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diff --git a/old/14664.txt b/old/14664.txt new file mode 100644 index 0000000..3949c09 --- /dev/null +++ b/old/14664.txt @@ -0,0 +1,7869 @@ +The Project Gutenberg EBook of Things To Make, by Archibald Williams + +This eBook is for the use of anyone anywhere 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 www.gutenberg.org + + +Title: Things To Make + +Author: Archibald Williams + +Release Date: January 11, 2005 [EBook #14664] + +Language: English + +Character set encoding: ASCII + +*** START OF THIS PROJECT GUTENBERG EBOOK THINGS TO MAKE *** + + + + +Produced by Don Kostuch + + + + + +Transcriber's Note: + +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. + +Notations of the form "(1,650) 2" appear at the bottom of some pages; +they are probably printer's references for assembling to book. + +The text only version is of limited use because of the many figures used. I +recommend the pdf or rtf versions. + +Some of the projects should be approached with care since they involve +corrosive or explosive chemicals, electricity and steam boilers. + +Do not use lead solder, particularly on cooking utensils. + +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. + +The following are definitions of unusual (to me) terms used +frequently in the text. + + +Terms + +Batten - Narrow strip of wood. + +Bevel (Bevelling) - A cut that is not a right angle. + +Bradawl - Awl with a beveled tip to make holes in wood for brads or +screws. + +Chamfer - Cut off the edge or corner; bevel. + +Boss - Enlarged part of a shaft where another shaft is coupled or a wheel +or gear is keyed. + +Broach - To shape a hole with a tapered tool. + +Carbide - Calcium carbide, used to produce acetylene (C2H2) gas for +lighting and welding. + +Compo - "Composition", like plastic. + +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. + +Deal - A fir or pine board of standard dimensions + +Fish-plate - A plate bolted to the sides of two abutting railroad tracks. + +Fretworking - Ornamental design, often in relief. + +Gasholder +Gasometer - Storage container for fuel gas, especially a large, +telescoping, cylindrical tank. + +Gland - The outer sleeve of a stuffing box that prevents leakage past a +moving machine part. + +Glass paper - Paper faced with pulverized glass, like sandpaper. + +Gudgeon - A metal pivot or journal at the end of a shaft or an axle, around +which a wheel or other device turns. + +Joiner - A cabinetmaker. + +Linoleum - A floor covering made in sheets by pressing heated linseed oil, +rosin, powdered cork, and pigments onto a burlap or canvas backing. + +Lissom - Easily bent; supple + +Longitudinal - Relating to length. + +Mortice - Cavity in a piece of wood or other material, prepared to receive +a tenon and form a joint. + +Panel saw - Handsaw with fine teeth. + +Pinion - Gear with a small number of teeth designed to mesh with a larger +gear. + +Plinth - Architectural support or base. + +Rasp - Coarse file with sharp, raised, pointed projections. + +Sleeper - Railroad crosstie. + +Spanner - Wrench + +Spirit Lamp - Alcohol lamp; see example on page 188. + +Spirit - Alcohol + +Strake - Ridge of thick planking on the side of a wooden ship. + +Strut - Any part designed to hold things apart or resist compressive +stress; + +Tap - Cut screw threads + +Tenon - Projection on the end of a piece of wood shaped for insertion into +a mortise to make a joint. + +Tenon saw - Saw with a thin blade for cutting tenons. + +Tinning - Coating with soft solder. + +Turner - Person who operates a lathe or similar device. + +Tyre - Tire + +Vestas - Matches; Vestai is the Roman goddess of the hearth, worshiped in a +temple containing the sacred fire tended by the vestal virgins. + +Currency Conversion + +Prices are quoted in old English currency, pounds, shillings, pence. + +"12s. 6d." is read as "12 Shillings and 6 Pence." + +Pence/penny +Shilling--12 pence. +Crown--5 shillings. +Pound--20 shillings. +Guinea--21 shillings. + +The approximate value of 1900 prices in 2002 is: +1900 Unit Value in 2002 Currency + English Pound US Dollars +Pence .26 .48 +Shilling 3.10 5.80 +Crown 15.50 29.00 +Pound 62.00 116.00 + +[End Transcriber's note.] + +[Illustration: Large model locomotive] + +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. + + + +THINGS TO MAKE +BY +ARCHIBALD WILLIAMS +AUTHOR OF +"VICTORIES OF THE ENGINEER," +"HOW IT WORKS," +"HOW IT IS MADE," +ETC., ETC. +THOMAS NELSON AND SONS, LTD. +LONDON, EDINBURGH, AND NEW YORK + + + +PREFACE. + +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. + +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. + +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. + +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. + + + +CONTENTS. + +I. SAWING TRESTLE +II. A JOINER'S BENCH +III. A HANDY BOOKSTAND +IV. A HOUSE LADDER +V. A DEVELOPING SINK +VI. A POULTRY HOUSE AND RUN +VII. A SHED FOR YOUR BICYCLE +VIII. A TARGET APPARATUS FOR RIFLE SHOOTING +IX. CABINET-MAKING +X. TELEGRAPHIC APPARATUS +XI. A RECIPROCATING ELECTRIC MOTOR +XII. AN ELECTRIC ALARM CLOCK +XIII. A MODEL ELECTRIC RAILWAY +XIV. A SIMPLE RECIPROCATING ENGINE +XV. A HORIZONTAL SLIDE-VALVE ENGINE +XVI. MODEL STEAM TURBINES +XVII. STEAM TOPS +XVIII. MODEL BOILERS +XIX. QUICK-BOILING KETTLES +XX. A HOT-AIR ENGINE +XXI. A WATER MOTOR +XXII. MODEL PUMPS +XXIII. KITES +XXIV. PAPER GLIDERS +XXV. A SELF-LAUNCHING MODEL AEROPLANE +XXVI. APPARATUS FOR SIMPLE SCIENTIFIC EXPERIMENTS +XXVII. A RAIN GAUGE +XXVIII. WIND VANES WITH DIALS +XXIX. A STRENGTH-TESTING MACHINE +XXX. LUNG-TESTING APPARATUS +XXXI. HOME-MADE HARMONOGRAPHS +XXXII. A SELF-SUPPLYING MATCHBOX +XXXIII. A WOODEN WORKBOX +XXXIV. WRESTLING PUPPETS +XXXV. DOUBLE BELLOWS +XXXVI. A HOME-MADE PANTOGRAPH +XXXVII. A SILHOUETTE DRAWING MACHINE +XXXVIII. A SIGNALLING LAMP +XXXIX. A MINIATURE GASWORKS + + + +THINGS TO MAKE. + + + +I. A SAWING TRESTLE + +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. + +The top, a, 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." + +[Illustration: Fig I.--Leg of sawing trestle (left). Trestle seen from +above (right).] + +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. + +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. + +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. + +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). + +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.) + +[Illustration: FIG. 2.-Showing how to cut sloping joint for trestle leg.] + +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. + +[Illustration: Fig.3--End elevation of sawing trestle.] + +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. + +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. + +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. + + + +II. A JOINER'S BENCH. + +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. + +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. + +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. + +[Illustration: Fig. 4.