +<p> +The making for oneself of toys and other objects of a more or less useful +character has certain advantages over buying them. In the case of the more +elaborate and costly articles, it may enable one to possess things which +otherwise would be unobtainable. Secondly, a home-made article may give a +satisfaction more lasting than is conferred by a bought one, though it may be +less beautiful to look upon. Thirdly, the mere making should be a pleasure, and +must be an education in itself. +</p> + +<p> +To encourage readers to “use their hands” the following chapters +have been written. The subjects chosen provide ample scope for the exercise of +ingenuity and patience; but in making my selection I have kept before me the +fact that a well-equipped workshop falls to the lot of but a few of the boys +who are anxious to develop into amateur craftsmen. Therefore, while the easiest +tasks set herein are very easy, the most difficult will not be found to demand +a very high degree of skill, or more than a very moderate outlay on tools. I +may say here that I have been over the ground myself to find out its +difficulties for my readers, and that I made an engine similar to that +described in Chapter XV (the most elaborate mechanism included in the book) +with very simple tools. Some of the items which I had on my original list were +abandoned, because they presupposed the possession of comparatively expensive +machines. +</p> + +<p> +My selection has also been guided by the desire to cater for different tastes. +In some cases the actual manufacture of the thing described may be regarded as +the most instructive and valuable element, and may appeal most forcibly to the +“handy” boy; in others—the Harmonograph provides a good +instance—the interest centres round the experiments made possible by the +construction of a simple piece of apparatus; in some the utility of the article +manufactured is its chief recommendation. +</p> + +<p> +I feel certain that anyone who follows out the pages of this volume with hand +as well as with eye, will have little reason to regret the time so spent. The +things made may in course of time be put aside and forgotten, but the manual +skill acquired will remain. Nowadays one can buy almost anything ready-made, or +get it made without difficulty; yet he who is able to make things for himself +will always have an advantage over the person to whom the use of tools is an +unprobed mystery. +</p> + +<h2>Contents</h2> + +<table summary="" style=""> + +<tr> +<td> <a href="#chap01">I. SAWING TRESTLE</a></td> +</tr> + +<tr> +<td> <a href="#chap02">II. A JOINER’S BENCH</a></td> +</tr> + +<tr> +<td> <a href="#chap03">III. A HANDY BOOKSTAND</a></td> +</tr> + +<tr> +<td> <a href="#chap04">IV. A HOUSE LADDER</a></td> +</tr> + +<tr> +<td> <a href="#chap05">V. A DEVELOPING SINK</a></td> +</tr> + +<tr> +<td> <a href="#chap06">VI. A POULTRY HOUSE AND RUN</a></td> +</tr> + +<tr> +<td> <a href="#chap07">VII. A SHED FOR YOUR BICYCLE</a></td> +</tr> + +<tr> +<td> <a href="#chap08">VIII. A TARGET APPARATUS FOR RIFLE SHOOTING</a></td> +</tr> + +<tr> +<td> <a href="#chap09">IX. CABINET-MAKING</a></td> +</tr> + +<tr> +<td> <a href="#chap10">X. TELEGRAPHIC APPARATUS</a></td> +</tr> + +<tr> +<td> <a href="#chap11">XI. A RECIPROCATING ELECTRIC MOTOR</a></td> +</tr> + +<tr> +<td> <a href="#chap12">XII. AN ELECTRIC ALARM CLOCK</a></td> +</tr> + +<tr> +<td> <a href="#chap13">XIII. A MODEL ELECTRIC RAILWAY</a></td> +</tr> + +<tr> +<td> <a href="#chap14">XIV. A SIMPLE RECIPROCATING ENGINE</a></td> +</tr> + +<tr> +<td> <a href="#chap15">XV. A HORIZONTAL SLIDE-VALVE ENGINE</a></td> +</tr> + +<tr> +<td> <a href="#chap16">XVI. MODEL STEAM TURBINES</a></td> +</tr> + +<tr> +<td> <a href="#chap17">XVII. STEAM TOPS</a></td> +</tr> + +<tr> +<td> <a href="#chap18">XVIII. MODEL BOILERS</a></td> +</tr> + +<tr> +<td> <a href="#chap19">XIX. QUICK-BOILING KETTLES</a></td> +</tr> + +<tr> +<td> <a href="#chap20">XX. A HOT-AIR ENGINE</a></td> +</tr> + +<tr> +<td> <a href="#chap21">XXI. A WATER MOTOR</a></td> +</tr> + +<tr> +<td> <a href="#chap22">XXII. MODEL PUMPS</a></td> +</tr> + +<tr> +<td> <a href="#chap23">XXIII. KITES</a></td> +</tr> + +<tr> +<td> <a href="#chap24">XXIV. PAPER GLIDERS</a></td> +</tr> + +<tr> +<td> <a href="#chap25">XXV. A SELF-LAUNCHING MODEL AEROPLANE</a></td> +</tr> + +<tr> +<td> <a href="#chap26">XXVI. APPARATUS FOR SIMPLE SCIENTIFIC EXPERIMENTS</a></td> +</tr> + +<tr> +<td> <a href="#chap27">XXVII. A RAIN GAUGE</a></td> +</tr> + +<tr> +<td> <a href="#chap28">XXVIII. WIND VANES WITH DIALS</a></td> +</tr> + +<tr> +<td> <a href="#chap29">XXIX. A STRENGTH-TESTING MACHINE</a></td> +</tr> + +<tr> +<td> <a href="#chap30">XXX. LUNG-TESTING APPARATUS</a></td> +</tr> + +<tr> +<td> <a href="#chap31">XXXI. HOME-MADE HARMONOGRAPHS</a></td> +</tr> + +<tr> +<td> <a href="#chap32">XXXII. A SELF-SUPPLYING MATCHBOX</a></td> +</tr> + +<tr> +<td> <a href="#chap33">XXXIII. A WOODEN WORKBOX</a></td> +</tr> + +<tr> +<td> <a href="#chap34">XXXIV. WRESTLING PUPPETS</a></td> +</tr> + +<tr> +<td> <a href="#chap35">XXXV. DOUBLE BELLOWS</a></td> +</tr> + +<tr> +<td> <a href="#chap36">XXXVI. A HOME-MADE PANTOGRAPH</a></td> +</tr> + +<tr> +<td> <a href="#chap37">XXXVII. A SILHOUETTE DRAWING MACHINE</a></td> +</tr> + +<tr> +<td> <a href="#chap38">XXXVIII. A SIGNALLING LAMP</a></td> +</tr> + +<tr> +<td> <a href="#chap39">XXXIX. A MINIATURE GASWORKS</a></td> +</tr> + +</table> + +</div><!--end chapter--> + +<div class="chapter"> + +<h2>THINGS TO MAKE.</h2> + +</div><!--end chapter--> + +<div class="chapter"> + +<h2><a name="chap01"></a>I.<br /> +A SAWING TRESTLE</h2> + +<p> +A strong and stable sawing trestle is one of the most important accessories of +the carpenter’s shop, whether amateur or professional. The saw is +constantly being used, and for it to do its work accurately the material must +be properly supported, so that it cannot sway or shift. Anybody who has been in +the habit of using a wobbly chair or box to saw on will be surprised to find +how much more easily wood can be cut when resting on a trestle like that +illustrated by Figs. 1 to 3. +</p> + +<p> +The top, <i>a</i>, of the trestle is 29 inches long, 4 inches wide, and 2 +inches thick. At one end it has a deep nick, to serve much the same purpose as +the notched board used in fretworking; also to hold on edge such things as +doors while their edges are planed up. Pushed back against the wall the trestle +is then “as good as a boy.” +</p> + +<p> +[Illustration: Fig I.—Leg of sawing trestle (left). Trestle seen from +above (right).] +</p> + +<p> +The four legs are made of 2 by 2 inch stuff. To start with, the pieces should +be 24 inches long, to allow for the waste of cutting on the angle. +</p> + +<p> +Cutting the Notches.—Make four marks 7 inches from the four corners of +the top, set your bevel to an angle of 70 degrees (or cut an angle out of a +card with the help of a protractor), and lay a leg against each mark in turn, +the end projecting an inch or so above the top. Move the leg about till it +makes the proper angle at the mark, and draw a pencil line down each side of +the leg as close up as possible. Since the legs may vary slightly in size, use +each once only for marking, and number it and the place to which it belongs. +</p> + +<p> +Lines must now be drawn along the upper and under sides of the top, parallel to +and 3/4-inch from the edge, to complete the marking out of the notches. +</p> + +<p> +Cut just inside the side marks with a fine tenon saw, and remove the wood +between the cuts back to the top and bottom marks with a broad, sharp chisel, +making the surface of the cut as true and flat as you can. Then +“offer” the leg that belongs to the cut, its end projecting an inch +or so. If it won’t enter, bevel off the sides of the cut very slightly +till it will. A good driving fit is what one should aim at. While the leg is in +place, draw your pencil in the angles which it makes with the top above and +below, to obtain the lines AB, CD (Fig. 2, a). +</p> + +<p> +Bevelling the Legs.-The marking out of the bevels will be much expedited if a +template is cut out of tin or card. It should be just as wide as the legs, and +at a point 4 inches from one end run off at an angle of 162 degrees from one +edge. (See Fig. 2,b.) +</p> + +<p> +[Illustration: FIG. 2.-Showing how to cut sloping joint for trestle leg.] +</p> + +<p> +Draw with a square a line, EEl, across what is to be the inside of the leg. The +template is applied to the end side of the leg and moved up till its sloping +edge occupies a position in which a perpendicular dropped on to it from C is +1/2 inch long. Mark the line EF (Fig. 2, b) and the perpendicular CG. The bevel +is marked on the other side of the leg, the, angle of the template being at E1 +(Fig. 2, a) to guide the saw, which is passed down through the leg just outside +the marks till in line with CD. The piece is detached by a cross cut along CG, +CD. This procedure, which sounds very complicated, but is really very simple, +and performed much more quickly than it can be described, yields a leg properly +bevelled and provided with a shoulder to take the weight of the top. +</p> + +<p> +[Illustration: Fig.3—End elevation of sawing trestle.] +</p> + +<p> +The leg at the diagonally opposite corner is an exact replica of the one first +made; the other two are similar, but the direction of the bevels is reversed, +as will be evident after a little consideration. +</p> + +<p> +When all the legs are ready, knock them into place, driving the shoulders tight +up against the top, and nail them on. The projections are sawn off roughly and +planed down flush with the top. Then affix the tie C at each end, and plane its +edges off neatly. +</p> + +<p> +Truing the Legs.—Stand the stool on end, top flat against the wall. +Measure off a 20-inch perpendicular from the wall to the outside corner of each +of the two upper legs. (Fig. 3.) Lay a straightedge from mark to mark, and draw +lines across the legs. Reverse the trestle, and do the same with the legs at +the other end. Then turn the trestle on its side, and draw lines on the other +outside faces of the legs, using the lines already made as guides. If the +operation has been carried through accurately, all eight lines will be in a +plane parallel to the top. Cut off the ends of the legs below the lines, and +the trestle is finished. +</p> + +</div><!--end chapter--> + +<div class="chapter"> + +<h2><a name="chap02"></a>II.<br /> +A JOINER’S BENCH.</h2> + +<p> +After finishing his sawing trestle the reader may be willing to undertake a +larger job, the manufacture of a joiner’s bench—if he does not +already possess a good article—heavy and rigid enough to stand firm under +plane and hammer. +</p> + +<p> +For the general design and detailed measurements he is referred to Figs. 4 and +5, in which the dimensions of each part are figured clearly. The length of 5 +feet, width of 2 feet (exclusive of the back E), and height of 2 feet 7-1/2 +inches will be found a good average. If the legs prove a bit long for some +readers, it is a simple matter to lay a plank beside the bench to raise the +(human) feet an inch or two. +</p> + +<p> +In order to give rigidity, the struts S1S2 of the trestles at the end and the +braces DD on the front are “halved” where they overlap the legs and +front so as to offer the resistance of a “shoulder” to any thrust. +</p> + +<p> +[Illustration: Fig. 4.—Front elevation of Joiner’s bench] +</p> + +<p> +Materials.—The cost of these will be, approximately: wood, 12s. 6d.; [12 +Shillings. 6 Pence] bench screw, 1s. 6d.; nails and screws, 1s.; or 15s. in +all. It is advisable to show the timber merchant the specifications, so that he +may cut up the stuff most economically. +</p> + +<p> +If the wood is mill-planed before delivery a lot of trouble will be saved, as +no further finish will be required, except perhaps at the top corners. In +passing, one should remark that the boards used should be of the widths and +lengths given; while as regards thickness the figures must be taken as nominal, +as in practice the saw cut is included. Thus a 1-inch board would, when planed, +be only 7/8 to 15/16 inch thick, unless the actual size is specified, in which +case something extra might be charged. +</p> + +<p> +Construction. +</p> + +<p> +The Trestles.—These should be made first. Begin by getting all the legs +of exactly the same length, and square top and bottom. Then cut off two 22-inch +lengths of the 6 by 1 inch wood, squaring the ends carefully. Two of the legs +are laid on the floor, one end against the wall or a batten nailed to the floor +and arranged parallel to one another, as gauged by the piece C, which is nailed +on perfectly square to both, and with its top edge exactly flush with the ends +of the legs. +</p> + +<p> +Next take the 3 by 1 inch wood for the struts, and cut off a piece 32 inches +long. Two inches from one end of it make a cross mark with the square, and from +the ends of the mark run lines towards the end at an angle of 45 degrees. Cut +along these lines, and lay one of the edges just cut up against C, and flush +with the outer edge of L1 (Fig. 5). Tack the strut on temporarily to both legs, +turn the trestle over, and draw your pencil (which should have a sharp point) +along the angles which the strut makes with the legs. This gives you the limits +of the overlaps. Detach the strut. +</p> + +<p> +The marking-gauge now comes into use. Set it at 3/8 inch, and make marks on the +sides of the strut down to the limits, pressing the guide against what will be +the inner face of the board. The ends must now be divided down along the gauge +scratches to the limit mark with a tenon or panel saw, the saw being kept on +the inside of the mark, So that its cut is included in the 3/8 inch, and a +cross cut made to detach the piece and leave a shoulder. The strut is +“offered” again to the legs, and a mark is drawn across the bottom +parallel to the ends or the legs for the final saw cut. Nail on the strut, +pressing the legs well up against the shoulders. Its fellow on the other side +of the legs is prepared in exactly the same manner; and the second trestle is a +duplicate of the first, with the exception that the directions of the struts +are reversed relatively to the C piece, to preserve the symmetry—which, +however, is not an important point. +</p> + +<p> +[Illustration: FIG. 5.—End elevation of joiner’s bench.] +</p> + +<p> +Back and Front.—The only operation to be performed on the front piece B +and the back G is the notching of them both on the inside faces at the centre +to take the ends of the bearer F, which performs the important function of +preventing any bending of the top planks. Lay the boards together, top edges +and ends level, and mark them at the same time. The square is then used on the +faces to give the limits for the notches, which should be 1/4 inch deep and +chiselled out carefully. +</p> + +<p> +Draw cross lines with your square 3 inches from each end of both pieces, on the +inside, to show where the legs are to be. Bore holes in the boards for the +3-inch screws which will hold them to the legs. +</p> + +<p> +Attaching the Trestles.—Stand the trestles on their heads and lay the +back and front up to them, using the guide marks just drawn. A nail driven part +way in through one of the screw holes, and a batten tacked diagonally on the DD +lines, will hold a leg in position while the screws are inserted. (Make sure +that the tops of the legs and the top edges of B and G are in the same plane.) +</p> + +<p> +Affixing the Braces.—The braces DD, of 3 by 1 inch stuff, can now be +marked off and cut exactly down the middle to the limits of the overlap. Screw +on the braces. +</p> + +<p> +The bearer F is next cut out. Its length should be such as to maintain the +exact parallelism of B with G, and the ends be as square as you can cut them. +Fix it in position by two 2-inch screws at each end. +</p> + +<p> +The bench is now ready for covering. Begin with the front board, A1. Bore +countersunk holes for 3-inch screws over the centre of the legs and half an +inch from the front edge, 1 foot apart. Arrange Al with its front edge +perfectly flush with the face of B, and tack it in place by nails driven +through a couple of screw holes, and insert all the screws. The middle board, +A2, is laid up against it, and the back board, A3 (bored for screws like the +front board), against that. Screw down A3. +</p> + +<p> +You must now measure carefully to establish lines over the centres of CC and F. +Attach each board to each of these by a couple of screws. All screws in the top +of the bench are countersunk 1/8 inch below the surface. Screw the ledge E, of +4 by 5/8 inch wood, on to the back of G, with 2-1/2 inches projecting. This +will prevent tools, etc., slipping off the bench. +</p> + +<p> +[Illustration: Fig. 6.—Perspective view of joiner’s bench] +</p> + +<p> +The Vice.—This important accessory consists of an 8 by 2 by 15 inch +piece, V, a 2-inch diameter wooden bench screw and threaded block, and a guide, +F. (Note.—A 1-1/8-inch diameter wrought iron screw is very preferable to +the wooden, but its cost is about 4s. more.) V should be tacked to B while the +2-inch hole for the bench screw is bored through both with a centre bit, at a +point 8 inches from the guide end on the centre line of V. This hole must be +made quite squarely to enable the screw to work freely. If a 2-inch bit is not +available, mark out a 2-inch ring and bore a number of small holes, which can +afterwards be joined by a pad-saw; and finish, the hole thus formed with a +half-round rasp. The threaded block for the screw is attached to the inner side +of H in the angle formed by the leg and the board A1. The guide F is then +fitted. This is pinned in to V, and the slides through B. If a rectangular +piece is used, cut the hole in V first; then screw V up tightly, and mark B +through V. It may be found more convenient to use a circular piece, in which +case the holes for it can be centre-bitted through V and B in one operation. If +after fitting V projects above A, plane it down level. +</p> + +<p> +The finishing touches are rounding off all corners which might catch and fray +the clothes, and boring the 3/4-inch holes, HH, for pegs on which planks can be +rested for edge planing. +</p> + +<p> +For a “stop” to prevent boards slipping when being planed on the +flat, one may use an ordinary 2-inch wood screw, the projection of which must +of course be less than the thickness of the board planed. Many carpenters +employ this very simple expedient; others, again, prefer a square piece of wood +sliding stiffly through a hole in A1 and provided on top with a fragment of old +saw blade having its teeth projecting beyond the side facing the work. The +bench is countersunk to allow the teeth to be driven down out of the way when a +“clear bench” is required. +</p> + +<p> +Just a word of warning in conclusion. Don’t be tempted to nail the parts +together—with the exception of the trestle components—to save +trouble. The use of screws entails very little extra bother, and gives you a +bench which can be taken to pieces very quickly for transport, and is therefore +more valuable than a nailed one. +</p> + +</div><!--end chapter--> + +<div class="chapter"> + +<h2><a name="chap03"></a>III.<br /> +A HANDY BOOKSTAND.</h2> + +<p> +A bookstand of the kind shown in Fig. 7 has two great advantages: first, it +holds the books in such a position that their titles are read more easily than +when the books stand vertically; second, it can be taken to pieces for packing +in a few moments, as it consists of but four pieces held together by eight +removable wedges. We recommend it for use on the study table. +</p> + +<p> +Oak or walnut should preferably be chosen as material, or, if the maker wishes +to economize, American whitewood or yellow pine. Stuff 1/4 inch (actual) thick +will serve throughout if the stronger woods are used; 3/8 inch for the shelf +parts in the case of whitewood or pine. +</p> + +<p> +The ends (Fig. 8) are sawn out of pieces 5-1/2 by 10 inches, and nicely rounded +off on all but the bottom edge, which is planed flat and true. The positions +for the holes through which the shelf eyes will project must be marked +accurately, to prevent the stand showing a twist when put together. The +simplest method of getting the marks right is to cut a template out of thin +card and apply it to the two ends in turn, using the base of each as the +adjusting line. Fret-saw the holes, cutting just inside the lines to allow for +truing up with a coarse file. +</p> + +<p> +[Illustration: Fig. 7.—Perspective view of bookstand.] +</p> + +<p> +The shelves a and b are 15 inches long, exclusive of the lugs c, c, c, c, and +4-1/2 and 4-3/4 inches wide respectively. As will be seen from Fig. 8, b +overlaps a. Both have their top edges rounded off to prevent injury to book +bindings, but their bottom edges are left square. +</p> + +<p> +As the neatness of the stand will depend largely on a and b fitting closely +against the sides, their ends should be cut out and trued carefully, special +attention being paid to keeping the shoulders between and outside the lugs in a +straight line. The wedge holes in c, c, c, c measure 1/2 by 1/4 inch, and are +arranged to be partly covered by the sides, so that the wedges cannot touch +their inner ends. (See Fig. 9.) This ensures the shelves being tightly drawn up +against the sides when the wedges are driven home. +</p> + +<p> +[Illustration: Fig. 8.—End elevation of bookstand.] +</p> + +<p> +The wedges should be cut on a very slight taper of not more than half an inch +in the foot run, in order to keep their grip. Prepare a strip as thick as the +smaller dimension of the holes, 3/8 inch wide at one end, and 7/8 inch wide at +the other. Assemble the parts and push the piece through a hole until it gets a +good hold, mark it across half an inch above the hole, and cut it off. Then +plane the strip down parallel to the edge that follows the grain until the end +will project half an inch beyond the lug next fitted. Mark and cut off as +before, and repeat the process until the eight wedges are ready in the rough. +Then bevel off the outside corners and smooth them—as well as the rest of +the woodwork—with fine glass paper. +</p> + +<p> +Shelves and sides should be wax-polished or given a coat or two of varnish. +</p> + +<p> +[Illustration: Fig. 9. Plan or bookstand shelf.] +</p> + +<p> +Don’t drive the wedges in too tight, or yon may have to lament a split +lug. +</p> + +<p> +If the stand is to be used for very heavy books, or the shelves are much longer +than specified here, it is advisable to bring the angle of the shelves down to +the bottom of the standards, to relieve the shelves of bending strain at the +centre; or to use stouter material; or to unite the shelves at two or three +points by thin brass screws inserted through holes drilled in the overlapping +part. +</p> + +</div><!--end chapter--> + +<div class="chapter"> + +<h2><a name="chap04"></a>IV.<br /> +A HOUSE LADDER.</h2> + +<p> +The preparation and putting together of the parts of a ladder having round, +tapered rungs let into holes in the two sides is beyond the capacity of the +average young amateur; but little skill is needed to manufacture a very fairly +efficient substitute for the professionally-built article—to wit, a +ladder of the kind to which builders apply the somewhat disparaging adjective +“duck.” +</p> + +<p> +The rungs of such a “duck” ladder are merely nailed to the outside +if the ladder is required for temporary purposes only; but as we are of course +aiming at the construction of a thing made to last, we shall go to the trouble +of “notching-in” each rung (see Fig. 10), so that the sides shall +take the weight directly, and the nails only have to keep the rungs firmly in +position. The objection to notching-in is that it reduces the strength of the +ladder, which is of course only that of the wood between the bottom of the +notches and the plain side. Therefore it is necessary to have sides somewhat +deeper than would be required for a centrally-runged ladder; which is pierced +where the wood is subjected to little tension or compression. +</p> + +<p> +[Illustration: Fig. 10—House ladder and details of letting in a rung] +</p> + +<p> +Materials.—The length of the ladder will decide what the stoutness of the +sides should be. For a ladder about 12 feet long, such as we propose to +describe, larch battens 3 by 1-1/8 inches (actual) in section and free from +knots, especially at the edges, will be sufficiently strong to carry all +reasonable weights without danger of collapse. But be sure to get the best wood +obtainable. The rungs may be of 2 by 1 inch stuff, though 2 by 3/4 inch will +suffice for the upper half-dozen, which have less wear, and are shorter than +those below. +</p> + +<p> +The rungs are 10 inches apart (Fig. 10), centre to centre. The distance may be +increased to a foot, Or even more if weight-saving is an object. +</p> + +<h4>CONSTRUCTION.</h4> + +<p> +Preparing the Sides.—These are cut to exactly the same length, which we +will assume to be 11 feet 6 inches, planed quite smooth and rounded off +slightly at the corners to make handling comfortable. Before marking them for +the rungs it is important that they shall be so arranged that both incline +equally towards a centre line. +</p> + +<p> +Stretch a string tightly three inches above the ground, and lay the sides of +the ladder on edge to right and left of it, their ends level. Adjust the bottom +ends 8-1/2, the top ends 6-1/2 inches from the string, measuring from the +outside. Tack on cross pieces to prevent shifting, and then, starting from the +bottom, make a mark every 10 inches on the outside corners, to show the +position of the tops of the rungs. A piece of the wood to be used for making +the rungs of is laid up to the pairs of marks in turn, and lines are drawn on +both sides of it. +</p> + +<p> +Cutting the Notches.—The work of marking the ends of the notches will be +quickened, and rendered more accurate, if a template (Fig. 10) is cut out of +tin. The side AC is 3/8 to 1/2 inch deep. Apply the template to both faces of +the side in turn, with its corner A at the line below the rung, and DE flush +with the upper corner. When all the notches have been marked cut down the AC +line of each with a tenon saw, and chisel along BC till the wedge-shaped chip +is removed. Finish off every notch as neatly as possible, so that the rungs may +make close contact and keep water out. +</p> + +<p> +Preparing the Rungs.—Lay a piece of rung batten across the lowest +notches, the end overhanging the side by a quarter of an inch or so to allow +for the taper of the ladder, and draw your pencil along the angles which it +makes with the sides. Mark the positions of the nail holes. Cut off the rung at +the cross lines; drill the four nail holes on the skew, as shown in Fig. 10; +and round off all the corners. The other rungs are treated in the same manner, +and the sides are then separated, for the inside top corner and both back +corners, which will be handled most, to be well rounded off and rubbed smooth +with glass paper. +</p> + +<p> +Assembling.—Before putting the parts together give them a coating of +paint, as the contact surfaces will not be accessible to the brush afterwards. +When the paint has dried, lay the sides out as before, and nail on the rungs +with 3-inch nails. To counteract any tendency of the sides to draw apart, a +light cross bar should be fixed on the back of the ladder behind the top and +bottom rungs. +</p> + +<p> +Round off the end angles of the rungs, and apply a second coating of paint. +</p> + +<p> +Note.—A ladder of this kind is given a more presentable appearance if the +rungs are let in square to the sides and flush, but at the sacrifice either of +strength or lightness, unless narrow rungs of a hard wood, such as oak, be +used. Moreover, square notches are not so easy to cut out as triangular. +</p> + +<p> +For a short ladder, not more than 9 feet long, the section of the sides may +safely be reduced to 2-3/4 by 1 inch (actual), if good material is selected. +</p> + +</div><!--end chapter--> + +<div class="chapter"> + +<h2><a name="chap05"></a>V.<br /> +A DEVELOPING SINK.</h2> + +<p> +Many amateur photographers are obliged to do their developing in odd corners +and under conditions which render the hobby somewhat irksome if a large number +of plates have to be treated. The main difficulty is to secure an adequate +water supply and to dispose of the waste water. At a small expenditure of money +and energy it is easy, however, to rig up a contrivance which, if it does not +afford the conveniences of a properly equipped dark room, is in advance of the +jug-and-basin arrangement with which one might otherwise have to be content. A +strong point in favour of the subject of this chapter is that it can be moved +without any trouble if the photographer has to change his quarters. +</p> + +<p> +The foundation, so to speak, of the developing sink is a common wooden +washstand of the kind which has a circular hole in the top to hold the basin. A +secondhand article of this sort can be purchased for a shilling or two. A +thoroughly sound specimen should be selected, even if it is not the cheapest +offered, especial attention being paid to its general rigidity and the good +condition of the boards surrounding the basin shelf. +</p> + +<p> +[Illustration: Fig. 11.—A home-made developing sink for the darkroom.] +</p> + +<p> +The area of the top is generally about 20 by 15 inches; but if a stand of +larger dimensions can be found, choose it by preference. +</p> + +<p> +The general design of the sink and its equipment is shown in Fig. 11. For the +uprights, which rest on the beading of the washstand, use two boards 9 inches +wide, 1/2 inch (actual) thick, and 36 inches long. The top shelf, to carry the +pail or other water container, should be of 1-inch stuff; and the two lower +shelves be not more than 5 inches wide and 3/4 inch thick. Space the shelves at +least 11 inches apart, so that they may accommodate tall bottles. The +superstructure will gain in rigidity if the intermediate shelves are screwed to +the uprights, in addition to being supported on ledges as indicated; and if the +back is boarded over for at least half its height, there will be no danger of +sideways collapse, when a full bucket is put in position. +</p> + +<p> +The top of the washstand, on which the developing will be done, must be +provided with a tray of lead or zinc. Lead is preferable, as lying flatter; but +the jointing at the corners is more difficult than the soldering of sheet zinc, +which, though more liable to chemical corrosion, is much lighter than the +thinnest lead—weighing about 1-1/2 lbs. to the square foot—that +could well be used. If lead is selected, the services of a plumber had better +be secured, if the reader has had no experience in “wiping a +joint.” +</p> + +<p> +A zinc tray is prepared by cutting out of a single sheet a piece of the shape +shown in Fig. 12. The dimensions between the bending lines (dotted) are 1/8 +inch less in both directions than those of the shelf. The turn-ups a, a, b, b, +should not be less than 1-1/2 inches wide. Allow half an inch at each end of b +b for the turnover c. Turn a a up first, then b b, and finally bend c c round +the back of a a, to which they are soldered. A drop of solder will be needed in +each corner to make it water-tight. When turning up a side use a piece of +square-cornered metal or wood as mould, and make the angles as clean as +possible, especially near the joints. +</p> + +<p> +[Illustration: FIG. 12.—Showing how the tray for sink is marked out.] +</p> + +<p> +A drain hole, an inch or so in diameter, is cut in the centre of the tray. To +prevent the hands being injured by the tray, the front should be covered by a +1/2-inch strip of zinc doubled lengthwise, or be made a bit deeper than 1-1/2 +inches in the first instance and turned over on itself. +</p> + +<p> +Before the tray is put in position the basin hole must be filled in, except for +an opening to take the waste pipe. The plug is pad-sawed out of wood of the +same thickness as the top, to which it is attached by crossbars on the under +side. The whole of the woodwork, or at least those parts which are most likely +to get wetted, should then be given a coat or two of paint. +</p> + +<p> +A waste pipe, somewhat larger than the drain hole and 3 inches long, having +been firmly soldered to the tray, beat the edges of the hole down into the +pipe. Then prepare a wooden collar to fit the pipe outside, and drill a hole on +the centre line to take a carpenter’s screw. If the edges of the tray are +supported on slats 3/16 to 1/4 inch thick, and its centre is kept in contact +with the wood by the collar pressing against the underside of the shelf, any +water will naturally gravitate to the centre and escape by the waste pipe. This +automatic clearance of “slops” is a very desirable feature of a +developing sink. +</p> + +<p> +To prevent water splashing on to the sides of the stand and working down +between tray and wood, tack pieces of American cloth on the sides with their +edges overlapping the tray edges by an inch or so. +</p> + +<p> +A small two-handled bath is the most convenient receptacle for the waste water. +It should hold at least a quarter as much again as the water tank, so as to +avoid any danger of overfilling. A piece of old cycle tyre tubing, tied to the +waste pipe and long enough to reach below the edge of the bath, will prevent +splashing—which, when chemicals are being poured away, might prove +disastrous to light-coloured clothes. +</p> + +<p> +The supply pipe has a siphon-piece of “compo” tubing at the top, to +draw off the water when the tube has been filled by suction, and a small tap at +the bottom. This tap, when not in use, should be held back out of the way by a +wire hook attached to the lowest of the upper shelves. A piece of linoleum +should be cut to fit the bath-shelf and protect the drawer below. +</p> + +</div><!--end chapter--> + +<div class="chapter"> + +<h2><a name="chap06"></a>VI.<br /> +A POULTRY HOUSE AND RUN.</h2> + +<p> +This chapter should be of interest to the keeper of poultry on a small scale, +for even if the instructions given are not followed out quite as they stand, +they may suggest modifications to suit the taste and means of the reader. +</p> + +<p> +The principle of the combined run and house—which will accommodate a +dozen fowls without overcrowding, especially if it be moved from time to time +on to fresh ground—will be understood from Figs. 13 and 14. The first of +these shows the framework to which the boards for the house and the wire for +the run are nailed. Its over-all length of 10 feet is subdivided into five +“bays” or panels, 2 feet long (nearly) between centres of rafters. +Two bays are devoted to the house, three to the run. +</p> + +<p> +[Illustration: Fig. 13.—Frame for poultry house and run (above).<br /> +Completed house and run (below).]<br /> +</p> + +<p> +One square (10 by 10 feet) of weather boarding 6 inches wide, for covering in +the house. 44 feet of 4 by 1, for base and ridge. 56 feet of 3 by 1, for eight +rafters. 28 feet of 3 by 1-1/2, for four rafters. 50 feet of 2 by 1-1/2, for +door frames and doors. 6 feet of 2 by 2, for tie t. 45 feet of 2-foot wire +netting. Two pairs of hinges; two locks; staples, etc. +</p> + +<p> +The materials used comprise:— The total cost as estimated from prices +current at the time of writing is 25s. This cost could be considerably reduced +by using lighter stuff all through for the framework and doors and by covering +in the house with old boards, which may be picked up cheaply if one is lucky. +Whether it is advisable to sacrifice durability and rigidity to cost must be +left to the maker to decide. Anyhow, if the specifications given are followed, +an outfit warranted to last for several years will be produced. +</p> + +<p> +A Few Points.—The vertical height of the run is just under 6 feet, the +tips being cut away from the rafters at the apex. The width at the ground is +exactly 6 feet. The base angles made by AA with B (Fig. 14) are 63 degrees; +that which they make with one another, 54 degrees. The rafters r1 and r3 at +each end of the house are half an inch thicker than the rest, as they have to +stand a lot of nailing. +</p> + +<h4>CONSTRUCTION.</h4> + +<p> +Cutting the Rafters.—If floor space is available, chalk out accurately +the external outline of a pair of rafters (80 inches long each before shaping) +and a line joining their lower ends. Then draw a line bisecting the ridge +angle. With this template as guide the rafters can be quickly cut to shape. +Another method is to cut one rafter out very carefully, making a notch for half +the width of the ridge, and to use it as a pattern for the rest. In any case +the chalked lines will prove useful in the next operation of pairing the +rafters and uniting them by a tie just under the ridge notch. Cut a 4 by 1 inch +notch at the bottom of each rafter, on the outside, for the base piece. The two +end pairs have the B pieces (Fig. 14) nailed on to them, and r3 the tie t, +which should be in line with the rafters. The other three pairs require +temporary ties halfway up to prevent straddling during erection. +</p> + +<p> +Door Frames and Doors.—The method of fixing the frame of the door at the +run end is shown in Fig. 14. The material for the frame being 1/2 inch thicker +than that of the rafters, there is room for shoulders at the top angles, as +indicated by dotted lines. The door frame at the house end is of the same +thickness as r1 so that no overlapping is possible. This being the case, screws +should be used in preference to nails, which are liable to draw a sloping face +out of position as they get home. +</p> + +<p> +[Illustration: Fig. 14.—On left, elevation of end of run; on right, door +for run.] +</p> + +<p> +The doors are made of 2 by 2 inch stuff, halved at the corners. Cut out the top +and bottom of the two sides; lay them on the floor so as to form a perfect +rectangle, and nail them together. The strut is then prepared, care being taken +to get a good fit, as any shortness of strut will sooner or later mean sagging +of the door. Cut the angles as squarely as possible, to ensure the strut being +of the same length both inside and out. +</p> + +<p> +Note.—As the door is rectangular, it does not matter which corners are +occupied by the ends of the strut; but when the door is hung, the strut must +run relatively to the side on which the hinges are, as shown in Fig. 14. +Amateurs—even some professionals—have been known to get the strut +the wrong way up, and so render it practically useless. +</p> + +<p> +Covering the Ends of the House.—The ends of the house should be covered +before erection, while it is still possible to do the nailing on the flat. The +run end is boarded right over, beginning at the bottom, and allowing each board +to overlap that below it by 1 inch. The board ends are flush with the outer +sides of the rafters. When boarding is finished, cut (with a pad saw) a +semicircular-topped run hole, 14 inches high and 8 inches wide, in the middle +of the bottom. Any structural weakness caused by severing the two lowest boards +is counteracted by the two grooved pieces in which the drop-door moves. +</p> + +<p> +Odds and ends of weather boards should be kept for the door end of the house, +which requires short pieces only, and is not boarded below the top of b2. The +door may be weather-boarded to match the rest of the end, or covered by a few +strakes of match-boarding put on vertically. +</p> + +<p> +The two base pieces, b1 and b2, and the ridge should be marked off for the +rafters at the same time. All three are 10-foot lengths of 4 by 1 wood, unless +you prefer the ridge to project a bit, in which case you must allow +accordingly. +</p> + +<p> +Stand all three pieces together on edge, and make the marks with a square +across the tops. Allow a distance of 4 feet between the outside faces of r1 and +r3; halve this distance to get the centre of r2; and subdivide the distance +between r3 and r6 so that each rafter is separated from its neighbours by an +equal space, which will be 1 foot 11 inches. Number the marks and continue them +down the sides of the boards with the square. There should be a mark on each +side of the place to be occupied by the intermediate rafters, to prevent +mistakes; for it is obvious that if a rafter is fixed on the left side of a +single ridge mark and on the right of the corresponding mark on the base, the +result will not be pleasing. +</p> + +<p> +Erection.—The services of a second pair of hands are needed here, to hold +while nailing is done. Nail holes having been drilled in the tops of the +rafters and in the base pieces, the ends are stood upright and tacked to the +ridge at the places marked for them, and after them the intermediate rafters, +working from one end to the other. Then tack on the base pieces, b1, b3. Get +the ends quite perpendicular, and nail a temporary cross strut or two on the +outside of the rafters to prevent shifting while the final nailing up is done. +</p> + +<p> +Covering the Shed.—Sixteen boards, 4 feet 2 inches long, are needed for +each side, as, owing to the overlap of one inch, each tier covers only five of +the 80 inches. The ridge is made watertight by a strip of sheet zinc, a foot +wide, bent over the top and nailed along each edge. +</p> + +<p> +Waterproofing.—All the woodwork should now be given a coating of +well-boiled tar, paint, creosote, or some other preservative, worked well down +into the cracks. Creosote and stoprot are most convenient to use, as they dry +quickly. +</p> + +<p> +Netting.—When the preservative has dried, fix on the netting with +3/4-inch wire staples. Begin at the base on one side, strain the netting over +the ridge, and down to the base on the other side. Be careful not to draw the +rafters out of line sideways. The last edge stapled should be that on the roof +of the house. +</p> + +<p> +Note.—When driving nails or staples into a rafter or other part, get a +helper to hold up some object considerably heavier than the hammer on the +farther side to deaden the blow. Lack of such support may cause damage, besides +making the work much more tedious and difficult. +</p> + +<p> +Finishing off.—The doors are now hung, and fitted with buttons and +padlocks. The stops should be on the doors, not on the frames, where they would +prove an obstruction in a somewhat narrow opening. Perches should be of 2 by 1 +inch wood, rounded off at the top, and supported in sockets at each end so as +to be removable for cleaning; and be all on the same level, to avoid fighting +for the “upper seats” among the fowls. A loose floor, made in two +pieces for convenience of moving, will help to keep the fowls warm and make +cleaning easier, but will add a few shillings to the cost. The inside of the +house should be well whitewashed before fowls are admitted. To prevent draughts +the triangular spaces between the roof boards and rafters should be plugged, +but ample ventilation must be provided for by holes bored in the ends of the +house at several elevations, the lowest 2 feet above the base. Handles for +lifting may be screwed to the faces of b and b2 halfway between the door frame +and the corners. +</p> + +</div><!--end chapter--> + +<div class="chapter"> + +<h2><a name="chap07"></a>VII.<br /> +A SHED FOR YOUR BICYCLE.</h2> + +<p> +The problem, how to house one or more cycles, often gives trouble to the +occupiers of small premises. The hall-way, which in many cases has to serve as +stable, is sadly obstructed by the handles of a machine; and if one is kept +there, the reason generally is that no other storage is available. +</p> + +<p> +If accommodation is needed permanently for two or three cycles belonging to the +house, and occasionally for the machine of a visitor, and if room is obtainable +in a backyard or garden in direct communication with the road, the question of +constructing a really durable and practical cycle shed is well worth +consideration. I say constructing, because, in the first place, a bought shed +costing the same money would probably not be of such good quality as a +home-made one; and secondly, because the actual construction, while not +offering any serious difficulty, will afford a useful lesson in carpentry. +</p> + +<p> +[Illustration: FIG. 16.—Cycle shed completed.] +</p> + +<p> +Cycle sheds are of many kinds, but owing to the limitations of space it is +necessary to confine attention to one particular design, which specifies a shed +composed of sections quickly put together or taken apart—portability +being an important feature of “tenants’ fixtures”—and +enables fullest advantage to be taken of the storage room. As will be seen from +the scale drawings illustrating this chapter, the doors extend right across the +front, and when they are open the whole of the interior is easily accessible. +The fact that the cycles can be put in sideways is a great convenience, as the +standing of the machines head to tail alternately economizes room considerably. +</p> + +<p> +[Illustration: FIG. 16.—Plan of corner joints of cycle shed.] +</p> + +<p> +I ought to mention before going further that the shed to be described is very +similar, as regards design and dimensions, to one in a back issue of Cycling. +By the courtesy of the proprietors of the journal I have been permitted to +adapt the description there given.[1] +</p> + +<p> +[Footnote 1: By Mr. Hubert Burgess. ] +</p> + +<p> +Dimensions and General Arrangements.—The shed is 8 feet long over all, 5 +feet 6 inches high in front, 5 feet high at the back, 3 feet deep over all, +under the roof, which projects 3 inches fore and aft, and 2 inches at each end. +It consists of seven parts: two sides, roof, back, front frame and doors, and a +bottom in two sections. +</p> + +<p> +The reader should examine the diagrams (Figs. 16 to 24) to get a clear +understanding of the disposal of the parts at the corners. Fig. 16 makes it +plain that the frames of the back and front overlap the frames of the sides, to +which they are bolted; and that the covering of the back overlaps the covering +of the sides, which in turn overlaps the front frame. +</p> + +<p> +All corner joints are halved. In order to allow the doors to lie flush with the +front of the doorframe uprights, the last must project the thickness of the +door boards beyond the frame longitudinals; and to bring the front uprights of +the sides up against the uprights of the door frame, the longitudinals are +notched, as shown (Fig. 16), to the depth of the set-back for the doors. +</p> + +<p> +Materials.—The question of cost and the question of materials cannot be +separated. A shed even of the dimensions given consumes a lot of wood, and the +last, that it may withstand our variable and treacherous climate for a good +number of years, should, as regards those parts directly exposed to the +weather, be of good quality. Yellow deal may be selected for the boards; pitch +pine is better, but it costs considerably more. For the frames and non-exposed +parts generally ordinary white deal will suffice. +</p> + +<p> +[Illustration: FIG. 17.-Types of match boarding: (a) square joint; (b) +double.-V; (c) single-V.] +</p> + +<p> +The scale drawings are based on the assumption that matching of one of the +forms shown in Fig. 17, and measuring 4 inches (actual) across, exclusive of +the tongue, and 5/8 inch (actual) thick, is used. +</p> + +<p> +As advised in the case of the carpenter’s bench, (p. 15) the prospective +constructor should let the wood merchant have the specifications, so that he +may provide the material in the most economical lengths. The following is a +rough estimate of the wood required, allowing a sufficient margin for waste: +</p> + +<p> +4-1/2 (over tongue) by 5/8 inch (actual) yellow match boarding for sides, roof, +back, and doors: +</p> + +<p> +1-1/2 squares = 150 sq. feet. = 450 feet run. White 4-1/2 by 3/4 inch +square-shouldered flooring: 1/4 square = 25 sq. feet. = 75 feet run. 3 by 1-1/2 +inch battens = 88 feet run. 4 by 1-1/2 inch battens = 26 feet run. 3 by 2 inch +battens = 27 feet run. 5 by 1-1/2 inch battens = 8 feet run. 2 by 1-1/2 inch +battens = 21 feet run. +</p> + +<p> +There will also be required:<br /> +Twelve 6-inch bolts and nuts.<br /> +Two pairs 18-inch cross-garnet hinges.<br /> +Two door bolts.<br /> +One lock (a good one).<br /> +Four yards of roofing felt.<br /> +Two gallons of stoprot.<br /> +Three lbs. wire-nails<br /> +A few dozen 3-inch and I-1/2-inch screws.<br /> +</p> + +<p> +The total cost of the materials will come to about 2 pounds, 2s. +</p> + +<h4>CONSTRUCTION.</h4> + +<p> +The scale drawings are so complete as to dimensions that, assuming the +materials to be of the sizes specified, they may be followed implicitly. It is, +of course, easy to modify the design to suit any slight differences in +dimensions; and to avoid mistakes all the stuff should be gauged carefully +beforehand. +</p> + +<p> +[Illustration: FIG. 18.-Side of cycle shed.] +</p> + +<p> +The Sides.—When laying out the frames for these it is necessary to bear +in mind that the front upright is somewhat less than 5 feet 6 inches long, and +the back upright rather more than 5 feet, owing to the slope of the roof, and +to the fact that they are set in 2 inches from the back and front. To get the +lengths and angle of the half-joints right, lay the verticals, which should be +5 feet 6 inches and 5 feet 1 inch long before trimming, on the floor, at right +angles to the bottom of the frame (2 feet 7-3/4 inches long) and quite parallel +to one another. (We will assume the half-joints to have been made at the +bottom.) The batten for the top is laid across the ends of the verticals, its +top edge in line with a 5-foot 6-inch mark at a point 2 inches beyond the front +vertical, and with a 5-foot mark 2 inches beyond the back vertical, the +distances being measured perpendicularly from the bottom of the frames +produced. The lines for the joints can then be marked, and the joints cut. The +notches for the roof stays should not be cut till the roof is being fitted. +</p> + +<p> +[Illustration: FIG. 19.—Boards at top of side, fixed ready for cutting +off.] +</p> + +<p> +Use the side frame first made as template for the other. +</p> + +<p> +The shelves are notched at the ends, so that their back faces shall be flush +with the board side of the frame. +</p> + +<p> +Fix the corners with the screws, and plane off the projecting angles of the +uprights. +</p> + +<p> +When putting on the boards, start at the back of the frame. Plane down the +groove edge of the first board until the groove is out of the board, and apply +the board with 1-1/2 inches projecting beyond the frame. Leave a little spare +at each end of every board, and when the side is covered run a tenon-saw across +both ends of all the boards close to the frame, and finish up with the plane. +This is quicker and makes a neater job than cutting each board to size +separately. +</p> + +<p> +[Illustration: FIG. 20.