--Front elevation of Joiner's bench] + +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. + +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. + + +Construction. + +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. + +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. + +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. + +[Illustration: FIG. 5.--End elevation of joiner's bench.] + +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. + +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. + +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.) + +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. + +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. + +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. + +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. + +[Illustration: Fig. 6.--Perspective view of joiner's bench] + +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. + +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. + +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. + +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. + + + +III. A HANDY BOOKSTAND. + +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. + +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. + +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. + +[Illustration: Fig. 7.--Perspective view of bookstand.] + +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. + +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. + +[Illustration: Fig. 8.--End elevation of bookstand.] + +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. + +Shelves and sides should be wax-polished or given a coat or two of varnish. + +[Illustration: Fig. 9. Plan or bookstand shelf.] + +Don't drive the wedges in too tight, or yon may have to lament a split lug. + +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. + + + +IV. A HOUSE LADDER. + +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." + +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. + +[Illustration: Fig. 10--House ladder and details of letting in a rung] + +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. + +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. + + +CONSTRUCTION. + +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. + +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. + +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. + +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. + +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. + +Round off the end angles of the rungs, and apply a second coating of paint. + +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. + +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. + + + +V. A DEVELOPING SINK. + +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. + +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. + +[Illustration: Fig. 11.--A home-made developing sink for the darkroom.] + +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. + +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. + +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." + +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. + +[Illustration: FIG. 12.--Showing how the tray for sink is marked out.] + +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. + +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. + +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. + +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. + +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. + +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. + + + +VI. A POULTRY HOUSE AND RUN. + +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. + +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. + +[Illustration: Fig. 13.--Frame for poultry house and run (above). +Completed house and run (below).] + + +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. + + +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. + +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. + + +CONSTRUCTION. + +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. + +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. + +[Illustration: Fig. 14.--On left, elevation of end of run; on right, +door for run.] + +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. + +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. + +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. + +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. + +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. + +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. + +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. + +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. + +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. + +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. + +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. + +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. + + + +VII. A SHED FOR YOUR BICYCLE. + +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. + +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. + +[Illustration: FIG. 16.--Cycle shed completed.] + +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. + +[Illustration: FIG. 16.--Plan of corner joints of cycle shed.] + +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] + +[Footnote 1: By Mr. Hubert Burgess. ] + +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. + +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. + +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. + +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. + +[Illustration: FIG. 17.-Types of match boarding: (a) square joint; (b) +double.-V; (c) single-V.] + +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. + +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: + +4-1/2 (over tongue) by 5/8 inch (actual) yellow match boarding for sides, +roof, back, and doors: + +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. + +There will also be required: +Twelve 6-inch bolts and nuts. +Two pairs 18-inch cross-garnet hinges. +Two door bolts. +One lock (a good one). +Four yards of roofing felt. +Two gallons of stoprot. +Three lbs. wire-nails +A few dozen 3-inch and I-1/2-inch screws. + +The total cost of the materials will come to about 2 pounds, 2s. + + +CONSTRUCTION. + +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. + +[Illustration: FIG. 18.-Side of cycle shed.] + +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. + +[Illustration: FIG. 19.--Boards at top of side, fixed ready for cutting +off.] + +Use the side frame first made as template for the other. + +The shelves are notched at the ends, so that their back faces shall be +flush with the board side of the frame. + +Fix the corners with the screws, and plane off the projecting angles of the +uprights. + +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. + +[Illustration: FIG. 20.