-Back of cycle shed.] +</p> + +<p> +The Back (Fig. 20).—When laying out the frame for this, remember that +there is a bevel to be allowed for along the top, and that the height of the +frame at the front must be that of the back of a side frame. (See Fig. 21.) The +boards should be cut off to the same slope. +</p> + +<p> +Twenty-four boards should exactly cover the back. Cut the tongue neatly off +that last fixed, and glue it into the groove of the first board. +</p> + +<p> +The Front.—The frame requires careful making. For details of corner +joints see Fig. 16. The 3-inch faces of the top and bottom bars are vertical. +The upper side of the top bar is planed off to the angle of the slope. (Fig. +23.) +</p> + +<p> +[Illustration: FIG. 21. Detail of eaves.] +</p> + +<p> +The Doors (Fig. 22).—These are the most difficult parts to construct, as +the braces which prevent the front edges dropping must be carefully fitted in +order to do their work properly. +</p> + +<p> +The eleven outside boards of each door are held together by two 4-inch ledges 6 +inches away from the ends, and one 5-inch central ledge. Allow a little +“spare” on the boards for truing up. Boards and ledges having been +nailed together, lay a piece of 4 by 1-1/2 inch batten across the ledges on the +line which the braces will take, and mark the ledges accordingly. Next mark on +the batten the ends of the braces. These project half an inch into the ledges, +and terminate on the thrust side in a nose an inch long, square to the edge of +the brace. The obtuse angle is flush with the edge of the ledge. Cut out the +braces, lay them in position on the ledges, and scratch round the ends. Chisel +out the notches very carefully, working just inside the lines to ensure the +brace making a tight fit. If there is any slackness at either end, the brace +obviously cannot carry the weight of the door until the door has settled +slightly, which is just what should be prevented. Therefore it is worth while +taking extra trouble over this part of the work. +</p> + +<p> +[Illustration: FIG. 22.-Doors of shed.] +</p> + +<p> +Cautions.—Don’t get the nose of the brace too near the end of the +ledge. Nail the boards on specially securely to the ledges near the ends of the +braces. +</p> + +<p> +Fitting the Doors.—The doors should now be laid on the top of the frame +and secured to it by the four hinges. The long ends of these are held by screws +driven through the boards into the bearers; the cross pieces are screwed to the +uprights of the door frame. The doors when closed should make a good but not +tight fit with one another. +</p> + +<h4>PUTTING THE PARTS TOGETHER.</h4> + +<p> +The two sides, front, and back are now assembled, on a level surface, for +drilling the holes for the bolts which hold them together. The positions of the +bolts will be gathered from the drawings. Get the parts quite square before +drilling, and run the holes through as parallel to the sides as possible. If +the bolts are a bit too long, pack washers between nut and wood until the nut +exerts proper pressure. +</p> + +<p> +Caution.—The hole must not be large enough to allow the square part just +under the head to revolve, for in such a case it would be impossible to screw +up the nut. Its size ought to be such as to require the head to be driven up +against the wood. +</p> + +<p> +[Illustration: Fig. 23 Roof attachment] +</p> + +<p> +The Roof.—The boards of this are attached to a frame which fits closely +inside the tops of the sides, back, and front. To get the fit of the frame +correct, it must be made a bit too wide in the first instance, and then be +bevelled off at the front, as shown in Fig. 23, and the reverse way at the +back. The ends are notched for the stays AA, and the frame then tacked firmly, +by driving nails into the sides, etc., below it, in the position which it will +occupy when the roof is on, except that it projects upwards a little. Cut off +twenty-five boards 3 feet 7 inches long. Omitting the end ones for the present, +lay the remainder up to one another in order, their ends an equal distance from +the frame, and nail to the frame. Lift off the roof, insert and secure AAAA, +and nail on the end boards. Then rule parallel straight lines 3 feet 6 inches +apart across all the boards from end to end of the roof, and cut along these +lines. The roof is replaced after notches have been cut in the tops of the +sides to take AAAA, and secured to the vertical parts by six bolts, the +positions of which are shown in Fig. 24. +</p> + +<p> +[Illustration:<br /> +FIG. 24.—Top of cycle shed.<br /> +FIG. 25.—Floor of shed.]<br /> +</p> + +<p> +The Floor (Fig. 25).—The making of this is so simple a matter that one +need only point out the need for notching the end boards to allow the floor to +touch the sides and back, and the doors when closed. It should be screwed to +the frames, on which it rests, in a few places. +</p> + +<p> +Preserving the Wood.—All outside wood is dressed with stoprot or +creosote, rubbed well into the joints of the boarding. +</p> + +<p> +Felting the Roof.—The felt is cut into 4-foot lengths, and each length +has its ends turned over and nailed to the underside of the roof. The strips +must overlap an inch or two. When the felt is on, dress it with boiled tar, and +sprinkle sand over it while the tar is still liquid. +</p> + +<p> +Fitting.—The two bolts to hold one door top and bottom and the lock are +now fitted, and a couple of hooks screwed into the door frame clear of the +door, to sling a machine from while it is being cleaned or adjusted. +</p> + +<p> +Mounting the Shed.—The shed must be raised a few inches above the ground, +on bricks or other suitable supports. Don’t stand it close to a wall. Air +should be able to circulate freely under and all round it. +</p> + +<h4>CUTTING DOWN EXPENSE.</h4> + +<p> +If the cost appears prohibitive, it may be reduced somewhat (1) by using +thinner boards; (2) by reducing the height of the shed by 1 foot. A very cheap +shed, but of course not comparable in quality with the one described, can be +made by using odd rough boards for the outside, and covering them with roofing +felt well tarred. +</p> + +</div><!--end chapter--> + +<div class="chapter"> + +<h2><a name="chap08"></a>VIII.<br /> +A TARGET APPARATUS FOR RIFLE SHOOTING.</h2> + +<p> +The base is a 1-inch board, 18 inches long and 7 inches wide. +</p> + +<p> +The target-holder is a piece of wood 1-1/2 inches square, and a couple of +inches longer than the side of the largest target to be used. To one face nail +a piece of strip lead as weight; and to the parallel face attach, by means of +brads driven in near one edge, a piece of thin wood of the same size as the +face. The free long edge of this should be chamfered off slightly on the inside +to enable the target to be slipped easily between it and the roller. +</p> + +<p> +The roller is pivoted on two short spindles—which can be made out of +stout wire nails—driven into the ends near the face farthest from the +weight. (See Fig. 26.) +</p> + +<p> +For standards use a couple of the small angle irons used for supporting +shelves, and sold at about a penny each. These are screwed on to the board 2 +inches from what may be considered to be the rear edge, and are so spaced as to +leave room for a washer on each spindle between the roller and the standards, +to diminish friction. +</p> + +<p> +[Illustration: FIG. 26.-Side elevation of disappearing target apparatus.] +</p> + +<p> +Remove one standard, and drive into the roller a piece of stout wire with its +end bent to form an eye. The inclination of the arm to the roller is shown in +Fig. 26. +</p> + +<p> +To the front of the board now nail a rectangle of stout sheet iron, long and +deep enough to just protect the standards and roller. Place the roller in +position, insert a target, and revolve the roller to bring the target vertical. +A small wire stop should now be fixed into the baseboard to prevent the arm +coming farther forward, and a hole for the operating string be drilled in the +protection plate at the elevation of the eye on the arm. The edges of this hole +need careful smoothing off to prevent fraying of the string. A small eyelet or +brass ring soldered into or round the hole will ensure immunity from chafing. +</p> + +<p> +Drive a couple of long wire nails into the front edge of the board outside the +iron screen to wind the string on when the target is put away. +</p> + +<p> +It may prove a convenience if plain marks are made on the string at the +distances from which shooting will be done. +</p> + +<p> +The above description covers apparatus for working two or more targets +simultaneously on a long roller, or separately on separate rollers mounted on a +common baseboard. +</p> + +<p> +If it is desired to combine with the apparatus a “stop” for the +bullets, the latter (a sheet of stout iron of the requisite strength) may be +affixed to the rear of the baseboard, and furnished with a handle at the top to +facilitate transport. +</p> + +</div><!--end chapter--> + +<div class="chapter"> + +<h2><a name="chap09"></a>IX.<br /> +CABINET-MAKING.</h2> + +<p> +A Match-box Cabinet. +</p> + +<p> +This is useful for the storage of small articles, such as stamps, pens, seeds, +needles, and a number of other minor things which easily go astray if put in a +drawer with larger objects. +</p> + +<p> +The best boxes for the purpose are those used for the larger Bryant and May +matches. Select only those boxes of which the tray moves easily in the case. +</p> + +<p> +The cases should be stood on end on some flat surface while being glued +together. A box or drawer with truly square corners is useful for assembling +them in; if they are packed into one corner they cannot slew about. Press the +boxes together while the glue is setting. +</p> + +<p> +Now glue the back ends of the cases (from which the trays should have been +removed), and press them against a piece of thin card. When the glue is dry, +apply some more with a small brush to the back angles inside the covers, to +ensure a good hold on the backing. Trim off the card to the outline of the +pile. +</p> + +<p> +[Illustration: FIG. 27.—Match-box cabinet.] +</p> + +<p> +Select for the front end of the drawer that for which the wood is doubled over. +Paste outside the end a piece of white paper, whereon words and numbers will be +more plainly visible. The life of the trays will be increased if the insides +are neatly lined with thin paper. +</p> + +<p> +For “handles” use boot buttons, or loops of thin brass wire, or +brass paper clips. To give the cabinet a neat appearance you should cover it +outside with paper of some neutral tint; and if you wish it to be stable and +not upset when a rather sticky drawer is pulled out, glue it down to a solid +wooden base of the proper size. +</p> + +<p> +A Cardboard Cabinet. +</p> + +<p> +We now proceed to a more ambitious undertaking—the manufacture of a +cabinet for the storage of note-paper, envelopes, labels, etc. The only +materials needed are some cardboard and glue; the tools, a ruler and a very +sharp knife. For the marking out a drawing board and T-square are invaluable. +The cardboard should be fairly stout, not less than 1/16 inch thick. +</p> + +<p> +Begin with the drawers; it is easier to make the case fit the drawers than vice +versa. +</p> + +<p> +Mark out the drawers as shown in Fig. 28. The areas AA are the front and back; +BB the sides. The dotted lines indicate the lines along which the cardboard is +bent up. The sides are of exactly the same length as the bottom, but the front +and back are longer than the bottom by twice the thickness of the cardboard, so +as to overlap the sides. (The extra length is indicated by the heavy black +lines.) +</p> + +<p> +[Illustration: FIG. 28.—Drawer of cardboard cabinet marked ready for +cutting.] +</p> + +<p> +Measure and cut out very carefully to ensure all the drawers being of the same +size. Lay a piece of card under the thing cut to avoid blunting the knife or +damaging the table. When the blanks are ready, cut them almost through along +the dotted lines. Use several strokes, and after each stroke test the +stubbornness of the bend. When the card is almost severed it will bend up quite +easily. Note.—Bend as shown in the inset C; not the other way, or you +will snap the card. If you should be so unlucky as to cut the card through in +places, paste a strip of thin paper along the line before turning up. +</p> + +<p> +The four flaps are now bent up, glued together, and covered outside with paper. +This part of the business is easy enough if a small square-cornered wooden box +be used as a support inside at each angle in turn. It is advisable to glue +strips along all the bends both inside and outside. The external strips should +be flattened down well, so as to offer no loose edges. +</p> + +<p> +Compare the drawers, and if one is slightly wider than the rest, use it to +guide you in making the measurements for the case. +</p> + +<p> +The sides and back of the case are cut out of a single piece. The sides should +be a quarter of an inch deeper than the drawers to allow some overlap; the back +slightly wider than the drawer. +</p> + +<p> +As each drawer will be separated from that above it by a shelf, allowance must +be made for the shelves, and also for a twentieth of an inch or so of +“play” to each drawer. To keep on the safe side leave a little +extra stuff to be removed later on. +</p> + +<p> +Cut out the bottom to fit inside the back and sides exactly, and a sufficient +number of shelves of precisely the same size as the bottom. Attach the bottom +to the sides and back with internal and external strips. When the glue has set, +place the guide drawer in position, and lay on it a piece of thin card to cover +it over. This card is merely a removable “spacer.” Along the side +and back edges of the shelf stick projecting strips of stout paper. When the +adhesive is dry, turn the strips round the end at right angles to the division, +glue them outside, and lay the division in position on top of the +“spacer.” +</p> + +<p> +Place the second drawer and shelf in like manner, and continue till the top of +the cabinet is reached. Then mark off and cut away any superfluous card. Glue +the top edges, and stand the cabinet head downwards on a piece of cardboard. +Trim off the edges of this, and the top is completed, except for binding the +corners. +</p> + +<p> +Then attend to the outside back corners of the case, and paste strips in the +angles under the shelves. The strips should be forced well into the angles. +</p> + +<p> +For handles use brass rings let sufficiently far through the fronts of the +drawers for a wedge of card to be slipped through them and stuck in position. +The appearance of the cabinet will be enhanced by a neatly applied covering of +paper. +</p> + +<p> +A Cigar-box Cabinet. +</p> + +<p> +At the rate of a halfpenny or less apiece one may buy the cigar boxes made to +hold twenty-five cigars. These boxes, being fashioned by machinery, are +all—at any rate all those devoted to a particular +“brand”—of the same dimensions; they are neatly constructed, +and their wood is well seasoned. Anyone who wishes to make a useful little +cabinet may well employ the boxes as drawers in the said cabinet (Fig. 29). +</p> + +<p> +Each box should be prepared as follows:-Remove the lid and paper lining, and +rub all the paper binding off the outside angles with a piece of coarse glass +paper. This is a safer method than soaking-off, which may cause warping and +swelling of the wood. Then plane down the tops of the two sides till they are +flush with the back and front, and glue into the corners small pieces of wood +of right-angled-triangle section to hold the sides together and the bottom to +the sides. To secure the parts further cut a number of large pins down to 3/4 +inch, and drive these into the sides through holes carefully drilled in the +bottom. Finally, rub the outside of the drawer well with fine glass paper or +emery cloth till the surface is smooth all over. +</p> + +<p> +The Case.—If mahogany can be obtained for this, so much the better, as +the wood will match the boxes. In default of it, a white wood, stained, will +have to serve. +</p> + +<p> +[Illustration: FIG. 29.—Cabinet with cigar-box drawers.] +</p> + +<p> +The two sides of the case should be prepared first Wood 3/8 inch thick is +advised. Each side is 1 inch wider than the depth (outside) of a drawer from +front to back. (Whether the drawers shall slide in lengthways or flatways is +for the maker to decide.) The length of a side is calculated on the basis that +the drawers will be separated from one another by runners 1/4 to 5/16 inch +deep, and that a slight clearance must be allowed for the drawers to slide in +and out freely. In the first instance cut the sides a bit too long. If it be +preferred to insert the bottom between the sides, the length must be increased +accordingly. +</p> + +<p> +The runners are cut out of the box lids, and planed till their top and bottom +edges are parallel. Their length is 1/4 inch less than the depth of a drawer. +To fill up the spaces between the drawers in front you will need some slips of +the same depth as the runners, and 3/8 inch longer than the drawer, so that +they may be let 3/16 inch into the sides of the case at each end. +</p> + +<p> +Affixing the Runners.—This is a very easy matter if a wooden spacer, +slightly wider than the depth of the drawer, is prepared. Having decided which +is to be the inside face and the forward edge of a side, lay the side flat, and +apply the spacer with one edge flush with the bottom of the side, or as far +away from it as the thickness of the bottom, as the case may be, and fix it +lightly in position with a couple of tacks. The first runner is laid touching +the spacer and a little back from the edge to give room for the cross-bar, and +fastened by means of short tacks, for which holes had better be drilled in the +runner to prevent splitting. The spacer is now transferred to the other side of +the runner, and the second runner is fastened on above it; and so on till all +the runners are in position. The square should be used occasionally to make +sure that the tops of the runners are parallel to one another. The other side +having been treated in like manner, any spare wood at the top is sawn off. +</p> + +<p> +The notches for the front cross-bars between drawers are cut out with a very +sharp narrow chisel. +</p> + +<p> +The Top and Bottom.—Make the top of the same thickness as the sides; the +bottom of somewhat stouter wood. If the bottom is cut a bit longer than the +width of the case, and neatly bevelled off, it will help to smarten the +appearance of the cabinet. +</p> + +<p> +When fixing the sides to the bottom and top get the distance correct by placing +the top and bottom drawers in position, and insert a piece of thin card between +one end of the drawer and the side. This will ensure the necessary clearance +being allowed for. +</p> + +<p> +The Back.—Cut this out of thin wood. The top of a sweetstuff box-costing +about a halfpenny—will do well enough. It should be quite rectangular and +make a close fit, as it plays the important part of keeping the case square +laterally. Bevel its back edges off a bit. Push it in against the back ends of +the runners, and fix it by picture brads driven in behind. +</p> + +<p> +The front bars should now be cut to a good fit and glued in the notches.<br /> +This completes the construction.<br /> +</p> + +<p> +Drop handles for the drawers may be made out of semicircles of brass wire with +the ends turned up. The handles are held up to the drawer by loops of finer +wire passed through the front and clinched inside. +</p> + +<p> +The finishing of the outside must be left to the maker’s taste. +Varnishing, or polishing with warmed beeswax, will add to the general +appearance, and keep out damp. +</p> + +<p> +The total cost of a ten-drawer cabinet ought not to exceed eighteen pence. +</p> + +<p> +A Tool Cabinet. +</p> + +<p> +The wooden cabinet shown in Fig. 30 is constructed, as regards its case, in the +same way as that just described, but the drawers are built up of several +pieces. The over-all dimensions of the cabinet represented are as follows: +Height, including plinth, 25 inches; width, 17-3/8 inches; depth, 10-1/2 +inches. The drawers are 16 inches wide (outside), by 10-1/8 inches from back to +front, and, reckoning from the bottom upwards, are 3-1/4, 3, 2-1/2, 2, 2, 2, 2, +and 1-3/4 inches deep. +</p> + +<p> +[Illustration: FIG. 30.—Large cabinet (a), details of drawer joints (b, +c, d), and padlock fastening (e).] +</p> + +<p> +The construction of the drawers is indicated by the diagrams, Fig. 30, b, c, d. +The fronts are of 5/8-inch, the sides and backs of 3/8-inch, and the bottoms of +(barely) 1/4-inch wood. The grooves should not come nearer than 1/8-inch to the +bottom edge, or be more than 5/16 inch wide and deep. The possessor of a +suitable “plough” plane will have no difficulty in cutting them +out; in the absence or such a tool the cutting gauge and chisel must be used. +</p> + +<p> +The back piece of a drawer has 1/4-inch less height than the front, to allow +the bottom to be introduced. The ends or the bottom are bevelled off towards +the top edge to fit the grooves, so that no part may be above the grooves. +</p> + +<p> +Glue should be used to attach the sides of a drawer to the back and front in +the first place, and nails be added when the glue has set. As an aid to +obtaining perfect squareness, without which the drawers will fit badly, it is +advisable to mark out on a board a rectangle having the exact inside dimensions +of a drawer, and to nail strips of wood up to the lines on the inside. If the +parts are put together round this template they will necessarily fit squarely. +</p> + +<p> +Divisions.—If the drawers are to be subdivided in one direction only, the +partitions should run preferably from back to front, as this enables the +contents of a compartment to be more easily seen. Where two-direction division +is needed the partitions are cut as shown in Fig. 31. All partitions should +touch the bottom, and be made immovable by gluing or nailing. It is a mistake +to have so many divisions in a drawer that the fingers cannot get into them +easily. +</p> + +<p> +Wooden knobs for the drawers can be bought very cheaply of any turner, or +suitable brass knobs at any ironmonger’s. Take care that the knobs are in +line with one another; otherwise the general appearance of the cabinet will +suffer. +</p> + +<p> +[Illustration: FIG. 31.—Divisions of drawer notched to cross each other.] +</p> + +<p> +Lock and Key.—If a cabinet is intended for storage of articles of any +value it should be provided with lock and key. One lock will secure all the +drawers if attached to a flap hinged on one side to the cabinet, as shown in +Fig. 30 a, to engage a catch projecting from one of the drawers. A special form +of lock is sold for the purpose. If the single flap seems to give a lop-sided +effect, place a fellow on the other side, and fit it with sunk bolts to shoot +into the overhanging top and plinth. If you wish to avoid the expense and +trouble of fitting a lock, substitute a padlock and a staple clinched through +the front of a drawer and passing through a slot in the flap (Fig. 30, e). +</p> + +<p> +Alternative Method.—The fixing of the front bars can be avoided if the +front of each drawer (except the lowest) be made to overhang the bottom by the +depth of the runner. This method, of course, makes it impossible to stand a +drawer level on a level surface. +</p> + +</div><!--end chapter--> + +<div class="chapter"> + +<h2><a name="chap10"></a>X.<br /> +TELEGRAPHIC APPARATUS.</h2> + +<p> +The easily made but practical apparatus described in this chapter supplies an +incentive for learning the Morse telegraphic code, which is used for sending +sound signals, and for visible signals transmitted by means of flags, lamps, +and heliograph mirrors. Signalling is so interesting, and on occasion can be so +useful, that no apology is needed for introducing signalling apparatus into +this book. +</p> + +<p> +The apparatus in question is a double-instrument outfit, which enables an +operator at either end of the line to cause a “buzzer” or +“tapper” to work at the other end when he depresses a key and +closes an electric circuit. Each unit consists of three main parts—(1) +the transmitting key; (2) the receiving buzzer or tapper; (3) the electric +battery. +</p> + +<p> +The principles of an installation are shown in Fig. 33. One unit only is +illustrated, but, as the other is an exact duplicate, the working of the system +will be followed easily. +</p> + +<p> +[Illustration: Fig. 32.—Morse alphabet] +</p> + +<p> +A wooden lever, L, is pivoted on a support, A. Passing through it at the +forward end is a metal bar having at the top a knob, K, which can be grasped +conveniently in the fingers; at the other a brass screw, O, which is normally +pulled down against the contact, N, by the spiral spring, S. The contact M +under K is in connection with the binding post T1 and N with binding post T3; K +is joined up to T2, and O to T4. +</p> + +<p> +T3 and T4 are connected with one of the line wires; T1 with the other wire +through a battery, B; T3 with the other wire through the buzzer, R. [1] +</p> + +<p> +[Footnote 1: For the buzzer may be substituted the tapper, described on a later +page.] +</p> + +<p> +Assuming both keys to be at rest, as in Fig. 33, the two buzzers are evidently +in circuit with the line wires, though no current is passing. If the stem of K +is depressed to make contact with M, the electric circuit of which the battery, +B, forms part is completed, and the buzzer at the other end of the lines comes +into action. Since the depression of K raises O off N, the “home” +buzzer’s connection with the line wires is broken, to prevent the current +being short-circuited. The fact that this buzzer is periodically in circuit, +even when the key is being worked, makes it possible for the operator at the +other end to attract attention by depressing his key, if he cannot read the +signals sent. +</p> + +<p> +[Illustration: Fig.33—Telegraphic apparatus; sending key, buzzer and +battery] +</p> + +<p> +Making the Keys. +</p> + +<p> +Transmitting keys can be bought cheaply, but not so cheaply as they can be +made. The only expense entailed in home manufacture is that of the screw +terminals for connecting the keys with the lines and buzzers. These cost only a +penny each, and, if strict economy is the order of the day, can be dispensed +with should the apparatus not have to be disconnected frequently. +</p> + +<p> +The size of the key is immaterial. The keys made by me have levers 1 inch wide +and 5-1/2 inches long, oak being chosen as material, on account of its +toughness. K is in each case a small wooden knob on a piece of 3/16-inch brass +rod; O a 1-1/2-inch brass screw; A a piece of sheet brass 3-1/2 inches long, +marked off carefully, drilled 1/8 inch from the centre of each end for the +pivot screws, and in four places for the holding-down screws, and bent up at +the ends to form two standards. If you do not possess any brass strip, the +lever may be supported on wooden uprights glued and screwed to the base. +</p> + +<p> +[Illustration: Fig. 34—Telegraphic apparatus mounted on baseboard] +</p> + +<p> +Contact M is a small piece of brass attached to the base by a screw at one end +and by T1 at the other. K was drilled near the end to take the short coil of +insulated wire joining it to T2, and O was similarly connected with T4. +</p> + +<p> +The spring, S, should be fairly strong. A steel spiral with a loop at each end +is most easily fitted. Drill holes in the lever and base large enough for the +spring to pass through freely, make a small cross hole through the lever hole +for a pin, and cut a slot across the base hole for a pin to hold the bottom of +the spring. Adjust the lever by means of screw O so that there is a space of +about 1/4-inch between K and M when O and N are in contact, and after the +spring has been put in position give the screw a turn or two to bring K down to +within 1/16 inch of M. This will put the required tension on the spring. +</p> + +<p> +The Buzzers.—For these I selected a couple of small electric bells, +costing 2s. 6d. each. Their normal rate of vibration being much too slow for +telegraphic purposes, I cut off the hammers to reduce the inertia, and so +adjusted the contact screw that the armature had to move less than one +hundredth of an inch to break the circuit. This gave so high a rate of +vibration that the key could not make and break the circuit quickly enough to +prevent the buzzer sounding. +</p> + +<p> +A Morse Tapper or Sounder. +</p> + +<p> +In postal telegraph offices a “sounder,” and not a +“buzzer,” is generally used to communicate the signals. Instead of +a continuous noise, lasting as long as the key at the transmitting station is +held down, the operator at the receiving station hears only a series of taps +made by an instrument called a “sounder.” The principle of this +simple device is illustrated by the working diagrams in Fig. 35. M is a +horseshoe magnet fixed to a base, A. Close to it is an armature, AR, of soft +iron, attached to a lever, L, which works on a pivot and is held up against a +regulating screw, P1, by the pull of the spring SP. When current passes through +the magnet the armature is attracted, and the point of the screw S2 strikes +against P2; while the breaking of the circuit causes L to fly back against S1. +The time intervening between the “down” and “up” clicks +tells the operator whether a long or a short—dash or a dot—is being +signalled. +</p> + +<p> +[Illustration: FIG. 35.-Elevation and plan of telegraphic sounder.] +</p> + +<p> +Materials.—A horseshoe magnet and armature taken from an electric bell +provide the most essential parts of our home-made instrument in a cheap form. +If these are available, expense will be limited to a few pence. Oak or walnut +are the best woods to use for the lever, being more resonant than the softer +woods, and for the standard B and stop V. Any common wood is good enough for +the base A. +</p> + +<p> +The lever L is 6 inches long, 1/2 inch deep, and 3/8-inch wide, and is pivoted +at a point 4-1/4 inches from the stop end. The hole should be bored through it +as squarely as possible, so that it may lie centrally without B being out of +the square. A piece of metal is screwed to its top face under the adjusting +screw S1. +</p> + +<p> +The spring is attached to L and A in the manner already described on p. 89 in +connection with the “buzzer.” +</p> + +<p> +The plate P2 should be stout enough not to spring under the impact of the +lever. Fig. 36 is an end view of the standard B. The drilling of the pivot hole +through this requires care. The screw S2 should be so adjusted as to prevent +the armature actually touching the cores of the magnets when attracted. The +ends of the magnet winding wire, after being scraped, are clipped tightly +against the base by the binding posts T1 T2. +</p> + +<p> +If sounders are used in place of buzzers they are connected up with the keys, +batteries, and line wires in the manner shown in Fig. 33. +</p> + +<p> +Batteries. +</p> + +<p> +The dry cells used for electric bells are the most convenient batteries to use. +They can now be purchased at all prices from a shilling upwards, and give about +1-1/2 volts when in good condition. One cell at each end will suffice for short +distances, or for considerable distances if large conductors are used. If a +single cell fails to work the buzzer strongly through the circuit, another cell +must be added. +</p> + +<p> +[Illustration: FIG. 36.—Standard for sounder.] +</p> + +<p> +For ease in transport it will be found advisable to mount key, buzzer, and +battery on a common baseboard, which should be provided with a cover and +handle. The three parts are interconnected with one another, and the line wire +terminals as sketched in Fig. 34. This arrangement makes the apparatus very +compact and self-contained. As a finishing touch fit the lid inside with clips +for holding a stiff-backed writing pad and pencil for the recording of +messages. +</p> + +<p> +Lines.—Fencing made of stout galvanized iron wires strung on wooden posts +supplies excellent conductors for practice purposes, provided the posts be +quite dry. In wet weather there will be leakage. (Fencing with metal posts is, +of course, unsuitable, as every post short-circuits the current.) The two wires +selected for land lines must be scraped quite bright at the points where the +connections are to be made. +</p> + +<p> +It is an easy matter to rig up a telegraph line of galvanized wire 1/12 to 1/8 +inch in diameter, strung along insulators (the necks of bottles serve the +purpose excellently) supported on trees, posts, or rough poles. The length of +the line will be limited by the battery power available, but a 6-volt battery +at each end will probably suffice for all experimental purposes. A second wire +is not needed if one terminal at each end is connected with a copper plate sunk +in the ground, or with a metal fence, drain-pipe, etc. +</p> + +</div><!--end chapter--> + +<div class="chapter"> + +<h2><a name="chap11"></a>XI.<br /> +A RECIPROCATING ELECTRIC MOTOR.</h2> + +<p> +The electric motor to be treated in this chapter illustrates very prettily the +attractive force of a hollow, wire-wound bobbin on a movable core, when the +electric current is passed through the wire. If one inserts the end of an iron +rod into the coil, the coil exerts a pull upon it, and this pull will cease +only when the centre of the rod is opposite the centre of the coil. This +principle is used in the “electric gun,” which in its simplest form +is merely a series of powerful coils arranged one behind another on a tube +through which an iron or steel projectile can pass. The projectile closes +automatically the circuit of each coil in turn just before reaching it, and +breaks it before its centre is halfway through the coil, being thus passed +along from one coil to the other with increasing velocity. +</p> + +<p> +Our motor is essentially a very inefficient one, its energy being small for the +current used, as compared with a revolving motor of the usual kind. But it has +the advantage of being very easy to make. +</p> + +<p> +[Illustration: FIG. 37.—Electric reciprocating engine and battery.] +</p> + +<p> +How it works.—The experimental engine, constructed in less than a couple +of hours, which appears in Fig. 38, consists of a coil, C, strapped down by a +piece of tin to a wooden bedplate; a moving plunger, P, mounted on a +knitting-needle slide rod, SR; a wire connecting rod, SR; a wooden crank, K; +and a piece of knitting-needle for crank shaft, on which are mounted a small +eccentric brass wipe, W, and a copper collar, D. Against D presses a brass +brush, B1 connected with the binding post, T1; while under W is a long strip of +springy brass against which W presses during part of every revolution. T2 is +connected to one end of the coil winding, and T1 through a 4-volt accumulator +or three dry cells, with the other end of the coil. When W touches B2 the +circuit is completed, and the coil draws in the plunger, the contact being +broken before the plunger gets home. The crank rotates at a very high speed if +there is plenty of battery power, all the moving parts appearing mere blurs. +</p> + +<h4>CONSTRUCTION.</h4> + +<p> +The coil is made by winding 4 oz. of No. 32 cotton-covered wire (price 6d. to +8d.) on a boxwood reel 2 inches long and 1-1/2 inches in diameter, with a +9/16-inch central hole. Before winding, bore a hole for the wire through one +end of the reel, near the central part, and mount the reel on a lathe or an +improvised spindle provided with a handle of some kind. The wire should be +uncoiled and wound on some circular object, to ensure its paying out regularly +without kinking; which makes neat winding almost impossible. +</p> + +<p> +Draw a foot of the wire through the hole in the reel, and drive in a tiny +peg—which must not protrude inwards—to prevent it slipping. Lay the +turns on carefully, forcing them into close contact, so that the next layer may +have a level bed. On reaching the end of the layer, be equally careful to +finish it neatly before starting back again. When the wire is all on, bore a +hole as near the edge of the finishing edge as possible, and draw the spare +wire through. Then cut a strip of tough paper of the width of the coils, coat +one side with paste, and wrap it tightly round the outside to keep the wire in +place. +</p> + +<p> +Note.—Insulation will be improved if every layer of wire is painted over +with shellac dissolved in alcohol before the next layer is applied. +</p> + +<p> +Flatten the reel slightly with a file at the points of contact with the +baseboard, to prevent rolling. +</p> + +<p> +The plunger is a tube of thin iron, 1/16 inch less in diameter than the hole in +the reel, and 1/4 inch longer than the reel. If a ready-made tube is not +available, construct one by twisting a piece of tin round a metal rod, and +soldering the joint. As it is difficult to make a jointed tube cylindrical, and +a close fit is needed to give good results, it is worth going to a little +trouble to get a plunger of the right kind. +</p> + +<p> +The ends of the plunger are plugged with wood and bored centrally for the slide +rod, which should not be cut to its final length until the parts are assembled. +</p> + +<p> +The crank shaft is 2-3/4 inches of a stout knitting needle mounted in a sheet +brass bearing. The crank, a fragment of oak or other tough wood, is balanced, +and has a throw of 5/8 inch. The crank-shaft hole should be a trifle small, so +that the crank shall get a tight hold of the shaft without pinning. The collar, +D, and wipe, W, are soldered to the shaft after this has been passed through +its bearings. The brush B1 should press firmly, but not unnecessarily so, +against the collar. For B2 one must use very springy brass strip, a piece about +3 inches long and 1/4 inch wide being needed. Bend it to the arc of a large +circle, and screw one end down to the base by the binding screw T2. The other +end, which should not touch the base, is confined by the heads of a couple of +small screws, by means of which the strip is adjusted relatively to the wipe. +</p> + +<p> +Fixing the Coil.—Cut a strip of tin 1-3/4 inches wide and 4 inches long. +Punch a couple of holes near one end, and nail this to the side of the base, +with its forward end 4-1/4 inches from the crank shaft. Pass the strip over the +coil, and bend it down towards the base. Drill a couple of screw holes, and +screw the other end down so that the coil is gripped fairly tight. +</p> + +<p> +Fixing the Plunger. Two small guides, G1 G2, are made for the plunger. The +holes through which the slide rod moves should be a good fit, and their centres +at the level of the centre of the coil. Screw holes are bored in the feet. +</p> + +<p> +Pass the plunger through the coil, and place the guides on the rod. Then draw +the plunger forward till 1/2 inch projects. Bring G1 close up to it, mark its +position, and screw it to the base. The other guide, G2, should be 1-1/2 inches +away from the rear of the coil. +</p> + +<p> +[Illustration: Fig. 38.—Plan of electric reciprocating engine.] +</p> + +<p> +The coil and guides must be adjusted so that the plunger does not touch the +coil anywhere during a stroke, packings being placed, if necessary, under coil +or guides. When the adjustment is satisfactory, screw the coil down tightly, +and cut off any superfluous parts of the rod. +</p> + +<p> +The Connecting Rod.—Bore a hole near the end of the plunger for a screw +to hold the rear end of the connecting rod. Pull the plunger out till 1-3/4 +inches project, turn the crank full forward, and measure off the distance +between the centres of the plunger hole and the crank pin. Drive a couple of +wire nails into a board, and twist the ends of a piece of 1/20-inch wire round +them twice. This wire constitutes a connecting rod amply strong enough to stand +the pulls to which it will be subjected. Fix the rod in position. +</p> + +<p> +Adjusting the Wipe.—Turn the wipe, W, round until it makes contact with +B2, and, holding the crank shaft with a pair of pliers, twist the crank on it +till it just begins the return stroke. Then turn the crank to find out how long +the wipe remains in contact, and adjust the crank relatively to the wipe so +that the crank is vertical when the period of contact is half finished. The +length of this period is controlled by the set screws at the free end of B2. +</p> + +<h4>OTHER DETAILS.</h4> + +<p> +The fly wheel may be a disc of wood. +</p> + +<p> +Oil all the rubbing parts slightly. Connect T1 to one terminal of the battery, +T2 to the coil, and the other terminal of the battery to the coil. Set the +engine going. If it refuses to run, make sure that B1 is pressing against D. +The speed of the engine may possibly be improved by careful adjustment of B2 +and an alteration in the setting of the crank, and will certainly be +accelerated by increasing the number of battery cells. +</p> + +<p> +The cost of the engine described was about 1s, 3d., exclusive of the battery. +</p> + +</div><!--end chapter--> + +<div class="chapter"> + +<h2><a name="chap12"></a>XII.<br /> +AN ELECTRIC ALARM CLOCK.</h2> + +<p> +Anybody who possesses an alarm clock with an external gong, an electric bell, +and a battery, may easily make them combine to get the drowsiest of mortals out +of bed on the chilliest of winter mornings. The arrangement has as its +secondary advantages and capabilities— +</p> + +<p> +(l) That the clock can be placed where its ticking will not disturb the person +whom it has to arouse in due course (some of the cheaper clocks are very +self-advertising); +</p> + +<p> +(2) That one clock can be made to operate any number of bells in different +parts of the house. +</p> + +<p> +The main problem to be solved is, how to make the alarm mechanism of the clock +complete an electric circuit when the alarm “goes off.” +</p> + +<p> +If you examine an alarm clock of the type described, you will find that the +gong hammer lies against the gong when at rest, and that its shaft when in +motion vibrates to and fro about a quarter of an inch. +</p> + +<p> +[Illustration: FIG. 89.—Plan of release gear of electric alarm, as +attached to clock.] +</p> + +<p> +Fig. 39 shows a. method of utilizing the movement of the hammer. A piece of +wood, 2 inches long, wide enough to fill the space between the rear edge of the +clock and the hammer slot, and 1/2 inch thick, has its under side hollowed out +to the curvature of the clock barrel. This block serves as a base for two +binding posts or terminals, T1 T2. A vertical slit is made in T1 and in this +is soldered [to] one end of a little piece of spring brass strip, 1 inch long +and 1/4 inch wide. To the back of the other end of the strip solder a piece of +1/20 inch wire, projecting l inch below the strip. The strip must be bent so +that it presses naturally against T2. A little trigger, B, which you can cut +out of sheet brass, is pivoted at a, where it must be raised off the base by a +small washer. It projects 1/4 inch beyond the base on the gong support side. A +square nick is cut in it at such a distance from a that, when the wire spike on +C is in the nick, the strip is held clear of T2. The other end of the trigger, +when the trigger is set, must be 1/8 inch from the shank of the alarm +hammer—at any rate not so far away that the hammer, when it vibrates, +cannot release C from the nick. +</p> + +<p> +To fix the base on to the top of the clock, the works must be removed (quite an +easy matter to accomplish) and holes bored for a couple of screws put through +from the inside. If the underside of the base is not quite correctly curved, +take care not to force in the screws far enough to distort the barrel. It is +advisable to do the fitting of the parts of the release after the base has been +fixed, and before the works are replaced. The position of the hammer shaft can +be gauged accurately enough from the slot in the case. +</p> + +<p> +The tails of the terminals T1 T2 must be truncated sufficiently not to +penetrate the base and make contact with the barrel, or a “short +circuit” will be evident as soon as the battery is connected up. +</p> + +<p> +[Illustration: Fig. 40.—Electric alarm releaser, as attached to separate +wooden clock casing.] +</p> + +<p> +If the bell, battery, and clock are in the same room, a single dry cell will +give sufficient current; but if the circuit is a long one, or several bells +have to be operated, two or more cells will be required. +</p> + +<p> +An Alternative Arrangement.—Should the reader prefer to have the clock +quite free from the release—and this is certainly convenient for winding +and setting the alarm—he should make a little wooden case for the clock +to stand in, just wide enough to take the clock, and the back just as high as +the top of the barrel. The release is then attached to a little platform +projecting from the back, care being taken that the lever is arranged in the +correct position relatively to the hammer when the clock is pushed back as far +as it will go (Fig. 40). +</p> + +<p> +If a self-contained outfit is desired, make the case two-storied: the upper +division for the clock, the lower for the cell or cells. The bell may be +attached to the front. A hinged fretwork front to the clock chamber, with an +opening the size of the face; a door at the back of the cell chamber; and a +general neat finish, staining and polishing, are refinements that some readers +may like to undertake. +</p> + +<p> +Setting the Alarm.—A good many alarm clocks are not to be relied upon to +act within a quarter of an hour or so of the time to which they are set. But +absolute accuracy of working may be obtained if the clock hands are first set +to the desired hour, and the alarm dial hand revolved slowly till the alarm is +released. The hands are then set at the correct time, and the alarm fully +wound. +</p> + +</div><!--end chapter--> + +<div class="chapter"> + +<h2><a name="chap13"></a>XIII.<br /> +A MODEL ELECTRIC RAILWAY.</h2> + +<p> +The rapid increase in the number of electrically worked railways, and the +substitution of the electric for the steam locomotive on many lines, give +legitimate cause for wondering whether, twenty or so years hence, the +descendants of the “Rocket” will not have disappeared from all the +railways of the world, excepting perhaps those of transcontinental character. +</p> + +<p> +[Illustration: Fig. 41.—Electric Locomotive.] +</p> + +<p> +The change is already spreading to model plant, and not without good reason, as +the miniature electric railway possesses decided advantages of its own. Instead +of having to chase the locomotive to stop or reverse it, one merely has to +press a button or move a switch. The fascinations of a model steam locomotive, +with its furnace, hissing of steam, business-like puffings, and a visible +working of piston and connecting rods, are not to be denied, any more than that +a full-sized steam locomotive is a more imposing object at rest or in motion +than its electric rival. On the other hand, the ease of control already +noticed, and the absence of burning fuel, water leakage, smoke and fumes, are +strong points in favour of the electric track, which does no more harm to a +carpet than to a front lawn, being essentially clean to handle. Under the head +of cost the electric locomotive comes out well, as motors can be purchased +cheaply; and connecting them up with driving wheels is a much less troublesome +business than the construction of an equally efficient steamer. One may add +that the electric motor is ready to start at a moment’s notice: there is +no delay corresponding to that caused by the raising of steam. +</p> + +<p> +The Track +</p> + +<p> +We will consider this first, as its design must govern, within certain limits, +the design of the locomotive. There are three systems of electrical +transmission available. +</p> + +<p> +1. The trolley system, with overhead cable attached to insulators on posts, to +carry the current one way, the rails being used as the “return.” +This system has the disadvantages associated with a wire over which the human +foot may easily trip with disastrous effect. +</p> + +<p> +2. That in which one of the wheel rails is used for taking the current to the +motor, and the other as the return. The objection to the system is that the +wheels must be insulated, to prevent short circuiting; and this, besides +causing trouble in construction, makes it impossible to use the ordinary model +rolling stock. To its credit one may place the fact that only two rails are +needed. +</p> + +<p> +3. The third and, we think, best system, which has an insulated third rail as +one half of the circuit, and both wheel rails as the return, the motor being +kept in connection with the third rail by means of a collector projecting from +the frame and pressing against the top of the third rail. The last, for reasons +of convenience, is placed between the wheel rails. We will assume that this +system is to be employed. +</p> + +<p> +[Illustration: FIG. 42.—Details of rails for electric track.] +</p> + +<p> +Gauge.—For indoor and short tracks generally it is advisable to keep the +gauge narrow, so that sharp curves may be employed without causing undue +friction between rails and wheels. In the present instance we specify a 2-inch +gauge, for which, as also for 1-1/2 and 1-1/4 inch, standard rolling stock is +supplied by the manufacturers. +</p> + +<p> +Track Construction.—It is essential that the centre rail and at least one +of the wheel rails shall have all joints bonded together to give a clear course +to the electric current, and the centre rail must be insulated to prevent +leakage and short-circuiting. Where a track is laid down more or less +permanently, the bonding is most positively effected by means of little +fish-plates, screwed into the sides of the abutting rails; but in the case of a +track which must be capable of quick coupling-up and uncoupling, some such +arrangement as that shown in Fig. 42 is to be recommended. +</p> + +<p> +Fig. 42 (a) is a cross vertical section of the track; Fig. 42 (c) a +longitudinal view; while Fig. 42 (b) shows in plan a point of junction of two +lengths of rail. +</p> + +<p> +The wheel rails are made of carefully straightened brass strip 3/8 inch wide +and 1/16 inch thick, sunk rather more than 1/8 inch into wooden sleepers (Fig. +42, a), 3-1/2 inches long and 3/4 inch wide (except at junctions). The sleepers +are prepared most quickly by cutting out a strip of wood 3-1/2 inches wide in +the direction of the grain, and long enough to make half a dozen sleepers. Two +saw cuts are sunk into the top, 2 inches apart, reckoning from the inside +edges, to the proper depth, and the wood is then subdivided along the grain. +The saw used should make a cut slightly narrower than the strip, to give the +wood a good hold. If the cut is unavoidably too large, packings of tin strip +must be forced in with the rail on the outside. To secure the rails further, +holes are bored in them on each side of the sleeper (see Fig. 42, c), and fine +iron or, brass wire is passed through these, round the bottom of the sleeper, +and made fast. +</p> + +<p> +[Illustration: FIG. 43.—Tin chair for centre rail of electric track.] +</p> + +<p> +The centre rail is soldered to small tin chairs, the feet of which are pinned +down to the sleepers. The top of the rails must project slightly above the +chairs, so that the current collector may not be fouled. +</p> + +<p> +Junctions.—At these points one 3/4-inch sleeper is reduced to 1/2-inch +width, and the other increased to 1 inch, this sleeper being overlapped 3/8 +inch by the rails of the other section. To the outsides of the wheel rails are +soldered the little angle plates, AA, BB, attached to the sleepers by brass +tacks, which project sufficiently to take the brass wire hooks. These hooks +must be of the right length to pull upon the tacks in AA and make a good +contact. The centre rails are bonded by two strips of springy brass, riveted to +one section, and forced apart at their free end by the interposed strip. Two +pins projecting from the narrower sleeper fit into holes in the wider to keep +the sections in line at a junction. +</p> + +<p> +General.—The sleepers of straight sections are screwed down to 3/4 by 1/4 +inch longitudinals, which help to keep the track straight and prevent the +sleepers slipping. Sections should be of the same length and be +interchangeable. Make straight sections of the greatest convenient length, to +reduce the number of junctions. Sleepers need not be less than 6 inches apart. +Fix the sleepers on the longitudinals before hammering the rails into the +slots. +</p> + +<p> +[Illustration: FIG. 44.—Laying out a curve for electric track.] +</p> + +<p> +Curves.—A simple method of laying out a semi-circular curve is shown in +Fig. 44. Sleepers and longitudinals are replaced by 1/2-inch boards, 8 inches +wide. Three pieces, about 32 inches long each, have their ends bevelled off at +an angle of 60 degrees, and are laid with their ends touching. Two semi-circles +of 24 and 22 inch radius are drawn on the boards to indicate the positions of +the rails, and short decapitated brass nails are driven in on each side of a +rail, about an inch apart, as it is laid along one of these lines. (See Fig. +44. A.) The inside nails must not project sufficiently to catch the wheel +flanges. The spring of the brass will prevent the rail falling out of place, +but to make sure, it should be tied in with wire at a few points. The centre +rail should on the curves also be 3/8 inch deep, and raised slightly above the +bed so as to project above the wheel rails. The method already described of +bonding at joints will serve equally well on curves. If the outer rail is +super-elevated slightly, there will be less tendency for the rolling stock to +jump the track when rounding the curve. +</p> + +<p> +When the rails are in place the boards may be cut with a pad-saw to curves +corresponding with the breadth of the track on the straight. If the boards +incline to warp, screw some pieces of 1/8-inch strip iron to the under side +across the grain, sinking the iron in flush with the wood. +</p> + +<p> +The brass strip for the rails costs about one penny per foot run. Iron strip is +much cheaper, but if it rusts, as it is very likely to do, the contact places +will need constant brightening. +</p> + +<p> +Points.—Fig. 45 shows the manner of laying out a set of points, and +connecting up the rails. The outside wheel rails, it will be seen, are +continuous, and switching is effected by altering the position of the moving +tongues, pivoted at PP, by means of the rod R, which passes through a hole in +the continuous rail to a lever or motor of the same reversible type as is used +for the locomotive. If a motor is employed, R should be joined to a crank pin +on the large driven cog—corresponding to that affixed to the driving +wheel (Fig. 47)—by a short rod. The pin is situated at such a distance +from the axle of the cog wheel that a quarter of a revolution suffices to move +the points over. The points motor must, of course, have its separate +connections with the “central station.” To show how the points lie, +the rod R also operates a semaphore with a double arm (Fig. 46), one end of +which is depressed—indicating that the track on that side is +open—when the other is horizontal, indicating “blocked.” The +arms point across the track. +</p> + +<p> +[Illustration: FIG. 45.—Points for electric railway.] +</p> + +<p> +Details.—The tongues must be bevelled off to a point on the sides +respectively nearest to the continuous rails. The parts AA are bent out at the +ends to make guides, which, in combination with the safety rails, will prevent +the wheels jumping the track. Care should be taken to insulate centre rail +connecting wires where they pass through or under the wheel rails. +</p> + +<p> +It is advisable to lay out a set of points, together with motor and signals, on +a separate board. +</p> + +<p> +[Illustration: Fig. 46.—Double-armed signal, operated by points.] +</p> + +<p> +Preservation of Track.—All the wooden parts of an outdoor track should be +well creosoted before use. +</p> + +<p> +The Electric Locomotive. +</p> + +<p> +An elevation and a plan of this are given in Fig. 47. The two pairs of wheels +are set close together, so that they may pass easily round curves. +</p> + +<p> +[Illustration: Fig. 47.—Plan and elevation of electric locomotive.] +</p> + +<p> +The Motor.—A motor of ordinary type, with electro field magnets, is +unsuitable for traction, as it cannot be reversed by changing the direction of +the current, unless a special and rather expensive type of automatic switch be +used. While a motor of this kind is, in conjunction with such a switch, the +most efficient, the motor with permanent field magnets is preferable as regards +cost and ease of fixing. It can be reversed through the rails. The armature or +revolving part must be tripolar to be self-starting in all positions. +</p> + +<p> +A motor of sufficient power can be bought for half a crown or less—in any +case more cheaply than it can be made by the average amateur. +</p> + +<p> +The motor used for the locomotive illustrated was taken to pieces, and the +magnet M screwed to a strip of wood 1-5/8 inches wide; and for the original +armature bearings were substituted a couple of pieces of brass strip, HH, +screwed to two wooden supports, SS, on the base, E (Fig. 47, a). It was found +necessary to push the armature along the spindle close to the commutator piece, +C, and to shorten the spindle at the armature end and turn it down to the size +of the original bearing, in order to bring the motor within the space between +the wheels. +</p> + +<p> +The place of the small pulley was taken by an 8-toothed pinion wheel, engaging +with a pinion soldered to the near driving wheel, the diameter of which it +exceeded by about 3/16 inch. The pair, originally parts of an old clock +purchased for a few pence, gave a gearing-down of about 9 times. +</p> + +<p> +The position of the driven wheels relatively to the armature must be found +experimentally. There is plenty of scope for adjustment, as the wheels can be +shifted in either direction longitudinally, while the distance between wheel +and armature centres may be further modified in the length of the bearings, BE. +These last are pieces of brass strip turned up at the ends, and bored for +axles, and screwed to the under side of the base. To prevent the axles sliding +sideways and the wheels rubbing the frame, solder small collars to them in +contact with the inner side of the bearings. +</p> + +<p> +The Frame.—Having got the motor wheels adjusted, shorten E so that it +projects 2 inches beyond the centres of the axles at each end. Two cross bars, +GG, 3-1/2 inches long, are then glued to the under side of E, projecting 1/8 +inch. To these are glued two 3/8-inch strips, FF, of the same length as E. A +buffer beam, K, is screwed to G. A removable cover, abedfg, is made out of +cigar-box wood or tin. The ends rest on GG; the sides on FF. Doors and windows +are cut out, and handrails, etc., added to make the locomotive suggest the real +thing—except for the proportionate size and arrangement of the wheels. +</p> + +<p> +Electrical Connections.—The current collector, CR, should be well turned +up at the end, so as not to catch on the centre rail joints, and not press hard +enough on the rail to cause noticeable resistance. The fixed end of CR is +connected through T2 with one brush, B, and both wheel bearings with T1. +</p> + +<p> +[Illustration: FIG. 48.—Reversing switch.] +</p> + +<p> +Electrical Fittings.—The best source of power to use is dry cells giving +1-1/2 to 2 volts each. These can be bought at 1s. apiece in fairly large sizes. +Four or five connected in series will work quite a long line if the contacts +are in good condition. +</p> + +<p> +A reversing switch is needed to alter the direction of the current flow. The +construction of one is an exceedingly simple matter. Fig. 48 gives a plan of +switch and connection, from which the principle of the apparatus will be +gathered. The two links, LL, are thin springy brass strips slightly curved, and +at the rear end pivoted on the binding posts T1 T2. Underneath the other ends +solder the heads of a couple of brass nails. The links are held parallel to one +another by a wooden yoke, from the centre of which projects a handle. The three +contacts C1 C2 C3 must be the same distance apart as the centres of the link +heads, and so situated as to lie on the arcs of circles described by the links. +The binding post T3 is connected with the two outside contacts—which may +be flat-headed brass nails driven in almost flush with the top of the wooden +base—by wires lying in grooves under the base, and T4 with the central +contact. As shown, the switch is in the neutral position and the circuit +broken. +</p> + +<p> +[Illustration: Fig. 49.—Multiple battery switch.] +</p> + +<p> +Multiple Battery Switch.—To control the speed of the train and economize +current a multiple battery switch is useful. Fig. 49 explains how to make and +connect up such a switch. The contacts, C1 to C5, lie in the path of the switch +lever, and are connected through binding posts T1 to T6 with one terminal of +their respective cells. The cells are coupled up in series to one another, and +one terminal of the series with binding posts T0 and T6. By moving the lever, +any number of the cells can be put in circuit with T7. The button under the +head of the lever should not be wide enough to bridge the space between any two +contacts. Change the order of the cells occasionally to equalize the +exhaustion. +</p> + +<p> +[Illustration: FIG. 50.—Adjustable resistance for controlling current.] +</p> + +<p> +Resistance.—With accumulators, a “resistance” should be +included in the circuit to regulate the flow of current. The resistance shown +in Fig. 50 consists of a spiral of fine German silver wire lying in the grooved +circumference of a wood disc. One of the binding posts is in connection with +the regulating lever pivot, the other with one end of the coil. By moving the +lever along the coil the amount of German silver wire, which offers resistance +to the current, is altered. When starting the motor use as little current as +possible, and open the resistance as it gets up speed, choking down again when +the necessary speed is attained. +</p> + +<p> +General.—All the three fittings described should for convenience be +mounted on the same board, which itself may form the cover of the box holding +the dry cells or accumulators. +</p> + +<h4>SOME SUGGESTIONS.</h4> + +<p> +Instead of dry cells or accumulators a small foot or hand operated dynamo +generating direct, not alternating current, might be used. Its life is +indefinitely long, whereas dry cells become exhausted with use, and +accumulators need recharging from time to time. On occasion such a dynamo might +prove very convenient. +</p> + +<p> +Anyone who possesses a fair-sized stationary engine and boiler might increase +the realism of the outdoor track by setting up a generating station, which will +give a good deal of extra fun. +</p> + +</div><!--end chapter--> + +<div class="chapter"> + +<h2><a name="chap14"></a>XIV.<br /> +A SIMPLE RECIPROCATING ENGINE.</h2> + +<p> +Figs. 51 and 52 illustrate a very simple form of fixed-cylinder engine +controlled by a slide valve. +</p> + +<p> +An open-ended “trunk” piston, similar in principle to that used in +gas engines, is employed; and the valve is of the piston type, which is less +complicated than the box form of valve, though less easily made steam-tight in +small sizes. The engine is single-acting, making only one power stroke per +revolution. +</p> + +<p> +The cylinder is a piece of brass tubing; the piston another piece of tubing, +fitting the first telescopically. Provided that the fit is true enough to +prevent the escape of steam, while not so close as to set up excessive +friction, a packing behind the piston is not needed; but should serious leakage +be anticipated, a packing of thick felt or cloth, held up by a washer and nuts +on the gudgeon G, will make things secure. Similarly for the built-up piston +valve P may be substituted a piece of close-fitting brass rod with diameter +reduced, except at the ends, by filing or turning, to allow the passage of +steam. +</p> + +<h4>CONSTRUCTION.</h4> + +<p> +[Illustration: FIG. 51.—Elevation of simple reciprocating steam engine.] +</p> + +<p> +The bed is made of wood, preferably oak, into the parts of which linseed oil is +well rubbed before they are screwed together, to prevent the entry of water. A +longitudinal groove is sawn in the top of the bed, as indicated by the dotted +line in Fig. 51, to give room for the connecting rod in its lowest position, +and a cross groove is scooped in line with the crank shaft to accommodate the +lower part of the crank disc and the big end of the rod. (If the wing W under +the cylinder is screwed to the side of the bed, instead of passing through it, +as shown, a slight cutting away of the edge will give the necessary clearance +in both cases. ) +</p> + +<p> +[Illustration: FIG. 52.—Plan of simple reciprocating steam engine.] +</p> + +<p> +The cylinder and valve tube A should be flattened by filing and rubbing on +emery cloth, so that they may bed snugly against one another and give a good +holding surface for the solder. A steam port, S P, should next be bored in +each, and the “burr” of the edges cleaned off carefully so as not +to obstruct valve or piston in the slightest degree. “Tin” the +contact surfaces thinly, and after laying valve tube and cylinder in line, with +the portholes corresponding exactly, bind them tightly together with a turn or +two of wire, or hold them lightly in a vice, while the solder is made to run +again with the aid of a spirit lamp. If it seems necessary, run a little extra +solder along the joint, both sides, and at the ends. +</p> + +<p> +The valve, if built up, consists of a central rod, threaded at the rear end, +four washers which fit the tube, and a central spacing-piece. The forward +washer is soldered to the rod. Behind this is placed a felt packing. Then come +in order the central spacing-piece, with a washer soldered to each end, a +second packing, and a fourth washer. The series is completed by an adjusting +nut to squeeze the packings, and a lock nut to prevent slipping. The back end +of the valve must be wide enough to just more than cover the steam port. If the +felt proves difficult to procure or fit, one may use a ring or two of brass +tubing, with an external packing of asbestos cord. +</p> + +<p> +The cylinder wing W should have the top edge turned over for an eighth of an +inch or so to give a good bearing against the cylinder, and be held in position +by a wire while the soldering is done. It is important that the line of the +wing should be at right angles to a line passing through the centres of the +valve tube and cylinder. +</p> + +<p> +Shaft Bearings.—Take a piece of strip brass half an inch or so wide and +3-1/2 inches long. Bore four holes for screws, and scratch cross lines an inch +from each extremity. Turn up the ends at these lines at right angles to the +central part, stand the piece on some flat surface, and on the outer faces of +the uprights scratch two cross lines at the height of the centre of the +cylinder above the bed. Mark the central points of these lines. +</p> + +<p> +Next select a piece of brass tubing which fits the rod chosen for the crank +shaft, and bore in the bearing standards two holes to fit this tubing. Slip the +tubing through the standards and solder it to them. The ends and central parts +of the tubing must now be so cut away as to leave two bearings, BB—that +at the fly-wheel end projecting far enough to allow the fly wheel, when brought +up against it, to just clear the bed; that at the crank end being of the proper +length to allow the eccentric to be in line with the valve rod, and the crank +disc to occupy its proper position relatively to the central line of the +cylinder. Finish off the standards by filing the tops concentrically with the +bearings. +</p> + +<p> +The eccentric may be built up from a metal disc about 3/4 inch diameter and two +slightly larger discs soldered concentrically to the sides. The width of the +middle disc should be the same as that of the eccentric rod. A careful filer +could make a passable eccentric by sinking a square or semicircular groove in +the edge of a wide disc. The centre of the eccentric must be found carefully, +and a point marked at a distance from it equal to half the travel of the valve. +To ascertain this, pull the valve forward until the steam port is fully +exposed, insert a bar at the rear end of the valve tube, and mark it. Then push +the valve back until a wire pushed through the port from the cylinder side +shows that the port is again fully exposed. Insert and mark the bar again. The +distance between the marks gives you the “travel” required. +</p> + +<p> +Order of Assembly.—The following list of operations in their order may +assist the beginner: +</p> + +<p> +Make the bed. +</p> + +<p> +Cut out cylinder barrel, piston, and valve tube. +</p> + +<p> +Bevel off the ends of the last inside to allow the valve to enter easily. +</p> + +<p> +Make the valve. +</p> + +<p> +Bore the steam ports, and solder valve tube and cylinder together. +</p> + +<p> +Solder holding-down wing, W, to cylinder. +</p> + +<p> +Finish off the piston. +</p> + +<p> +Solder the bearings in their standards. +</p> + +<p> +Prepare shaft, crank disc, crank pin, and piston rod. +</p> + +<p> +Fix the cylinder to the bed, in which a slot must be cut for the wing and +holding-down bolt. +</p> + +<p> +Attach the piston rod to the piston, and insert piston in cylinder. +</p> + +<p> +Bore hole for shaft in centre of crank disc, and another, 9/16 inch away +(centre to centre), for crank pin. +</p> + +<p> +Solder in crank pin squarely to disc. +</p> + +<p> +Pass shaft through bearings and slip on the crank disc. +</p> + +<p> +Pass front end of piston rod over the crank pin. +</p> + +<p> +Lay bearing standard on bed squarely to the centre line of the cylinder, turn +crank fully back, and move the standard about till the back end of the piston +clears the back end of the cylinder by about 1/32 inch. +</p> + +<p> +Get standard quite square, and adjust sideways till connecting rod is in line +with axis of cylinder. +</p> + +<p> +Mark off and screw down the standard. +</p> + +<p> +Make the eccentric, eccentric rod, and strap. Slip eccentric on shaft. +</p> + +<p> +Put valve in position and draw it forward till the port is exposed. +</p> + +<p> +Turn the eccentric forward, and mark the rod opposite centre of valve pin. +</p> + +<p> +Bore hole for pin, and insert pin. +</p> + +<p> +Hold the crank shaft firmly, and revolve eccentric till the port just begins to +open on its forward stroke. Rotate crank disc on shaft till the crank pin is +full forward. +</p> + +<p> +Solder eccentric and disc to shaft. +</p> + +<p> +Solder steam pipe to cylinder, and a brass disc to the rear end of the +cylinder. +</p> + +<p> +Fit a fly wheel of metal or wood. This must be fairly heavy, as it has to +overcome all friction during the return or exhaust stroke. +</p> + +<p> +Action of Engine.—During the forward motion of the piston the valve is +pushed back by the eccentric until the steam port is fully opened, and is then +drawn forward, covering the port. At the end of the power stroke the port has +begun to open to the air, to allow the steam to escape throughout the exhaust +stroke, in the course of which the valve is pushed back until, just at the end +of the stroke, the steam port begins to open again. +</p> + +<p> +Notes.— (l.) The connecting rod may be made shorter than shown in Figs. +51 and 52; but in that case the piston also must be shortened to allow for the +greater obliquity of the rod at half-stroke. +</p> + +<p> +(2.) If two opposed cylinders are made to operate the one crank, a +double-acting engine is obtained. Both valves may be operated by a single +eccentric, the connecting rod of one being pivoted to a small lug projecting +from the eccentric strap. If three cylinders are set 120 degrees apart round +the crank shaft, a continuous turning effect is given. This type will be found +useful for running small dynamos. +</p> + +<p> +(3.) If it is desired to use the exhaust steam to promote a draught in the +boiler furnace, it should be led away by a small pipe from the rear end of the +valve tube. +</p> + +</div><!--end chapter--> + +<div class="chapter"> + +<h2><a name="chap15"></a>XV.<br /> +A HORIZONTAL SLIDE-VALVE ENGINE.</h2> + +<p> +The reader who has succeeded in putting together the simple engine described in +the preceding chapter may wish to try his hand on something more ambitious in +the same line. The engine illustrated in Figs. 53 to 66 will give sufficient +scope for energy and handiness with drill and soldering iron. The writer made +an engine of the same kind, differing only from that shown in the design of the +crosshead guides, without the assistance of a lathe, except for turning the +piston and fly wheel—the last bought in the rough. Files, drills, taps, a +hack saw, and a soldering iron did all the rest of the work. +</p> + +<p> +Solder plays so important a part in the assembling of the many pieces of the +engine that, if the machine fell into the fire, a rapid disintegration would +follow. But in actual use the engine has proved very satisfactory; and if not +such as the highly-skilled model-maker with a well-equipped workshop at his +command would prefer to expend his time on, it will afford a useful lesson in +the use of the simpler tools. Under 50 lbs. of steam it develops sufficient +power to run a small electric-lighting installation, or to do other useful work +on a moderate scale. +</p> + +<p> +[Illustration: Fig. 53.—Elevation of a large horizontal engine.] +</p> + +<p> +The principal dimensions of the engine are as follows: +</p> + +<p> +Bedplate (sheet zinc), 13-1/2 inches long; 4-1/2 inches wide; 1/8 inch thick. +</p> + +<p> +Support of bedplate (1/20 inch zinc), 3 inches high from wooden base to +underside of bedplate. +</p> + +<p> +Cylinder (mandrel-drawn brass tubing), 1-1/2 inches internal diameter; 2-13/16 +inches long over all. +</p> + +<p> +Piston, 1-1/2 inches diameter; 1/2 inch long. +</p> + +<p> +Stroke of piston, 2-1/4 inches. +</p> + +<p> +Connecting rod, 5 inches long between centres; 5/16 inch diameter. +</p> + +<p> +Piston rod, 5-1/8 inches long; 1/4 inch diameter. +</p> + +<p> +Valve rod, 4-1/8 inches long; 3/16 inch diameter. +</p> + +<p> +Crank shaft, 5 inches long; 1/2 inch diameter. +</p> + +<p> +Centre line of piston rod, 1-1/4 inches laterally from near edge of bed; 1-5/8 +inches from valve-rod centre line; 1-5/8 inches vertically above bed. +</p> + +<p> +Centre line of crank shaft, 10-3/8 inches from cross centre line of cylinder. +</p> + +<p> +Bearings, 1 inch long. +</p> + +<p> +Eccentric, 9/32-inch throw. +</p> + +<p> +Fly wheel, diameter, 7-1/2 inches; width, 1 inch; weight, 6 lbs. +</p> + +<p> +Pump, 3/8-inch bore; 3/8-inch stroke; plunger, 2 inches long. +</p> + +<p> +[Illustration: Fig. 54.—Plan of a large horizontal engine.] +</p> + +<p> +Other dimensions will be gathered from the various diagrams of details. +</p> + +<p> +The reader will, of course, suit his own fancy in following these dimensions, +or in working to them on a reduced scale, or in modifying details where he +considers he can effect his object in a simpler manner. +</p> + +<p> +The diagrams are sufficiently explicit to render it unnecessary to describe the +making of the engine from start to finish, so remarks will be limited to those +points which require most careful construction and adjustment. +</p> + +<p> +[Illustration: Fig. 55.—Standards of Bedplate.] +</p> + +<p> +The Bedplate.—This should be accurately squared and mounted on its four +arch-like supports. (For dimensions, consult Fig. 55.) Half an inch is allowed +top and bottom for the turnovers by which the supports are screwed to the +bedplate and base. The ends of the longer supports are turned back so as to lie +in front of the end supports, to which they may be attached by screws or +solder, after all four parts have been screwed to the bed. Care must be taken +that the parts all have the same height. Drill all holes in the turnovers +before bending. Use 1/8-inch screws. Turn the bed bottom upwards, and stand the +four supports, temporarily assembled, on it upside down and in their correct +positions, and mark off for the 3/32-inch holes to be drilled in the bed. A +hole 3/4 inch in diameter should be cut in the bedplate for the exhaust pipe, +round a centre 2 inches from the end and 1-5/8 inches from the edge on the +fly-wheel side, and two more holes for the pump. +</p> + +<p> +Making the Cylinder Slide and Valve.—The cylinder barrel must be +perfectly cylindrical and free from any dents. Mandrel-drawn brass tubing, +1/16-inch thick, may be selected. If you cannot get this turned off at the ends +in a lathe, mark the lines round it for working to with the aid of a perfectly +straight edged strip of paper, 2-13/16 inches wide, rolled twice round the +tube. The coils must lie exactly under one another. Make plain scratches at +each end of the paper with a sharp steel point. Cut off at a distance of +1/16-inch from the lines, and work up to the lines with a file, finishing by +rubbing the ends on a piece of emery cloth resting on a hard, true surface. +</p> + +<p> +[Illustration: FIG. 56.-Cylinder standard before being bent.] +</p> + +<p> +A square-cornered notch 1/8 inch deep and 7/8 inch wide must now be cut in each +end of the barrel, the two notches being exactly in line with one another. +These are to admit steam from the steam ways into the cylinder. +</p> + +<p> +Cylinder Standards.-Use 5/64 or 3/32 inch brass plate for these. Two pieces of +the dimensions shown in Fig. 56 are needed. Scratch a line exactly down the +middle of each, and a cross line 1/2 inch from one end. The other end should be +marked, cut, and filed to a semicircle. Drill three 3/16-inch holes in the +turnover for the holding-down screws. The two standards should now be soldered +temporarily together at the round ends and trued up to match each other +exactly. Place them in the vice with the bending lines exactly level with the +jaws, split the turnovers apart, and hammer them over at right angles to the +main parts. Whether this has been done correctly may be tested by placing the +standards on a flat surface. Take the standards apart, and scratch a cross line +on each 1-5/8 inch from the lower surface of the foot on the side away from the +foot. Make a punch mark where the line crosses the vertical line previously +drawn, and with this as centre describe a circle of the diameter of the outside +of the barrel. Cut out the inside and file carefully up to the circle, stopping +when the barrel makes a tight fit. On the inside of the hole file a nick 1/8 +inch deep, as shown in Fig. 56. Remember that this nick must be on the left of +one standard and on the right of the other, so that they shall pair off +properly. +</p> + +<p> +Standards and barrel must now be cleaned for soldering. Screw one standard down +to a wood base; slip one end of the barrel into it; pass the other standard +over the other end of the barrel, and adjust everything so that the barrel ends +are flush with the, outer surfaces of the standard, and the nicks of the barrel +in line with the standard nicks. Then screw the other standard to the base. +Solder must be run well into the joints, as these will have to stand all the +longitudinal working strain. +</p> + +<p> +The next step is the fitting of the cylinder covers. If you can obtain two +stout brass discs 2-1/8 inches in diameter, some trouble will be saved; +otherwise you must cut them out of 3/32-inch plate. The centre of each should +be marked, and four lines 45 degrees apart be scratched through it from side to +side. A circle of 15/16-inch radius is now drawn to cut the lines, and punch +marks are made at the eight points of intersection. Solder the covers lightly +to the foot side of their standards, marked sides outwards, and drill 1/8-inch +holes through cover and standard at the punch marks. Make matching marks on the +edges. Unsolder the covers, enlarge the holes in them to take 5/32-inch screws; +and tap the holes in the standards. This method will ensure the holes being in +line, besides avoiding the trouble of marking off the standards separately. +</p> + +<p> +Bore a 1/4-inch hole in the centre of one cover—be sure that it is the +right one—for the piston rod. +</p> + +<p> +You can now proceed to the making of the piston-rod gland (Fig. 54, G1). Fig. +57 shows how this is built up of pieces of tubing and brass lugs for the +screws. If possible, get the tubular parts trued in a lathe. +</p> + +<p> +[Illustration: FIG. 57.—Vertical section of cylinder.] +</p> + +<p> +Before the gland is soldered to the cover, the cover should be put in place, +the piston rod attached to the piston, and the parts of the gland assembled. +Push the piston rod through the cover until the piston is hard up against the +back of the cover. Slip the gland over the rod, turn it so that the screws are +parallel to the foot of the standard, and make the solder joint. This is the +best way of getting the gland exactly concentric with the cylinder so that the +piston rod shall move without undue friction. But you must be careful not to +unsolder the cylinder from its standard or the parts of the gland. Blacken the +piston rod in a candle flame to prevent solder adhering. +</p> + +<p> +Steam Chest.—The walls of the steam chest are best made in one piece out +of 1/2-inch brass by cutting out to the dimension given in Fig. 58. A sharp +fret saw will remove the inside rectangle. Get both inside and outside surfaces +as square as possible in all directions, and rub down the two contact faces on +emery cloth supported by an old looking-glass. +</p> + +<p> +[Illustration: FIG. 68.-Wall-piece for steam chest, with gland and valve rod in +position.] +</p> + +<p> +Two perfectly flat plates of 1/8-inch brass are cut to the size given in Fig. +59, or a little longer both ways, to allow for working down to the same area as +the wall-piece. This operation should be carried out after soldering the three +pieces together. File and rub the sides until no projections are visible. Then +drill twelve 3/32-inch holes right through the three parts. After separating +them, the holes in the walls and what will be the cover must be enlarged to an +easy fit for 1/8-inch bolts, and the valve plate tapped. +</p> + +<p> +Now drill 3/16-inch holes centrally through the ends of the walls for the valve +rod. If the first hole is drilled accurately, the second hole should be made +without removing the drill, as this will ensure the two holes being in line. +If, however, luck is against you, enlarge the holes and get the rod into its +correct position by screwing and soldering small drilled plates to the outside +of the chest. Also drill and tap a hole for the lubricator. The attachment of +the gland (Fig. 54, G2) is similar to that of the cylinder gland, and therefore +need not be detailed. +</p> + +<p> +The Valve Plate (Fig. 59).—Three ports must be cut in this—a +central one, 7/8 by 3/32 inch, for the exhaust; and two inlets, 7/8 by 3/32 +inch, 1/8 inch away from the exhaust. These are easily opened out if a series +of holes be drilled along their axes. +</p> + +<p> +[Illustration: FIG. 69.—Valve plate.] +</p> + +<p> +The Steam Ways.—The formation of the steam ways between valve plate and +cylinder is the most ticklish bit of work to be done on the engine as it +entails the making of a number of solder joints close together. +</p> + +<p> +[Illustration: FIG. 60.—Piece for steam ways.] +</p> + +<p> +We begin by cutting out of 1/20-inch sheet brass a piece shaped as in Fig. 60. +Parallel to the long edges, and 3/8 inch away, scribe bending lines. Join these +by lines 5/8 inch from the short edges, and join these again by lines 1/4 inch +from the bending lines. Cuts must now be made along the lines shown double in +Fig. 60. Bend parts CC down and parts BB upwards, so that they are at right +angles to parts AA. The positions of these parts, when the piece is applied to +the cylinder, are shown in Fig. 62. +</p> + +<p> +[Illustration: FIG. 61.—Valve plate and steam ways in section.] +</p> + +<p> +One must now make the bridge pieces (Fig. 61, a, a) to separate the inlet +passages from the exhaust. Their width is the distance between the bent-down +pieces CC of Fig. 60, and their bottom edges are shaped to the curvature of the +cylinder barrel. Finally, make the pieces bb (Fig. 61), which form part of the +top of the steam ways. +</p> + +<p> +In the assembling of these parts a blowpipe spirit lamp or a little +“Tinol” soldering lamp will prove very helpful. +</p> + +<p> +The following order should be observed: +</p> + +<p> +(1.) Solder the piece shown in Fig. 60 to the cylinder barrel by the long +edges, and to the cylinder supports at the ends. This piece must, of course, +cover the steam ports in the cylinder. +</p> + +<p> +(2.) Put pieces aa (Fig. 61) in position, with their tops quite flush with the +tops of BB (Fig. 62), and solder them to the cylinder barrel and sides of the +steam-way piece. +</p> + +<p> +(3.) Solder the valve plate centrally to BB, and to the tops of aa, which must +lie between the central and outside ports. Take great care to make steam-tight +joints here, and to have the plate parallel to the standards in one direction +and to the cylinder in the other. +</p> + +<p> +(4.) Solder in pieces bb. These should be a tight fit, as it is difficult to +hold them in place while soldering is done. +</p> + +<p> +(5.) Bore a 5/16-inch hole in the lower side of the central division and solder +on the exhaust pipe. +</p> + +<p> +Slide Valve.—The contact part of this is cut out of flat sheet brass +(Fig. 63), and to one side is soldered a cap made by turning down the edges of +a cross with very short arms. The little lugs aa are soldered to this, and +slotted with a jeweller’s file to engage with notches cut in the valve +rod (see Figs. 58 and 62). +</p> + +<p> +[Illustration: FIG. 63.-Parts of slide valve.] +</p> + +<p> +The Crank and Crank Shaft.—The next thing to take in hand is the fixing +of the crank shaft. This is a piece of 3/8 or 1/2 inch steel rod 5 inches long. +</p> + +<p> +The bearings for this may be pieces of brass tubing, fitting the rod fairly +tight. By making them of good length—1 inch—the wear is reduced to +almost nothing if the lubricating can is used as often as it should be. +</p> + +<p> +Each bearing is shown with two standards. The doubling increases rigidity, and +enables an oil cup to be fixed centrally. +</p> + +<p> +The shape of the standards will be gathered from Fig. 53, their outline being +dotted in behind the crank. +</p> + +<p> +Cut out and bend the standards—after drilling the holes for the foot +screws—before measuring off for the centres of the holes; in fact, follow +the course laid down with regard to the cylinder standards. +</p> + +<p> +Make a bold scratch across the bedplate to show where the centre line of the +shaft should be, and another along the bed for the piston-rod centre line. +(Position given on p. 138.) +</p> + +<p> +Bore holes in the bearings for the oil cups, which may be merely forced in +after the engine is complete. +</p> + +<p> +The crank boss may be made out of a brass disc 2-3/4 inches diameter and 3/16 +inch thick, from which two curved pieces are cut to reduce the crank to the +shape shown in Fig. 53. The heavier portion, on the side of the shaft away from +the crank pin, helps to counterbalance the weight of the connecting and piston +rods. In Fig. 54 (plan of engine) you will see that extra weight in this part +has been obtained by fixing a piece of suitably curved metal to the back of the +boss. +</p> + +<p> +The mounting of the crank boss on the shaft and the insertion of the crank pin +into the boss might well be entrusted to an expert mechanic, as absolute +“squareness” is essential for satisfactory working. Screw-thread +attachments should be used, and the crankshaft should project sufficiently to +allow room for a flat lock nut. The crank pin will be rendered immovable by a +small lock screw penetrating the boss edgeways and engaging with a nick in the +pin. +</p> + +<p> +Fixing the Standards and Bearings.—Place the two bearings in their +standards and slip the crank shaft through them. Place standards on the bed, +with their centre lines on the crank-shaft centre line. The face of the crank +should be about 3/8 inch away from the piston rod centre line. Bring the nearer +bearing up against the back of the disc, and arrange the standards +equidistantly from the ends of the bearing. The other bearing should overlap +the edge of the bed by about 1/8 inch. Get all standards square to the edge of +the bed, and mark off the positions of screw holes in bed. Remove the +standards, drill and tap the bed-plate holes, and replace parts as before, +taking care that the lubricating holes in the bearings point vertically +upwards. Then solder bearings to standards. +</p> + +<p> +If any difficulty is experienced in getting all four standards to bed properly, +make the bearing holes in the two inner ones a rather easy fit. The presence of +the crank-shaft will assure the bearings being in line when the soldering is +completed. +</p> + +<p> +The standards and bed should have matching marks made on them. +</p> + +<p> +The Eccentric.—This can be formed by soldering two thin brass discs +1-15/16-inch diameter concentrically to the sides of a disc of 1-15/16-inch +diameter and 5/16 inch thick. The centre of the shaft hole must be exactly 9/32 +inch from the centre of the eccentric to give the proper valve-travel. Drill +and tap the eccentric edgeways for a lock screw. +</p> + +<p> +A piece to which the eccentric strap, eccentric rod, and pump rod are attached +is cut out of 5/16-inch brass. Its shape is indicated in Fig. 53. The side next +the eccentric must be shaped as accurately as possible to the radius of the +eccentric. The strap, of strip brass, is fastened to the piece by four screws, +the eccentric rod by two screws. +</p> + +<p> +Crosshead and Guides.—The crosshead (Figs. 53 and 54) is built up by +soldering together a flat foot of steel, a brass upright, and a tubular top +fitting the piston rod. The guides, which consist of a bed, covers, and +distance-pieces united by screws (Fig. 64), have to withstand a lot of wear, +and should preferably be of steel. The importance of having them quite flat and +straight is, of course, obvious. +</p> + +<p> +[Illustration: FIG. 64.—Cross section of crosshead and guide.] +</p> + +<p> +The last 1-3/8 inches of the piston rod has a screw thread cut on it to engage +with a threaded hole in the fork (cut out of thick brass plate), to which the +rear end of the connecting rod is pinned, and to take the lock nut which +presses the crosshead against this fork. +</p> + +<p> +Assuming that all the parts mentioned have been prepared, the cylinder should +be arranged in its proper place on the bed, the piston rod centrally over its +centre line. Mark and drill the screw holes in the bed. +</p> + +<p> +The Valve Gear.—We may now attend to the valve gear. A fork must be made +for the end of the valve rod, and soldered to it with its slot at right angles +to the slots which engage with the valve lugs. Slip the rod into the steam +chest, put the valve on the rod, and attach the chest (without the cover) to +the valve plate by a bolt at each corner. Pull the valve forward till the rear +port is just uncovered, and turn the eccentric full forward. You will now be +able to measure off exactly the distance between the centres of the valve-rod +fork pin and the rear screw of the eccentric. The valve connecting rod (Fig. +53, VCR) should now be made and placed in position. If the two forward holes +are filed somewhat slot-shaped, any necessary adjustment of the valve is made +easier. If the adjustment of VCR and the throw of the eccentric are correct, +the valve will just expose both end ports alternately when the crank is +revolved. If one port is more exposed than the other, adjust by means of the +eccentric screws till a balance is obtained. Should the ports still not be +fully uncovered, the throw of the eccentric is too small, and you must either +make a new eccentric or reduce the width of the valve. (The second course has +the disadvantage of reducing the expansive working of the steam.) Excess +movement, on the other hand, implies too great an eccentric throw. +</p> + +<p> +Setting the Eccentric.—Turn the crank full forward, so that a line +through the crank pin and shaft centres is parallel to the bed. Holding it in +this position, revolve the eccentric (the screw of which should be slackened +off sufficiently to allow the eccentric to move stiffly) round the shaft in a +clockwise direction, until it is in that position below the shaft at which the +front steam port just begins to show. Then tighten up the eccentric lock +screw.[1] +</p> + +<p> +[Footnote 1: The reader is referred to an excellent little treatise, entitled +“The Slide Valve” (Messrs. Percival Marshall and Co., 26 +Poppin’s Court, Fleet Street, E.C. Price 6d.), for a full explanation of +the scientific principles of the slide valve.] +</p> + +<p> +The Connecting Rod.—The length of this from centre to centre of the pins +on which it works should be established as follows:—Slip over the piston +rod a disc of card 1/32 inch thick. Then pass the rod through the gland and +assemble the crosshead and fork on its end, and assemble the guides round the +crosshead foot. Turn the crank pin full forward, pull the piston rod out as far +as it will come, measure the distance between pin centres very carefully, and +transfer it to a piece of paper. +</p> + +<p> +The rod consists of a straight central bar and two rectangular halved ends. The +ends should be cut out of brass and carefully squared. Through their exact +centres drill 1/8-inch holes, and cut the pieces squarely in two across these +holes. The sawed faces should be filed down to a good fit and soldered +together. Now drill holes of the size of the pins, using what remains of the +holes first made to guide the drill. The bolt holes are drilled next, and +finally the holes for lubrication and those to take the rods. Then lay the two +ends down on the piece of paper, so that their pinholes are centred on the +centre marks, and the holes for the rod are turned towards one another. Cut off +a piece of steel rod of the proper length and unsolder the ends. The rod pieces +must then be assembled on the rod, and with it be centred on the paper and held +in position while the parts are soldered together. +</p> + +<h4>OTHER DETAILS.</h4> + +<p> +Adjusting the Guides.—Put the connecting rod in place on its pins, and +revolve the crank until the guides have taken up that position which allows the +crosshead to move freely. Then mark off the holes for the guide holding-down +screws, and drill and tap them. +</p> + +<p> +Packings.—The glands and piston should be packed with asbestos string. +Don’t be afraid of packing too tightly, as the tendency is for packing to +get slacker in use. The rear end of the cylinder should be bevelled off +slightly inside, to allow the packed piston to enter easily. +</p> + +<p> +Joints.—The cylinder head and valve chest joints should be made with +stout brown paper soaked in oil or smeared with red lead. All screw holes +should be cut cleanly through the paper, and give plenty of room for the +screws. +</p> + +<p> +[Illustration: FIG. 66.-Vertical section of force pump driven by engine.] +</p> + +<p> +When making a joint, tighten up the screws in rotation, a little at a time so +as not to put undue strain on any screw. Wait an hour or two, and go round with +the screw-driver again. +</p> + +<p> +Lubrication.—When the engine is first put under steam, lubrication should +be very liberal, to assure the parts “settling down” without undue +wear. +</p> + +<p> +The Pump.—Fig. 65 shows in section the pump, which will be found a useful +addition to the engine. (For other details, see Figs. 53 and 54.) Its stroke is +only that of the eccentric, and as the water passages and valves are of good +size, it will work efficiently at high speed. The method of making it will be +obvious from the diagrams, and space will therefore not be devoted to a +detailed description. The valve balls should, of course, be of gun-metal or +brass, and the seatings must be prepared for them by hammering in a steel ball +of the same size. +</p> + +<p> +In practice it is advisable to keep the pump always working, and to regulate +the delivery to the boiler by means of a by-pass tap on the feed pipe, through +which all or some of the water may be returned direct to the tank. +</p> + +<p> +The tank, which should be of zinc, may conveniently be placed under the engine. +If the exhaust steam pipe be made to traverse the tank along or near the +bottom, a good deal of what would otherwise be wasted heat will be saved by +warming the feed water. +</p> + +<p> +Making a Governor. +</p> + +<p> +[Illustration: FIG. 66.—Elevation of governor for horizontal +engine.<br /> +Above is plan of valve and rod gear.]<br /> +</p> + +<p> +It is a great advantage to have the engine automatically governed, so that it +may run at a fairly constant speed under varying loads and boiler pressures. In +the absence of a governor one has to be constantly working the throttle; with +one fitted, the throttle can be opened up full at the start, and the automatic +control relied upon to prevent the engine knocking itself to pieces. +</p> + +<p> +The vertical centrifugal apparatus shown in Fig. 66 was made by the writer, and +acted very well. The only objection to it is its displacement of the pump from +the bed. But a little ingenuity will enable the pump to be driven off the fly +wheel end of the crank shaft, or, if the shaft is cut off pretty flush with the +pulley, off a pin in the face of the pulley. +</p> + +<p> +Turning to Fig. 66, A is a steel spindle fixed in a base, L, screwed to the +bed. B is a brass tube fitting A closely, and resting at the bottom on a +1/4-inch piece of similar tubing pinned to A. +</p> + +<p> +A wooden pulley jammed on B transmits the drive from a belt which passes at its +other end round a similar, but slightly larger, pulley on the crank shaft. This +pulley is accommodated by moving the eccentric slightly nearer the crank and +shortening the fly-wheel side bearing a little. +</p> + +<p> +The piece G, fixed to B by a lock screw, has two slots cut in it to take the +upper ends of the weight links DD; and C, which slides up and down B, is +similarly slotted for the links EE. Each of the last is made of two similarly +shaped plates of thin brass, soldered together for half their length, but +separated 3/32 inch at the top to embrace the projections of D. To prevent C +revolving relatively to B, a notch is filed in one side of the central hole, to +engage with a piece of brass wire soldered on B (shown solid black in the +diagram). A spiral steel spring, indicated in section by a number of black +dots, presses at the top against the adjustable collar F, and at the bottom +against C. +</p> + +<p> +The two weights WW are pieces of brass bar slotted for driving on to DD, which +taper gently towards the outer edge. +</p> + +<p> +When the pulley revolves, centrifugal force makes WW fly outwards against the +pressure of the spring, and the links EE raise C, which in turn lifts the end +of lever M. A single link, N, transmits the motion from a pin on M to the +double bell-crank lever O (see Fig. 66) pivoted on a standard, P, attached to +the bedplate. The slotted upper ends of P engage with pins on an adjustable +block, R, which moves the governing valve V (solid black), working in the tube +S through a gland. The higher M is raised the farther back is V moved, and its +annular port is gradually pushed more out of line with two ports in the side of +the valve tube, thus reducing the flow of steam from the supply pipe to the +cylinder connection on the other side of the tube. This connection, by-the-bye, +acts as fulcrum for lever M, which is made in two parts, held together by +screws, to render detachment easy. +</p> + +<p> +The closer the fit that V makes with S the more effective will the governing +be. The gland at the end of S was taken from an old cylinder cover. +</p> + +<p> +Regulation of the speed may be effected either +</p> + +<p> +(1) by driving the governor faster or slower relatively to the speed of the +crank shaft; +</p> + +<p> +(2) by altering the position of W on D; +</p> + +<p> +(3) by altering the compression of the spring by shifting F; +</p> + +<p> +(4) by a combination of two or more of the above. +</p> + +<p> +Generally speaking, (3) is to be preferred, as the simplest. +</p> + +<p> +The belt may be made out of a bootlace or fairly stout circular elastic. In +either case the ends should be chamfered off to form a smooth joint, which may +be wrapped externally with thread. +</p> + +<h4>FINAL HINTS.