-Back of cycle shed.] + +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. + +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. + +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.) + +[Illustration: FIG. 21. Detail of eaves.] + +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. + +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. + +[Illustration: FIG. 22.-Doors of shed.] + +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. + +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. + + +PUTTING THE PARTS TOGETHER. + +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. + +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. + +[Illustration: Fig. 23 Roof attachment] + +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. + +[Illustration: +FIG. 24.--Top of cycle shed. +FIG. 25.--Floor of shed.] + +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. + +Preserving the Wood.--All outside wood is dressed with stoprot or +creosote, rubbed well into the joints of the boarding. + +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. + +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. + +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. + + +CUTTING DOWN EXPENSE. + +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. + + + +VIII. A TARGET APPARATUS FOR RIFLE SHOOTING. + +The base is a 1-inch board, 18 inches long and 7 inches wide. + +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. + +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.) + +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. + +[Illustration: FIG. 26.-Side elevation of disappearing target apparatus.] + +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. + +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. + +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. + +It may prove a convenience if plain marks are made on the string at the +distances from which shooting will be done. + +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. + +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. + + + +IX. CABINET-MAKING. + +A Match-box Cabinet. + +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. + +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. + +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. + +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. + +[Illustration: FIG. 27.--Match-box cabinet.] + +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. + +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. + + +A Cardboard Cabinet. + +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. + +Begin with the drawers; it is easier to make the case fit the drawers than +vice versa. + +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.) + +[Illustration: FIG. 28.--Drawer of cardboard cabinet marked ready for +cutting.] + +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. + +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. + +Compare the drawers, and if one is slightly wider than the rest, use it to +guide you in making the measurements for the case. + +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. + +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. + +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." + +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. + +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. + +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. + + +A Cigar-box Cabinet. + +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). + +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. + +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. + +[Illustration: FIG. 29.--Cabinet with cigar-box drawers.] + +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. + +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. + +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. + +The notches for the front cross-bars between drawers are cut out with a +very sharp narrow chisel. + +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. + +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. + +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. + +The front bars should now be cut to a good fit and glued in the notches. +This completes the construction. + +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. + +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. + +The total cost of a ten-drawer cabinet ought not to exceed eighteen pence. + + +A Tool Cabinet. + +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. + +[Illustration: FIG. 30.--Large cabinet (a), details of drawer joints (b, +c, d), and padlock fastening (e).] + +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. + +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. + +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. + +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. + +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. + +[Illustration: FIG. 31.--Divisions of drawer notched to cross each +other.] + +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). + +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. + + + +X. TELEGRAPHIC APPARATUS. + +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. + +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. + +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. + +[Illustration: Fig. 32.--Morse alphabet] + +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. + +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] + +[Footnote 1: For the buzzer may be substituted the tapper, described on a +later page.] + +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. + +[Illustration: Fig.33--Telegraphic apparatus; sending key, buzzer and +battery] + + +Making the Keys. + +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. + +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. + +[Illustration: Fig. 34--Telegraphic apparatus mounted on baseboard] + +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. + +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. + +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. + + +A Morse Tapper or Sounder. + +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. + +[Illustration: FIG. 35.-Elevation and plan of telegraphic sounder.] + +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. + +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. + +The spring is attached to L and A in the manner already described on p. 89 +in connection with the "buzzer." + +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. + +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. + + +Batteries. + +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. + +[Illustration: FIG. 36.--Standard for sounder.] + +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. + +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. + +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. + + + +XI. A RECIPROCATING ELECTRIC MOTOR. + +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. + +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. + +[Illustration: FIG. 37.--Electric reciprocating engine and battery.] + +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. + + +CONSTRUCTION. + +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. + +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. + +Note.