</h4> + +<p> +All parts which have to be fitted together should have matching marks made on +them with the punch. To take the parts of the valve chest as an example. As we +have seen, these should be soldered together, finished off outside, and +drilled. Before separating them make, say, two punch marks on what will be the +upper edge of the valve plate near the end, and two similar marks on the chest +as near the first as they can conveniently be. In like manner mark the chest +cover and an adjacent part of the chest with three marks. It is utterly +impossible to reassemble the parts incorrectly after separation if the marks +are matched. Marking is of greatest importance where one piece is held up to +another by a number of screws. If it is omitted in such a case, you may have a +lot of trouble in matching the holes afterwards. +</p> + +<p> +Jacket the cylinder with wood or asbestos, covered in neatly with sheet brass, +to minimize condensation. If the steam ways, valve chest, and steam pipe also +are jacketed, an increase in efficiency will be gained, though perhaps somewhat +at the expense of appearance. +</p> + +<p> +Boiler.—The boiler described on pp. 211-216, or a vertical multitubular +boiler with about 800 sq. inches of heating surface will drive this engine +satisfactorily. +</p> + +</div><!--end chapter--> + +<div class="chapter"> + +<h2><a name="chap16"></a>XVI.<br /> +MODEL STEAM TURBINES.</h2> + +<p> +Steam turbines have come very much to the fore during recent years, especially +for marine propulsion. In principle they are far simpler than cylinder engines, +steam being merely directed at a suitable angle on to specially shaped vanes +attached to a revolving drum and shaft. In the Parsons type of turbine the +steam expands as it passes through successive rings of blades, the diameter of +which rings, as well as the length and number of the blades, increases towards +the exhaust end of the casing, so that the increasing velocity of the expanding +steam may be taken full advantage of. The De Laval turbine includes but a +single ring of vanes, against which the steam issues through nozzles so shaped +as to allow the steam to expand somewhat and its molecules to be moving at +enormous velocity before reaching the vanes. A De Laval wheel revolves at +terrific speeds, the limit being tens of thousands of turns per minute for the +smallest engines. The greatest efficiency is obtained, theoretically, when the +vane velocity is half that of the steam, the latter, after passing round the +curved inside surfaces of the vanes, being robbed of all its energy and speed. +(For a fuller description of the steam turbine, see How It Works, Chap. III., +pp.74-86.) +</p> + +<p> +The turbines to be described work on the De Laval principle, which has been +selected as the easier for the beginner to follow. +</p> + +<p> +A Very Simple Turbine. +</p> + +<p> +We will begin with a very simple contrivance, shown in Fig. 67. As a +“power plant” it is confessedly useless, but the making of it +affords amusement and instruction. For the boiler select a circular tin with a +jointless stamped lid, not less than 4 inches in diameter, so as to give plenty +of heating surface, and at least 2-1/2 inches deep, to ensure a good steam +space and moderately dry steam. A shallow boiler may “prime” badly, +if reasonably full, and fling out a lot of water with the steam. +</p> + +<p> +Clean the metal round the joints, and punch a small hole in the lid, half an +inch from the edge, to give egress to the heated air during the operation of +soldering up the point or joints, which must be rendered absolutely +water-tight. +</p> + +<p> +[Illustration: FIG. 67.—Simple steam turbine.] +</p> + +<p> +For the turbine wheel take a piece of thin sheet iron or brass; flatten it out, +and make a slight dent in it an inch from the two nearest edges. With this dent +as centre are scribed two circles, of 3/4 and 1/2 inch radius respectively. +Then scratch a series of radial marks between the circles, a fifth of an inch +apart. Cut out along the outer circle, and with your shears follow the radial +lines to the inner circle. The edge is thus separated into vanes (Fig. 68), the +ends of which must then be twisted round through half a right angle, with the +aid of a pair of narrow-nosed pliers, care being taken to turn them all in the +same direction. +</p> + +<p> +[Illustration: FIG. 68.—Wheel for steam turbine, showing one vane twisted +into final position.] +</p> + +<p> +A spindle is made out of a large pin, beheaded, the rough end of which must be +ground or filed to a sharp point. Next, just break through the metal of the +disc at the centre with a sharpened wire nail, and push the spindle through +till it projects a quarter of an inch or so. Soldering the disc to the spindle +is most easily effected with a blowpipe or small blow-lamp. +</p> + +<p> +The Boiler.—In the centre of the boiler make a dent, to act as bottom +bearing for the spindle. From this centre describe a circle of 5/8-inch radius. +On this circle must be made the steam port or ports. Two ports, at opposite +ends of a diameter, give better results than a single port, as equalizing the +pressure on the vanes, so that the spindle is relieved of bending strains. +Their combined area must not, however, exceed that of the single port, if one +only be used. It is important to keep in mind that for a turbine of this kind +velocity of steam is everything, and that nothing is gained by increasing the +number or size of ports if it causes a fall in the boiler pressure. +</p> + +<p> +The holes are best made with a tiny Morse twist drill. As the metal is thin, +drill squarely, so that the steam shall emerge vertically. +</p> + +<p> +For the upper bearing bend a piece of tin into the shape shown in Fig. 67. The +vertical parts should be as nearly as possible of the same length as the +spindle. In the centre of the underside of the standard make a deep dent, +supporting the metal on hard wood or lead, so that it shall not be pierced. If +this accident occurs the piece is useless. +</p> + +<p> +Place the wheel in position, the longer part of the spindle upwards, and move +the standard about until the spindle is vertical in all directions. Scratch +round the feet of the standard to mark their exact position, and solder the +standard to the boiler. The top of the standard must now be bent slightly +upwards or downwards until the spindle is held securely without being pinched. +</p> + +<p> +A 3/16-inch brass nut and screw, the first soldered to the boiler round a hole +of the same size as its internal diameter, make a convenient +“filler;” but a plain hole plugged with a tapered piece of wood, +such as the end of a penholder, will serve. +</p> + +<p> +Half fill the boiler by immersion in hot water, the large hole being kept +lowermost, and one of the steam vents above water to allow the air to escape. +</p> + +<p> +A spirit lamp supplies the necessary heat. Or the boiler may be held in a wire +cradle over the fire, near enough to make the wheel hum. Be careful not to +over-drive the boiler. As a wooden plug will probably be driven out before the +pressure can become dangerous, this is a point in favour of using one. +Corrosion of the boiler will be lessened if the boiler is kept quite full of +water when not in use. +</p> + +<p> +A Practical Steam Turbine. +</p> + +<p> +The next step takes us to the construction of a small turbine capable of doing +some useful work. It is shown in cross section and elevation in Fig. 69. +</p> + +<p> +[Illustration: FIG. 69.—Model steam turbine, showing vertical cross +section (left) and external steam pipe (right).] +</p> + +<p> +The rotor in this instance is enclosed in a case made up of two stout brass +discs, D and E, and a 3/4-inch length of brass tubing. The plates should be +1/2-inch larger in diameter than the ring, if the bolts are to go outside. The +stouter the parts, within reason, the better. Thick discs are not so liable to +cockle as thin ones, and a stout ring will make it possible to get steam-tight +joints with brown-paper packing. +</p> + +<p> +The wheel is a disc of brass, say, 1/25 inch thick and 4 inches in diameter; +the spindle is 3/16 inch, of silver steel rod; the bearings, brass tubing, +making a close fit on the rod. +</p> + +<p> +If you cannot get the ring ends turned up true in a lathe—a matter of but +a few minutes’ work—rub them down on a piece of emery cloth +supported on a true surface, such as a piece of thick glass. +</p> + +<p> +Now mark out accurately the centres of the discs on both sides, and make marks +to show which face of each disc is to be outside. +</p> + +<p> +On the outside of both scribe circles of the size of the bearing tubes, and +other circles at the proper radius for the bolt hole centres. +</p> + +<p> +On the outside of D scribe two circles of 2-inch and 1-11/16-inch radius, +between which the steam pipe will lie. +</p> + +<p> +On the inside of D scribe a circle of 1-27/32-inch radius for the steam ports. +</p> + +<p> +On the outside of E mark a 7/8-inch circle for the exhaust pipe. +</p> + +<p> +On the inside of both mark the circles between which the ring must lie. +</p> + +<p> +Bolt Holes.—The marks for these, six or twelve in number, are equally +spaced on the outside of one plate, and the two plates are clamped or soldered +together before the boring is done, to ensure the holes being in line. If the +bolts are to screw into one plate, be careful to make the holes of the tapping +size in the first instance, and to enlarge those in D afterwards. Make guide +marks in the plates before separating, between what will be the uppermost holes +and the circumference. +</p> + +<p> +Bolts.—These should be of brass if passed inside the ring. Nuts are not +necessary if E is tapped, but their addition will give a smarter appearance +and prevent-the bolts becoming loose. +</p> + +<p> +Bearings.—Bore central holes in the discs to a good fit for the bearings, +and prepare the hole for the exhaust pipe. This hole is most easily made by +drilling a ring of small holes just inside the mark and cutting through the +intervening metal. +</p> + +<p> +For A, B, and C cut off pieces of bearing pipe, 1/2, 1/4, and 3/4 inch long +respectively, and bevel the ends of B and C as shown, to minimize friction if +they rub. File all other ends square. (Lathe useful here.) +</p> + +<p> +Bore oil holes in B and C, and clear away all the “burr.” Make +scratches on the bearings to show how far they should be pushed through the +case. +</p> + +<p> +Now assemble the case, taking care that the edge of the ring corresponds +exactly with the circles marked on the discs, and clean the metal round the +bearing holes and the bearings themselves. The last are then placed in +position, with the lubricating holes pointing upwards towards the guide marks +on the discs. Push the spindle rod through the bearings, which must be adjusted +until the rod can be revolved easily with the fingers. Then solder in the +bearing with a “Tinol” lamp. +</p> + +<p> +The Wheel.—Anneal this well by heating to a dull red and plunging it in +cold water. Mark a circle of 1-1/4-inch radius, and draw radial lines 1/4 inch +apart at the circumference from this circle to the edge. Cut out along the +lines, and twist the vanes to make an angle of about 60 degree with the central +part, and bend the ends slightly backward away from the direction in which the +rotor will revolve. (The directions given on p. 189 for making a steam top +wheel can be applied here.) +</p> + +<p> +Bore a hole in the centre to make a tight fit with the spindle, and place the +rotor in position, with piece B in contact on the C side. Get everything square +(rotation will betray a bad wobble), and solder the three parts together with +the blow-lamp. +</p> + +<p> +Mount the rotor squarely by the spindle points between two pieces of wood held +lightly in the vice, and, with the aid of a gauge fixed to the piece nearest +the wheel, true up the line of the vanes. (Lathe useful here.) +</p> + +<p> +The Steam Pipe is 15 inches (or more) of 5/16-inch copper tubing, well +annealed. To assist the bending of it into a ring one needs some circular +object of the same diameter as the interior diameter of the ring round which to +curve it. I procured a tooth-powder box of the right size, and nailed it firmly +to a piece of board. Then I bevelled off the end of the pipe to the +approximately correct angle, laid it against the box, and drove in a nail to +keep it tight up. Bending was then an easy matter, a nail driven in here and +there holding the pipe until the ring was complete. I then soldered the end to +the standing part, and detached the ring for flattening on one side with a file +and emery cloth. This done, I bored a hole through the tube at F to open up the +blind end of the ring. +</p> + +<p> +Attaching the ring to disc D is effected as follows:—Tin the contact +faces of the ring and disc pretty heavily with solder, after making poppet +marks round the guide circles so that they may not be lost under the solder. +The ring must be pressed tightly against its seat while heating is done with +the lamp. An extra pair of hands makes things easier at this point. Be careful +not to unsolder the spindle bearing, a thing which cannot happen if the bearing +is kept cool by an occasional drop or two of water. A little extra solder +should be applied round the points where the ports will be. +</p> + +<p> +The Steam Ports.—These are drilled (with a 1/32-inch twist drill), at an +angle of about 30 degrees to the plate, along the circle already scribed. If +you have any doubt as to your boiler’s capacity, begin with one hole +only, and add a second if you think it advisable. As already remarked, pressure +must not be sacrificed to steam flow. +</p> + +<p> +Lubricators.—These are short pieces of tubing hollowed at one end by a +round file of the same diameter as the bearings. A little “Tinol” +is smeared over the surfaces to be joined, and the lubricators are placed in +position and heated with the blow-lamp until the solder runs. To prevent the +oil flowing too freely, the lubricators should be provided with airtight wooden +plugs. +</p> + +<p> +Escape Pipes.—The pipe for the exhaust steam is now soldered into disc E, +and a small water escape into the ring at its lowest point. This pipe should be +connected with a closed chamber or with the exhaust at a point lower than the +base of the turbine case. +</p> + +<p> +Stirrup.—Fig. 69 shows a stirrup carrying a screw which presses against +the pulley end of the spindle. This attachment makes it easy to adjust the +distance between the rotor and the steam ports, and also concentrates all end +thrust on to a point, thereby minimizing friction. The stirrup can be fashioned +in a few minutes out of brass strip. Drill the holes for the holding-on screws; +drill and tap a hole for the adjusting screw; insert the screw and centre it +correctly on the spindle point. Then mark the position of the two screw holes +in E; drill and tap them. +</p> + +<p> +Feet are made of sheet brass, drilled to take the three (or two) lowermost +bolts, and bent to shape. Note.—A side and foot may be cut out of one +piece of metal. The difficulty is that the bending may distort the side, and +prevent a tight joint between side and ring. +</p> + +<p> +Assembling.—Cut out two rings of stout brown paper a quarter of an inch +wide and slightly larger in diameter than the casing ring. In assembling the +turbine finally, these, after being soaked in oil, should be inserted between +the ring and the discs. Put in four screws only at first, and get the ring +properly centred and the bearings exactly in line, which will be shown by the +spindle revolving easily. Then tighten up the nuts and insert the other bolts, +the three lowest of which are passed through the feet. Affix the pulley and +stirrup, and adjust the spindle longitudinally until the rotor just does not +rub the casing. The soldering on of the cap of A completes operations. +</p> + +<p> +To get efficiency, heavy gearing down is needed, and this can be managed easily +enough with the help of a clockwork train, decreasing the speed five or more +times for driving a dynamo, and much more still for slow work, such as pumping. +</p> + +<p> +A More Elaborate Turbine. +</p> + +<p> +[Illustration: FIG. 70.—Vertical section of steam turbine with formed +blades (left); outside view of turbine, gear side (right).] +</p> + +<p> +The turbine just described can hardly be termed an efficient one, as the vanes, +owing to their simple formation, are not shaped to give good results. We +therefore offer to our readers a design for a small turbine of a superior +character. This turbine is shown in elevation and section in Fig. 70. The +casing is, as in the preceding instance, made up of flat brass plates and a +ring of tubing, and the bearings, BG1, BG2, of brass tube. But the wheel is +built up of a disc 3 inches in diameter, round the circumference of which are +32 equally-spaced buckets, blades, or vanes, projecting 5/8 inch beyond the +edge of the disc. The wheel as a whole is mounted on a spindle 3-1/8 inches +long, to which it is secured by three nuts, N1 N2 N3. One end of the spindle is +fined down to take a small pinion, P1, meshing with a large pinion, P2, the +latter running in bearings, BG3, in the wheel-case and cover. The drive of the +turbine is transmitted either direct from the axle of P2 or from a pulley +mounted on it. +</p> + +<h4>CONSTRUCTION.</h4> + +<p> +[Illustration: FIG. 71.—Plate marked out for turbine wheel blades. B is +blade as it appears before being curved.] +</p> + +<p> +The Wheel.—If you do not possess a lathe, the preparation of the spindle +and mounting the wheel disc on it should be entrusted to a mechanic. Its +diameter at the bearings should be 5/32 inch or thereabouts. (Get the tubing +for the bearings and for the spindle turned to fit.) The larger portion is +about twice as thick as the smaller, to allow room for the screw threads. The +right-hand end is turned down quite small for the pinion, which should be of +driving fit. +</p> + +<p> +The Blades.—Mark out a piece of sheet iron as shown in Fig. 71 to form 32 +rectangles, 1 by l/2 inch. The metal is divided along the lines aaaa, bbbb, and +ab, ab, ab, ab, etc. The piece for each blade then has a central slot 5/16 inch +long and as wide as the wheel disc cut very carefully in it. +</p> + +<p> +Bending the Blades.—In the edge of a piece of hard wood 1 inch thick file +a notch 3/8 inch wide and 1/8 inch deep with a 1/2-inch circular file, and +procure a metal bar which fits the groove loosely. Each blade is laid in turn +over the groove, and the bar is applied lengthwise on it and driven down with a +mallet, to give the blade the curvature of the groove. When all the blades have +been made and shaped, draw 16 diameters through the centre of the wheel disc, +and at the 32 ends make nicks 1/16 inch deep in the circumference. +</p> + +<p> +True up the long edges of the blades with a file, and bring them off to a sharp +edge, removing the metal from the convex side. +</p> + +<p> +Fixing the Blades.—Select a piece of wood as thick as half the width of a +finished blade, less half the thickness of the wheel disc. Cut out a circle of +this wood 2 inches in diameter, and bore a hole at the centre. The wheel disc +is then screwed to a perfectly flat board or plate, the wooden disc being used +as a spacer between them. +</p> + +<p> +Slip a blade into place on the disc, easing the central slit, if necessary, to +allow the near edge to lie in contact with the board—that is parallel to +the disc. Solder on the blade, using the minimum of solder needed to make a +good joint. When all the blades are fixed, you will have a wheel with the +blades quite true on one side. It is, therefore, important to consider, before +commencing work, in which direction the concave side of the blades should be, +so that when the wheel is mounted it shall face the nozzle. +</p> + +<p> +To make this point clear: the direction of the nozzle having been decided, the +buckets on the trued side must in turn present their concave sides to the +nozzle. In Fig. 70 the nozzle points downwards, and the left side of the wheel +has to be trued. Therefore B1 has its convex, B2 its concave, side facing the +reader, as it were. +</p> + +<p> +The Nozzle is a 1-1/2 inch piece of brass bar. Drill a 1/20-inch hole through +the centre. On the outside end, enlarge this hole to 1/8 inch to a depth of 1/8 +inch. The nozzle end is bevelled off to an angle of 20 degrees, and a broach is +inserted to give the steam port a conical section, as shown in Fig. 72, so that +the steam may expand and gain velocity as it approaches the blades. Care must +be taken not to allow the broach to enter far enough to enlarge the throat of +the nozzle to more than 1/20 inch. +</p> + +<p> +[Illustration: FIG. 72.—Nozzle of turbine, showing its position +relatively to buckets.] +</p> + +<p> +Fixing the Nozzle.—The centre of the nozzle discharge opening is +1-13/16-inches from the centre of the wheel. The nozzle must make an angle of +20 degrees with the side of the casing, through which it projects far enough to +all but touch the nearer edges of the vanes. (Fig. 72.) The wheel can then be +adjusted, by means of the spindle nuts, to the nozzle more conveniently than +the nozzle to the wheel. To get the hole in the casing correctly situated and +sloped, begin by boring a hole straight through, 1/4 inch away laterally from +where the steam discharge hole will be, centre to centre, and then work the +walls of the hole to the proper angle with a circular file of the same diameter +as the nozzle piece, which is then sweated in with solder. It is, of course, an +easy matter to fix the nozzle at the proper angle to a thin plate, which can be +screwed on to the outside of the casing, and this method has the advantage of +giving easy detachment for alteration or replacement. +</p> + +<p> +Balancing the Wheel.—As the wheel will revolve at very high speed, it +should be balanced as accurately as possible. A simple method of testing is to +rest the ends of the spindle on two carefully levelled straight edges. If the +wheel persists in rolling till it takes up a certain position, lighten the +lower part of the wheel by scraping off solder, or by cutting away bits of the +vanes below the circumference of the disc, or by drilling holes in the disc +itself. +</p> + +<p> +Securing the Wheel.—When the wheel has been finally adjusted relatively +to the nozzle, tighten up all the spindle nuts hard, and drill a hole for a pin +through them and the disc parallel to the spindle, and another through N3 and +the spindle. (Fig. 70.) +</p> + +<p> +Gearing.—The gear wheels should be of good width, not less than 3/16 +inch, and the smaller of steel, to withstand prolonged wear. Constant +lubrication is needed, and to this end the cover should make an oil-tight fit +with the casing, so that the bottom of the big pinion may run in oil. To +prevent overfilling, make a plug-hole at the limit level, and fit a draw-off +cock in the bottom of the cover. If oil ducts are bored in the bearing inside +the cover, the splashed oil will lubricate the big pinion spindle +automatically. +</p> + +<p> +[Illustration: FIG. 73.—Perspective view of completed turbine.] +</p> + +<p> +General—The sides of the casing are held against the drum by six screw +bolts on the outside of the drum. The bottom of the sides is flattened as shown +(Fig. 70), and the supports, S1 S2, made of such a length that when they are +screwed down the flattened part is pressed hard against the bed. The oil box on +top of the casing has a pad of cotton wool at the bottom to regulate the flow +of oil to the bearings. Fit a drain pipe to the bottom of the wheel-case. +</p> + +<p> +Testing.—If your boiler will make steam above its working pressure faster +than the turbine can use it, the nozzle may be enlarged with a broach until it +passes all the steam that can be raised; or a second nozzle may be fitted on +the other end of the diameter on which the first lies. This second nozzle +should have a separate valve, so that it can be shut off. +</p> + +</div><!--end chapter--> + +<div class="chapter"> + +<h2><a name="chap17"></a>XVII.<br /> +STEAM TOPS.</h2> + +<p> +A very interesting and novel application of the steam turbine principle is to +substitute for a wheel running in fixed bearings a “free” wheel +pivoted on a vertical spindle, the point of which takes the weight, so that the +turbine becomes a top which can be kept spinning as long as the steam supply +lasts. +</p> + +<p> +These toys, for such they must be considered, are very easy to make, and are +“warranted to give satisfaction” if the following instructions are +carried out. +</p> + +<p> +A Small Top.—Fig. 74 shows a small specimen, which is of the +self-contained order, the boiler serving as support for the top. +</p> + +<p> +[Illustration: FIG. 74.-Simplest form of steam top.] [1] +</p> + +<p> +[Footnote 1: Spirit lamp shown for heating boiler.] +</p> + +<p> +For the boiler use a piece of brass tubing 4 inches or so in diameter and 3 +inches long. (The case of an old brass “drum” clock, which may be +bought for a few pence at a watchmaker’s, serves very well if the small +screw holes are soldered over.) The ends should be of brass or zinc, the one +which will be uppermost being at least 1/16 inch thick. If you do not possess a +lathe, lay the tube on the sheet metal, and with a very sharp steel point +scratch round the angle between tube and plate on the inside. Cut out with cold +chisel or shears to within 1/16 inch of the mark, and finish off +carefully—testing by the tube now and then—to the mark. Make a dent +with a centre punch in the centre of the top plate for the top to spin in. +</p> + +<p> +[Illustration: FIG. 75.—Wheel of steam top, ready for blades to be +bent.<br /> +A hole is drilled at the inner end of every slit to make bending easier.]<br /> +</p> + +<p> +Solder the plates into the tube, allowing an overlap of a quarter of an inch +beyond the lower one, to help retain the heat. +</p> + +<p> +The top wheel is cut out of a flat piece of sheet iron, zinc, or brass. Its +diameter should be about 2-1/2 inches, the vanes 1/2 inch long and 1/4 inch +wide at the circumference. Turn them over to make an angle of about 45 degrees +with the spindle. They will be more easily bent and give better results if +holes are drilled, as shown in Fig. 75. +</p> + +<p> +The spindle is made out of a bit of steel or wire—a knitting-needle or +wire-nail—not more than 1 inch in diameter and 1-1/2 inches long. The +hole for this must be drilled quite centrally in the wheel; otherwise the top +will be badly balanced, and vibrate at high speeds. For the same reason, the +spindle requires to be accurately pointed. +</p> + +<p> +The steam ports are next drilled in the top of the boiler. Three of them should +be equally spaced (120 degrees apart) on a circle of 1-inch radius drawn about +the spindle poppet as centre. The holes must be as small as possible—1/40 +to 1/50 inch—and inclined at an angle of not more than 45 degrees to the +top plate. The best drills for the purpose are tiny Morse twists, sold at from +2d. to 3d. each, held in a pin vice rotated by the fingers. The points for +drilling should be marked with a punch, to give the drills a hold. Commence +drilling almost vertically, and as the drill enters tilt it gradually over till +the correct angle is attained. +</p> + +<p> +If a little extra trouble is not objected to, a better job will be made of this +operation if three little bits of brass, filed to a triangular section (Fig. 76 +a), are soldered to the top plate at the proper places, so that the drilling +can be done squarely to one face and a perfectly clear hole obtained. The one +drawback to these additions is that the vanes of the turbine may strike them. +As an alternative, patches may be soldered to the under side of the plate (Fig. +76, b) before it is joined to the barrel; this will give longer holes and a +truer direction to the steam ports. +</p> + +<p> +[Illustration: FIG. 76. Steam port details.] +</p> + +<p> +Note that it is important that the ports should be all of the same diameter and +tangential to the circle on which they are placed, and all equally inclined to +the plate. Differences in size or direction affect the running of the top. +</p> + +<p> +Solder the spindle to the wheel in such a position that the vanes clear the +boiler by an eighth of an inch or so. If tests show that the top runs quite +vertically, the distance might be reduced to half, as the smaller it is the +more effect will the steam jets have. +</p> + +<p> +A small brass filler should be affixed to the boiler halfway up. A filler with +ground joints costs about 6d. +</p> + +<p> +A wick spirit lamp will serve to raise steam. Solder to the boiler three legs +of such a length as to give an inch clearance between the lamp wick and the +boiler. If the wick is arranged to turn up and down, the speed of the top can +be regulated. +</p> + +<p> +A Large Top.—The top just described must be light, as the steam driving +it is low-pressure, having free egress from the boiler, and small, as the steam +has comparatively low velocity. The possessor of a high-pressure boiler may be +inclined to make something rather more ambitious—larger, heavier, and +useful for displaying spectrum discs, etc. +</p> + +<p> +The top shown in Fig. 77 is 3 inches in diameter, weighs 1 oz., and was cut out +of sheet-zinc. It stands on a brass disc, round the circumference of which is +soldered a ring of 5/32-inch copper tubing, furnished with a union for +connection with a boiler. +</p> + +<p> +[Illustration: FIG. 77.—-Large steam top and base.] +</p> + +<p> +The copper tubing must be well annealed, so as to bend quite easily. Bevel off +one end, and solder this to the plate. Bend a couple of inches to the curve of +the plate, clamp it in position, and solder; and so on until the circle is +completed, bringing the tube snugly against the bevelled end. A hole should now +be drilled through the tube into this end—so that steam may enter the +ring in both directions-and plugged externally. +</p> + +<p> +By preference, the ring should be below the plate, as this gives a greater +thickness of metal for drilling, and also makes it easy to jacket the tube by +sinking the plate into a wooden disc of somewhat greater diameter. +</p> + +<p> +Under 50 lbs. of steam, a top of this kind attains a tremendous velocity. Also, +it flings the condensed steam about so indiscriminately that a ring of zinc 3 +inches high and 18 inches in diameter should be made wherewith to surround it +while it is running. +</p> + +<p> +If a little bowl with edges turned over be accurately centred on the wheel, a +demonstration of the effects of centrifugal force may be made with water, +quicksilver, or shot, which fly up into the rim and disappear as the top +attains high speed, and come into sight again when its velocity decreases to a +certain figure. A perforated metal globe threaded on the spindle gives the +familiar humming sound. +</p> + +<p> +A spectrum disc of the seven primary colours—violet, indigo, blue, green, +yellow, orange, red—revolved by the top, will appear more or less white, +the purity of which depends on the accuracy of the tints used. +</p> + +</div><!--end chapter--> + +<div class="chapter"> + +<h2><a name="chap18"></a>XVIII.<br /> +MODEL BOILERS.</h2> + +<p> +A chapter devoted to the construction of model boilers may well open with a few +cautionary words, as the dangers connected with steam-raisers are very real; +and though model-boiler explosions are fortunately rare, if they do occur they +may be extremely disastrous. +</p> + +<p> +Therefore the following warnings:— +</p> + +<p> +(1.) Do not use tins or thin sheet iron for boilers. One cannot tell how far +internal corrosion has gone. The scaling of 1/100 inch of metal off a +“tin” is obviously vastly more serious than the same diminution in +the thickness of, say, a 1/4-inch plate. Brass and copper are the metals to +employ, as they do not deteriorate at all provided a proper water supply be +maintained. +</p> + +<p> +(2.) If in doubt, make the boiler much more solid than is needed, rather than +run any risks. +</p> + +<p> +(3.) Fit a steam gauge, so that you may know what is happening. +</p> + +<p> +(4.) Test your boiler under steam, and don’t work it at more than half +the pressure to which it has been tested. (See p. 220.) +</p> + +<p> +In the present chapter we will assume that the barrels of all the boilers +described are made out of solid-drawn seamless copper tubing, which can be +bought in all diameters up to 6 inches, and of any one of several thicknesses. +Brass tubing is more easily soldered, but not so good to braze, and generally +not so strong as copper, other things being equal. Solid-drawn tubing is more +expensive than welded tubing or an equivalent amount of sheet metal, but is +considerably stronger than the best riveted tube. +</p> + +<p> +Boiler ends may be purchased ready turned to size. Get stampings rather than +castings, as the first are more homogeneous, and therefore can be somewhat +lighter. +</p> + +<p> +Flanging Boiler Ends.—To make a good job, a plate for an end should be +screwed to a circular block of hard wood (oak or boxwood), having an outside +diameter less than the inside diameter of the boiler barrel by twice the +thickness of the metal of the end, and a rounded-off edge. The plate must be +annealed by being heated to a dull red and dipped in cold water. The process +must be repeated should the hammering make the copper stubborn. +</p> + +<p> +Stays should be used liberally, and be screwed and nutted at the ends. As the +cutting of the screw thread reduces the effective diameter, the strength of a +stay is only that of the section at the bottom of the threads. +</p> + +<p> +Riveting.—Though stays will prevent the ends of the boiler blowing off, +it is very advisable to rivet them through the flanges to the ends of the +barrel, as this gives mutual support independently of soldering or brazing. +Proper boiler rivets should be procured, and annealed before use. Make the +rivet holes a good fit, and drill the two parts to be held together in one +operation, to ensure the holes being in line. Rivets will not close properly if +too long. Dies for closing the rivet heads may be bought for a few pence. +</p> + +<p> +Soldering, etc.—Joints not exposed directly to the furnace flames may be +soldered with a solder melting not below 350 degrees Fahr. Surfaces to be +riveted together should be “tinned” before riveting, to ensure the +solder getting a good hold afterwards. The solder should be sweated right +through the joint with a blow-lamp to make a satisfactory job. +</p> + +<p> +All joints exposed to the flames should be silver-soldered, and other joints as +well if the working pressure is to exceed 50 lbs. to the square inch. +Silver-soldering requires the use of a powerful blow—lamp or gas-jet; +ordinary soft soldering bits and temperatures are ineffective. Brazing is +better still, but should be done by an expert, who may be relied on not to burn +the metal. It is somewhat risky to braze brass, which melts at a temperature +not far above that required to fuse the spelter (brass solder). Getting the +prepared parts of a boiler silver-soldered or brazed together is inexpensive, +and is worth the money asked. +</p> + +<p> +[Illustration: FIG. 78.] +</p> + +<p> +Some Points in Design. +</p> + +<p> +The efficiency of a boiler is governed chiefly (1) by the amount of heating +surface exposed to the flames; (2) by the distribution of the heating surface; +(3) by the amount of fuel which can be burnt in the furnace in a given time; +(4) by avoiding wastage of heat. +</p> + +<p> +The simplest form of boiler, depicted in Fig. 78, is extremely inefficient +because of its small heating surface. A great deal of the heat escapes round +the sides and the ends of the boiler. Moreover, a good deal of the heat which +passes into the water is radiated out again, as the boiler is exposed directly +to the air. +</p> + +<p> +Fig. 79 shows a great improvement in design. The boiler is entirely enclosed, +except at one end, so that the hot gases get right round the barrel, and the +effective heating surface has been more than doubled by fitting a number of +water-tubes, aaa, bbbb, which lie right in the flames, and absorb much heat +which would otherwise escape. The tubes slope upwards from the chimney end, +where the heat is less, to the fire-door end, where the heat is fiercer, and a +good circulation is thus assured. The Babcock and Wilcox boiler is the highest +development of this system, which has proved very successful, and may be +recommended for model boilers of all sizes. The heating surface may be +increased indefinitely by multiplying the number of tubes. If a solid +fuel-coal, coke, charcoal, etc.-fire is used, the walls of the casing should be +lined with asbestos or fire-clay to prevent the metal being burnt away. +</p> + +<p> +[Illustration: FIG. 79—Side and end elevations of a small water-tube +boiler.] +</p> + +<p> +The horizontal boiler has an advantage over the vertical in that, for an equal +diameter of barrel, it affords a larger water surface, and is, therefore, less +subject to “priming,” which means the passing off of minute +globules of water with the steam. This trouble, very likely to occur if the +boiler has to run an engine too large for it, means a great loss of efficiency, +but it may be partly cured by making the steam pass through coils exposed to +the furnace gases on its way to the engine. This “superheating” +evaporates the globules and dries the steam, besides raising its temperature. +The small water-tube is preferable to the small fire-tube connecting furnace +and chimney, as its surface is exposed more directly to the flames; also it +increases, instead of decreasing, the total volume of water in the boiler. +</p> + +<p> +A Vertical Boiler. +</p> + +<p> +[Illustration: FIG. 80.—Details of vertical boiler.] +</p> + +<p> +The vertical boiler illustrated by Fig. 80 is easily made. The absence of a +water jacket to the furnace is partly compensated by fitting six water-tubes in +the bottom. As shown, the barrel is 8 inches long and 6 inches in outside +diameter, and the central flue 1-1/2 inches across outside solid-drawn +1/16-inch tubing, flanged ends, and four 1/4-inch stays—disposed as +indicated in Fig. 80 (a) and (b)—are used. The 5/16 or 3/8 inch +water-tubes must be annealed and filled with lead or resin before being bent +round wooden templates. After bending, run the resin or lead out by heating. +The outflow end of each pipe should project half an inch or so further through +the boiler bottom than the inflow end. +</p> + +<p> +Mark out and drill the tube holes in the bottom, and then the flue hole, for +which a series of small holes must be made close together inside the +circumference and united with a fret saw. Work the hole out carefully till the +flue, which should be slightly tapered at the end, can be driven through an +eighth of an inch or so. The flue hole in the top should be made a good fit, +full size. +</p> + +<p> +Rivet a collar, x (Fig. 80, a), of strip brass 1/4 inch above the bottom of the +flue to form a shoulder. Another collar, y (Fig. 80, c), is needed for the flue +above the top plate. Put the ends and flue temporarily in place, mark off the +position of y, and drill half a dozen 5/32-inch screw holes through y and the +flue. Also drill screw holes to hold the collar to the boiler top. +</p> + +<p> +The steam-pipe is a circle of 5/16-inch copper tube, having one end closed, +and a number of small holes bored in the upper side to collect the steam from +many points at once. The other end is carried through the side of the boiler. +</p> + +<p> +[Illustration: FIG. 81.—Perspective view of horizontal boiler mounted on +wooden base.] +</p> + +<p> +Assembling.—The order of assembling is:—Rivet in the bottom; put +the steam-pipe in place; rivet in the top; insert the flue, and screw collar y +to the top; expand the bottom of the flue by hammering so that it cannot be +withdrawn; insert the stays and screw them up tight; silver-solder both ends of +the flue, the bottom ends of the stays, and the joint between bottom and +barrel. The water-tubes are then inserted and silver-soldered, and one finishes +by soft-soldering the boiler top to the barrel and fixing in the seatings for +the water and steam gauges, safety-valve, mud-hole, filler, and pump-if the +last is fitted. +</p> + +<p> +The furnace is lined with a strip of stout sheet iron, 7 inches wide and 19-1/4 +inches long, bent round the barrel, which it overlaps for an inch and a half. +Several screws hold lining and barrel together. To promote efficiency, the +furnace and boiler is jacketed with asbestos—or fire-clay round the +furnace—secured by a thin outer cover. The enclosing is a somewhat +troublesome business, but results in much better steaming power, especially in +cold weather. Air-holes must be cut round the bottom of the lining to give good +ventilation. +</p> + +<p> +A boiler of this size will keep a 1 by 1-1/2 inch cylinder well supplied with +steam at from 30 to 40 lbs. per square inch. +</p> + +<p> +A Horizontal Boiler. +</p> + +<p> +[Illustration: FIG. 82.—Longitudinal section of large water-tube boiler.] +</p> + +<p> +The boiler illustrated by Fig. 81 is designed for heating with a large paraffin +or petrol blow-lamp. It has considerably greater water capacity, heating +surface—the furnace being entirely enclosed—and water surface than +the boiler just described. The last at high-water level is about 60, and at +low-water level 70, square inches. +</p> + +<p> +The vertical section (Fig. 82) shows 1/16-inch barrel, 13 inches long over all +and 12 inches long between the end plates, and 6 inches in diameter. The +furnace flue is 2-1/2 inches across outside, and contains eleven 1/2-inch cross +tubes, set as indicated by the end view (Fig. 83), and 3/4 inch apart, centre +to centre. This arrangement gives a total heating surface of about 140 square +inches. If somewhat smaller tubes are used and doubled (see Fig. 84), or even +trebled, the heating surface may be increased to 180-200 square inches. With a +powerful blow-lamp this boiler raises a lot of steam. +</p> + +<p> +Tubing the Furnace Flue.—Before any of the holes are made, the lines on +which the centres lie must be scored from end to end of the flue on the +outside. The positions of these lines are quickly found as follows:—Cut +out a strip of paper exactly as long as the circumference of the tube, and plot +the centre lines on it. The paper is then applied to the tube again, and poppet +marks made with a centre punch opposite to or through the marks on the paper. +Drive a wire-nail through a piece of square wood and sharpen the point. Lay the +flue on a flat surface, apply the end of the nail to one of the poppet marks, +and draw it along the flue, which must be held quite firmly. When all the lines +have been scored, the centring of the water tubes is a very easy matter. +</p> + +<p> +[Illustration: FIG. 83.-End of horizontal boiler, showing position of holes for +stays and fittings.] +</p> + +<p> +The two holes for any one tube should be bored independently, with a drill +somewhat smaller than the tube, and be opened to a good fit with a reamer or +broach passed through both holes to ensure their sides being in line. Taper the +tubes—2-7/8 inches long each—slightly at one end, and make one of +the holes a bit smaller than the other. The tapered end is passed first through +the larger hole and driven home in the other, but not so violently as to +distort the flue. If the tubes are made fast in this way, the subsequent +silver-soldering will be all the easier. +</p> + +<p> +[Illustration: FIG. 84.—Doubled cross tubes In horizontal boiler flue.] +</p> + +<p> +The Steam Dome.—The large holes—2 inches in diameter—required +for the steam dome render it necessary to strengthen the barrel at this point. +Cut out a circular plate of metal 4 inches across, make a central hole of the +size of the steam dome, and bend the plate to the curve of the inside of the +barrel. Tin the contact faces of the barrel and “patch” and draw +them together with screws or rivets spaced as shown in Fig. 85, and sweat +solder into the joint. To make it impossible for the steam dome to blowout, let +it extend half an inch through the barrel, and pass a piece of 1/4-inch brass +rod through it in contact with the barrel. The joint is secured with hard +solder. Solder the top of the dome in 1/8 inch below the end of the tube, and +burr the end over. The joint should be run again afterwards to ensure its being +tight. +</p> + +<p> +[Illustration: FIG. 85.—Showing how to mark out strengthening patch round +steam dome hole.] +</p> + +<p> +The positions of stays and gauges is shown in Fig. 83. +</p> + +<p> +Chimney.—This should be an elbow of iron piping fitting the inside of the +flue closely, made up of a 9-inch and a 4-inch part. The last slips into the +end of the flue; the first may contain a coil for superheating the steam. +</p> + +<p> +A Multitubular Boiler. +</p> + +<p> +[Illustration: FIG. 86.—Cross section of multitubular boiler.] +</p> + +<p> +Figs. 86 and 87 are respectively end and side elevations of a multitubular +boiler having over 600 square inches of heating surface—most of it +contributed by the tubes—and intended for firing with solid fuel. +</p> + +<p> +The boiler has a main water-drum, A, 5 inches in diameter and 18 inches long, +and two smaller water-drums, B and C, 2-1/2 by 18 inches, connected by two +series of tubes, G and H, each set comprising 20 tubes. The H tubes are not +exposed to the fire so directly as the G tubes, but as they enter the main drum +at a higher point, the circulation is improved by uniting A to B and C at both +ends by large 1-inch drawn tubes, F. In addition, B and C are connected by +three 3/4-inch cross tubes, E, which prevent the small drums spreading, and +further equalize the water supply. A 1-1/2-inch drum, D, is placed on the top +of A to collect the steam at a good distance from the water. +</p> + +<p> +Materials.—In addition to 1-1/2 feet of 5 by 3/32 inch solid-drawn tubing +for the main, and 3 feet of 2-1/2 by 1/16 inch tubing for the lower drums, the +boiler proper requires 22-1/2 feet of 1/2-inch tubing, 19 inches of 3/4-inch +tubing, 2-1/4 feet of 1-inch tubing, 1 foot of 1-1/2-inch tubing, and ends of +suitable size for the four drums. +</p> + +<p> +[Illustration: FIG. 87.—Longitudinal section of multitubular boiler.] +</p> + +<h4>CONSTRUCTION.</h4> + +<p> +[Illustration: FIG. 88.-Two arrangements for tube holes in multi tubular +boiler.] +</p> + +<p> +The centres for the water-tubes, G and H, should be laid out, in accordance +with Fig. 88, on the tops of B and C and the lower part of A, along lines +scribed in the manner explained on p. 207. Tubes H must be bent to a template +to get them all of the same shape and length, and all the tubes be prepared +before any are put in place. If the tubes are set 7/8 inch apart, centre to +centre, instead of 1-1/4 inches, the heating surface will be greatly increased +and the furnace casing better protected. +</p> + +<p> +Assembling.—When all necessary holes have been made and are of the +correct size, begin by riveting and silver-soldering in the ends of the drums. +Next fix the cross tubes, E, taking care that they and B and C form rectangles. +Then slip the F, G, and H tubes half an inch into the main drum, and support A, +by means of strips passed between the G and H tubes, in its correct position +relatively to B and C. The E tubes can now be pushed into B and C and +silver-soldered. The supports may then be removed, and the a and H tubes be got +into position and secured. Drum D then demands attention. The connecting tubes, +KK, should be silver-soldered in, as the boiler, if properly made, can be +worked at pressures up to 100 lbs. per square inch. +</p> + +<p> +The casing is of 1/20-inch sheet iron, and in five parts. The back end must be +holed to allow A, B, and C to project 1 inch, and have a furnace-door opening, +and an airway at the bottom, 5 inches wide and 1 inch deep, cut in it. The +airway may be provided with a flap, to assist in damping down the fire if too +much steam is being raised. In the front end make an inspection opening to +facilitate cleaning the tubes and removing cinders, etc. +</p> + +<p> +The side plates, m m, are bent as shown in Fig. 86, and bolted to a +semicircular top plate, n, bent to a radius of 6 inches. A slot, 1-1/2 inches +wide and 11-1/2 inches long, must be cut in the top, n, to allow it to be +passed over drum D; and there must also be a 3 or 3-1/2 inch hole for the +chimney. A plate, p, covers in D. A little plate, o, is slipped over the slot +in n, and asbestos is packed in all round D. The interior of the end, side, and +the top plates should be lined with sheet asbestos held on by large tin washers +and screw bolts. To protect the asbestos, movable iron sheets may be interposed +on the furnace side. These are replaced easily if burnt away. The pieces m m +are bent out at the bottom, and screwed down to a base-plate extending the +whole length of the boiler. +</p> + +<p> +The fire-bars fill the rectangle formed by the tubes B, El, and E2. A plate +extends from the top of E2 to the front plate of the casing, to prevent the +furnace draught being “short circuited.” +</p> + +<p> +Boiler Fittings. +</p> + +<p> +[Illustration: FIG. 89.-Safety valve.] +</p> + +<p> +Safety Valves.—The best all-round type is that shown in Fig. 89. There is +no danger of the setting being accidentally altered, as is very possible with a +lever and sliding weight. The valve should be set by the steam gauge. Screw it +down, and raise steam to the point at which you wish the safety valve to act, +and then slacken off the regulating nuts until steam issues freely. The lock +nuts under the cross-bar should then be tightened up. In the case of a boiler +with a large heating surface, which makes steam quickly, it is important that +the safety-valve should be large enough to master the steam. If the valve is +too small, the pressure may rise to a dangerous height, even with the steam +coming out as fast as the valve can pass it. +</p> + +<p> +[Illustration: FIG. 90.-Steam gauge and siphon.] +</p> + +<p> +Steam Gauges.—The steam gauge should register pressures considerably +higher than that to be used, so that there may be no danger of the boiler being +forced unwittingly beyond the limit registered. A siphon piece should be +interposed between boiler and gauge (Fig. 90), to protect the latter from the +direct action of the steam. Water condenses in the siphon, and does not become +very hot. +</p> + +<p> +[Illustration: FIG. 91.-Water gauge.] +</p> + +<p> +Water Gauges should have three taps (Fig. 91), two between glass and boiler, to +cut off the water if the glass should burst, and one for blowing off through. +Very small gauges are a mistake, as the water jumps about in a small tube. When +fitting a gauge, put packings between the bushes and the glass-holders, +substitute a piece of metal rod for the glass tube, and pack the rod tightly. +If the bushes are now sweated into the boiler end while thus directed, the +gauge must be in line for the glass. This method is advisable in all cases, and +is necessary if the boiler end is not perfectly flat. +</p> + +<p> +Pumps.—Where a pump is used, the supply should enter the boiler below +low-water level through a non-return valve fitted with a tap, so that water can +be prevented from blowing back through the pump. As regards the construction of +pumps, the reader is referred to p. 164 and to Chapter XXII. +</p> + +<p> +Filling Caps.—The filling cap should be large enough to take the nozzle +of a good-sized funnel with some room to spare. Beat the nozzle out of shape, +to give room for the escape of the air displaced by the water. +</p> + +<p> +The best form of filling cap has a self-seating ground plug, which, if properly +made, is steam-tight without any packing. If needed, asbestos packing can +easily be inserted between plug and cap. +</p> + +<p> +Mud-holes.—All but the smallest boilers should have a mud-hole and plug +in the bottom at a point not directly exposed to the furnace. In Fig. 82 it is +situated at the bottom of the barrel. In Figs. 86 and 87 there should be a +mud-hole in one end of each of the three drums, A, B, and C. The plug may be +bored at the centre for a blow-off cock, through which the boiler should be +emptied after use, while steam is up, and after the fire has been +“drawn.” Emptying in this way is much quicker than when there is no +pressure, and it assists to keep the boiler free from sediment. +</p> + +<p> +[Illustration: FIG. 92.—Steam cock.] +</p> + +<p> +Steam Cocks.-The screw-down type (Fig. 92) is very preferable to the +“plug” type, which is apt to leak and stick. +</p> + +<p> +Testing Boilers.—The tightness of the joints of a boiler is best tested +in the first instance by means of compressed air. Solder on an all-metal cycle +valve, “inflate” the boiler to a considerable pressure, and +submerge it in a tub of water. The slightest leak will be betrayed by a string +of bubbles coming directly from the point of leakage. Mark any leaks by plain +scratches, solder them up, and test again. +</p> + +<p> +[Illustration: FIG. 94.—Benzoline lamp for model central-flue boiler.] +</p> + +<p> +The boiler should then be quite filled with cold water, and heated gradually +until the pressure gauge has risen to over the working pressure. There is no +risk of an explosion, as the volume of the water is increased but slightly. +</p> + +<p> +The third test is the most important and most risky of all-namely, that +conducted under steam to a pressure well above the working pressure. +</p> + +<p> +In order to carry out the test without risk, one needs to be able to watch the +steam-gauge from a considerable distance, and to have the fire under control. +My own method is to set the boiler out in the open, screw down the safety-valve +so that it cannot lift, and raise steam with the help of a blow-lamp, to which +a string is attached wherewith to pull it backwards along a board. If the +boiler is to be worked at 50 lbs., I watch the steam gauge through a telescope +until 100 lbs. is recorded, then draw the lamp away. After passing the test, +the boiler, when pressure has fallen, say, 20 lbs., may safely be inspected at +close quarters for leaks. +</p> + +<p> +This test is the only quite satisfactory one, as it includes the influence of +high temperature, which has effects on the metal not shown by +“cold” tests, such as the hydraulic. +</p> + +<p> +Do not increase your working pressure without first re-testing the boiler to +double the new pressure to be used. +</p> + +<p> +Fuels.—For very small stationary boilers the methylated spirit lamp is +best suited, as it is smell-less, and safe if the reservoir be kept well apart +from the burner and the supply is controllable by a tap or valve. (See Fig. +104.) +</p> + +<p> +[Illustration: FIG. 95.-Paraffin burner for vertical boiler.] +</p> + +<p> +For medium-sized model boilers, and for small launch boilers, benzoline or +petrol blow-lamps and paraffin stoves have become very popular, as they do away +with stoking, and the amount of heat is easily regulated by governing the fuel +supply. Fig. 94 is a sketch of a blow-lamp suitable for the horizontal boiler +shown on pp. 204, and 206, while Fig. 95 shows a convenient form of paraffin +stove with silent “Primus” burner, which may be used for a +horizontal with considerable furnace space or for vertical boilers. In the case +of all these liquid fuel consumers, the amount of heat developed can be +increased by augmenting the number of burners. Where a gas supply is available +its use is to be recommended for small stationary boilers. +</p> + +<p> +Solid Fuels.—The chief disadvantages attaching to these are smoke and +fumes; but as a solid fuel gives better results than liquid in a large furnace, +it is preferred under certain conditions, one of them being that steam is not +raised in a living room. Charcoal, coke, anthracite coal, and ordinary coal +partly burned are the fuels to use, the fire being started with a liberal +supply of embers from an open fire. Every solid-fuel boiler should have a +steam-blower in the chimney for drawing up the fire; and if a really fierce +blaze is aimed at, the exhaust from the engine should be utilized for the same +purpose. +</p> + +</div><!--end chapter--> + +<div class="chapter"> + +<h2><a name="chap19"></a>XIX.<br /> +QUICK BOILING KETTLES.</h2> + +<p> +[Transcriber’s note: Do not use lead solder on articles associated with +human or animal consumption.] +</p> + +<p> +The principles of increasing the area of heating surface in model boilers may +be applied very practically to the common kettle. The quick-boiling kettle is +useful for camping out, for heating the morning tea water of the very early +riser, and for the study “brew,” which sometimes has to be made in +a hurry; and, on occasion, it will be so welcome in the kitchen as to +constitute a very useful present to the mistress of the house. +</p> + +<p> +As the putting in of the tubes entails some trouble, it is worth while to +select a good kettle for treatment. Get one that is made of thick tinned sheet +iron (cast-iron articles are unsuitable), or even of copper, if you are intent +on making a handsome gift which will last indefinitely. The broad shallow +kettle is best suited for tubing, as it naturally has a fair heating surface, +and its bottom area gives room for inserting plenty of tubes. Also, the tubes +can be of good length. Let us, therefore, assume that the kettle will be of at +least 8 inches diameter. +</p> + +<p> +In Figs. 96 (a) and 96 (b) are shown two forms of fire-tube kettles (a and b) +and two of water-tube (c and d). For use over a spirit or Swedish petroleum +stove the first two types are most convenient; the third will work well on a +stove or an open fire; and the last proves very efficient on an open fire. One +may take it that, as a general rule, areas of heating surface being equal, the +water-tube kettle will boil more quickly than the fire-tube. +</p> + +<p> +Fire-tube Kettles. +</p> + +<p> +The tubing of Figs. 96 (a) and 96 (b) presents a little difficulty in each +case. The straight tube is the more difficult to insert, owing to the +elliptical shape of the ends; whereas the bent tube requires only circular +holes, but must be shaped on a template. +</p> + +<p> +The tubing used for (a) should have at least 5/8-inch internal diameter, for +(b) 1/2 inch, and be of thin copper. Hot gases will not pass willingly through +tubes much smaller than this, in the absence of induced or forced draught. +</p> + +<p> +For convenience in fitting, the tubes should run at an angle of 45 degrees to +the bottom and side of the kettle, as this gives the same bevel at each end. +Find the centre of the bottom, and through it scratch plainly four diameters 45 +degrees apart. From their ends draw perpendiculars up the side of the kettle. +</p> + +<p> +[Illustration: FIG. 96 (a).] +</p> + +<p> +Now draw on a piece of paper a section of the kettle, and from what is selected +as a convenient water-level run a line obliquely, at an angle of 45 degrees, +from the side to the bottom. Measuring off from this diagram, you can establish +the points in the side and bottom at which the upper and longer side of the +tubes should emerge. Mark these off. +</p> + +<p> +Next bevel off a piece of tubing to an angle of 45 degrees, cutting off roughly +in the first instance and finishing up carefully with a file till the angle is +exact. Solder to the end a piece of tin, and cut and file this to the precise +shape of the elliptical end. Detach by heating, scribe a line along its longest +axis, and attach it by a small countersunk screw to the end of a convenient +handle. +</p> + +<p> +Place this template in turn on each of the eight radii, its long axis in line +with it, being careful that the plate is brought up to the marks mentioned +above, and is on the bottom corner side of it. Scratch round plainly with a +fine steel point. +</p> + +<p> +To remove the metal for a tube hole, it is necessary to drill a succession of +almost contiguous holes as near the scratch as possible without actually +cutting it. When the ring is completed, join the holes with a cold chisel held +obliquely. Then file carefully with a round file, just not cutting the scratch. +As the side of the hole nearest to the bottom corner should run obliquely to +enable the tube to pass, work this out with the file held at an angle. +</p> + +<p> +As soon as a pair of holes (one in the bottom, the other in the side) have been +made, true up the side hole until a piece of tubing will run through it at the +correct angle. Then bevel off the end to 45 degrees and pass the tube through +again, bringing the bevel up against the bottom hole from the inside. If it is +a trifle difficult to pass, bevel off the edge slightly on the inside to make a +fairly easy driving fit. (Take care not to bulge the bottom of the kettle.) +Mark off the tube beyond the side hole, allowing an eighth of an inch extra. +Cut at the mark, and number tube and hole, so that they may be paired correctly +later on. +</p> + +<p> +When all the tubes are fitted, “tin” the ends with a wash of solder +before returning them to their holes. If there is a gap at any point wide +enough to let the solder run through, either beat out the tube from the inside +into contact, or, if this is impracticable, place a bit of brass wire in the +gap. Use powdered resin by preference as flux for an iron kettle, as it does +not cause the rusting produced by spirit of salt. If the latter is used, wipe +over the solder with a strong ammonia or soda solution, in order to neutralize +the acid. +</p> + +<p> +As the hot gases may tend to escape too quickly through large tubes, it is well +to insert in the upper end of each a small “stop,” x—a circle +of tin with an arc cut away on the bottom side. To encourage the gases to pass +up the tubes instead of along the bottom, a ring of metal, y, may be soldered +beyond the bottom holes, if an oil or spirit stove is to be used. This ring +should have notches cut along the kettle edge, so as not to throttle the flame +too much. +</p> + +<p> +[Illustration: FIG. 96—(b), (c), and (d).] +</p> + +<p> +As the tubes for these require bending to shape in each case, the three types +may be grouped together. The tubes of c and d, which require bending to +somewhat sharp curves, may be of 3/8-inch internal diameter. In the last two +cases the direction of the water travel is shown. The up-flow end, which +projects farther through the bottom than the down-flow, is nearer the centre, +where, if a gas stove is used, the heat is more intense than at the +circumference of the bottom. (Note.-If type c is for use on a three-support +stove, increase the number of tubes to 9, equally spaced, 40 degrees apart, so +that the kettle may be adjusted easily.) +</p> + +<p> +The copper tubing should be annealed or softened by heating to a dull red and +plunging in cold water. Cut a wooden template of the exact outline of the +inside line of the shape that the tube is to assume, and secure this firmly to +a board. Fill the tube with melted resin, to prevent, as much as possible, +“buckling” or flattening on the curves. The tube must be kept up to +the template by a stop of hard wood, at the end at which bending commences. +Don’t cut the tube into lengths before bending, as short pieces are more +difficult to handle. When a piece sufficient for a tube has been bent, cut it +oft, and remove the resin by heating. +</p> + +<p> +The fitting of the tubes is an easy matter, as the holes are circular. Pair off +a tube with its holes and number it. A fluted reamer will be found invaluable +for enlarging them to the correct size. Tin all tubes at points where they are +to be attached to the kettle. +</p> + +<p> +In Fig. 96 (c) and (d) care should be taken to make all the tubes project the +same distance, so that the kettle may be level when resting on them. +</p> + +</div><!--end chapter--> + +<div class="chapter"> + +<h2><a name="chap20"></a>XX.<br /> +A HOT-AIR ENGINE.</h2> + +<p> +The pretty little toy about to be described is interesting as a practical +application to power-producing purposes of the force exerted by expanding air. +It is easy to make, and, for mere demonstration purposes, has an advantage over +a steam-engine of the same size in that it can be set working in less than a +minute, and will continue to act as long as a small spirit flame is kept +burning beneath it; it cannot explode; and its construction is a simpler matter +than the building of a steam-engine. +</p> + +<p> +[Illustration: FIG. 97.—Vertical section of hot-air engine.] +</p> + +<p> +Principles of the Hot-air Engine.—Fig. 97 gives a sectional view of the +engine. The place of what would be the boiler in a steam-engine of similar +shape is taken by an air chamber immediately above the lamp, and above that is +a chamber through which cold water circulates. In what we will call the heating +chamber a large piston, known as the displacer, is moved up and down by a rod D +and a connecting rod CR1. This piston does not touch the sides of the chamber, +so that the bulk of the air is pushed past it from one end of the chamber to +the other as the piston moves. When the displacer is in the position +shown—at the top of its stroke—the air is heated by contact with +the hot plate C, and expands, forcing up the piston of the power cylinder, seen +on the left of the engine. (The power crank and the displacer crank are, it +should be mentioned, set at right angles to one another.) During the second +half of the power stroke the displacer is moved downwards, causing some of the +air to pass round it into contact with the cold plate D. It immediately +contracts, and reduces the pressure on the power piston by the time that the +piston has finished its stroke. When the power piston has reached the middle of +its downward stroke, the displacer is at its lowest position, but is halfway up +again when the power piston is quite down. The air is once again displaced +downwards, and the cycle begins anew. The motive power is, therefore, provided +by the alternate heating and cooling of the same air. +</p> + +<p> +Construction.—The barrel and supports were made out of a single piece of +thin brass tubing, 2-7/16 inch internal diameter and 5-5/8 inch long. The +heating end was filed up true, the other cut and filed to the shape indicated +in Fig. 98 by dotted lines. The marking out was accomplished with the help of a +strip of paper exactly as wide as the length of the tube, and as long as the +tube’s circumference. This strip had a line ruled parallel to one of its +longer edges, and 2-1/2 inches from it, and was then folded twice, parallel to +a shorter edge. A design like the shaded part of Fig. 98 was drawn on an end +fold, and all the four folds cut through along this line with a pair of +scissors. When opened out, the paper appeared as in Fig. 98. +</p> + +<p> +[Illustration: FIG. 98.] +</p> + +<p> +We now—to pass into the present tense—wrap this pattern round the +tube and scratch along its edges. The metal is removed from the two hollows by +cutting out roughly with a hack saw and finishing up to the lines with a file. +</p> + +<p> +The next things to take in hand are the displacer rod D and the guide tube in +which it works. These must make so good a fit that when slightly lubricated +they shall prevent the passage of air between them and yet set up very little +friction. If you cannot find a piece of steel rod and brass tubing which fit +close enough naturally, the only alternative is to rub down a rod, slightly too +big to start with, until it will just move freely in the tube. This is a +somewhat tedious business, but emery cloth will do it. The rod should be 3-3/8 +inches, the tube 2-1/8 inches, long. I used rod 3/16 inch in diameter; but a +smaller rod would do equally well. +</p> + +<p> +[Illustration: FIG. 99.] +</p> + +<p> +The two plates, A and B, are next prepared by filing or turning down thin +brass[1] discs to a tight fit. (Note.—For turning down, the disc should +be soldered centrally to a piece of accurately square brass rod, which can be +gripped in a chuck. I used a specially-made holder like that shown in Fig. 99 +for this purpose.) +</p> + +<p> +[Footnote 1: Thin iron plate has the disadvantage of soon corroding.] +</p> + +<p> +When a good fit has been obtained, solder the two discs together so that they +coincide exactly, and bore a central hole to fit the guide tube tightly. Before +separating the plates make matching marks, so that the same parts may lie in +the same direction when they are put in position. This will ensure the guide +tube being parallel to the barrel. +</p> + +<p> +The power cylinder is a piece of brass tubing 2 inches long and of 7/8-inch +internal diameter. The piston is of 7/8-inch tubing, fitting the cylinder +easily, and thick enough to allow a shallow packing recess to be turned in the +outside. Brass washers turned or filed to size form the ends of cylinder and +piston. The connecting rod CR2 is a piece of strip brass, 3-3/16 inches long, +between centres of holes. This had better be cut off a bit long in the first +instance, and be fitted to the little stirrup which attaches its lower end to +the piston. The drilling of the crank pinhole should be deferred till the +cylinder and crank are in position. +</p> + +<p> +[Illustration: FIG. 100.—Exterior view of hot air engine.] +</p> + +<p> +Putting in the Water-chamber Discs.—Clean the inside of the barrel +thoroughly with sandpaper; also discs A and B round the edges and the central +holes. Disc A is forced in from the crank end a little further down than it is +to be finally, and then driven up from below until at all points its lower side +is exactly three inches from the bottom edge of the barrel. Disc B is then +forced up 1-1/2 inches from the bottom end. The guide tube— which should +have been cleaned—having been driven into place, solder is run all round +the joints. If the barrel is heated over a spirit lamp, this operation is +performed very quickly. (“Tinol” soldering paste is recommended.) +Before soldering in B, drill a small hole in the barrel between A and B to +allow the air to escape. +</p> + +<p> +Attaching the Cylinder.—Scratch a bold line through the centre of one of +the crank holes to the bottom of the barrel, to act as guide. Drill a 5/32-inch +hole in the barrel on this line just below plate B, and a similar hole in the +bottom of the cylinder. (The cylinder end should be put in position temporarily +while this is done to prevent distortion.) Flatten down the cylinder slightly +on the line of the hole, so that it may lie snugly against the barrel, and +clean the outside of the barrel. Lay the cylinder against the barrel with the +holes opposite one another, and push a short piece of wood through to exclude +solder from the holes and keep the holes in line. Half a dozen turns of fine +wire strained tightly round cylinder and barrel will hold the cylinder in place +while soldering is done with a bit or lamp. The end of the cylinder should then +be made fast. +</p> + +<p> +The Displacer.—This is a circular block of wood—well dried before +turning—5/8 inch thick and 3/32 inch less in diameter than the inside of +the barrel. The rod hole in it should be bored as truly central as possible. A +hole is drilled edgeways through the block and through the rod to take a pin to +hold the two together. To prevent it splitting with the heat, make a couple of +grooves in the sides to accommodate a few turns of fine copper wire, the +twisted ends of which should be beaten down flush with the outside of the +block. The bottom of the block is protected by a disc of asbestos card held up +to the wood by a disc of tin nailed on. +</p> + +<p> +The Crank Shaft and Crank.—The central crank of the crank +shaft—that for the displacer—has a “throw” of 1/4 inch, +as the full travel of the displacer is 1/2 inch. If the bending of a rod to the +proper shape is beyond the reader’s capacity, he may build up a crank in +the manner shown in Fig. 101. Holes for the shaft are bored near the tops of +the supports, and the shaft is put in place. After this has been done, smoke +the shaft in a candle flame and solder two small bits of tubing, or bored +pieces of brass, to the outside of the supports to increase the length of the +bearing. The power-crank boss is a 1-1/2-inch brass disc. This crank has a +“throw” of 1/2 inch. +</p> + +<p> +[Illustration: FIG. 101.-Details of built-up crank.] +</p> + +<p> +Connecting Rods.—Put a piece of card 1/16 inch thick in the bottom of the +cylinder and push the piston home. Turn the power crank down and mark off the +centre of the hole for the crank pin in the connecting rod CR2. Solder a piece +of strip brass on each side of the rod at this point; measure again, and drill. +</p> + +<p> +The top of the displacer rod D is now filed flat on two sides and drilled. Slip +a ring 1/16 inch thick over the rod and push the rod upwards through the guide +tube till the displacer can go no farther. Turn the displacer crank up and +measure from the centre of the hole in the rod to the centre of the crank. The +top of the connecting rod should be filed to fit the under side of the crank, +against which it should be held by a little horseshoe-shaped strap pinned on. +(Fig. 102). (Be sure to remove the ring after it has served its purpose.) +</p> + +<p> +The Water Circulation.—The water chamber is connected by two rubber tubes +with an external tank. In Fig. 97 the cooling water tank is shown, for +illustrative purposes, on the fly-wheel side of the engine, but can be placed +more conveniently behind the engine, as it were. Two short nozzles, E1 and E2, +of 1/4-inch tube are soldered into the water chamber near the top and bottom +for the rubber pipes to be slipped over, and two more on the water tank. For +the tank one may select a discarded 1 lb. carbide tin. Cut off the top and +solder on a ring of brass wire; make all the joints water-tight with solder, +and give the tin a couple of coatings of paint inside and outside. +</p> + +<p> +[Illustration: FIG. 102.] +</p> + +<p> +Closing the Hot-air Chamber.—When all the parts except the lamp chamber +have been prepared, assemble them to make sure that everything is in order. The +lower end of the hot-air chamber has then to be made air-tight. Soldering is +obviously useless here, as the heat of the lamp would soon cause the solder to +run, and it is impossible to make a brazed joint without unsoldering the joints +in the upper parts of the engine. I was a bit puzzled over the problem, and +solved it by means of the lower part of an old tooth-powder box stamped out of +a single piece of tin. This made a tight fit on the outside of the barrel, and +as it was nearly an inch deep, I expected that if it were driven home on the +barrel and soldered to it the joint would be too near the water chamber to be +affected by the lamp. This has proved to be the case, even when the water is +nearly at boiling point. If a very close-fitting box is not procurable, the +space between box and barrel must be filled in with a strip of tin cut off to +the correct length. +</p> + +<p> +The Lamp Chamber.—Cut out a strip of tin 4 inches wide and 1 inch longer +than the circumference of the lower end of the hot-air chamber. Scratch a line +1/2 inch from one of the sides, a line 3/4 inch from the other, and a line 1/2 +inch from each of the ends. +</p> + +<p> +A lamp hole is cut in the centre, and ventilation holes 1 inch apart, as shown +in Fig. 103. If the latter holes are made square or triangular (base +uppermost), and the metal is cut with a cold chisel so as to leave the side +nearest the edge unsevered, the parts may be turned up to form supports for the +barrel. +</p> + +<p> +[Illustration: FIG. 103.—Plate for lamp chamber cut out ready for +bending.] +</p> + +<p> +The slit lower side of the plate is splayed out into a series of +“feet,” by three or more of which, the chamber is secured to the +base. Bend the plate round the barrel and put the two screws and bolts which +hold the ends in place, and tighten them until the barrel is gripped firmly. +Screw the engine to its base, fit on the rubber water connections, and fasten +down the tank by a screw through the centre of the bottom. The screw should +pass through a brass washer, between which and the tank should be interposed a +rubber washer to make a water-tight joint. +</p> + +<p> +The Lamp.—The lamp shown in Fig. 104 was made out of a truncated brass +elbow, a piece of 5/16-inch brass tube, and a round tin box holding about +1/3-pint of methylated spirit. A tap interposed between the reservoir and +burner assists regulation of the flame, and prevents leakage when the lamp is +not in use. +</p> + +<p> +Running the Engine.—The power and displacer cranks must be set exactly at +right angles to one another, and the first be secured by soldering or otherwise +to the crank shaft. The fly wheel will revolve in that direction in which the +displacer crank is 90 degrees ahead of the other. +</p> + +<p> +[Illustration: FIG. l04.-Spirit lamp for hot-air engine, with regulating tap.] +</p> + +<p> +The packing of the piston should be sufficiently tight to prevent leakage of +air, but not to cause undue friction. When the packing has settled into place, +an occasional drop of oil in the cylinder and guide tube will assist to make +the piston and slide air-tight. +</p> + +<p> +The engine begins to work a quarter of a minute or so after the lamp is lit, +and increases its speed up to a certain point, say 300 revolutions per minute. +When the water becomes very hot it may be changed. The power might be applied, +through demultiplying gear, to a small pump drawing water from the bottom of +the tank and forcing it through the water chamber and a bent-over stand pipe +into the tank again. This will help to keep the water cool, and will add to the +interest of the exhibit by showing “work being done.” +</p> + +</div><!--end chapter--> + +<div class="chapter"> + +<h2><a name="chap21"></a>XXI.<br /> +A WATER MOTOR.</h2> + +<p> +FIG. 105 is a perspective view of a simple water motor which costs little to +make, and can be constructed by anybody able to use carpenter’s tools and +a soldering iron. It will serve to drive a very small dynamo, or do other work +for which power on a small scale is required. A water supply giving a pressure +of 40 lbs. upwards per square inch must be available. +</p> + +<p> +We begin operations by fashioning the case, which consists of three main parts, +the centre and two sides, held together by brass screws. For the centre, select +a piece of oak 1 inch thick. Mark off a square, 7 inches on the side; find the +centre of this, and describe a circle 5 inches in diameter. A bulge is given to +the circle towards one corner of the square, at which the waste-pipe will be +situated. +</p> + +<p> +Cut out along the line with a keyhole saw. Then saw out the square of wood. A +5/8-inch hole is now bored edgeways through the wood into the +“bulge” for the escape, and in what will be the top edge is drilled +a 1/4-inch hole to allow air to enter. +</p> + +<p> +[Illustration: FIG. l05.—Simple water turbine.] +</p> + +<p> +Cut out the sides, and screw them on to the centre at the four corners, taking +care that the grain runs the same way in all three pieces, so that they may all +expand or contract in the same direction. Plane off the edges of the sides +flush with the centre. +</p> + +<p> +The parts should now be separated, after being marked so that they can be +reassembled correctly, and laid for a quarter of an hour in a pan of melted +paraffin wax, or, failing this, of vaseline, until the wood is thoroughly +impregnated. Reassemble the parts, and put in the rest of the holding screws, +which should have their heads countersunk flush with the wood. +</p> + +<p> +[Illustration: FIG. 106.—Water turbine, with pulley side of casing +removed.] +</p> + +<p> +For the shaft select a piece of steel rod 5/32 inch in diameter, and 3 or 4 +inches long; for the bearings use two pieces, 3/4 inch long each, of +close-fitting brass tube. Now take a drill, very slightly smaller in diameter +than the bearings, and run holes right through the centres of, and square to, +the sides. Both holes should be drilled at one operation, so that they may be +in line. +</p> + +<p> +With a wooden mallet drive the bearings, which should be tapered slightly at +the entering end, through the sides. Push the shaft through them. If it refuses +to pass, or, if passed, turns very unwillingly, the bearings must be out of +line; in which case the following operation will put things right. Remove the +bearing on the pulley side, and enlarge the hole slightly. Then bore a hole in +the centre of a metal disc, 1 inch in diameter, to fit the bearing; and drill +three holes for screws to hold the disc against the case. Rub disc and bearing +bright all over. +</p> + +<p> +Replace the bearing in its hole, slip the disc over it, and push the shaft +through both bearings. Move the disc about until the shaft turns easily, mark +the screw holes, and insert the screws. Finally, solder the bearing to the disc +while the shaft is still in place. +</p> + +<p> +The wheel is a flat brass disc 4 inches in diameter. Polish this, and scratch +on one side twelve equally spaced radii. At the end of each radius a small cup, +made by bending a piece of strip brass 1/4 inch wide and 1/2 inch long into an +arc of a circle, is soldered with its extremities on the scratch. A little +“Tinol” soldering lamp (price 1s. 6d.) comes in very handy here. +</p> + +<p> +To fix the wheel of the shaft requires the use of a third small piece of +tubing, which should be turned off quite square at both ends. Slip this and the +wheel on the shaft, and make a good, firm, soldered joint. Note.— Consult +Fig. 107 for a general idea of the position of the wheel, which must be kept +just clear of the case by the near bearing. +</p> + +<p> +[Illustration: FIG. 107.—Plan of water turbine, showing arrangement of +nozzle.] +</p> + +<p> +The nozzle should be a straight, tapered tube of some kind—the nose of a +large oil can will serve the purpose. The exit must be small enough to allow +the water to leave it at high velocity; if too large, the efficiency of the +wheel will be diminished. To the rear end of the nozzle should be soldered a +piece of brass tubing, which will make a tight fit with the hose pipe leading +from the water supply. A few small brass rings soldered round this piece will +prevent the hose blowing off if well wired on the outside. +</p> + +<p> +Now comes the boring of the hole for the nozzle. Fig. 106 shows the line it +should take horizontally, so that the water shall strike the uppermost bucket +just below the centre; while Fig. 107 indicates the obliquity needed to make +the stream miss the intervening bucket. A tapered broach should be used to +enlarge the hole gradually till the nozzle projects sufficiently. If the line +is not quite correct, the tip should be bent carefully in the direction +required. One must avoid distorting the orifice, which should be perfectly +circular; clean it out with a small twist drill of the proper size. +</p> + +<p> +A brass elbow, which may be purchased for a few pence, should be driven into +the waste hole, and a small shield be nailed under the air hole. A couple of +screwed-on cross pieces are required to steady the motor sideways and raise the +elbow clear of the ground. +</p> + +<p> +The motor may be geared direct to a very small dynamo, if the latter is +designed to run at high speeds. If a geared-down drive is needed, a small +pulley—such as is used for blinds, and may be bought for a +penny—should be attached to the shaft, and a bootlace be employed as +belt. Avoid overloading the wheel, for if it is unable to run at a high speed +it will prove inefficient. +</p> + +<p> +[Illustration: FIG. l08.-Water motor working a photographic dish-rocker.] +</p> + +<p> +Lubrication.—The water will keep the bearings cool, but the bearings +should be well lubricated. The most convenient method of effecting this is to +bore holes in the bearings, and from them run small pipes to an oil reservoir +on the top of the case (as in Fig. 70), where they are fed on the siphon +principle through strands of worsted. +</p> + +<p> +Alternative Construction.—If an all-metal case is preferred, the reader +might utilize the description given of a steam turbine on pp. 170-178. The +details there given will apply to water as well as steam, the one exception +being that a nozzle of the kind described above must be substituted for the +steam pipe and small ports. +</p> + +</div><!--end chapter--> + +<div class="chapter"> + +<h2><a name="chap22"></a>XXII.<br /> +MODEL PUMPS.</h2> + +<p> +Every steam boiler which has to run for long periods and evaporate considerable +quantities of water should be in connection with a pump capable of forcing +water in against the highest pressure used. On a previous page (p. 158) we have +described a force pump driven directly off the crank shaft of an engine. As the +action of this is dependent on the running of the engine, it is advisable, in +cases where the boiler may have to work an engine not provided with a pump of +its own, to install an independent auxiliary pump operated by hand or by steam, +and of considerable capacity, so that in an emergency water may be supplied +quickly. +</p> + +<p> +[Illustration: FIG. l09.-Vertical section of force pump.] +</p> + +<p> +Making a Hand pump.—Fig. 109 shows the details of a hand pump which is +easy to make. The barrel is a length of brass tubing; the plunger a piece of +brass or preferably gun-metal rod, which fits the tube closely, but works +easily in it. The gland at the top of the barrel, E, is composed of a piece, D, +of the same tubing as the barrel, sliding in a collar, C, soldered to E. The +bottom of D and top of E are bevelled to force the packing against the plunger. +The plates A and B, soldered to D and C respectively, are drawn together by +three or more screws. A brass door-knob makes a convenient top for the plunger. +When the knob touches A, the bottom of the plunger must not come lower than the +top of the delivery pipe, lest the water flow should be impeded and the valve, +V, injured. Round off the end of the plunger, so that it may be replaced easily +and without disarranging the packing if pulled out of the pump. +</p> + +<p> +The valves are gun-metal balls, for which seats have been prepared by hammering +in steel cycle balls of the same size. Be careful to select balls considerably +larger than the bore of the pipes on which they rest, to avoid all possibility +of jamming. An eighth of an inch or so above the ball, cross wires should be +soldered in to prevent the ball rising too far from its seat. +</p> + +<p> +[Illustration: FIG. 110.] +</p> + +<p> +A convenient mounting for a hand pump is shown in Fig. 110. The plate, F, of +the pump is screwed to a wooden base resting on a framework of bent sheet zinc, +which is attached to the bottom of a zinc water tray. The delivery pipe, G, +will be protected against undue strains if secured by a strap to the side of +the wooden base. +</p> + +<p> +The same pump is easily adapted to be worked by a lever, which makes the work +of pumping easier. Fig. 111 gives details of the top of the plunger and the +links, B. A slot must be cut in the plunger for the lever, A, to pass through, +and the sides bored for a pivot pin. The links are straddled (see sketch of end +view) to prevent the back end of the lever wobbling from side to side. +</p> + +<p> +[Illustration: FIG. 111.—Details of lever for force pump.] +</p> + +<p> +A Steam Pump.—The pump illustrated in Fig. 112 belongs to what is +probably the simplest self-contained type, as no fly wheel, crank, or eccentric +is needed for operating the valve. +</p> + +<p> +The steam cylinder and the pump are set in line with one another (in the case +shown, horizontally), and half as far apart again as the stroke of the +cylinder. The plunger is either a continuation of the piston rod, or attached +to it. +</p> + +<p> +[Illustration: FIG. 112—View of steam pump, showing details.] +</p> + +<p> +An arm, S, fixed at right angles to the piston rod, has a forked end which +moves along the rod. This rod is connected with the slide valve through the +rocking arm, R1 and the rod, R2. On it are two adjustable stops, T1 T2, which S +strikes alternately towards the end of a stroke, causing the valve to shift +over and expose the other side of the piston to steam pressure. The absence of +the momentum of a fly wheel makes it necessary for the thrust exerted by the +piston to be considerably greater than the back pressure of the water, so that +the moving parts may work with a velocity sufficient to open the valve. If the +speed falls below a certain limit, the valve opens only part way, the speed +falls, and at the end of the next stroke the valve is not shifted at all. +</p> + +<p> +The diameter of the plunger must be decided by the pressure against which it +will have to work. For boiler feeding it should not exceed one-third that of +the piston; and in such case the piston rod and plunger may well be one. +</p> + +<p> +A piston valve, being moved more easily than a box valve, is better suited for +a pump of this kind, as friction should be reduced as much as possible. +</p> + +<h4>CONSTRUCTION.</h4> + +<p> +The cylinder will not be described in detail, as hints on making a slide-valve +cylinder have been given on earlier pages. The piston rod should be three times +as long as the stroke of the cylinder, if it is to serve as pump plunger; and +near the pump end an annular groove must be sunk to take a packing. +</p> + +<p> +The pump, if designed to work horizontally, will have the valves arranged like +the pump illustrated in Fig. 65; if vertically, like the pump shown in Fig. +109. Both suction and delivery pipes should be of ample size, as the pump works +very fast. The pump is mounted on a foot, F, made by turning up the ends of a +piece of brass strip, and filing them to fit the barrel. +</p> + +<p> +The bed can be fashioned out of stout sheet brass or zinc. Let it be of ample +size to start with, and do not cut it down until the pump is complete. Rule a +centre line for cylinder and pump, and mount the cylinder. Pull out the piston +rod plunger as far as it will go, and slip the pump barrel on it. The foot of +the pump must then be brought to the correct height by filing and spreading the +ends until the plunger works quite easily in the pump, when this is pressed +down firmly against the bed. When adjustment is satisfactory, mark the position +of the foot on the bed, solder foot to barrel, and drill and tap the foot for +the holding-down screws. Don’t forget that the distance between pump and +cylinder gland must be at least 1-1/3 times the stroke. +</p> + +<p> +The valve motion can then be taken in hand. Cut off for the guides, G1 G2, two +pieces of stout brass strip, 2-1/2 inches long and 3/4 inch wide. Lay them +together in a vice, and bore the holes (Fig. 113) 1-1/4 inches apart, centre to +centre, for the 1/8-inch rods, R1 R2. The feet are then turned over and a third +hole bored in G1, midway between those previously made, to take the end of the +support, PP, of the rocking lever. +</p> + +<p> +[Illustration: FIG. 113.—End view of striking mechanism of steam pump.] +</p> + +<p> +Screw G1 G2 down to the bedplate, 3/4 inch away from the cylinder centre line. +G1 is abreast of the mouth of the pump, G2 about half an inch forward of the +end of the cylinder. +</p> + +<p> +The striker, S, is a piece of brass strip soldered to 1/2 inch of tubing +fitting the piston rod. (See Fig. 113.) Its length is decided by running a rod +through the upper holes in G1 G2, allowance being made for the notch in the +end. The collar is tapped for two screws, which prevent S slipping on the +piston rod. The rods for R1 R2 are now provided with forks, made by cutting and +filing notches in bits of brass tubing. The notches should be half as deep +again as the rocking lever is wide, to give plenty of room for movement. Solder +the forks to the rods, and put the rods in place in the guides, with the forks +as far away from G1 as the travel of the slide valve. Then measure to get the +length of the rocking lever support. One end of this should be filed or turned +down to fit the hole drilled for it; the other should be slotted to fit the +lever accurately. +</p> + +<p> +The rocking lever, RL, which should be of steel, is slotted at each end to +slide on the pins in the forks, and bored for the pivot pin, which, like those +in the forks, should be of hardened steel wire. Assemble the rocking lever in +its support and the rod forks, and solder on the support. +</p> + +<p> +To the back end of R2 solder a steel plate, A, which must be bored for the pin +in the valve fork, after the correct position has been ascertained by careful +measurement. +</p> + +<p> +The stops, T1 T2, are small, adjustable collars, kept tightly in place on<br /> +R1 by screws.<br /> +</p> + +<p> +Setting the Striker.—Assemble all the parts. Pull out the piston rod as +far as it will go, and push the slide valve right back. Loosen the striker and +the forward stop, and slide them along in contact until the striker is close to +the pump. Tighten up their screws. Then push the piston rod fully in, draw the +valve rod fully out, and bring the rear stop up against the striker, and make +it fast. Each stop may now be moved 1/16 inch nearer to a point halfway between +them to cause “cushioning” of the piston, by admitting steam before +the stroke is quite finished. +</p> + +<p> +A pump made by the author on this principle, having a 1-1/4 inch stroke and a +1/2-inch bore, will deliver water at the rate of half a gallon per minute +against a head of a few feet. +</p> + +<p> +Note.—To steady the flow and prevent “water hammer,” a small +air-chamber should be attached to the delivery pipe. +</p> + +<p> +An Alternative Arrangement.—If the reader prefers a steam pump which will +work at slow speeds, and be available, when not pumping, for driving purposes, +the design may be modified as shown diagrammatically in Fig. 114. The striker +becomes a cross head, and is connected by a forked rod passing on each side of +the pump with the crank of a fly wheel overhanging the base. The valve is +operated in the ordinary manner by an eccentric on the crankshaft. The +steadying effect of the fly wheel and the positive action of the valve make it +possible to use a larger pump plunger than is advisable with the striking gear. +With a pump piston of considerably greater diameter than the piston rod, the +pump may be made double-acting, a gland being fitted at the front end for the +piston rod to work through, and, of course, a second set of valves added. +</p> + +<p> +[Illustration: Fig. 114.—Plan of steam pump with fly wheel.] +</p> + +<h4>A SUGGESTION.</h4> + +<p> +For exhibition purposes a small, easily running, double-action pump might be +worked by the spindle of a gramophone. A crank of the proper throw and a +connecting rod must be provided. Both delivery pipes feed, through an +air-chamber, a fountain in the centre of a bowl, the water returning through an +overflow to the source of supply, so that the same water may be used over and +over again. +</p> + +</div><!--end chapter--> + +<div class="chapter"> + +<h2><a name="chap23"></a>XXIII.<br /> +KITES.</h2> + +<p> +Plain Rectangular Box Kites.—The plain box kite is easy to make and a +good flier. Readers should try their hands on it before attempting more +complicated models. +</p> + +<p> +Lifting pressure is exerted only on the sides facing the wind, but the other +sides have their use in steadying the kite laterally, and in holding in the +wind, so that they justify their weight. +</p> + +<p> +Proportions of Box.—Each box has wind faces one and a third times as long +as the sides, and the vertical depth of the box is about the same as its fore +and aft dimensions. That is, the ends of the boxes are square, and the wind +faces oblong, with one-third as much area again as the ends. Little advantage +is to be gained from making the boxes proportionately deeper than this. The +distance between the boxes should be about equal to the depth of each box. +</p> + +<h4>CONSTRUCTION.</h4> + +<p> +After these general remarks, we may proceed to a practical description of +manufacture, which will apply to kites of all dimensions. It will be prudent to +begin on small models, as requiring small outlay. +</p> + +<p> +Having decided on the size of your kite, cut out two pieces of material as wide +as a box is to be deep, and as long as the circumference of the box plus an +inch and a half to spare. Machine stitch 5/8 inch tapes along each edge, using +two rows of stitching about 1/8 inch from the edges of the tape. Then double +the piece over, tapes inside, and machine stitch the ends together, three +quarters of an inch from the edge. Note.—All thread ends should be tied +together to prevent unravelling, and ends of stitching should be hand-sewn +through the tape, as the greatest strain falls on these points. +</p> + +<p> +The most convenient shape for the rods is square, as fitting the corners and +taking tacks most easily. The sectional size of the rods is governed by the +dimensions of the kite, and to a certain extent by the number of stretchers +used. If four stretchers are employed in each box, two near the top and two +near the bottom, the rods need not be so stout as in a case where only a single +pair of central stretchers is preferred. +</p> + +<p> +Lay the two boxes flat on the floor, in line with one another, and the joins at +the same end. Pass two rods through, and arrange the boxes so that the outer +edges are 1/2 inch from the ends of the rods. (These projections protect the +fabric when the kite strikes the ground). +</p> + +<p> +Lay the rods on one corner, so that the sides make an angle of 45 degrees with +the floor, pull the boxes taut—be careful that they are square to the +rods—and drive three or four tacks through each end of the box into the +rods. Then turn them over and tack the other sides similarly. Repeat the +process with the other rods after measuring to get the distances correct. +</p> + +<p> +The length of the stretchers is found approximately by a simple arithmetical +sum, being the square root of the sum of the squares of the lengths of two +adjacent sides of the box. For example, if each box is 20 by 15 inches, the +diagonal is the square root of (20 squared plus 15 squared) = square root of +625 = 25 inches. The space occupied by the vertical rods will about offset the +stretch of the material, but to be on the safe side and to allow for the +notches, add another half-inch for small kites and more proportionately for +large ones. It is advisable to test one pair of stretchers before cutting +another, to reduce the effect of miscalculations. +</p> + +<p> +The stretcher notches should be deep enough to grip the rods well and prevent +them twisting, and one must take care to have those on the same stretcher +exactly in line, otherwise one or other cannot possibly “bed” +properly. A square file is useful for shaping the notches. +</p> + +<p> +Ordinarily stretchers do not tend to fall out, as the wind pressure puts extra +strain on them and keeps them up tight. But to prevent definitely any movement +one may insert screw eyes into the rods near the points at which the stretchers +press on them, and other eyes near the ends of the stretchers to take string +fastenings. These attachments will be found useful for getting the first pair +of stretchers into position, and for preventing the stretchers getting lost +when the kite is rolled up. +</p> + +<p> +The bridle is attached to four eyes screwed into the rods near the tops of the +boxes. (See Fig. 118.) The top and bottom elements of the bridle must be paired +off to the correct length; the top being considerably shorter than the bottom. +All four parts may be attached to a brass ring, and all should be taut when the +ring is pulled on. The exact adjustment must be found by experiment. In a very +high wind it is advisable to shorten the top of the bridle if you have any +doubt as to the strength of your string, to flatten the angle made by the kite +with the wind. +</p> + +<p> +[Illustration: FIG. 115.—Details of stretcher attachment for +diamond-shaped box kites.] +</p> + +<p> +Diamond Box Kites.—In another type of box kite the boxes have four equal +sides, but the boxes are rhombus-shaped, as in Fig. 116, the long diagonal +being square to the wind, and the bridle attached at the front corner. +</p> + +<p> +For particulars of design and construction I am much indebted to Mr. W. H. +Dines, F.R.S., who has used the diamond box kite for his meteorological +experiments to carry registering meteorographs several thousands of feet into +the air. +</p> + +<p> +The longitudinal sticks used at the corners have the section shown in Fig. 115. +They are about four times as wide at the front edge, which presses against the +fabric, as at the back, and their depth is about twice the greater width. This +shape makes it easy to attach the shorter stretchers, which have their ends +notched and bound to prevent splitting. +</p> + +<p> +[Illustration: FIG. 116.—Plan of diamond box kite, showing arrangement of +stretchers.] +</p> + +<p> +Fig. 117 is a perspective diagram of a kite. The sail of each box measures from +top to bottom one-sixth the total circumference of the box, or, to express the +matter differently, each face of the box is half as long again as its depth. +The distance separating the boxes is equal to the depth of a box. +</p> + +<p> +The sides of a box make angles of 60 degrees and 120 degrees with one another, +the depth of the space enclosed from front to back being the same as the length +of a side. With these angles the effective area of the sails is about +six-sevenths of the total area. Therefore a kite of the dimensions given in +Fig. 117 will have an effective area of some thirty square feet. +</p> + +<p> +[Illustration: FIG. 117.—Diamond box kite in perspective. Ties are +indicated by fine dotted lines.] +</p> + +<p> +The long stretchers pass through holes in the fabric close to the sticks, and +are connected with the sticks by stout twine. Between stretcher and stick is +interposed a wedge-shaped piece of wood (A in Fig. 115), which prevents the +stick being drawn out of line. This method of attachment enables the boxes to +be kept tight should the fabric stretch at all—as generally happens after +some use; also it does away with the necessity for calculating the length of +the stretchers exactly. +</p> + +<p> +The stretchers are tied together at the crossing points to give support to the +longer of the pair. +</p> + +<p> +The dotted lines AB, AC, AD, EM, and EN in Fig. 117 indicate ties made with +wire or doubled and hemmed strips of the fabric used for the wings. AB, running +from the top of the front stick to the bottom of the back stick, should be of +such a length that, when the kite is stood on a level surface, the front and +back sticks make right angles with that surface, being two sides of a rectangle +whereof the other two sides are imaginary lines joining the tops and bottoms of +the sticks. This tie prevents the back of the kite drooping under pressure of +the wind, and increases the angle of flight. The other four ties prevent the +back sails turning over at the edges and spilling the wind, and also keep them +flatter. This method of support should be applied to the type of kite described +in the first section of this chapter. +</p> + +<p> +String Attachment.—A box kite will fly very well if the string is +attached to the top box only. The tail box is then free to tilt up and trim the +kite to varying pressures independently of the ascent of the kite as a whole. +When the bottom box also is connected to the string it is a somewhat risky +business sending a kite up in a high wind, as in the earlier part of the ascent +the kite is held by the double bridle fairly square to the wind. If any doubt +is entertained as to the ability of the string to stand the pressure, the +one-box attachment is preferable, though possibly it does not send the kite to +as great a height as might be attained under similar conditions by the two-box +bridle. +</p> + +<p> +[Illustration: FIG. 118.—Box kite with rear wings.] +</p> + +<p> +When one has to attach a string or wire to a large kite at a single point, the +ordinary method of using an eye screwed into the front stick is attended by +obvious risks. Mr. Dines employs for his kites (which measure up to nine feet +in height) an attachment which is independent of the front stick. Two sticks, +equal in length to the width of the sail, are tacked on to the inner side of +the sail close to the front stick. Rings are secured to the middle of the +sticks and connected by a loop of cord, to which the wire (in this case) used +for flying the kite is made fast. +</p> + +<p> +A Box Kite with Wings.—The type of kite shown in Fig. 118 is an excellent +flyer, very easy, to make and very portable. The two boxes give good +longitudinal stability, the sides of the boxes prevent quick lateral movements, +and the two wings projecting backwards from the rear corners afford the +“dihedral angle” effect which tends to keep the kite steadily +facing the wind. The “lift,” or vertical upward pull, obtained with +the type is high, and this, combined with its steadiness, makes the kite useful +for aerial photography, and, on a much larger scale, for man-lifting. +</p> + +<p> +The materials required for the comparatively small example with which the +reader may content himself in the first instance are: +</p> + +<p> +8 wooden rods or bamboos, 4 feet long and 1/2 inch in diameter. 4 yards of lawn +or other light, strong material, 30 inches wide. 12 yards of unbleached tape, +5/8 inch wide. 8 brass rings, 1 inch diameter. +</p> + +<p> +The Boxes.—Cut off 2 yards 8 inches of material quite squarely, fold down +the middle, crease, and cut along the crease. This gives two pieces 80 by 15 +inches. +</p> + +<p> +Double-stitch tape along the edges of each piece. +</p> + +<p> +Lay the ends of a piece together, tapes inside, and stitch them together half +an inch from the edge. Bring a rod up against the stitching on the inside, and +calculate where to run a second row of stitching parallel to the first, to form +a pocket into which the rod will slip easily but not loosely. (See Fig. 119, +a.) +</p> + +<p> +Remove the rod and stitch the row. +</p> + +<p> +Now repeat the process at the other end of the folded piece. The positions of +the other two rod pockets must be found by measuring off 15 inches from the +inner stitching of those already made. (Be careful to measure in the right +direction in each case, so that the short and long sides of the box shall be +opposite.) Fold the material beyond the 15-inch lines to allow for the pockets +and the 1/2-inch “spare,” and make the two rows of stitching. +</p> + +<p> +[Illustration: FIG. 119.—Plan of box kite with rear wings.] +</p> + +<p> +Repeat these operations with the second strip of material, and you will have +prepared your two boxes, each measuring, inside the pockets, 15 by about 20 +inches. (See Fig. 119.) Now cut out the wings in accordance with the dimensions +given in Fig. 120. Each is 47-1/2 inches long and 15 inches across at the +broadest point. It is advisable to cut a pattern out of brown paper, and to +mark off the material from this, so arranging the pattern that the long +47-1/2-inch side lies on a selvedge. [The edge of a fabric that is woven so +that it will not fray or ravel.] +</p> + +<p> +[Illustration: FIG. 120.—Wing for box kite.] +</p> + +<p> +Double stitch tapes along the three shorter sides of each wing, finishing off +the threads carefully. Then sew the wings to what will be the back corners of +the boxes when the kite is in the air—to the “spares” outside +the rod pockets of a long side. +</p> + +<p> +Take your needle and some strong thread, and make all corners at the ends of +pockets quite secure. This will prevent troublesome splitting when the kite is +pulling hard. +</p> + +<p> +Sew a brass ring to each of the four wing angles, AA, BB, at the back, and as +many on the front of the spares of the rod pockets diagonally opposite to those +to which the wings are attached, halfway up the boxes. These rings are to take +the two stretchers in each box. +</p> + +<p> +Slip four rods, after rounding off their ends slightly, through the pockets of +both boxes, and secure them by sewing the ends of the pockets and by the +insertion of a few small tacks. These rods will not need to be removed. +</p> + +<p> +The cutting and arrangement of the stretchers and the holes for the same +require some thought. Each stretcher lies behind its wing, passes in front of +the rod nearest to it, and behind that at the corner diagonally opposite. (See +Fig. 119.) The slits through which it is thrust should be strengthened with +patches to prevent ripping of the material. +</p> + +<p> +Two persons should hold a box out as squarely as possible while a stretcher is +measured. Cut a nick 3/8 inch deep in one end of the stretcher, and pass the +end through the fabric slits to the ring not on the wing. Pull the wing out, +holding it by its ring, and cut the stretcher off 1 inch from the nearest point +of the ring. The extra length will allow for the second nick and the tensioning +of the material. Now measure off the second stretcher by the first, nick it, +and place it in position. If the tension seems excessive, shorten the rods +slightly, but do not forget that the fabric will stretch somewhat in use. +</p> + +<p> +[Illustration: FIG. 121.—Box kite with front and back wings.] +</p> + +<p> +Make the stretchers for the second box, and place them in position. The wings +ought to be pretty taut if the adjustments are correct, but should they show a +tendency to looseness, a third pair of stretchers of light bamboo may be +inserted between the other two, being held up to the rods by loops of tape. In +order to be able to take up any slackness, the wing end of each stretcher may +be allowed to project a couple of inches, and be attached by string to the near +ring, as described on p. 271. The bridle to which the flying string is attached +is made up of four parts, two long, two short, paired exactly as regards +length. These are attached to eyes screwed into the front rods three inches +below the tops of the boxes. Adjustment is made very easy if a small slider is +used at the kite end of each part. These sliders should be of bone or some +tough wood, and measure 1 inch by 3/8 inch. The forward ends of the bridle are +attached to a brass ring from which runs the flying string. +</p> + +<p> +It is advisable to bind the stretchers with strong thread just behind the +notches to prevent splitting, and to loosen the stretchers when the kite is not +in use, to allow the fabric to retain as much as possible of its elasticity. +</p> + +<p> +The area of the kite affected by wind is about 14 square feet; the total +weight, 1-1/2 lb. The cost of material is about 2s. +</p> + +<p> +The experience gained from making the kite described may be used in the +construction of a larger kite, six or more feet high, with boxes 30 by 22 by 22 +inches, and wings 24 inches wide at the broadest point. If a big lift is +required, or it is desired to have a kite usable in very light breezes, a +second pair of wings slightly narrower than those at the back may be attached +permanently to the front of the boxes, or be fitted with hooks and eyes for use +on occasion only. (Fig. 121.) In the second case two sets of stretchers will be +needed. +</p> + +<p> +[Illustration: FIG. 122.—Simple string winder for kite.] +</p> + +<p> +Note.—If all free edges of boxes and wings are cut on the curve, they +will be less likely to turn over and flap in the wind; but as the curvature +gives extra trouble in cutting out and stitching, the illustrations have been +drawn to represent a straight-edged kite. +</p> + +<p> +Kite Winders.—The plain stick which small children flying small kites on +short strings find sufficient for winding their twine on is far too primitive a +contrivance for dealing with some hundreds of yards, may be, of string. In such +circumstances one needs a quick-winding apparatus. A very fairly effective form +of winder, suitable for small pulls, is illustrated in Fig. 122. +</p> + +<p> +Select a sound piece of wood, 3/8-inch thick, 5 inches wide, and about 1 foot +long. In each end cut a deep V, the sides of which must be carefully smoothed +and rounded with chisel and sandpaper. Nail a wooden rod, 15 inches long and +slightly flattened where it makes contact, across the centre of the board, +taking care not to split the rod, and clinch the ends of the nails securely. +The projecting ends of the rods are held in the hands while the string runs +out. The projecting piece, A, which must also be well secured, is for winding +in. The winding hand must be held somewhat obliquely to the board to clear the +spindle. Winding is much less irksome if a piece of tubing is interposed +between the spindle and the other hand, which can then maintain a firm grip +without exercising a braking effect. +</p> + +<p> +This kind of winder is unsuited for reeling in a string on which there is a +heavy pull, as the hands are working at a great disadvantage at certain points +of a revolution. +</p> + +<p> +[Illustration: FIG. 123.—Plan of string-winding drum, frame, and brake.] +</p> + +<p> +A far better type is shown in Figs. 123 and 124. Select a canister at least 6 +inches in diameter, and not more than 6 inches long, with an overlapping lid. +Get a turner to make for you a couple of wooden discs, 3/8 inch thick, and +having a diameter 2 inches greater than that of the tin. Holes at least 3/8 +inch across should be bored in the centre of each. Cut holes 1 inch across in +the centre of the lid and the bottom of the canister, and nail the lid +concentrically to one disc, the canister itself to the other. Then push the lid +on the tin and solder them together. This gives you a large reel. For the +spindle you will require a piece of brass tubing or steel bar 1 foot long and +large enough to make a hard driving fit with the holes in the wood. Before +driving it in, make a framework of 3/4-inch strip iron (Fig. 123), 3/32 or 1/8 +inch thick, for the reel to turn in. The width of this framework is 1 inch +greater than the length of the reel; its length is twice the diameter of the +canister. Rivet or solder the ends together. Halfway along the sides bore holes +to fit the spindle. +</p> + +<p> +Make a mark 1 inch from one end of the spindle, a second l/8 inch farther away +from the first than the length of the reel. Drill 3/16-inch holes at the marks. +Select two wire nails which fit the holes, and remove their heads. Next cut two +1/4-inch pieces off a tube which fits the spindle. The reel, spindle, and +framework are now assembled as follows: +</p> + +<p> +[Illustration: FIG. 124.—End view of string winder, showing brake and +lever.] +</p> + +<p> +Push the end of the spindle which has a hole nearest to it through one of the +framework holes, slip on one of the pieces of tubing, drive the spindle through +the reel until half an inch projects; put on the second piece of tubing, and +continue driving the spindle till the hole bored in it shows. Then push the +nails half-way through the holes in the spindle, and fix them to the ends of +the reel by small staples. A crank is made out of 1/2-inch wood (oak by +preference) bored to fit the spindle, to which it must be pinned. A small +wooden handle is attached at a suitable distance away. If there is any fear of +the wood splitting near the spindle, it should be bound with fine wire. An +alternative method is to file the end of the spindle square, and to solder to +it a piece of iron strip in which a square hole has been made to fit the +spindle. The crank should be as light as is consistent with sufficient +strength, and be balanced so that there shall not be unpleasant vibration when +the string runs out fast, and of course it must be attached very securely to +the spindle. +</p> + +<p> +What will be the front of the framework must be rounded off on the top edge, +which has a wire guide running parallel to it (Fig. 123) to direct the string +on to the reel; and into the back are riveted a couple of eyes, to which are +attached the ends of a cord passing round the body, or some stationary object. +</p> + +<p> +[Illustration: FIG. 125.—String winder in operation.] +</p> + +<p> +A pin should be provided to push into a hole at one end of the reel and lock +the reel by striking the framework, and it will be found a great convenience to +have a brake for controlling the reel when the kite is rising. Such a brake is +easily fitted to the side of the frame, to act on the left end of the reel when +a lever is depressed by the fingers. There should be a spring to keep it off +the reel when it is not required. The diagrams show where the brake and brake +lever are situated. +</p> + +<p> +Note.—To obtain great elevations a fine wire (piano wire 1/32 inch in +diameter) is generally used, but to protect the user against electric shocks +the wire must be connected with an “earthed” terminal, on the +principle of the lightning conductor. +</p> + +</div><!--end chapter--> + +<div class="chapter"> + +<h2><a name="chap24"></a>XXIV.<br /> +PAPER GLIDERS.</h2> + +<p> +In this chapter are brought to your notice some patterns of paper gliders +which, if made and handled carefully, prove very satisfactory. Gliders are +sensitive and “moody” things, so that first experiments may be +attended by failure; but a little persistence will bring its reward, and at the +end of a few hours you will, unless very unlucky, be the possessor of a good +specimen or two. +</p> + +<p> +The three distinguishing features of a good glider are stability, straightness +of flight, and a small gliding angle. If the last is as low as 1 in 10, so that +the model falls but 1 foot vertically while progressing 10 feet horizontally, +the glider is one to be proud of. +</p> + +<p> +Materials.—The materials needed for the gliders to be described are +moderately stout paper—cream-laid notepaper is somewhat heavy for the +purpose—and a little sealing wax or thin sheet metal for weighting. +</p> + +<p> +[Illustration: FIG. 126.—Paper glider: Model “A.”] +</p> + +<p> +[Illustration: FIG. 127.—How to launch Model “A.”] +</p> + +<p> +Model “A.”—Double a piece of paper 8 inches long and 2-1/2 +inches wide, and cut out, through both folds, the shape shown in Fig. 126. +Flatten the piece and fold the “head” inwards four times on the +side away from the direction in which the paper was folded before being cut +out. Flatten the folds and fix to the centre a little clip formed by doubling a +piece of thin metal 3/16 by 1/2 inch. Make certain that the wings are quite +flat, and then, holding the glider between thumb and first finger, as shown in +Fig. 127, push it off gently. If the balance is right, it will fly quite a long +way with an undulating motion. If too heavy in front, it will dive; if too +light, it will rise suddenly and slip backwards to the ground. The clip or the +amount of paper in the head must be modified accordingly. This type is +extraordinarily efficient if the dimensions, weighting, and shape are correct, +and one of the easiest possible to make. +</p> + +<p> +Model “B.”—The next model (Fig. 128), suggesting by its shape +the Langley steam-driven aeroplane, has two sets of wings tandem. Double a +piece of paper and cut out of both folds simultaneously a figure of the shape +indicated by the solid lines in the diagram. The portion A is square, and forms +the head weight; B indicates the front planes, C the rear planes. Bend the +upper fold of each pair into the positions B1, C1, marked by dotted lines. +Their front edges make less than a right angle with the keel, to ensure the +wings slanting slightly upwards towards the front when expanded. +</p> + +<p> +The model is now turned over, and the other wings are folded exactly on top of +their respective fellows. Then the halves of the head are folded twice inwards, +to bring the paper into as compact a form as possible. It remains to open out +the wings at right angles to the keel, and then raise their tips slightly so +that the two planes of a pair shall make what is called a +“dihedral” angle with one another. +</p> + +<p> +[Illustration: FIG. 128.—Details of paper gliders: Model “B” +above,<br /> +Model “C” below.]<br /> +</p> + +<p> +Before launching, look at your model endways and make sure that the rear planes +are exactly in line with those in front. It is essential that they should be so +for straight flight. Then grip the keel at its centre between finger and thumb +and launch gently. Mark how your glider behaves. If it plunges persistently, +trim off a very little of the head. If, on the contrary, it settles almost +vertically, weight must be added in front. The position of the weight is soon +found by sliding a metal clip along the keel until a good result is obtained. +</p> + +<p> +Note that if the leading edges of the front wings are bent slightly downwards +the glider may fly much better than before. +</p> + +<p> +A good specimen of this type is so stable that if launched upside down it will +right itself immediately and make a normal flight. +</p> + +<p> +Model “C.”—This is cut out of doubled paper according to the +solid lines of Fig. 128. The three sets of planes are bent back in the manner +already described, but the front planes are given a somewhat steeper angle than +the others. This type is very stable and very fairly efficient. +</p> + +<p> +General Remarks.—Always pick up a glider by the keel or middle, not by +one of the wings, as a very little distortion will give trouble. +</p> + +<p> +The merits of a glider depend on length, and on straightness of flight; so in +competition the launching height should be limited by a string stretched across +the room, say 6 feet above the floor. If the room be too short for a glider to +finish its flight, the elevation at which it strikes the wall is the measure of +its efficiency. +</p> + +<p> +Out-of-door flights are impracticable with these very frail models when there +is the slightest breeze blowing. On a perfectly calm day, however, much better +fun can be got out of doors than in, owing to the greater space available. A +good glider launched from a second-floor window facing a large lawn should +travel many yards before coming to grass. +</p> + +<p> +Large gliders of the types detailed above can be made of very stout paper +stiffened with slips of cane or bamboo; but the time they demand in +construction might perhaps be more profitably spent on a power-driven aeroplane +such as forms the subject of the next chapter. +</p> + +</div><!--end chapter--> + +<div class="chapter"> + +<h2><a name="chap25"></a>XXV.<br /> +A SELF-LAUNCHING MODEL AEROPLANE.</h2> + +<p> +By V. E. Johnson, M.A. +</p> + +<p> +This article deals not with a scale model—a small copy of some full-sized +machine—but with one designed for actual flight; with one not specially +intended to create records either of length or duration, but which, although +small details must perforce be omitted, does along its main lines approximate +to the “real thing.” +</p> + +<p> +Partly for this reason, and partly because it proves a far more interesting +machine, we choose a model able to rise from the ground under its own power and +make a good flight after rising, assuming the instructions which we give to +have been carefully carried out. It is perhaps hardly necessary to add that +such a machine can always be launched by hand when desired. +</p> + +<p> +Before entering into special details we may note some broad principles which +must be taken into account if success is to attend our efforts. +</p> + +<p> +Important Points.—It is absolutely essential that the weight be kept down +as much as possible. It is quite a mistake to suppose that weight necessarily +means strength. On the contrary, it may actually be a cause of weakness if +employed in the wrong place and in the wrong way. The heavier the machine, the +more serious the damage done in the event of a bad landing. One of the best and +easiest ways of ensuring lightness is to let the model be of very simple +construction. Such a model is easier to build and more efficient when +constructed than one of more complicated design. Weigh every part of your model +as you construct it, and do not be content until all symmetrically arranged +parts which should weigh the same not only look alike but do actually balance +one another. (Note.—The writer always works out the various parts of his +models in grammes, not ounces.) If a sufficiently strong propeller bearing +weighing only half a gramme can be employed, so much the better, as you have +more margin left for some other part of the model in which it would be +inadvisable to cut down the weight to a very fine limit. +</p> + +<p> +Details.—To pass now to details, we have four distinct parts to deal +with:— +</p> + +<p> +1. The framework, or fuselage. +</p> + +<p> +2. The supporting surfaces, consisting of the main plane, or aerofoil, behind, +and the elevator in front. +</p> + +<p> +3. The propellers. +</p> + +<p> +4. The motor, in this case two long skeins of rubber; long, because we wish to +be able to give our motor many turns, from 700 to, say, 1,000 as a limit, so +that the duration of flight may be considerable. +</p> + +<p> +[Illustration: FIG. 129.-Sections of backbone for model aeroplane.] +</p> + +<p> +The Backbone.—For the backbone or central rod take a piece of pitch pine +or satin walnut 52 inches long, 5/8 inch deep, and 1/2 inch broad, and plane it +down carefully until it has a T-shaped section, as shown in Fig. 129, and the +thickness is not anywhere more than 1/8 inch. It is quite possible to reduce +the thickness to even 1/16 inch and still have a sufficient reserve of strength +to withstand the pull of 28 strands of 1/16-inch rubber wound up 1,000 times; +but such a course is not advisable unless you are a skilful planer and have had +some experience in model-making. +</p> + +<p> +If you find the construction of the T-shaped rod too difficult, two courses are +open— +</p> + +<p> +(l) To get a carpenter to do the job for you, or +</p> + +<p> +(2) To give the rod the triangular section shown in Fig. 129, each side of the +equilateral triangle being half an inch long. +</p> + +<p> +[Illustration: FIG. 150—Side elevation of model aeroplane.] +</p> + +<p> +The top of the T or the base of the triangle, as the case may be, is used +uppermost. This rod must be pierced in three places for the vertical masts +employed in the bracing of the rod, trussing the main plane, and adjusting the +elevator. These are spaced out in Fig. 130, which shows a side elevation of the +model. Their sectional dimensions are 1/16 by 1/4 inch; their respective +lengths are given in Fig. 130. Round the front edges and sharpen the rear. +</p> + +<p> +In Fig. 130 is shown the correct attitude or standing pose necessary to make +the model rise quickly and sweep boldly up into the air without skimming the +ground for some 10 to 20 yards as so many models do. E is the elevator (7 by 3 +inches); A the main plane (5-1/2 by 29 inches); W the wheels; and RS the rear +skid, terminating in a piece of hooked steel wire. The vertical bracing of +these masts is indicated. The best material to use for the purpose is Japanese +silk gut, which is very light and strong. To brace, drill a small, neat hole in +the mast and rod where necessary, pass through, and tie. Do the same with each +one. +</p> + +<p> +To return to the central mast, which must also form the chassis. This is double +and opened out beneath as shown in Fig. 131, yz being a piece similar to the +sides, which completes, the triangle x y z and gives the necessary rigidity. +Attach this piece by first binding to its extremities two strips of aluminium, +or by preference very thin tinned iron, Tl and T2. Bend to shape and bind to +xy, xz as shown in Fig. 131. +</p> + +<p> +[Illustration: FIG. 131.—Front elevation of chassis.] +</p> + +<p> +[Illustration: FIG. l32.-Wheel for model aeroplane chassis.] +</p> + +<p> +[Illustration: FIG. 133.—Plan of model aeroplane.] +</p> + +<p> +The Wheels and Chassis.—WW are the two wheels on which the model runs. +They are made of hollow brass curtain rings, 1 inch in diameter, such as can be +bought at four a penny. For spokes, solder two strips of thin tinned iron to +the rings, using as little solder as possible. (Fig. 132.) To connect these +wheels with the chassis, first bind to the lower ends of xy, xz two strips of +thin tinned iron, T3 and T4, after drilling in them two holes of sufficient +size to allow a piece of steel wire of “bonnet pin” gauge to pass +freely, but not loosely, through them. Soften the wire by making it red hot and +allowing it to cool slowly, and solder one end of this wire (which must be +quite straight and 5-1/4 inches long) to the centre of the cross pieces or +spokes of one wheel. Pass the axle through the holes in the ends of xy, xz, and +solder on the other wheel. Your chassis is then finished. +</p> + +<p> +The rear skid (RS in Fig. 130) is attached to the central rod by gluing, and +drilling a hole through both parts and inserting a wooden peg; or the upright +may be mortised in. On no account use nail, tack, or screw. Attach the vertical +masts and the horizontal ones about to be described by gluing and binding +lightly with thread, or by neatly glued strips of the Hart’s fabric used +for the planes. +</p> + +<p> +Horizontal Spars, etc.—To consider now the horizontal section or part +plan of the model, from which, to avoid confusion, details of most vertical +parts are omitted. Referring to Fig. 133, it will be seen that we have three +horizontal masts or spars—HS1, 4 inches; HS2, 6 inches; and HS3, slightly +over 12 inches long. The last is well steamed, slightly curved and left to dry +while confined in such a manner as to conform to the required shape. It should +so remain at least twenty-four hours before being fixed to the model. All the +spars are attached by glue and neat cross bindings. If the central rod be of +triangular instead of T section, the join can be made more neatly. The same +remarks apply to the two 9 and 10 inch struts at the propeller end of the rod, +which have to withstand the pull of the rubber motor on PPl. These two pieces +will have a maximum strength and minimum weight if of the T section used for +the rod. If the work is done carefully, 1/4 inch each way will be sufficient. +</p> + +<p> +Main Plane and Elevator.—The framework of each plane is simply four +strips of satin walnut or other suitable wood, 1/4 inch broad and 1/16 inch or +even less in thickness for the main plane, and about 1/16 by 1/16 inch for the +elevator. These strips are first glued together at the corners and left to set. +The fabric (Hart’s fabric or some similar very light material) is then +glued on fairly tight—that is, just sufficiently so to get rid of all +creases. The main plane is then fixed flat on to the top of the central rod by +gluing and cross binding at G and H. (A better but rather more difficult plan +is to fasten the rectangular frame on first and then apply the fabric.) The +same course is followed in dealing with the elevator, which is fixed, however, +not to the rod, but to the 4-inch horizontal spar, HS1, just behind it, in such +a manner as to have a slight hinge movement at the back. This operation +presents no difficulty, and may be effected in a variety of ways. To set the +elevator, use is made of the short vertical mast, M1. A small hole is pierced +in the front side of the elevator frame at Z, and through this a piece of thin, +soft iron wire is pushed, bent round the spar, and tied. The other end of the +wire is taken forward and wrapped three or four times round the mast M1, which +should have several notches in its front edge, to assist the setting of the +elevator at different angles. Pull the wire tight, so that the elevator shall +maintain a constant angle when once set. H H1 is a piece of 25 to 30 gauge wire +bent as shown and fastened by binding. It passes round the front of the rod, in +which a little notch should be cut, so as to be able to resist the pull of the +twin rubber motors, the two skeins of which are stretched between H H1 and the +hooks formed on the propeller spindles. If all these hooks are covered with +cycle valve tubing the rubber will last much longer. The rubber skeins pass +through two little light wire rings fastened to the underside ends of HS2. +(Fig. 133.) +</p> + +<p> +The front skid or protector, FS, is made out of a piece of thin, round, +jointless cane, some 9 inches in length, bent round as shown in Fig. 134, in +which A B represents the front piece of the T-shaped rod and x y z a the cane +skid; the portion x y passing on the near side of the vertical part of the T, +and z a on the far side of the same. At E and F thread is bound right round the +rod. Should the nose of the machine strike the ground, the loop of cane will be +driven along the underside of the rod and the shock be minimized. So adjust +matters that the skid slides fairly stiff. Note that the whole of the cane is +on the under side of the top bar of the T. +</p> + +<p> +[Illustration: FIG. 134.—Front skid and attachment to backbone.] +</p> + +<p> +Bearings.—We have still to deal with the propellers and their bearings. +The last, TN and TNl (Fig. 133), are simply two tiny pieces of tin about half a +gramme in weight, bent round the propeller spar HS3 at B and B1. Take a strip +of thin tin 1/4 inch wide and of sufficient length to go completely round the +spar (which is 1/4 by 1/8 inch) and overlap slightly. Solder the ends together, +using a minimum amount of solder. Now bore two small holes through wood and tin +from rear to front, being careful to go through the centre. The hole must be +just large enough to allow the propeller axle to run freely, but not loosely, +in it. Primitive though such a bearing may seem, it answers admirably in +practice. The wood drills out or is soon worn more than the iron, and the axle +runs quite freely. The pull of the motor is thus directed through the thin +curved spar at a point where the resistance is greatest—a very important +matter in model aeroplane construction. To strengthen this spar further against +torsional forces, run gut ties from B and Bl down to the bottom of the rear +vertical skid post; and from B to B1 also pass a piece of very thin piano wire, +soldered to the tin strips over a little wooden bridge, Q, like a violin +bridge, on the top of the central rod, to keep it quite taut. +</p> + +<p> +[Illustration: FIG. 135—“Centrale” wooden propeller.] +</p> + +<p> +Propellers.—To turn now to the propellers. Unless the reader has already +had fair experience in making model propellers, he should purchase a couple, +one right-handed and one left-handed, as they have to revolve in opposite +directions. It would be quite impossible to give in the compass of this article +such directions as would enable a novice to make a really efficient propeller, +and it must be efficient for even a decent flight with a self-launching model. +The diameter of the two propellers should be about 11-1/2 to 11-3/4 inches, +with a pitch angle at the extremities of about 25 to 30 degrees as a limit. The +“centrale” type (Fig. 135) is to be preferred. Such propellers can +be procured at Messrs. A. W. Gamage, Ltd., Holborn, E.C.; Messrs. T. W. K. +Clarke and Co., Kingston-on-Thames; and elsewhere. +</p> + +<p> +For the particular machine which we are considering, the total weight of the +two propellers, including axle and hook for holding the rubber, should not +exceed 3/4 oz. This means considerable labour in cutting and sandpapering away +part of the boss, which is always made much too large in propellers of this +size. It is wonderful what can be done by care and patience. The writer has in +more than one case reduced the weight of a propeller by more than one-half by +such means, and has yet left sufficient strength. +</p> + +<p> +The combined axle and hook should be made as follows:—Take a piece of +thin steel wire, sharpen one end, and bend it as shown at C (Fig. 136). Pass +the end B through a tight-fitting hole in the centre of the small boss of the +propeller, and drive C into the wood. Solder a tiny piece of 1/8-inch brass +tubing to the wire axle at A, close up to the rubber hook side of the +propeller, and file quite smooth. The only things now left to do are to bend +the wire into the form of a hook (as shown by the dotted line), and to cover +this hook, as already advised, with a piece of valve tubing to prevent fraying +the rubber skeins. +</p> + +<p> +[Illustration: FIG. 136.—Axle and hook for propeller.] +</p> + +<p> +Weight.—The weight of a model with a T-shaped central rod 1/16 inch thick +should be 4-1/2 oz. Probably it will be more than this—as a maximum let +us fix 6 oz.—although 4-1/2 oz. is quite possible, as the writer has +proved in actual practice. In any case the centre of gravity of the machine +without the rubber motor should be situated 1 inch behind the front or entering +edge of the main plane. When the rubber motor (14 strands of 1/16-inch rubber +for each propeller, total weight 2 oz.) is in position, the centre of gravity +will be further forward, in front of the main plane. The amount of rubber +mentioned is for a total weight of 6-1/2 oz. If the weight of the model alone +be 6 oz., you will probably have to use 16 strands, which again adds to the +weight, and makes one travel in a vicious circle. Therefore I lay emphasis on +the advice, Keep down the weight. +</p> + +<p> +The front edge of the elevator should be set about 3/8 inch higher than the +back, and the model be tried first as a glider, with the rubber and propellers +in position. If it glides satisfactorily, wind up the motor, say 500 turns, and +launch by hand. When a good flight has been obtained, and the correct angle of +the elevator has been determined, place the model on a strip of linoleum, wind +up, and release the propellers. The model should rise in its own length and +remain in the air (if wound up 900 turns) at least three quarters of a minute. +Choose a calm day if possible. If a wind blows, let the model face the breeze. +Remember that the model flies high, and select a wide open space. Do not push +the model forward; just release the propellers, held one in each hand near the +boss by the fingers and thumb. As a lubricant for the rubber use pure +glycerine. It is advisable to employ a geared-up mechanical winder, since to +make 1,800 turns with the fingers is rather fatiguing and very tedious. +</p> + +<p> +Simple as this model may seem in design, one built by the writer on exactly the +lines given has met the most famous flying models of the day in open +competition and proved successful against them. +</p> + +</div><!--end chapter--> + +<div class="chapter"> + +<h2><a name="chap26"></a>XXVI.<br /> +APPARATUS FOR SIMPLE SCIENTIFIC EXPERIMENTS.</h2> + +<p> +Colour Discs for the Gramophone.—The gramophone, by virtue of its table +revolving at a controllable speed, comes in useful for a series of optical +experiments made with coloured discs bearing designs of different kinds. +</p> + +<p> +The material needed for these discs is cardboard, covered with white paper on +one side, or the Bristol board used by artists. The discs on which the designs +are drawn should be made as large as the gramophone table will take +conveniently, so as to be viewed by a number of people at once. To encourage +readers who do not possess a gramophone, it may be pointed out that a +gramophone, is merely a convenience, and not indispensable for turning the +discs, which may be revolved on a sharpened pencil or any other spindle with +pointed ends. +</p> + +<p> +The Vanishing Spirals (Fig. 137).—This design, if spun slowly in a +clockwise direction, gives one the impression that the lines all move in +towards the centre. If the disc is turned in an anti-clockwise direction, the +lines seem to move towards the circumference and disappear. To get the proper +effect the gaze should be fixed and not attempt to follow the lines round. +</p> + +<p> +[Illustration: FIG. 137.] +</p> + +<p> +[Illustration: FIG. 138.] +</p> + +<p> +The Rolling Circles.—Figs. 138 and 139 are variations of the same idea. +In Fig. 138 two large circles are described cutting one another and enclosing a +smaller circle concentric with the disc. When spun at a certain rate the larger +circles will appear to run independently round the small. The effect is +heightened if the circles are given different colours. If black only is used +for the large circles, the eyes should be kept half closed. In Fig. 139 two +pairs of circles are described about two centres, neither of which is the +centre of the disc. The pairs appear to roll independently. +</p> + +<p> +[Illustration: FIG. 139.] +</p> + +<p> +[Illustration: FIG. 140.] +</p> + +<p> +The Wriggling Line (Fig. 140).—If this design is revolved at a low speed +and the eye is fixed on a point, the white (or coloured) line will seem to +undulate in a very extraordinary manner. The line is made up of arcs of +circles, and as the marking out is somewhat of a geometrical problem, a diagram +(Fig. 141) is added to show how it is done. The dotted curves are those parts +of the circles which do not enter into the design. +</p> + +<p> +Begin by marking out the big circle A for the disc. The circumference of this +is divided into six equal parts (chord equal to radius), and through the points +of division are drawn the six lines from the centre. Describe circles aaa, each +half the diameter of A. The circles bbb are then drawn from centres on the +lines RRR, and with the same radius as aaa., The same centres are used for +describing the circles a1 a1 a1 and b1 b1 b1, parts of which form the inner +boundary of the line. The background should be blackened and the belt left +white or be painted some bright colour. +</p> + +<p> +[Illustration: FIG. 141.] +</p> + +<p> +Another optical illusion is afforded by Fig. 142. Two sets of circles are +described about different centres, and the crescent-shaped areas between them +coloured, the remainder of the disc being left white. The disc is revolved +about the centre of the white areas, and one gets the impression that the +coloured parts are portions of separate discs separated by white discs. +</p> + +<p> +[Illustration: FIG. 142.] +</p> + +<p> +[Illustration: FIG. 143.] +</p> + +<p> +The Magic Spokes (Fig. 143).—Place a design like this on the gramophone +and let it turn at high speed. The radial lines seem but a blur. Now punch a +hole one-eighth of an inch in diameter in a piece of blackened card, and, +standing well away from the gramophone, apply your eye to the hole and move the +card quickly to and fro. The extreme briefness of the glimpses obtained of the +moving lines seems to rob them of motion, or even make them appear to be moving +in the direction contrary to the actual. Instead of a single hole, one may use +a number of holes punched at equal intervals round a circle, and revolve the +card on the centre. If a certain speed be maintained, the spokes will appear +motionless. +</p> + +<p> +The substitution of a long narrow slit for a circular hole gives other effects. +</p> + +<p> +[Illustration: FIG. 144.] +</p> + +<p> +A Colour Top.—Cut a 4-inch disc out of white cardboard and blacken +one-half with Indian ink. On the other half draw four series of concentric +black lines, as shown in Fig. 144. If the disc is mounted on a knitting needle +and spun in a horizontal plane, the black lines will appear of different +colours. A clockwise rotation makes the outermost lines appear a greenish blue, +those nearest the centre a dark red, and the intermediate groups yellow and +green. A reversal of the motion reverses the order of the colours, the red +lines now being farthest from the centre. The experiment is generally most +successful by artificial light, which contains a larger proportion of red and +yellow rays than does sunlight. The speed at which the top revolves affects the +result considerably. It should be kept moderate, any excess tending to +neutralize the colours. +</p> + +<p> +[Illustration: FIG. 145.] +</p> + +<p> +The Magic Windmill.—Mark a circle 2-1/2 inches in diameter on a piece of +notepaper, resting the centre leg [of the compass] so lightly that it dents +without piercing the paper. With the same centre describe a 3/4-inch circle. +Join the circles by eight equally spaced radial lines, and an eighth of an inch +away draw dotted parallel lines, all on the same side of their fellow lines in +order of rotation. Cut out along the large circle, and then with a. sharp knife +follow the lines shown double in Fig. 145. This gives eight little vanes, each +of which must be bent upwards to approximately the same angle round a flat +ruler held with an edge on the dotted line. Next make a dent with a lead pencil +at the exact centre on the vane side, and revolve the pencil until the dent is +well polished. +</p> + +<p> +[Illustration: FIG. 146.] +</p> + +<p> +Hold a pin, point upwards, in the right hand, and with the left centre the +mill, vanes pointing downwards, on the pin (Fig. 146). The mill will +immediately commence to revolve at a steady pace, and will continue to do so +indefinitely; though, if the head of the pin be stuck in, say, a piece of +bread, no motion will occur. The secret is that the heat of the hand causes a +very slight upward current of warmed air, which is sufficient to make the very +delicately poised windmill revolve. +</p> + +<p> +A Pneumatic Puzzle.—For the very simple apparatus illustrated by Fig. 147 +one needs only half a cotton reel, three pins, and a piece of glass or metal +tubing which fits the hole in the reel. Adjust a halfpenny centrally over the +hole and stick the pins into the reel at three equidistant points, so that they +do not quite touch the coin, and with their ends sloping slightly outwards to +allow the halfpenny to fall away. +</p> + +<p> +[Illustration: FIG. 147.—Apparatus for illustrating an apparent +scientific paradox.] +</p> + +<p> +Press the coin against the reel and blow hard through the tube. One would +expect the coin to fall; but, on the contrary, the harder you blow the tighter +will it stick, even if the reel be pointed downwards. Only when you stop +blowing will it fall to the floor. +</p> + +<p> +This is a very interesting experiment, and will mystify onlookers who do not +understand the reason for the apparent paradox, which is this. The air blown +through the reel strikes a very limited part of the nearer side of the +halfpenny. In order to escape, it has to make a right-angle turn and pass +between coin and reel, and, while travelling in this direction, loses most of +its repulsive force. The result is that the total pressure on the underside of +the coin, plus the effect of gravity, is exactly balanced by the atmospheric +pressure on the outside, and the coin remains at that distance from the reel +which gives equilibrium of forces. When one stops blowing, the air pressure on +both sides is the same, and gravity makes the coin fall away. +</p> + +<p> +The function of the pins is merely to keep the halfpenny centred on the hole. +If steam is used instead of human breath, a considerable weight may be hung +from the disc without dislodging it. +</p> + +<p> +The Magic Swingers.—The easily made toy illustrated next is much more +interesting than would appear from the mere picture, as it demonstrates a very +striking physical phenomenon, the transference of energy. If two pendulums are +hung close together from a flexible support and swung, their movements +influence one another in a somewhat remarkable way—the swing of the one +increasing as that of the other dies down, until a certain point is reached, +after which the process is reversed, and the “dying” or +“dead” pendulum commences to come to life again at the expense of +the other. This alternation is repeated over and over again, until all the +energy of both pendulums is exhausted. +</p> + +<p> +[Illustration: FIG. 148.-Magic pendulums.] +</p> + +<p> +To make the experiment more attractive, we substitute for the simplest possible +pendulums—weights at the end of strings—small swings, each +containing a figure sitting or standing on a seat, to the underside of which is +attached a quarter of a pound of lead. To prevent the swings twisting, they are +best made of strong wire bent as shown in Fig. 148, care being taken that the +sides are of equal length, so that both hooks may press equally on the strings. +Eighteen inches is a good length. The longer the swing, and the heavier the +weight, the longer will the experiment last. +</p> + +<p> +The swings are hung, six inches apart, from a stout string stretched tightly +between two well-weighted chairs or between two fixed points. The string should +be at least 4 feet long. +</p> + +<p> +With two equally long and equally weighted pendulums, the three following +experiments may be carried out:— +</p> + +<p> +1. Let one, A, start from rest. The other, B will gradually die, and A swing to +and fro more and more violently, till B at last comes to a dead stop. Then A +will die and B in turn get up speed. The energy originally imparted to B is +thus transferred through the string from one pendulum to the other an +indefinite number of times, with a slight loss at every alternation, until it +is finally exhausted by friction. +</p> + +<p> +2. Swing them in opposite directions, but start A from a higher point than B. +They will each alternately lose and gain motion, but will never come to rest, +and will continue to swing in opposite directions—that is, while A swings +north or east B will be swinging south or west, and vice versa. +</p> + +<p> +3. Start them both in the same direction, but one from a higher point than the +other. There will be the same transference of energy as in (2), but neither +will come to rest between alternations, and they will always swing in the same +direction. +</p> + +<p> +Unequal Lengths.—If for one of the original pendulums we substitute one a +couple of inches longer than the other, but of the same weight, the same set of +three experiments will provide six variations among them, as in each case +either the longer or the shorter may be started first or given the longer +initial swing, as the case may be. The results are interesting throughout, and +should be noted. +</p> + +<p> +Three or more Pendulums.—If the number of pendulums be increased to +three or more, the length of all being the same, a fresh field for observation +is opened. With an increase of number a decrease in the individual weighting is +advisable, to prevent an undue sagging of the string. +</p> + +<p> +In conclusion, we may remark that a strong chain stretched between two trees +and a suitable supply of rope will enable the reader and his friends to carry +out all the experiments on a life-size scale. +</p> + +<p> +A Smoke-ring Apparatus.—Get a large tin of the self-opening kind and cut +a hole 2 inches across in the bottom. Then make a neat circular hole 1-1/4 +inches in diameter in the centre of a paper disc somewhat smaller than the +bottom of the tin, to which it is pasted firmly on the outside. The other +end—from which the lid is removed—must be covered with a piece of +sheet rubber stretched fairly tight and secured to the tin by string passed +over it behind the rim. An old cycle or motor car air tube, according to the +size of the tin, will furnish the rubber needed; but new material, will cost +only a few pence (Fig. 149). +</p> + +<p> +[Illustration: FIG. 149.—Smoke-ring apparatus.] +</p> + +<p> +A dense smoke is produced by putting in the tin two small rolls of blotting +paper, one soaked in hydrochloric acid, the other in strong ammonia. The rolls +should not touch. To reduce corrosion of the tin by the acid, the inside should +be lined with thin card. +</p> + +<p> +[Illustration: FIG. 150.—Smoke-making apparatus.] +</p> + +<p> +A ring of smoke is projected from the hole in the card if the rubber diaphragm +is pushed inwards. A slow, steady push makes a fat, lazy ring come out; a smart +tap a thinner one, moving much faster. Absolutely still air is needed for the +best effects, as draughts make the rings lose shape very quickly and move +erratically. Given good conditions, a lot of fun can be got out of the rings by +shooting one through another which has expanded somewhat, or by destroying one +by striking it with another, or by extinguishing a candle set up at a distance, +and so on. The experimenter should notice how a vortex ring rotates in itself +while moving forward, like a rubber ring being rolled along a stick. +</p> + +<p> +A continuous supply of smoke can be provided by the apparatus shown in Fig. +150. The bulb of a scent spray is needed to force ammonia gas through a box, +made air-tight by a rubber band round the lid, in which is a pad soaked with +hydrochloric acid. The smoke formed in this box is expelled through a pipe into +the ring-making box. +</p> + +<p> +Caution.—When dealing with hydrochloric acid, take great care not to get +it on your skin or clothes, as it is a very strong corrosive. +</p> + +</div><!--end chapter--> + +<div class="chapter"> + +<h2><a name="chap27"></a>XXVII.<br /> +A RAIN-GAUGE.</h2> + +<p> +The systematic measurement of rainfall is one of those pursuits which prove +more interesting in the doing than in the prospect. It enables us to compare +one season or one year with another; tells us what the weather has been while +we slept; affords a little mild excitement when thunderstorms are about; and +compensates to a limited extent for the disadvantages of a wet day. +</p> + +<p> +The general practice is to examine the gauge daily (say at 10 a.m.); to measure +the water, if any, collected during the previous twenty-four hours; and to +enter the record at once. Gauges are made which record automatically the +rainfall on a chart or dial, but these are necessarily much more expensive than +those which merely catch the water for measurement. +</p> + +<p> +This last class, to which our attention will be confined chiefly, all include +two principal parts—a metal receiver and a graduated glass measure, of +much smaller diameter than the receiver, so that the divisions representing +hundredths of an inch may be far enough apart to be distinguishable. It is +evident that the smaller the area of the measure is, relatively to that of the +receiver, the more widely spaced will the graduation marks of the measure be, +and the more exact the readings obtained. +</p> + +<p> +[Illustration: FIG. 151.—Standard rain-gauge.] +</p> + +<p> +The gauge most commonly used is that shown in Fig. 151. It consists of an upper +cylindrical part, usually 5 or 8 inches in diameter, at the inside of the rim, +with its bottom closed by a funnel. The lower cylindrical part holds a glass +catcher into which the funnel delivers the water for storage until the time +when it will be measured in a graduated glass. The upper part makes a good fit +with the lower, in order to reduce evaporation to a minimum. +</p> + +<p> +Such a gauge can be bought for half a guinea or so, but one which, if carefully +made, will prove approximately accurate, can be constructed at very small +expense. One needs, in the first place, a cylindrical tin, or, better still, a +piece of brass tubing, about 5 inches high and not less than 3 inches in +diameter. (Experiments have proved that the larger the area of the receiver the +more accurate are the results.) The second requisite is a piece of stout glass +tubing having an internal diameter not more than one-quarter that of the +receiver This is to serve as measuring glass. +</p> + +<p> +[Illustration: FIG. 152.—Section of homemade rain-gauge.] +</p> + +<p> +The success of the gauge depends entirely upon ascertaining accurately how much +of the tube will be filled by a column of water 1 inch deep and having the same +area as the receiver. This is easily determined as follows:—If a tin is +to be used as receiver, make the bottom and side joints watertight with solder; +if a tube, square off one end and solder a flat metal to it temporarily. The +receptacle is placed on a perfectly level base, and water is poured in until it +reaches exactly to a mark made 4 inches from the end of a fine wire held +perpendicularly. Now cork one end of the tube and pour in the water, being +careful not to spill any, emptying and filling again if necessary. This will +give you the number of tube inches filled by the 4 inches in the receiver. +Divide the result by 4, and you will have the depth unit in the measure +representing 1 inch of rainfall. The measuring should be done several times +over, and the average result taken as the standard. If the readings all agree, +so much the better. +</p> + +<p> +Preparing the Scale.—The next thing is to graduate a scale, which will +most conveniently be established in indelible pencil on a carefully smoothed +strip of white wood 1 inch wide. First make a zero mark squarely across the +strip near the bottom, and at the unit distance above it a similar mark, over +which “One Inch” should be written plainly. The distance between +the marks is next divided by 1/2-inch lines into tenths, and these tenths by +1/4-inch lines into hundredths, which, if the diameter of the receiver is four +times that of the tube, will be about 3/16 inch apart. For reading, the scale +is held against the tube, with the zero mark level with the top of the cork +plugging the bottom. It will, save time and trouble if both tube and scale are +attached permanently to a board, which will also serve to protect the tube +against damage. +</p> + +<p> +Making the Receiver.—A tin funnel, fitting the inside of the receiver +closely, should be obtained, or, if the exact article is not available, a +longer one should be cut down to fit. Make a central hole in the bottom of the +receiver large enough to allow the funnel to pass through up to the swell, and +solder the rim of the funnel to the inside of the receiver, using as little +heat as possible. +</p> + +<p> +If you select a tin of the self-opening kind, you must now cut away the top +with a file or hack-saw, being very careful not to bend the metal, as +distortion, by altering the area of the upper end of the tin, will render the +gauge inaccurate. +</p> + +<p> +The receiver should be supported by another tin of somewhat smaller diameter, +and deep enough to contain a bottle which will hold 3 or 4 inches of rainfall. +In order to prevent water entering this compartment, tie a strip of rubber (cut +out of an old cycle air tube) or other material round the receiver, and +projecting half an inch beyond the bottom (Fig. 152). +</p> + +<p> +All tinned iron surfaces should be given a couple of thin coats or paint. +</p> + +<p> +The standard distance between the rain gauge and the ground is one foot. The +amount caught decreases with increase of elevation, owing to the greater effect +of the wind. The top of the gauge must be perfectly level, so that it may offer +the same catchment area to rain from whatever direction it may come. +</p> + +<p> +[Illustration: FIG. 153.—Self-measuring gauge.] +</p> + +<p> +Another Arrangement.—To simplify measurement, the receiver and tube may +be arranged as shown in Fig. 153. In this case the water is delivered directly +into the measure, and the rainfall may be read at a glance. On the top of the +support is a small platform for the receiver, its centre directly over the +tube. The graduations, first made on a rod as already described, may be +transferred, by means of a fine camel’s hair brush and white paint, to +the tube itself. To draw off the water after taking a reading, a hole should be +burnt with a hot wire through the bottom cork. This hole is plugged with a +piece of slightly tapered brass rod, pushed in till its top is flush with the +upper surface of the cork. +</p> + +<p> +If the tube has small capacity, provision should be made for catching the +overflow by inserting through the cork a small tube reaching to a convenient +height-say the 1-inch mark. The bottom of the tube projects into a closed +storage vessel. Note that the tube must be in position before the graduation is +determined, otherwise the readings will exaggerate the rainfall. +</p> + +<p> +[Illustration: FIG. 154.—Gauge in case.] +</p> + +<p> +Protection against the Weather.—A rain-gauge of this kind requires +protection against frost, as the freezing of the water would burst the tube. It +will be sufficient to hinge to the front of the support a piece of wood half an +inch thicker than the diameter of the tube, grooved out so as to fit the tube +when shut round it (Fig 154). +</p> + +</div><!--end chapter--> + +<div class="chapter"> + +<h2><a name="chap28"></a>XXVIII.<br /> +WIND VANES WITH DIALS.</h2> + +<p> +It is difficult to tell from a distance in which direction the arrow of a wind +vane points when the arrow lies obliquely to the spectator, or points directly +towards or away from him. In the case of a vane set up in some position where +it will be plainly visible from the house, this difficulty is overcome by +making the wind vane operate an arrow moving round a vertical dial set square +to the point of observation. Figs. 155 to 157 are sketches and diagrams of an +apparatus which does the work very satisfactorily. The vane is attached to the +upper end of a long rod, revolving freely in brackets attached to the side of a +pole. The bottom end of the rod is pointed to engage with a nick in a bearer, +in which it moves with but little friction. Near the end is fixed a horizontal +bevel-wheel, engaging with a vertical bevel of equal size and number of teeth +attached to a short rod running through a hole in the post to an arrow on the +other side. Between arrow and post is room for a dial on which the points of +the compass are marked. +</p> + +<p> +The construction of the apparatus is so simple as to call for little comment. +The tail of the vane is made of two pieces of zinc, tapering from 8 inches wide +at the rear to 4 inches at the rod, to which they are clipped by 4 screws and +nuts. A stay soldered between them near the stern keeps the broader ends a +couple of inches apart, giving to the vane a wedge shape which is more +sensitive to the wind than a single flat plate. The pointer also is cut out of +sheet metal, and is attached to the tail by means of the screws already +mentioned. It must, of course, be arranged to lie in a line bisecting the angle +formed by the two parts of the tail. +</p> + +<p> +[Illustration: FIG. 165—Wind vane with dial.] +</p> + +<p> +The rod should preferably be of brass, which does not corrode like iron. If the +uppermost 18 inches or so are of 1/4-inch diameter, and assigned a bracket some +distance below the one projecting from the top of the pole, the remainder of +the rod need not exceed 1/8 to 5/32 inch in diameter, as the twisting strain on +it is small. Or the rod may be built up of wooden rods, well painted, +alternating with brass at the points where the brackets are. +</p> + +<p> +[Illustration: FIG. 156.—Elevation and plan of vane.] +</p> + +<p> +The Bevel Gearing.—Two brass bevel wheels, about 1 inch in diameter, and +purchasable for a couple of shillings or less, should be obtained to transmit +the vane movements to the dial arrow. Grooved pulleys, and a belt would do the +work, but not so positively, and any slipping would, of course, render the dial +readings incorrect. The arrow spindle (of brass) turns in a brass tube, driven +tightly into a hole of suitable size bored through the centre of the post (Fig. +157). It will be well to fix a little metal screen over the bevel gear to +protect it from the weather. +</p> + +<p> +[Illustration: FIG. 157.—Details of bevel gear and arrow.] +</p> + +<p> +The Dial—This is made of tinned iron sheet or of 1/4-inch wood nailed to +1/2-inch battens. It is held up to the post by 3-inch screws passing through +front and battens. At the points of contact, the pole is slightly flattened to +give a good bearing; and, to prevent the dial being twisted off by the wind, +strip iron or stout galvanized wire stays run from one end of a batten to the +other behind the post, to which they are secured. +</p> + +<p> +The post should be well painted, the top protected by a zinc disc laid under +the top bracket, and the bottom, up to a point 6 inches above the ground level, +protected by charring or by a coat of boiled tar, before the dial and the +brackets for the vane rod to turn in are fastened on. A white dial and black +arrow and letters will be most satisfactory against a dark background; and vice +versa for a light background. The letters are of relatively little importance, +as the position of the arrow will be sufficient indication. +</p> + +<p> +It gives little trouble to affix to the top of the pole 4 arms, each carrying +the initial of one of the cardinal points of the compass. The position of these +relatively to the direction in which the dial will face must be carefully +thought out before setting the position in the ground. In any case the help of +a compass will be needed to decide which is the north. +</p> + +<p> +Having set in the post and rammed the earth tightly round it, loosen the +bracket supporting the vane rod so that the vane bevel clears the dial bevel. +Turn the vane to true north, set the dial arrow also to north, and raise the +bevel so that it meshes, and make the bracket tight. +</p> + +<p> +Note.—In the vicinity of London true north is 15 degrees east of the +magnetic north. +</p> + +<p> +The pole must be long enough to raise the vane clear of any objects which might +act as screens, and its length will therefore depend on its position. As for +the height of the dial above the ground, this must be left to individual +preference or to circumstances. If conditions allow, it should be near enough +to the ground to be examined easily with a lamp at night, as one of the chief +advantages of the system is that the reading is independent of the visibility +of the vane. +</p> + +<p> +A Dial Indoors.—If some prominent part of the house, such as a chimney +stack, be used to support the pole—which in such a case can be quite +short—it is an easy matter to connect the vane with a dial indoors, +provided that the rod can be run down an outside wall. +</p> + +<p> +An Electrically Operated Dial.—Thanks to the electric current, it is +possible to cause a wind vane, wherever it may be set, to work a dial situated +anywhere indoors. A suggested method of effecting this is illustrated in Figs. +158 to 161, which are sufficiently explicit to enable the reader to fill in +details for himself. +</p> + +<p> +[Illustration: FIG. 158.—Plan and elevation of electric contact on vane +post.] +</p> + +<p> +In-this case the vane is attached (Fig. 158) to a brass tube, closed at the +upper end, and supported by a long spike stuck into the top of the pole. A +little platform carries a brass ring, divided into as many insulated segments +as the points which the vane is to be able to register. Thus, there will be +eight segments if the half-points as well as the cardinal points are to be +shown on the dial. The centre of each of these segments lies on a line running +through the centre of the spike to the compass point to which the segment +belongs. The tube moves with it a rotating contact piece, which rubs against +the tops of the segments. +</p> + +<p> +Below it is a “brush” of strip brass pressing against the tube. +This brush is connected with a wire running to one terminal of a battery near +the dial. +</p> + +<p> +[Illustration: FIG. 159.—Magnetic recording dial.] +</p> + +<p> +The Dial.—This may be either vertical or horizontal, provided that the +arrow is well balanced. The arrow, which should be of some light non-magnetic +material, such as cardboard or wood, carries on its lower side, near the point, +a piece of soft iron. Under the path of this piece is a ring of equally spaced +magnets, their number equaling that of, the segments on the vane. Between arrow +and magnets is the dial on which the points are marked (Fig. 159). +</p> + +<p> +Each segment is connected by a separate wire with the corresponding dial +magnet, and each of these, through a common wire and switch, with the other +terminal of the battery (Fig. 161). +</p> + +<p> +In order to ascertain the quarter of the wind, the switch is closed. The magnet +which is energized will attract the needle to it, showing in what direction the +vane is pointing. To prevent misreading, the dial may be covered by a flap the +raising of which closes the battery circuit. A spring should be arranged to +close the flap when the hand is removed, to prevent waste of current. +</p> + +<p> +[Illustration: FIG. 160.—Another type of electric dial with compass +needle for pointer.] +</p> + +<p> +The exactitude of the indication given by the arrow depends on the number of +vane segments used. If these are only four, a N. read- ing will be given by any +position of the vane between N.E. and N.W.; if eight, N. will mean anything +between N.N.E. and N.N.W. Telephone cables, containing any desired number of +insulated wires, each covered by a braiding of a distinctive colour, can be +obtained at a cost only slightly exceeding that of an equal total amount of +single insulated wire. The cable form is to be preferred, on account of its +greater convenience in fixing. +</p> + +<p> +The amount of battery power required depends on the length of the circuit and +the delicacy of the dial. If an ordinary compass needle be used, as indicated +in Fig. 160, very little current is needed. In this case the magnets, which can +be made of a couple of dozen turns of fine insulated wire round a 1/8-in soft +iron bar, should be arranged spokewise round the compass case, and care must be +taken that all the cores are wound in the same direction, so as to have the +same polarity. Otherwise some will attract the N. end of the needle and others +repel it. The direction of the current flow through the circuit will decide the +polarity of the magnets, so that, if one end of the needle be furnished with a +little paper arrow-head, the “correspondence” between vane and dial +is easily established. An advantage attaching to the use of a compass needle is +that the magnet repels the wrong end of the needle. +</p> + +<p> +[Illustration: FIG. 161.—General arrangement of electric wind recorder.] +</p> + +<p> +The brush and segments must be protected from he weather by a cover, either +attached to the segment platform or to the tube on which the vane is mounted. +</p> + +<p> +The spaces between the segments must be filled in flush with some +non-conducting material, such as fibre, vulcanite, or sealing-wax; and be very +slightly wider than the end of the contact arm, so that two segments may not be +in circuit simultaneously. In certain positions of the vane no contact will be +made, but, as the vane is motionless only when there is no wind or none to +speak of, this is a small matter. +</p> + +</div><!--end chapter--> + +<div class="chapter"> + +<h2><a name="chap29"></a>XXIX.<br /> +A STRENGTH-TESTING MACHINE.</h2> + +<p> +The penny-in-the-slot strength-testing machine is popular among men and boys, +presumably because many of them like to show other people what their muscles +are capable of, and the opportunity of proving it on a graduated dial is +therefore tempting, especially if there be a possibility of recovering the +penny by an unusually good performance. +</p> + +<p> +For the expenditure of quite a small number of pence, one may construct a +machine which will show fairly accurately what is the value of one’s grip +and the twisting, power of the arms; and, even if inaccurate, will serve for +competitive purposes. The apparatus is very simple in principle, consisting of +but five pieces of wood, an ordinary spring balance registering up to 40 lbs., +and a couple of handles. The total cost is but a couple of shillings at the +outside. +</p> + +<p> +Fig. 162 is a plan of the machine as used for grip measuring. The base is a +piece of deal 1 inch thick, 2 feet long, and 5-1/2 inches wide. The lever, L, +is pivoted at P, attached to a spring balance at Q, and subjected to the pull +of the hand at a point, R. +</p> + +<p> +The pressure exerted at R is to that registered at Q as the distance PQ is to +the distance PR. As the spring balance will not record beyond 40 lbs., the +ratio of PQ to PR may conveniently be made 5 to 1, as this will allow for the +performances of quite a strong man; but even if the ratio be lowered to 4 to 1, +few readers will stretch the balance to its limit. +</p> + +<p> +The balance should preferably be of the type shown in Fig. 162, having an +indicator projecting at right angles to the scale through a slot, as this can +be very easily fitted with a sliding index, I, in the form of a 1/4-inch strip +of tin bent over at the ends to embrace the edges of the balance. +</p> + +<h4>CONSTRUCTION.</h4> + +<p> +[Illustration: FIG. 162.—Plan of strength tester.] +</p> + +<p> +[Illustration: FIG. 163.—Grips of strength tester.] +</p> + +<p> +As the pressures on the machine are high, the construction must be solid +throughout. The lever frame, A, and pivot piece, C, should be of one-inch oak, +and the two last be screwed very securely to the baseboard. The shape of A is +shown in Fig. 163. The inside is cut out with a pad saw, a square notch being +formed at the back for the lever to move in. The handles of an old rubber chest +expander come in useful for the grips. One grip, D, is used entire for +attachment to the lever; while of the other only the wooden part is required, +to be mounted on a 1/4-inch steel bar running through the arms of A near the +ends of the horns. If a handle of this kind is not available for D, one may +substitute for it a piece of metal tubing of not less than 1/2-inch diameter, +or a 3/4-inch wooden rod, attached to an eye on the lever by a wire passing +through its centre. +</p> + +<p> +A handle, if used, is joined to the lever by means of a brass plate 3/4 inch +wide and a couple of inches long. A hole is bored in the centre somewhat +smaller than the knob to which the rubber was fastened, and joined up to one +long edge by a couple of saw cuts. Two holes for good-sized screws must also be +drilled and countersunk, and a socket for the knob must be scooped out of the +lever. After making screw holes in the proper positions, pass the shank of the +knob through the slot in the plate, and screw the plate on the lever. This +method holds the handle firmly while allowing it to move freely. +</p> + +<p> +The lever tapers from 1-1/2 inches at the pivot to 5/8 inch at the balance end. +The hole for the pivot—5/16-inch steel bar—should be long enough to +admit a piece of tubing fitting the bar, to diminish friction, and an important +point, be drilled near the handle edge of the lever, so as to leave plenty of +wood to take the strain. The last remark also applies to the hole for the +balance pin at Q. +</p> + +<p> +The balance support, B, and the pivot piece, C, are 2-1/2 and 2-7/16 inches +high respectively. Run a hole vertically through C and the baseboard for the +pivot, which should be 4-1/2 inches long, so as to project 1 inch when driven +right home. Take some trouble over getting the holes in L and C quite square to +the baseboard, as any inaccuracy will make the lever twist as it moves. To +prevent the pivot cutting into the wood, screw to the top of C a brass plate +bored to fit the pivot accurately. The strain will then be shared by the +screws. +</p> + +<p> +The horns of A should be long enough to allow the outside of the fixed grip to +be 2-1/4 inches from the inside of the handle. +</p> + +<p> +The balance is secured first to the lever by a pin driven through the eye of +the hook, and then to B by a 3-inch screw passed through the ring. The balance +should just not be in tension. +</p> + +<p> +When the apparatus is so far complete, test it by means of a second balance +applied to D. Set the scale-marker at zero, and pull on the D balance till, +say, 35 lbs. is attained. If the fixed balance shows 7 lbs. on what is meant to +be a 5 to 1 ratio, the setting of R relatively to P and Q is correct. If, +however, there is a serious discrepancy, it would be worth while making tests +with a very strong balance, and establishing a corrected gradation on a paper +dial pasted to the face of E. +</p> + +<p> +For twisting tests we need a special handle (see Fig. 164), which is slipped on +to the pivot and transmits the twist to L through a pin pressing on the back of +the lever. The stirrup is made out of strip iron, bent to shape and drilled +near the ends for the grip spindle. To the bottom is screwed and soldered a +brass or iron plate, into the underside of which the pin is driven. +</p> + +<p> +[Illustration: FIG. 164.—Handle for twisting test.] +</p> + +<p> +To prevent the handle bending over, solder round the pivot hole 3/4 inch of +brass tubing, fitting the pivot closely. +</p> + +<p> +Tests.—Grip tests should be made with each hand separately. The baseboard +should lie flat on a table or other convenient support, and be steadied, but +not pushed, by the hand not gripping. +</p> + +<p> +Twisting tests may be made inwards with the right hand, and back-handedly with +the left. The apparatus is stood on edge, square to the performer, resting on +the horns of A and a support near the balance. +</p> + +<p> +Finger tests are made by placing the thumb on the front face of B, and two +fingers on the farther side of the lever, one to the left and the other to the +right of the tail of the balance. +</p> + +</div><!--end chapter--> + +<div class="chapter"> + +<h2><a name="chap30"></a>XXX.<br /> +LUNG-TESTING APPARATUS.</h2> + +<p> +The capacity of the lungs, and their powers of inspiration and expiration, can +be tested by means of easily constructed apparatus which will interest most +people who are introduced to it. The reduction of the capabilities of the lungs +to figures affords a not unprofitable form of entertainment, as even among +adults these figures will be found to vary widely. +</p> + +<p> +Air Volume Measuring.—The air which the lungs deal with is scientifically +classified under four heads: +</p> + +<p> +1. Tidal air, which passes into and out of the lungs in natural breathing. +About 30 cubic inches in an adult (average). +</p> + +<p> +2. Reserve air, which can be expelled after a normal expiration. About 100 +cubic inches. +</p> + +<p> +3. Complemental air, which can be drawn in after a normal inspiration. About +100 cubic inches. +</p> + +<p> +4. Residual air, which cannot be removed from the lungs under any conditions by +voluntary effort. About 120 cubic inches. +</p> + +<p> +The first three added together give the vital capacity. This, as an addition +sum will show, is very much greater than the volume of air taken in during a +normal inspiration. +</p> + +<p> +The simplest method of testing the capacity of an individual pair of lungs is +embodied in the apparatus shown in Figs. 165 and 166. A metal box is submerged, +bottom upwards, in a tank of somewhat larger dimensions, until the water is +level with the bottom inside and out. A counterweight is attached to the +smaller box to place it almost in equilibrium, so that if air is blown into the +box it will at once begin to rise. +</p> + +<p> +If we make the container 7-1/16 inches square inside, in plan, every inch it +rises will represent approximately 50 cubic inches of air blown in; and a +height of 7 inches, by allowing for 325 cubic inches, with a minimum immersion +of half an inch, should suffice even for unusually capacious lungs. The outside +box need not be more than 8 inches all ways. +</p> + +<p> +[Illustration: FIG. 166.—Section of lung-capacity tester.] +</p> + +<p> +Unless you are an expert with the soldering iron, the making of the boxes +should be deputed to a professional tinman, who would turn out the pair for +quite a small charge. Specify very thin zinc for the air vessel, and have the +top edges stiffened so that they may remain straight. +</p> + +<p> +On receiving the boxes, cut a hole 3/4-inch diameter in the centre of the +bottom of the air vessel, and solder round it a piece of tubing, A, 1 inch +long, on the outside of the box. In the centre of the larger box make a hole +large enough to take a tube, E, with an internal diameter of 1/8 inch. This +tube is 8 inches long and must be quite straight. Next procure a straight wire, +C, that fits the inside of the small tube easily; make an eye at the end, and +cut off about 9 inches. Bore a hole for the wire in a metal disc 1 inch across. +</p> + +<p> +[Illustration: FIG. 166.—Perspective view of lung-capacity tester.] +</p> + +<p> +The air container is then placed in the water box and centred by means of +wooden wedges driven in lightly at the corners. Push the small tube through its +hole in the water box, and thrust the wire—after passing it through the +disc and the projection on the air container—into the tube. The tube +should reach nearly to the top of the air container, and the wire to the bottom +of the water box. Solder the tube to the box, the wire to the disc, and the +disc to the container. A little stay, S, will render the tube less liable to +bend the bottom of the box. Plug the tube at the bottom. +</p> + +<p> +The wire sliding in the tube will counteract any tendency of the container to +tilt over as it rises. +</p> + +<p> +A nozzle, D, for the air tube is soldered into the side of A, as shown. +</p> + +<p> +The counterweight is attached to the container by a piece of fine strong twine +which passes over two pulleys, mounted on a crossbar of a frame screwed to the +sides of the water box, or to an independent base. The bottom of the central +pulley should be eight inches above the top of the container, when that is in +its lowest position. +</p> + +<p> +For recording purposes, make a scale of inches and tenths, and the +corresponding volumes of air, on the side of the upright next the +counterweight. The wire, W, is arranged between counterweight and upright so +that an easily sliding plate, P, may be pushed down it by the weight, to act as +index. +</p> + +<p> +[Illustration: FIG. 167.—Apparatus for showing lung power.] +</p> + +<p> +Notes.—The pulleys must work easily, to reduce friction, which renders +the readings inaccurate. Absolute accuracy is not obtainable by this apparatus, +as the rising of the container lowers the water level slightly, and the air has +to support part of the weight of the container which was previously borne by +the water. But the inaccuracy is so small as to be practically negligible. +</p> + +<p> +A Pressure Recorder. +</p> + +<p> +[Transcribers note: Even with the precautions used in this project, health +standards of 2004 would consider any exposure to mercury dangerous. Water could +be substituted and the column lengths scaled up by about 13.5.] +</p> + +<p> +If mercury is poured into a vertical tube closed at the bottom, a pressure is +exerted on the bottom in the proportion of approximately one pound per square +inch for every two inches depth of mercury. Thus, if the column is 30 inches +high the bottom pressure is slightly under 15 lbs. per square inch. +</p> + +<p> +This fact is utilized in the pressure recorder shown in Fig. 167, a U-shaped +glass tube half filled with mercury. A rubber tube is attached to the bent-over +end of one of the legs, so that the effects of blowing or suction may be +communicated to the mercury in that leg. Normally the mercury stands level in +both tubes at what may be called the zero mark. Any change of level in one leg +is accompanied by an equal change in the opposite direction in the other. +Therefore, if by blowing the mercury is made to rise an inch in the left leg, +the pressure exerted is obviously that required to support a two-inch column of +mercury—that is, 1 lb. per sq. inch. This gives a very convenient +standard of measurement, as every inch rise above the zero mark indicates 1 lb. +of pressure. +</p> + +<h4>CONSTRUCTION.</h4> + +<p> +The mercury tube should be made first. Take a piece of glass tubing 20 inches +long, and bend it at a point 9 inches from one end after heating in a spirit +flame. The legs should be kept as parallel as possible. Lay the tube, while the +heated part is still pliant, on a flat surface, the bend projecting over the +edge, So that the two legs shall be in line. When the glass has cooled, bend +over two inches of the longer leg to an angle of about 45 degrees. +</p> + +<p> +A standard for the tube is now made out of one-inch wood. Hollow out a bed in +which the tube shall lie and be completely protected. To the right of the tube +the standard is notched to take a small bottle. The notch should be slightly +narrower than the diameter of the bottle, and have its sides hollowed out to +fit. +</p> + +<p> +Halfway up the tube draw a zero mark across the standards, and above this a +scale of inches in fractions on both sides. Each inch represents 1 lb. +pressure. +</p> + +<p> +The cork of the bottle must be pierced with a red-hot wire for two glass tubes, +one of which is bent over for the blowing tube. Both tubes should be pointed at +the bottle end so that they may enter the cork easily. Make the top of the cork +air tight with sealing-wax. The purpose of the bottle is to catch any mercury +that might be sucked out of the tube; one does not wish mercurial poisoning to +result from the experiments. Also it prevents any saliva entering the mercury +tube. +</p> + +<p> +When the latter has been secured to the standard by a couple of slips of tin +nailed to the front, connect it up with the bottle, and fill it up to the zero +mark with mercury poured in through a small paper funnel. +</p> + +<p> +The open end of the tube should be provided with an inch of tubing. Clips +placed on this and on the rubber connection between tube and bottle will +prevent the escape of mercury should the apparatus be upset when not in use. +</p> + +<p> +The average blowing pressure of which the lungs are capable is about 1-1/2 lbs. +per square inch; inspiration pressure without mouth suction about 1 lb. per +square inch; suction pressure 2-1/2 to 3 lbs. per square inch. +</p> + +<p> +Caution.—Don’t ask people with weak lungs to try experiments with +the apparatus described in this chapter. +</p> + +</div><!--end chapter--> + +<div class="chapter"> + +<h2><a name="chap31"></a>XXXI.<br /> +HOME-MADE HARMONOGRAPHS.</h2> + +<p> +Have you ever heard of the harmonograph? If not, or if at the most you have +very hazy ideas as to what it is, let me explain. It is an instrument for +recording on paper, or on some other suitable surface, the figures described by +two or more pendulums acting in concert. +</p> + +<p> +The simplest form of harmonograph is shown in Fig. 168. Two pendulums are so +suspended on points that their respective directions of movement are at right +angles to one another—that is, pendulum A can swing only north and south, +as it were, and pendulum B only east and west. On the top of B is a platform to +carry a card, and on the upper end of A a lever is pivoted so as to be able to +swing only vertically upwards and downwards. At its end this lever carries a +pen, which when at rest lies on the centre of the card platform. +</p> + +<p> +[Illustration: FIG. 168.—Simple Rectilinear Harmonograph.] +</p> + +<p> +The bob, or weight, of a pendulum can be clamped at any point on its rod, so +that the rate or “period” of swing may be adjusted or altered. The +nearer the weight is brought to the point of suspension, the oftener will the +pendulum swing to and fro in a given time—usually taken as one minute. +From this it is obvious that the rates of swing of the two pendulums can be +adjusted relatively to one another. If they are exactly equal, they are said to +be in unison, and under these conditions the instrument would trace figures +varying in outline between the extremes of a straight line on the one hand and +a circle on the other. A straight line would result if both pendulums were +released at the same time, a circle,[1] if one were released when the other +had half finished a swing, and the intermediate ellipses would be produced by +various alterations of “phase,” or time of the commencement of the +swing of one pendulum relatively to the commencement of the swing of the other. +</p> + +<p> +[Footnote 1: It should be pointed out here that the presence of friction +reduces the “amplitude,” or distance through which a pendulum +moves, at every swing; so that a true circle cannot be produced by free +swinging pendulums, but only a spiral with coils very close together.] +</p> + +<p> +But the interest of the harmonograph centres round the fact that the periods of +the pendulums can be tuned to one another. Thus, if A be set to swing twice +while B swings three times, an entirely new series of figures results; and the +variety is further increased by altering the respective amplitudes of swing and +phase of the pendulums. +</p> + +<p> +We have now gone far enough to be able to point out why the harmonograph is so +called. In the case just mentioned the period rates of A and B are as 2: 3. +Now, if the note C on the piano be struck the strings give a certain note, +because they vibrate a certain number of times per second. Strike the G next +above the C, and you get a note resulting from strings vibrating half as many +times again per second as did the C strings—that is, the relative rates +of vibration of notes C and G are the same as those of pendulums A and +B—namely, as 2 is to 3. Hence the “harmony” of the pendulums +when so adjusted is known as a “major fifth,” the musical chord +produced by striking C and G simultaneously. +</p> + +<p> +In like manner if A swings four times to B’s five times, you get a +“major third;” if five times to B’s six times, a “minor +third;” and if once to B’s three times, a “perfect +twelfth;” if thrice to B’s five times, a “major sixth;” +if once to B’s twice, an “octave;” and so on. +</p> + +<p> +So far we have considered the figures obtained by two pendulums swinging in +straight lines only. They are beautiful and of infinite variety, and one +advantage attaching to this form of harmonograph is, that the same figure can +be reproduced exactly an indefinite number of times by releasing the pendulums +from the same points. +</p> + +<p> +[Illustration: FIG. 169.—Goold’s Twin Elliptic Pendulum +Hamonograph.] +</p> + +<p> +But a fresh field is opened if for the one-direction suspension of pendulum B +we substitute a gimbal, or universal joint, permitting movement in all +directions, so that the pendulum is able to describe a more or less circular +path. The figures obtained by this simple modification are the results of +compounded rectilinear and circular movements. +</p> + +<p> +[Illustration: FIG. 170.—Benham’s miniature Twin Elliptic +Pendulum<br /> +Harmonograph.]<br /> +</p> + +<p> +The reader will probably now see even fresh possibilities if both pendulums are +given universal movement. This can be effected with the independent pendulums; +but a more convenient method of obtaining equivalent results is presented in +the Twin Elliptic Pendulum invented by Mr. Joseph Goold, and shown in Fig. 169. +It consists of—(1) a long pendulum, free to swing in all directions, +suspended from the ceiling or some other suitable point. The card on which the +figure is to be traced, and the weights, are placed on a platform at the bottom +of this pendulum. (2) A second and shorter free pendulum, known as the +“deflector,” hung from the bottom of the first. +</p> + +<p> +This form of harmonograph gives figures of infinite variety and of extreme +beauty and complexity. Its chief drawback is its length and weight, which +render it more or less of a fixture. +</p> + +<p> +Fortunately, Mr. C. E. Benham of Colchester has devised a Miniature Twin +Elliptic Pendulum which possesses the advantages of the Goold, but can be +transported easily and set up anywhere. This apparatus is sketched in Fig. 170. +The main or platform pendulum resembles in this case that of the Rectilinear +Harmonograph, the card platform being above the point of suspension. +</p> + +<p> +Value of the Harmonograph.—A small portable harmonograph will be found to +be a good means of entertaining friends at home or elsewhere. The gradual +growth of the figure, as the card moves to and fro under the pen, will arouse +the interest of the least scientifically inclined person; in fact, the trouble +is rather to persuade spectators that they have had enough than to attract +their attention. The cards on which designs have been drawn are in great +request, so that the pleasure of the entertainment does not end with the mere +exhibition. An album filled with picked designs, showing different harmonies +and executed in inks of various colours, is a formidable rival to the choicest +results of the amateur photographer’s skill. +</p> + +<p> +Practical Instructions for making Harmonographs. +</p> + +<p> +Pendulums.—For the Rectilinear type of harmonograph wooden rods 5/8 to +3/4 inch in diameter will be found very suitable. They cost about 2d. each. Be +careful to select straight specimens. The upper pendulum of the Miniature Twin +Elliptic type should be of stouter stuff, say a broomstick; that of the Goold +apparatus stouter still. +</p> + +<p> +All pendulums on which weights are slid up and down should be graduated in +inches and fractions, reckoning from the point of suspension as zero. The +graduation makes it easy to re-establish any harmony after the weights have +been shifted. +</p> + +<p> +Suspensions.—For a harmonograph to give satisfaction it is necessary that +very little friction should be set up at the point of suspension, so that the +pendulums may lose amplitude of swing very slowly. +</p> + +<p> +One-way suspensions are easily made. Two types, the point and knife-edge +respectively, are shown in Fig. 168 and the top part of Fig. 172. The point +suspension is most suitable for small rods and moderate weights; the knife-edge +for large rods and heavy weights which would tend to crush a fine point. +</p> + +<p> +[Illustration: FIG. 171.—Gimbal giving universal movement: point +suspension.] +</p> + +<p> +Points should rest in cup-shaped depressions in a metal plate; knife-edges in +V-shaped grooves in a metal ring. +</p> + +<p> +[Illustration: FIG. 172.—Knife-edge universal-motion gimbal.] +</p> + +<p> +Screws turned or filed to a sharp end make convenient points, as they can be +quickly adjusted so that a line joining the points lies exactly at right angles +to the pendulum. The cups to take the points should not be drilled until the +points have been thus adjusted. Make a punch mark on the bedplate, and using +this as centre for one of the points, describe an arc of a circle with the +other. This will give the exact centre for the other cup. It is evident that if +points and cup centres do not coincide exactly there must be a certain amount +of jamming and consequent friction. +</p> + +<p> +In making a knife-edge, such as that shown in Fig. 172, put the finishing +touches on with a flat file drawn lengthwise to ensure the edge being +rectilinear. For the same reason the V slots in the ring support should be +worked out together. If they are formed separately, the chances are against +their being in line with one another. +</p> + +<p> +Gimbals, or universal joints, giving motion in all directions, require the +employment of a ring which supports one pair of edges or points (Fig. 172), and +is itself supported on another pair of edges or points set at right angles to +the first. The cups or nicks in the ring should come halfway through, so that +all four points of suspension shall be in the same plane. If they are not, the +pendulum will not have the same swing-period in all directions. If a gimbal +does not work with equal freedom in all ways, there will be a tendency for the +pendulum to lose motion in the direction in which most friction occurs. +</p> + +<p> +By wedging up the ring of a gimbal the motion of the pendulum is changed from +universal to rectilinear. If you are making a harmonograph of the type shown in +Fig. 168, use a gimbal for the platform pendulum, and design it so that the +upper suspension gives a motion at right angles to the pen pendulum. The use of +two little wedges will then convert the apparatus in a moment from +semirectilinear to purely rectilinear. +</p> + +<p> +Weights.—The provision of weights which can be slipped up and down a rod +may present some difficulty. Of iron and lead, lead is the more convenient +material, as occupying less space, weight for weight, and being more easily +cast or shaped. I have found thin sheet roofing lead, running 2 lbs. to the +square foot, very suitable for making weights, by rolling a carefully squared +strip of the material round the rod on which it will have to move, or round a +piece of brass tubing which fits the rod. When the weight has been rolled, +drill four holes in it, on opposite sides near the ends, to take nails, +shortened so that they just penetrate all the laps but do not enter the central +circular space. These will prevent the laps sliding over one another endways. A +few turns of wire round the weight over the heads makes everything snug. +</p> + +<p> +Just one caution here. The outside lap of lead should finish at the point on +the circumference where the first lap began, for the weight to be approximately +symmetrical about the centre. +</p> + +<p> +An alternative method is to melt up scrap lead and cast weights in tins or +flowerpots sunk in sand, using an accurately centred stick as the core. This +stick should be very slightly larger than the pendulum rod, to allow for the +charring away of the outside by the molten metal. (Caution.—The mould +must be quite dry.) +</p> + +<p> +Failing lead, tin canisters filled with metal scrap may be made to serve. It +will in this case be necessary to bore the lid and bottom centrally and solder +in a tube fitting the rod, and to make an opening through which the weighting +material can be inserted. +</p> + +<p> +Adjustment of Weights.—As lead is too soft a metal to give a satisfactory +purchase to a screw—a thread cut in it soon wears out—it is better +to support a leaden weight from underneath by means of a brass collar and +screw. A collar is easily made out of a bit of tubing thickened at the point +where the screw will pass by soldering on a suitably shaped piece of metal. +Drill through the reinforcement and tubing and tap to suit the screw used, +which may well be a camera tail screw, with a large flat head. +</p> + +<p> +I experienced some trouble from the crushing of wooden rods by a screw, but got +over it as follows. The tubing selected for the collar was large enough to +allow a piece of slightly smaller tubing to be introduced between it and the +rod. This inner piece was slit from one end almost to the other, on opposite +sides, and soldered at one end to the outer tube, a line joining the slots +being at right angles to the axis of the screw. The pressure of the screw point +was thus distributed over a sufficient area of the wood to prevent indentation. +(See Fig. 173.) +</p> + +<p> +[Illustration: FIG. 173.] +</p> + +<p> +[Illustration: FIG. 174.—Pivot for pen lever.] +</p> + +<p> +Pen Levers.—The pen lever, of whatever kind it be, must work on its +pivots with very little friction, and be capable of fine adjustment as regards +balance. For the Rectilinear Harmonograph the form of lever pivot shown in Fig. +174 is very suitable. The spindle is a wire nail or piece of knitting needle +sharpened at both ends; the bearings, two screws filed flat at the ends and +notched with a drill. +</p> + +<p> +The brass standard should be drilled and tapped to fit the screws fairly tight, +so that when once adjusted they may not slacken off. If the lever is made of +wood, the tail may be provided with a number of metal pegs on which to place +the weights; if of wire, the tail should be threaded so that a brass weight and +lock screw may be moved along it to any desired position. It is very important +that the pressure of the pen on the card should be reduced to a minimum by +proper balancing, as the friction generated by a “heavy” pen slows +the pendulum very quickly; and that the centre of gravity should be below the +point of suspension, to put the pen in stable equilibrium. The lever shown in +Fig. 169 is suitable for the Twin Elliptic Pendulum. +</p> + +<p> +In this case the lever is not moved about as a whole. Mr. C. E. Benham +advocates the use of wood covered with velvet to rest the lever points on. +</p> + +<p> +For keeping the pen, when not in use, off the platform, a small weight attached +to the lever by a thread is convenient. When the pen is working, the weight is +raised to slacken the thread. +</p> + +<p> +[Illustration: FIG. 175.—End of pen lever.] +</p> + +<p> +Attaching Pen to Lever.—In the case of wooden levers, it is sufficient to +slit the end centrally for a few inches after drilling a hole rather smaller +than the pen, at a point which lies over the centre of the card platform, and +quite squarely to the lever in all directions, so that the pen point may rest +squarely on the card. (Fig. 175.) +</p> + +<p> +Another method is to attach to the end of the lever a vertical half-tube of +tin, against which the pen is pressed by small rubber bands; but even more +convenient is a small spring clip shaped as in Fig. 176. +</p> + +<p> +[Illustration: FIG. 176.—Clip to hold glass pen.] +</p> + +<p> +The card platform should be perfectly flat. This is essential for the +production of good diagrams. If wood is used, it is advisable to glue two thin +pieces together under pressure, with the grain of one running at right angles +to the other, to prevent warping. +</p> + +<p> +Another important point is to have the card platform square to the rod. If a +piece of tubing fitting the rod is turned up true in the lathe and soldered to +a disc screwed to the underside of the table, perpendicularity will be assured, +and incidentally the table is rendered detachable. +</p> + +<p> +To hold the card in place on the table, slit a spring of an old photographic +printing frame down the middle, and screw the two halves, convex side upwards, +by one end near two opposite corners of the platform. (See Fig. 170.) If cards +of the same size are always used, the table should be marked to assist +adjustment. +</p> + +<p> +Making Pens.—The most satisfactory form of pen is undoubtedly a piece of +glass tubing drawn out to a point, which is ground down quite smooth. The +making of such pens is rather a tedious business, but if care be taken of the +pen when made it will last an indefinite time. +</p> + +<p> +Tubing 3/16 or 1/8 inch in external diameter is suitable. Break it up (by +nicking with a file) into 9-inch lengths. Take a piece and hold its centre in +the flame of a small spirit lamp, and revolve it till it softens. Then draw the +glass out in as straight a line as possible, so that the points may be central. +If the drawing is done too fast, the points will be much too long to be of any +use: half an inch of taper is quite enough. +</p> + +<p> +Assuming that a point of satisfactory shape has been attained—and one +must expect some failures before this happens—the pen may be placed in +the pen lever and ground down on a perfectly clean wet hone laid on the card +platform, which should be given a circular movement. Weight the lever so as to +put a fair pressure on the point. +</p> + +<p> +The point should be examined from time to time under a strong magnifying-glass, +and tested by blowing through it into a glass of water. For very liquid ink the +hole should be as small as you can possibly get it; thick inks, such as Indian, +require coarser pens. +</p> + +<p> +The sharp edge is taken off and the width of the point reduced by drawing the +pen at an angle along the stone, revolving it all the time. The nearer to the +hole you can wear the glass away the finer will be the line made by the pen. +</p> + +<p> +Another method is as follows:—Seal the point by holding it a moment in +the flame. A tiny bulb forms on the end, and this has to be ground away till +the central hole is reached. This is ascertained by the water test, or by +holding the pen point upwards, so that light is reflected from the tip, and +examining it under the magnifier. Then grind the edge off, as in the first +case. +</p> + +<p> +Care of Pens.—The ink should be well strained, to remove the smallest +particles of “suspended matter,” and be kept corked. Fill the pen +by suction. On no account allow the ink to dry in the pen. Squirt any ink out +of it when it is done with, and place it point downwards in a vessel of water, +which should have a soft rubber pad at the bottom, and be kept covered to +exclude dust. Or the pen may be cleaned out with water and slipped into a +holder made by rolling up a piece of corrugated packing-paper. If the point +gets stopped up, stand the pen in nitric or sulphuric acid, which will probably +dissolve the obstruction; and afterwards wash it out. +</p> + +<p> +Inks.—I have found Stephens’s coloured inks very satisfactory, and +can recommend them. +</p> + +<p> +Paper and Cards.—The paper or cards used to draw the figures on should +not have a coated surface, as the coating tends to clog the pen. The cheapest +suitable material is hot pressed paper, a few penny-worths of which will +suffice for many designs. Plain white cards with a good surface can be bought +for from 8s. to 10s. per thousand. +</p> + +<p> +Lantern Slides.—Moisten one side of a clean lantern slide plate with +paraffin and hold it over a candle flame till it is a dead black all over. Very +fine tracings can be obtained on the smoked surface if a fine steel point is +substituted for the glass pen. The design should be protected by a cover-glass +attached to it by a binding strip round the edges. +</p> + +<p> +Details of Harmonographs. +</p> + +<p> +The reader may be interested in details of the apparatus shown in Figs. 168 and +170, made by the writer. +</p> + +<p> +The Rectilinear Harmonograph, shown in Fig. 168, has pendulums of 5/8-inch +wood, 40 inches long, suspended 30 inches from the lower ends, and set 10 +inches apart, centre to centre. The suspensions are of the point type. The +weights scale 5 lbs. each. The platform pendulum is provided with a second +weight, which can be affixed above the suspension to slow that pendulum for +2:3, 4:5, 7:8, and higher harmonies. +</p> + +<p> +The baseboard is plain, and when the apparatus is in action its ends are +supported on boxes or books laid on two tables, or on other convenient +supports. The whole apparatus can be taken to pieces very quickly for +transport. The total cost of materials used did not exceed 3s. 6d. +</p> + +<p> +The Twin Elliptic Pendulum of Fig. 170 is supported on a tripod base made of +three pieces of 1-1/2 x 1-1/2 inch wood, 40 inches long, with ends cut off to +an angle of 72 degrees to give a convenient straddle, screwed at the top to an +oak head 3/4 inch thick, and braced a foot below the top by horizontal +crossbars 2 inches wide and 1/2 inch thick. For transport this stand can be +replaced by a flat baseboard similar to that of the Rectilinear Harmonograph +described in the last paragraph. +</p> + +<p> +The main pendulum is a straight ash rod, 33 inches long and 1-1/4 inches in +diameter, suspended 13-1/2 inches from its upper end. Two weights of 4-1/2 lbs. +each, made of rolled sheet lead, are provided for this pendulum. According to +the nature of the harmony, one only, or both together below the suspension, or +one above and one below, are used. +</p> + +<p> +The weight of the lower pendulum, or deflector, is supported on a disc, resting +on a pin passing through the bottom of a piece of brass tubing, which is +provided with an eye at its upper end. This eye is connected by a hook with +several strands of silk thread, which are attached to the upper pendulum by +part of a cycle tyre valve. The stem part of the valve was cut off from the +nut, and driven into a suitably sized hole in the end of the main pendulum. The +screw collar for holding the valve in place had a little brass disc soldered to +the outside, and this disc was bored centrally for the threads to pass through. +The edges of the hole had been rounded off carefully to prevent fraying of the +threads. (Fig. 177.) The over-all length of the pendulum, reckoning from the +point of suspension, is 20 inches. The weights of the lower pendulum are +several in number, ranging from l lb. to 3 lbs. +</p> + +<p> +[Illustration: FIG. 177.—Suspension for lower weight of Twin +Elliptic<br /> +Harmonograph.]<br /> +</p> + +<p> +Working the Harmonograph.—A preliminary remark is needed here. Harmonies +are, as we have seen, a question of ratio of swing periods. The larger the +number of swings made by the more quickly moving pendulum relatively to that of +the slower pendulum in a given time, the higher or sharper is the harmony said +to be. Thus, 1:3 is a higher harmony than 1:2, and 2:3 is lower or flatter than +3:8. +</p> + +<p> +The tuning of a harmonograph with independent pendulums is a simple matter. It +is merely necessary to move weights up or down until the respective numbers of +swings per minute bear to one another the ratio required. This type of +harmonograph, if made of convenient size, has its limitations, as it is +difficult to get as high a harmonic as 1:2, or the octave with it, owing to the +fact that one pendulum must in this case be very much shorter than the other, +and therefore is very sensitive to the effects of friction. +</p> + +<p> +[Illustration: FIG. 176a.—Hamonograms illustrating the ratio 1:3. The two +on the left are made by the pendulums of a twin elliptical harmonograph when +working concurrently; the three on the right by the pendulums when working +antagonistically.] +</p> + +<p> +[Illustration: FIG. 177a.—Harmonograms of 3:4 ratio +(antagonistically).<br /> +(Reproduced with kind permission of Mr. C. E. Benham.)]<br /> +</p> + +<p> +The action of the Twin Elliptic Pendulum is more complicated than that of the +Rectilinear, as the harmony ratio is not between the swings of deflector and +upper pendulum, but rather between the swings of the deflector and that of the +system as a whole. Consequently “tuning” is a matter, not of +timing, but of experiment. +</p> + +<p> +Assuming that the length of the deflector is kept constant—and in +practice this is found to be convenient—the ratios can be altered by +altering the weights of one or both pendulums and by adjustment of the upper +weight. +</p> + +<p> +For the upper harmonies, 1:4 down to 3:8, the two pendulums may be almost +equally weighted, the top one somewhat more heavily than the other. The upper +weight is brought down the rod as the ratio is lowered. +</p> + +<p> +To continue the harmonies beyond, say, 2:5, it is necessary to load the upper +pendulum more heavily, and to lighten the lower one so that the proportionate +weights are 5 or 6:1. Starting again with the upper weight high on the rod, +several more harmonies may be established, perhaps down to 4:7. Then a third +alteration of the weights is needed, the lower being reduced to about +one-twentieth of the upper, and the upper weight is once more gradually brought +down the rod. +</p> + +<p> +Exact figures are not given, as much depends on the proportions of the +apparatus, and the experimenter must find out for himself the exact position of +the main weight which gives any desired harmonic. A few general remarks on the +action and working of the Twin Elliptic will, however, be useful. +</p> + +<p> +1. Every ratio has two forms. +</p> + +<p> +(a) If the pendulums are working against each other— +antagonistically—there will be loops or points on the outside of the +figure equal in number to the sum of the figures in the ratio. +</p> + +<p> +(b) If the pendulums are working with each other—concurrently—the +loops form inside the figure, and are equal in number to the difference between +the figures of the ratio. To take the 1:3 ratio as an example. If the tracing +has 3+1=4 loops on the outside, it is a specimen of antagonistic rotation. If, +on the other hand, there are 3-1=2 loops on the inside, it is a case of +concurrent rotation. (Fig. 176, A.) +</p> + +<p> +2. Figures with a ratio of which the sum of the numbers composing it is an even +number (examples, 1:3, 3:5, 3:7) are symmetrical, one half of the figure +reproducing the other. If the sum is Uneven, as in 1:2, 2:3, 2:7, the figure is +unsymmetrical. (Fig. 177, A.) +</p> + +<p> +3. The ratio 1:3 is the easiest to begin upon, so the experimenter’s +first efforts may be directed to it. He should watch the growth of the figure +closely, and note whether the repeat line is made in front of or behind the +previous line of the same loop. In the first case the figure is too flat, and +the weight of the upper pendulum must be raised; in the second case the weight +must be lowered. Immediately an exact harmonic is found, the position of the +weight should be recorded. +</p> + +<p> +Interesting effects are obtained by removing the lower pendulum and allowing +the apparatus to describe two elliptical figures successively, one on the top +of the other, on the same card. The crossing of the lines gives a +“watered silk” appearance to the design, which, if the pen is a +very fine one and the lines very close together, is in many cases very +beautiful. +</p> + +<p> +Readers who wish for further information on this fascinating subject are +recommended to purchase “Harmonic Vibrations,” published by Messrs. +Newton and Co., 72 Wigmore Street, London, W. This book, to which I am much +indebted, contains, besides much practical instruction, a number of charming +reproductions of harmonograms. +</p> + +<p> +Before closing this chapter I should like to acknowledge the kind assistance +given me by Mr. C. E. Benham, who has made a long and careful study of the +harmonograph. +</p> + +</div><!--end chapter--> + +<div class="chapter"> + +<h2><a name="chap32"></a>XXXII.<br /> +A SELF-SUPPLYING MATCHBOX.</h2> + +<p> +This useful little article can be constructed in a couple of hours by a handy +person. In general idea it consists of a diamond-shaped box to hold vestas, +working up and down diagonally on a vertical member (A in Fig. 179 (1)), which +passes through slits at the top and bottom, and runs in grooves cut in the +sides of the box. The top of A is grooved to allow a match to rest on it. When +the box is drawn up to the full extent allowed by a transverse pin in the slot +shown in Fig. 179 (2), the groove is at the lowest point of the box, and is +covered by the matches. When the box is lowered, A catches a vesta and takes it +up through the top, as seen in Fig. 178, for removal by the fingers. +</p> + +<p> +The only materials required are a cigar-box, some pins, and a supply of glue. +The box should be carefully taken to pieces, and the parts soaked in hot water +till freed of all paper, and then allowed to dry under pressure, small slips of +wood being interposed across the grain to keep them separate and permit the +passage of air. +</p> + +<p> +[Illustration: FIG. 178.—Self-supplying matchbox, with match in position +for removal by fingers.] +</p> + +<p> +When the wood is dry, cut out with a fret saw two pieces shaped like Fig. 179 +(3), to form the ends of the box. Allow a little surplus, so that the edges may +be finished off neatly with chisel and plane. The two ends should match +exactly, or there will be trouble at a later stage. +</p> + +<p> +Now cut, down the centre of each a groove for one edge of A to run in. By +preference it should be square; but if you do not possess the necessary chisel, +a V groove made with a knife will suffice—and, of course, in this case +the edges of A will have to be bevelled to fit. +</p> + +<p> +[Illustration: FIG. 179.—Details of self suplying matchbox.] +</p> + +<p> +The four sides of the box, BB and CC, are next cut out. Their sectional shape +is shown in Fig. 179 (1). They should be rather longer than the length of the +ordinary vesta, and all of exactly the same length, and rectangular. A very +small hack saw (costing about 1s.) with fine teeth is the best possible tool +for close cutting, and a small 1 shilling iron plane is invaluable for truing +and bevelling the edges. +</p> + +<p> +The glue pot, which we will assume to be ready for use, is now needed to attach +the fixed B (the other B is hinged to form a lid for filling the box through) +and CC to the ends. This operation must be carried out accurately, so that the +slots may not be blocked. +</p> + +<p> +While the glue is setting, cut out A, allowing an extra 1/16 inch of width for +fitting. The slot down the centre is best made with a fret saw, and should be +smoothed internally by drawing a strip of fine glass paper to and fro through +it. The length of the slot is of great importance. It must reach to just that +distance from the top edge which brings that edge flush with the bottom of the +box when the box is raised; and in the other direction must permit the box to +settle on to its foot, so that the match lifted shall project above the box. +</p> + +<p> +Work the edges of A down carefully (double-bevelling them if the notches are +V-shaped) till A will run easily, but not loosely, in the box. Then cut out two +slips, DD, and bevel them at the top to an angle of 45 degrees. Put A in place +and glue them on, taking care that the glue does not hold them fast to A. +</p> + +<p> +Pierce a small hole through DD, in line with the slot, and insert a pin.<br /> +Draw the box fully up, and see if the top of A sinks to the proper place.<br /> +If it projects a little, lengthen the slot a trifle.<br /> +</p> + +<p> +Cut out the supports EE, finish them neatly, and glue them to A. Make sure that +the pin lets the box touch them. +</p> + +<p> +Fix on the lid B with two pins for pivots, and fit a little catch made of brass +wire. To give extra security, drive ordinary pins, cut off to 5/8 inch, through +the sides into fixed B, CC, and DD, and through EE into A. This is an easy +enough business if pilot holes are made with a very fine awl or a tiny drill, +and a small, light hammer is used. It now remains only to go over the whole box +with glass paper or emery cloth, and to glue a diamond of coarse glass paper to +one end for striking the matches on. +</p> + +<p> +Note that the lid must not be opened when the box is down, as it would be +wrenched off its pivots. +</p> + +</div><!--end chapter--> + +<div class="chapter"> + +<h2><a name="chap33"></a>XXXIII.<br /> +A WOODEN WORKBOX.</h2> + +<p> +The box illustrated by Fig. 181 was copied from an article of Norwegian +manufacture. Its construction is an extremely simple matter, provided that one +can get a piece of easily bent wood (birch, for instance), not exceeding 3/16 +inch in thickness, for the sides. +</p> + +<p> +[Illustration: FIG. 180.—Showing how to draw an ellipse.] +</p> + +<p> +[Illustration: FIG. 181.—Norwegian workbox.] +</p> + +<p> +The bottom of the box is made of 5/16 or 3/8 inch wood, cut to an oval or +elliptical shape. To mark out an ellipse about 8 inches long and 5-1/2 inches +wide—this will be a. convenient size—stick two pins into the board +5-1/8 inches apart, pass a loop of thread 14 inches in circumference round +these, and run the point of a pencil round the pins in the path which it has to +take when confined by the slack of the loop (Fig. 180). Fret-saw along the +line. +</p> + +<p> +The wood strip for the side is 4-1/2 inches deep, and 1-1/2 inches longer than +the circumference of the bottom. The ends are thinned off somewhat, as shown in +Fig. 181, to prevent the lap having a clumsy appearance, and the surface is +smoothed all over with sandpaper. Bore a number of small nail holes 3/16 inch +from one edge, and then steam the wood over a big saucepan or other suitable +vessel until it is quite lissom. +</p> + +<p> +When attaching the side piece to the bottom, begin at the middle, and work +first towards what will be the inside end of the lap, and then towards the +outside end. Nails are driven in through the holes already drilled. When +nailing is finished, clip the top of the overlap with a hand-vice or screw +spanner, to prevent the tops of the ends sliding over one another, and bore a +line of holes l/4 inch apart, and at the same distance from the outer end. Fine +copper wire drawn to and fro through alternate holes from one end of the row to +the other and back again, will secure the joint. +</p> + +<p> +The lid overlaps the side 1/4 inch in all directions and has a square notch cut +in it at one end to pass under the piece A, and at the other a deeper, +circular-ended nick to enable it to pass over the key B when that is turned +into the position shown in the illustration. A is cut out of 1/4-inch wood; B, +in one piece, out of 1/2-inch. Their length under the heads exceeds the inside +depth of the box by the thickness of the lid. +</p> + +<p> +A is affixed rigidly to the side by small screws or wire, while B must be +attached in a manner, which will allow the head to rotate. Cut two nicks round +the shank, and two horizontal slots at the same height through the end of the +box. A couple of brass rings must then be procured of such a size that, when +flattened into a somewhat oval shape, they will project beyond the slots +sufficiently to allow a piece of wire to pass through them and prevent their +being drawn back again. +</p> + +<p> +Quarter-inch wood will do for the lid. A handle is made out of a couple of +inches of small cane bent into a semicircle, let through the lid at each end, +glued, and cut off flush. +</p> + +<p> +The exterior may be decorated by a design in poker-work, or be stained and +varnished. This is left to the maker’s discretion. +</p> + +</div><!--end chapter--> + +<div class="chapter"> + +<h2><a name="chap34"></a>XXXIV.<br /> +WRESTLING PUPPETS.</h2> + +<p> +[Illustration: FIG. 182.—Peg marked for cutting and drilling.] +</p> + +<p> +The expenditure of a halfpenny, and a quarter of an hour’s use of a +pocket knife, bradawl, and pliers, will produce a toy which is warranted to +amuse grown-ups as well as children. Wrestlers made out of clothes pegs may be +bought for a copper or two in the street, and are hardly a novelty; yet a few +notes on home production will not be a waste of space, as making is cheaper, +and much more interesting, than buying. +</p> + +<p> +The clothes pegs used must be of the shape shown in Fig. 182, with a round top. +They cost one penny per dozen. +</p> + +<p> +Drill holes through body and legs as indicated in Fig. 182. Cut the legs from +the “trunk,” and whittle them to the shape of Fig. 183. The arms, +made out of any thin wood, are 2-1/4 inches long between centres of end holes. +</p> + +<p> +To get the best results the two arms and the four legs should be paired off to +exactly the same length. +</p> + +<p> +[Illustration: FIG. 183.—Clothes-peg wrestlers.] +</p> + +<p> +The neatest method of attaching the parts is to use small brass tacks, which +must, of course, be of somewhat larger diameter than the holes in the body. +Holes in arms and legs are a loose fit, so that the wrestlers may be very +loose-jointed, and the tacks must not be driven in far enough to cause any +friction. +</p> + +<p> +Instead of tacks one may use wire passed through the parts and secured by a +bend or loop at each end. Wire has the disadvantage of entangling the thread +which works the figures. +</p> + +<p> +When assembling is finished, bore holes in the centres of the arm pieces, pass +a piece of wire through, and twist it into a neat loop at each end. To one loop +tie 2 feet of strong thread (carpet thread is best), and to the free end of the +thread a large nail or hook. The other loop has 6 feet or so of thread tied to +it, to be worked by the hand. If the thread is stained black, it will be +practically invisible by artificial light. +</p> + +<p> +The nail or hook is stuck under the edge of the carpet, or into some crack or +cranny which affords a good hold, and the wrestlers are worked by motions of +the hand. The funniest antics are produced by very slight jerks. +</p> + +<p> +If the arms are set too close together the heads may stick between them, in +which case one must either flatten off the sides of the heads or insert fresh +arm wires of greater length. If a head persists in jamming against the thread +wire or getting under it and staying there, cut 1/2 inch off a pin and stick it +into the front of the crown, so that the head is arrested by the wire when the +wrestler bends forward. +</p> + +<p> +[Illustration: FIG. 184.—Large wrestlers made of stout wood.] +</p> + +<p> +Large Wrestlers.—A more elaborate and realistic pair is shown in Fig. +184. The originals of the sketch are 8 inches high. Half-inch deal was used for +the bodies, 3/8-inch for the legs and arms. The painting-in of hair, features, +tights, and shoes adds considerably to the effect. The heads and limbs are mere +profiles, but anyone with a turn for carving might spend a little time in +rounding off and adding details which will make the puppets appear more +lifelike. +</p> + +</div><!--end chapter--> + +<div class="chapter"> + +<h2><a name="chap35"></a>XXXV.<br /> +DOUBLE BELLOWS.</h2> + +<p> +The small-sized bellows which have become popular in sitting-rooms are usually +more ornamental than efficient, and make one think regretfully of the +old-fashioned article of ample capacity which is seldom seen nowadays. +</p> + +<p> +Fig. 185 illustrates a method of coupling up two small bellows in such a manner +as to provide an almost continuous blast, besides doubling the amount of air +sent through the fire in a given time, at the coat of but little extra +exertion. A piece of wood half an inch thick is screwed across one bellows just +behind the valve hole. The two bellows are then laid valve facing valve, and +are attached to one another by a strip of tin passed round the wood just behind +the nozzles and by tying the two fixed handles together. +</p> + +<p> +[Illustration: FIG. 185.—Double-acting bellows. Two methods of coupling +shown.] +</p> + +<p> +Make a rectangle of stout wire somewhat wider than the handles and long enough +to reach from the outer face of one moving handle to that of the other, when +one bellows is quite closed and the other full open. The ends of the wire +should be soldered together, and the ends of the link held up to the handles by +a couple of staples. +</p> + +<p> +An alternative method is to use a piece of wood with a screw driven into it at +right angles near each end through the staples on the handles (Fig. 185, a). In +place of the staples you may use screw-in eyes fitting the screws. +</p> + +</div><!--end chapter--> + +<div class="chapter"> + +<h2><a name="chap36"></a>XXXVI.<br /> +A HOME-MADE PANTOGRAPH.</h2> + +<p> +The pantograph is a simple apparatus for copying drawings, maps, designs, etc., +on a reduced or enlarged scale, or to the same size as the original. +</p> + +<p> +[Illustration: FIG. 186.—Details of simple pantograph.] +</p> + +<p> +A sketch of a pantograph is given in Fig. 186. Four rods are jointed together +to form a parallelogram, the sides of which can be lengthened or shortened to +suit the scale of reproduction. One is attached by a fixed pivot at a to the +board on which the drawing is done. At b and e are removable pivots, used for +adjusting the rods; at c is a pivot which projects an inch or so below the +rods. The pointer is inserted at d for enlargement, or at f for reduction, the +pencil being in the unoccupied hole at d or f. +</p> + +<p> +If a same-sized copy is desired, the fixed pivot is transferred to d, and the +pencil and pointer placed at a and f respectively. +</p> + +<p> +Construction of an Enlarging and Reducing Pantograph.—Cut out of 1/8-inch +oak, walnut, or beech four rods 5/8 inch wide and 19 inches long. Smooth them +well all over, and make marks near the ends of each, exactly 18 inches apart. +The graduation of the rods for the adjustment pivot holes is carried out in +accordance with the measurements given in Fig. 187. It is advisable to mark out +and bore each rod separately if you do not possess a machine which will drill +holes quite perpendicularly; if you do, all four rods can be drilled at one +operation. +</p> + +<p> +In Fig. 187 the lower row of numerals indicates the number of times (in +diameters) the original is enlarged when all four holes similarly figured are +used; the upper row, the size of the copy as compared with the original in case +of reduction. +</p> + +<p> +If proportions other than those given are required, a very little calculation +will locate the necessary holes. +</p> + +<p> +Pivots.—All the pivots must fit their holes accurately, as any looseness +at the joints detracts from the truth of reproduction. For pivots band b and e +may use brass screws and small pieces of hard wood as nuts to hold them in +position. The nuts should screw on rather stiffly, and not be forced hard +against the rods, as free motion with little friction at all joints is +essential for good work. +</p> + +<p> +[Illustration: FIG. 187.—Diagram showing how to mark off pantograph rods. +The dotted lines above rod give distances of holes from ends.] +</p> + +<p> +The fixed pivot at a may be merely the shank of a wire nail of the proper size +driven into the board, a cork collar being slipped over it to keep the rod the +proper distance from the board. For c use a screw to the head of which has been +soldered half an inch of a round-headed brass nail, which will move easily over +the paper. At d is needed a hollow pivot, fashioned out of a quarter of an inch +of pencil-point protector or some other thin tube, burred over slightly at the +ends so as not to fall out. The end of B at f has a slotted hole to grip the +pencil or pointer, as the case may be. +</p> + +<p> +A Same-size Pantograph.—For making a same-size copy, tracing may be +preferred to the use of a pantograph; but if a pantograph is adopted, a special +apparatus may be constructed for the purpose. The arrangement is exactly the +same as that already described, excepting that the only holes needed are those +at a, c, d, f, at the middle points of the four rods, the parallelogram formed +by the rods being equal-sided. The fixed pivot is situated at d, and pencil and +pointer holes are made at a and f. +</p> + +<p> +Using the Pantograph.—When adjusting the instrument for reduction or +enlargement, make sure that the adjustment pivots are in the holes +corresponding with the scale. The fixed pivot, pointer, and pencil must be +rigid, and, with pivot c, be of such a length that the pantograph as a whole +moves parallel to the paper. A little sliding weight to place on the rod near +the pencil will be found useful for keeping the pencil point in constant +contact with the paper. +</p> + +<p> +If the apparatus works stiffly, ease the holes a trifle and lead-pencil the +wood at all points where two surfaces rub. It is absolutely impossible to make +a good reproduction with a stiff, jerky pantograph. +</p> + +<p> +To decide the positions of original and the paper for the copy, get the pointer +centred on the original and adjust the paper till its centre is under the +pencil. +</p> + +</div><!--end chapter--> + +<div class="chapter"> + +<h2><a name="chap37"></a>XXXVII.<br /> +A SILHOUETTE DRAWING MACHINE.</h2> + +<p> +With this very simple apparatus you will be able to give good entertainment to +such of your friends as may wish to have black paper records of their faces in +profile. +</p> + +<p> +The machine is merely a long rod, with a sliding pencil attached to one end and +a metal pointer stuck into the other, supported near the pencil end on a pivot +which permits free movement in all directions. +</p> + +<p> +For heads and busts only, the rod and pointer combined need not be more than 4 +feet 6 inches long. The rod is a 1/2-inch blind rod, the pointer a stout +knitting-needle driven axially into one end of the rod. This pointer, being of +small diameter, follows the minor curves and angles of the features much more +closely than would be possible with the rod. +</p> + +<p> +The support is a piece of wood, 1-1/2 inches square and 12 to 15 inches long, +screwed on to a large foot, which should be fairly heavy, as any tilting or +slipping will, of course, spoil the silhouette. The universal joint for the rod +is made by soldering a small U-shaped piece of metal to the end of a short +metal bar. The ends of the U are drilled for a pin passing through the rod; and +a hole is sunk into the top of the support to take the bar. The fit should be +close, to prevent the pivot rocking about, and the hole in the support deep +enough to bring the bottom of the stirrup down against the wood. +</p> + +<p> +If a series of holes half an inch apart is drilled, through the rod, the +nearest 9 inches from the pencil end, the size of the silhouette +proportionately to the original can be varied by moving the pin from one hole +to another. +</p> + +<p> +[Illustration: FIG. 188.—Silhouettograph in use.] +</p> + +<p> +[Illustration: FIG. 188a.—Group of silhouettes drawn with the machine +described.] +</p> + +<p> +The pencil holder is 4 inches of tubing, in which the pencil can slide easily +without shaking. If necessary, the size of the pencil should be reduced by +rubbing with glass paper. Bind the holder tightly to the end of the rod away +from the pointer, so that one extremity just overhangs the rod. A piece of thin +elastic is tied to the unsharpened end of the pencil and to the pencil tube, +the adjustment allowing the pencil to project an inch when the elastic is taut +but not stretched. +</p> + +<p> +A fairly soft pencil and a thick, smooth paper or card give the best results. +Paper should be backed by something hard to prevent the pencil digging in. +Attach the paper to a firm vertical surface, such as the side of a box, a +drawing board, a wall, etc. +</p> + +<p> +Using the Machine.—The rod support, paper, and sitter should be arranged +so that the rod is level at the height of the sitter’s nose and the +pencil on the centre of the paper. Bring the support near enough to the paper +to drive the pencil back into the tube until the point projects only half an +inch. +</p> + +<p> +A thread attached to the pencil will enable you to keep the pencil off the +paper until you wish to begin drawing the profile. +</p> + +<p> +Begin with the pointer pressing against the sitter’s chest, and bring it +over the face and down the back of the head and neck. Do not press it into the +hair, but carry it along what you consider to be the outline; though it must be +in actual contact with the features and clothes. It is hardly necessary to +mention that the sitter must keep perfectly still if the silhouette is to be at +all accurate. +</p> + +<p> +The tracing is cut round with fine-pointed scissors, and the paper blacked and +stuck on a piece of white card. Some trouble is saved by using paper white on +one aide and black on the other. If duplicates are needed, two or more pieces +of paper should be stuck together by the corners and to the paper on which the +silhouette is drawn, and all be cut through at one operation. +</p> + +<p> +With a little practice the actual tracing of the outline occupies but a few +seconds. Things are expedited if an assistant adjusts the paper and pencil. +</p> + +</div><!--end chapter--> + +<div class="chapter"> + +<h2><a name="chap38"></a>XXXVII.<br /> +A SIGNALLING LAMP.</h2> + +<p> +Visual signalling is effected at night in the Morse code by means of a lamp +fitted with an easily-moved shutter, which passes or cuts off the light at the +will of the operator. Readers who know the Morse code might well go to the +trouble of constructing in duplicate the simple apparatus to be described, as +the possession of an outfit will enable them to extend their signalling +capabilities. +</p> + +<p> +The stand for the lamp is admirably supplied by the ordinary camera +tripod.<br /> +For the illuminant we may select any good acetylene cycle lamp.<br /> +</p> + +<p> +For this a holder is made of 1/2-inch wood, according to the sketch shown in +Fig. 189. The width of all the four parts should be about 2 inches greater than +the front glass of the lamp. B and C should be sufficiently far apart to allow +the lamp to rest on the rim above the carbide chamber; and the front, A, should +be at least an inch higher than the top of the lamp glass. +</p> + +<p> +[Illustration: FIG. 189.—Signalling lamp with quick-moving shutter.] +</p> + +<p> +The hole cut in B must be so situated as to bring the front of the lamp close +to the front of the holder, so that the greatest possible amount of light may +be utilized. The hole in A should be rather larger than the lamp front, and, of +course, be accurately centred. Mark these two holes off carefully, and cut out +with a pad saw or fret saw. +</p> + +<p> +A socket must be attached to the centre of the underside of the base to take +the camera screw; or, if such a socket is not easily obtainable, a hole should +be drilled in the base to take an ordinary wood screw of good size, the surplus +of which is cut off so as not to interfere with the lamp. +</p> + +<p> +The Shutter.—The woodwork is so simple that nothing further need be said +about it. The more difficult part of the business is the making of the shutter, +which must be so constructed that it can be opened and closed rapidly by +motions similar to those used in working the telegraph key described in a +preceding chapter. Speed of working is obtained by dividing the shutter into +two or three parts, each revolving on its own spindle, but all connected so as +to act in perfect unison. The thinnest sheet brass or iron obtainable should be +used, so that the tension of the spring used to close the shutter need not be +great. Our illustration shows a two-part shutter, each half an inch wider than +the hole in the front, and jointly a similar amount deeper. The upper half +overlaps the lower, outside, by a quarter of an inch. +</p> + +<p> +The spindles are two straight pieces of brass wire, revolving in sockets which +are most easily made of notched pieces of wood (as shown in Fig. 189), with +removable caps of strip tin. The lower spindle should be an inch longer than +the width of the front, to allow for a cranked end, to which the closing spring +will be attached. +</p> + +<p> +Having cut out the halves of the shutter, solder the spindle wires to one edge +of each on what will be the back side. The wires must be so arranged as to +allow a quarter of an inch to project beyond the left edge of the front, as the +opening mechanism is situated on this side as the most convenient for the +operator. +</p> + +<p> +Take a couple of metal discs, an inch or so in diameter, and bore a hole in +each near the circumference to fit the ends of the pivots fairly tight. +Three-eighths of an inch from this—centre to centre—bore and tap a +hole for a small screw. The tapping should be done with a taper tap and carried +just so far that the screw turns stiffly without danger of being broken off by +the screw-driver. +</p> + +<p> +Next find the correct positions of the parts of the shutter and the spindle +sockets on the front of the holder, and mark them off carefully. Screw the +wooden parts of the sockets to the front. Four little “distance +pieces” should now be cut out of small tubing, or made by twisting tin +round the spindle, to place on the spindles between shutter and sockets, so +that the shutters cannot shift sideways. +</p> + +<p> +The right-hand end of the lower spindle must be bent over (after slipping on +the distance piece) to form a 1/2-inch crank making an angle of 45 degrees with +the line of the front, in an upward direction, as it will be depressed by the +opening of the shutter. Flatten out the end with a hammer, and drill a small +hole near the tip. +</p> + +<p> +The shutters can now be placed in position, and the caps of the sockets be +screwed on. The next thing to make is the connecting rod to join the cranks at +the left side of the front. For this purpose we may use a piece of fairly stiff +strip metal—brass by preference—5 or 6 inches long. Half an inch +from one end make a mark with the centre punch; then measure off exactly the +distance between the shutter spindles, and make a second punch mark. Drill +holes at the marks large enough, for the disc screws to pass through easily, +but not loosely. +</p> + +<p> +Attach the rod to the discs by the screws, and slip the discs on to the ends of +the shutter spindles. (The free end of the rod should be upwards.) Press the +shutters against the front so that they cannot open, adjust the discs at an +angle of 45 degrees to the front in an upward direction, and solder them firmly +to the spindles. +</p> + +<p> +The upper end of the connecting rod should be turned over to form a finger +rest, or be sharpened off to take a knob. The last operation is the fitting of +the spring to close the shutter. A spiral spring attached at one end of the +crank on the lower spindle and at the other to a nail projecting from the side +of the front is the most convenient arrangement. If you have not got a spiral +spring, you can easily make a. fairly efficient substitute out of hard brass +wire wound a few times round a large wire nail. +</p> + +<p> +An alternative method of springing is to add an arm, a, to the connecting rod, +as shown by dotted lines in Fig. 189, and to use the projection for engaging a +spring, made by winding hard brass wire a few times round a nail. A screw +passed through the coil holds it to the front. +</p> + +<p> +The tension of the spring must be just sufficient to close the shutter smartly +and prevent it rebounding far enough to pass any light. +</p> + +</div><!--end chapter--> + +<div class="chapter"> + +<h2><a name="chap39"></a>XXXIX.<br /> +A MINIATURE GASWORKS.</h2> + +<p> +The most primitive method of making coal gas on a small scale is to fill a +tin—which must have folded, not soldered, joints—with small coal, +punch a hole in the bottom, and place it lid downwards in the fire. Gas soon +begins to issue, but, owing to the quantity of moisture and impurities present, +it will not ignite until some minutes have elapsed. The flame, when it does +make its appearance, is very smoky and gives little light, because, in addition +to the coal gas of commerce, there are present ammonia gas, sulphuretted +hydrogen, carbonic acid, tar vapour, etc., which prevent brightness of flame. +</p> + +<p> +[Illustration: FIG. 190.—General view of gas-making apparatus.] +</p> + +<p> +A miniature gasworks, if it is to be worthy of its name, must obviously +endeavour to separate the troublesome components from the useful gas. The doing +of this involves several processes, all simple enough in principle, and +requiring but simple apparatus for demonstration on a small scale. To take them +in order the processes are— +</p> + +<p> +(l) The formation of gas in a retort; +</p> + +<p> +(2) The condensation of the tar; +</p> + +<p> +(3) The condensation of steam; +</p> + +<p> +(4) The removal of the ammonia gas; +</p> + +<p> +(5) The removal of the sulphuretted hydrogen and carbonic acid. +</p> + +<p> +The last two processes are, in a real gasworks, usually separated, but for +simplicity’s sake we will combine them. Finally, the storage of the gas +has to be provided for. +</p> + +<p> +The Retort.—To get very good results, the retort should be of cast iron, +and have a removable air-tight cover; but, to keep down expense, we will use an +ordinary 2-pound self-opening coffee tin. A short piece of brass pipe is +soldered into the lid near one edge to carry off the gas as it is generated. To +get a fairly gas-tight joint, red-leaded asbestos string should be rammed +tightly between the lid and the tin. The tin may be laid on an open fire on the +slant, the lid end uppermost, and the pipe at the top, where the gas will +collect; or, if you wish to make things more realistic, you may easily +construct an oven with sides and back of fire-brick, and front of sheet iron, +through the hole in which the tin is pushed horizontally, so that only half an +inch projects. This is a. suitable arrangement for out of doors. +</p> + +<p> +[Illustration: FIG. 191.—Vertical section of condenser.] +</p> + +<p> +The Hydraulic Main.—This is represented in Fig. 190 by a double-necked +bottle, B, standing in a bowl of cold water. The pipe from the retort passes +through the cork in one neck and dips half an inch below the surface of the +water inside. The gas, on meeting the water, is cooled, and some of the steam +in it is condensed, also most of the tar present, which floats on the top of +the water. From the bottle the gas passes on to the Condensers, where the +process of cooling is completed gradually. The condenser (Fig. 191) is so +designed as to cause the gas to pass through several pipes in succession. The +base consists of a tin box, 6 inches long, 4 wide, and 1-3/4 deep. This is +divided longitudinally down the centre by a 1-1/2-inch partition, soldered to +the bottom and sides; and the two divisions are again subdivided, as shown in +Fig. 192, by shorter cross partitions. +</p> + +<p> +[Illustration: FIG. 192.—Plan of condenser.] +</p> + +<p> +For the condensing pipes, “compo” tubing of 1/2-inch outside +diameter is convenient. The amount required will, of course, depend on the +number of pipes used and the length of the individual pipes. The design shows 6 +pipes, each 3 feet long, bent to a semicircular curve (Fig. 191) at the middle +to form very long, narrow horse-shoes. The pipes are supported at the curve by +the crossbar, S (Fig. 191), of a frame, and their ends enter short pieces of +brass tubing soldered into holes in the bottom of the tin box. Rubber bands +make the joints air-tight. +</p> + +<p> +[Illustration: FIG. 193.—Vertical section of purifier.] +</p> + +<p> +The base is stood bottom upwards in a larger tin containing an inch and a half +of water. The water acts as a seal, preventing the passage of the gas from one +compartment to another through the pipes which it traverses, in the order +indicated by the arrows and numbers in Fig. 192, to reach the outlet. On its +way the gas is deprived of any water and of any traces of tar. The condensed +water and tar fall from the open ends of the pipes into the base. +</p> + +<p> +The Purifier is made of a large tin with overlapping lid. Near the bottom is +soldered on an inlet pipe; just below the lid an outlet pipe. Cut out two discs +of perforated zinc or sheet tin to fit inside the tin easily, but not loosely. +(If tin is used, make a number of small holes in it.) The lower of the discs +(Fig. 193, Bl) has three wire legs, AA, soldered to it, to support the upper +disc, B. Three short supports keep it clear of the bottom. +</p> + +<p> +The tin must be charged with a mixture of two parts green sulphate of iron and +one part lime. The lime should be slaked a short time before use. The sulphate, +lime, and sufficient water to moisten the whole are ground into a pulp and left +to dry. The dry mixture, which has a reddish-yellow colour, is broken up fine. +Put tray B1 into place and spread half the chemical over it; then lay B on the +top and cover it with the remainder. The lid joint is sealed by a broad rubber +band. +</p> + +<p> +While passing through the tin, the ammonia, sulphuretted hydrogen and carbonic +acid gases all combine with the chemical, and fairly pure gas issues from the +outlet. +</p> + +<p> +The Gasholder.—As the gasometer is an important feature of a gasworks, +our small plant should contain its counterpart, as it serves to regulate the +pressure of the gas, and, therefore, the steadiness of the flame, as well as +affording storage room. +</p> + +<p> +As a gasometer, one may use a container made on the principle of the +lung-testing apparatus described on p. 361; or the gasholder of a lantern +acetylene apparatus, which must, of course, be suitably counterweighted. +</p> + +<p> +Working the Plant.—When starting up the plant, leave the burner open +until inflammable gas issues, so that the air present in the various chambers +may be displaced. +</p> + +<p> +[Transcribers note: Premature lighting of the burner may cause the flame to +propagate into the system and explode. I speak from experience.] +</p> + +</div><!--end chapter--> + +<div class="chapter"> + +<h2>INDEX.</h2> + +<p> +Aeroplane, model, self-launching.<br /> +Bedplate for engine.<br /> +Bellows, double.<br /> +Bench, joiner’s.<br /> +Benham’s harmonograph.<br /> +Bicycle shed.<br /> +Boilers, model.<br /> +Bookstand.<br /> +Box kites.<br /> +</p> + +<p> +Cabinets, cardboard, cigar-box, match-box, tool.<br /> +Circles, rolling.<br /> +Clock, electric alarm.<br /> +Colour top.<br /> +Cylinder, double-acting steam.<br /> +</p> + +<p> +Developing sink.<br /> +Doors for shed.<br /> +Double-acting horizontal steam engine.<br /> +Double bellows.<br /> +</p> + +<p> +Eccentrics.<br /> +Electric alarm clock.<br /> +Electric motor, reciprocating.<br /> +Electric railway.<br /> +Engine, hot-air.<br /> +Experiments, apparatus for simple scientific.<br /> +</p> + +<p> +Fuels for model boilers. +</p> + +<p> +Gasworks, miniature.<br /> +Ganges, rain, water,<br /> +Gimbals, or universal joints.<br /> +Gliders, paper.<br /> +Goold’s harmonograph.<br /> +Governor for engine.<br /> +</p> + +<p> +Harmonographs.<br /> +Hot-air engines.<br /> +House ladder.<br /> +</p> + +<p> +Joiner’s bench. +</p> + +<p> +Kettles, quick-boiling.<br /> +Kites, box.<br /> +Kite winders.<br /> +</p> + +<p> +Ladder, house.<br /> +Lamp, signalling.<br /> +Locomotive, electric.<br /> +Lung-testing apparatus.<br /> +Magic swingers.<br /> +windmill.<br /> +Match-boarding.<br /> +Match-box, self-supplying.<br /> +Morse code.<br /> +Morse sounder.<br /> +Motor, electric.<br /> +Motor, water.<br /> +</p> + +<p> +Nozzle for steam turbine. +</p> + +<p> +Pantograph.<br /> +Pendulums for harmonograph.<br /> +Pens for harmonograph.<br /> +Pneumatic puzzle.<br /> +Poultry house.<br /> +Propellers for aeroplane.<br /> +Pumps.<br /> +Puppets, wrestling.<br /> +Puzzle, pneumatic.<br /> +</p> + +<p> +Railway, electric.<br /> +Rain gauges.<br /> +Reciprocating steam engine, simple.<br /> +Resistance, adjustable, for electric railway.<br /> +Reversing switch for electric railway.<br /> +Riveting.<br /> +</p> + +<p> +Safety Valves.<br /> +Sawing trestle.<br /> +Shed for bicycle.<br /> +Signalling lamp.<br /> +Silhouette drawing machine.<br /> +Simple scientific experiments.<br /> +Sink, developing.<br /> +Slide valve.<br /> +Smoke-ring apparatus.<br /> +Soldering.<br /> +Spokes, magic.<br /> +Steam cocks.<br /> +Steam engines.<br /> +Steam gauge.<br /> +Steam pump.<br /> +Steam tops.<br /> +Steam turbines.<br /> +Strength. testing machines.<br /> +Swingers, magic.<br /> +Switch, multiple battery.<br /> +Switch, reversing.<br /> +</p> + +<p> +Target apparatus.<br /> +Telegraphic apparatus.<br /> +Testing boilers.<br /> +Tool cabinet.<br /> +Top, colour.<br /> +Tops, steam.<br /> +Track for model railway.<br /> +Trestle, sawing.<br /> +Turbines, model steam.<br /> +</p> + +<p> +Vanishing spiral.<br /> +Vice for Joiner’s bench.<br /> +</p> + +<p> +Water gauge.<br /> +Water motor.<br /> +Weights for harmonograph pendulums.<br /> +Windmill, magic.<br /> +Wind vanes; electric.<br /> +Workbox, Norwegian.<br /> +Wrestling puppets.<br /> +Wriggling line.<br /> +</p> + +<h4>THE END.</h4> + +<h5>PRINTED IN GREAT BRITAIN AT THE PRESS OF THE PUBLISHERS.</h5> + +</div><!--end chapter--> + +<div style='display:block;margin-top:4em'>*** END OF THE PROJECT GUTENBERG EBOOK THINGS TO MAKE ***</div> +<div style='display:block;margin:1em 0;'>This file should be named 14664-h.htm or 14664-h.zip</div> +<div style='display:block;margin:1em 0;'>This and all associated files of various formats will be found in https://www.gutenberg.org/1/4/6/6/14664/</div> +<div style='display:block; margin:1em 0'> +Updated editions will replace the previous one—the old editions will +be renamed. +</div> + +<div style='display:block; margin:1em 0'> +Creating the works from print editions not protected by U.S. copyright +law means that no one owns a United States copyright in these works, +so the Foundation (and you!) can copy and distribute it in the United +States without permission and without paying copyright +royalties. 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