--Insulation will be improved if every layer of wire is painted over +with shellac dissolved in alcohol before the next layer is applied. + +Flatten the reel slightly with a file at the points of contact with the +baseboard, to prevent rolling. + +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. + +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. + +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. + +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. + +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. + +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. + +[Illustration: Fig. 38.--Plan of electric reciprocating engine.] + +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. + +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. + +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. + + +OTHER DETAILS. + +The fly wheel may be a disc of wood. + +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. + +The cost of the engine described was about 1s, 3d., exclusive of the +battery. + + + +XII. AN ELECTRIC ALARM CLOCK. + +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-- + +(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); + +(2) That one clock can be made to operate any number of bells in different +parts of the house. + +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." + +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. + +[Illustration: FIG. 89.--Plan of release gear of electric alarm, as +attached to clock.] + +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. + +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. + +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. + +[Illustration: Fig. 40.--Electric alarm releaser, as attached to separate +wooden clock casing.] + +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. + +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). + +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. + +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. + + + +XIII. A MODEL ELECTRIC RAILWAY. + +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. + +[Illustration: Fig. 41.--Electric Locomotive.] + +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. + + +The Track + +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. + +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. + +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. + +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. + +[Illustration: FIG. 42.--Details of rails for electric track.] + +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. + +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. + +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. + +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. + +[Illustration: FIG. 43.--Tin chair for centre rail of electric track.] + +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. + +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. + +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. + +[Illustration: FIG. 44.--Laying out a curve for electric track.] + +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. + +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. + +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. + +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. + +[Illustration: FIG. 45.--Points for electric railway.] + +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. + +It is advisable to lay out a set of points, together with motor and +signals, on a separate board. + +[Illustration: Fig. 46.--Double-armed signal, operated by points.] + +Preservation of Track.--All the wooden parts of an outdoor track should +be well creosoted before use. + + +The Electric Locomotive. + +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. + +[Illustration: Fig. 47.--Plan and elevation of electric locomotive.] + +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. + +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. + +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. + +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. + +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. + +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. + +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. + +[Illustration: FIG. 48.--Reversing switch.] + +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. + +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. + +[Illustration: Fig. 49.--Multiple battery switch.] + +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. + +[Illustration: FIG. 50.--Adjustable resistance for controlling current.] + +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. + +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. + + +SOME SUGGESTIONS. + +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. + +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. + + + +XIV. A SIMPLE RECIPROCATING ENGINE. + +Figs. 51 and 52 illustrate a very simple form of fixed-cylinder engine +controlled by a slide valve. + +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. + +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. + + +CONSTRUCTION. + +[Illustration: FIG. 51.--Elevation of simple reciprocating steam engine.] + +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. ) + +[Illustration: FIG. 52.--Plan of simple reciprocating steam engine.] + +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. + +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. + +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. + +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. + +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. + +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. + + +Order of Assembly.--The following list of operations in their order may +assist the beginner: + +Make the bed. + +Cut out cylinder barrel, piston, and valve tube. + +Bevel off the ends of the last inside to allow the valve to enter easily. + +Make the valve. + +Bore the steam ports, and solder valve tube and cylinder together. + +Solder holding-down wing, W, to cylinder. + +Finish off the piston. + +Solder the bearings in their standards. + +Prepare shaft, crank disc, crank pin, and piston rod. + +Fix the cylinder to the bed, in which a slot must be cut for the wing and +holding-down bolt. + +Attach the piston rod to the piston, and insert piston in cylinder. + +Bore hole for shaft in centre of crank disc, and another, 9/16 inch away +(centre to centre), for crank pin. + +Solder in crank pin squarely to disc. + +Pass shaft through bearings and slip on the crank disc. + +Pass front end of piston rod over the crank pin. + +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. + +Get standard quite square, and adjust sideways till connecting rod is in +line with axis of cylinder. + +Mark off and screw down the standard. + +Make the eccentric, eccentric rod, and strap. Slip eccentric on shaft. + +Put valve in position and draw it forward till the port is exposed. + +Turn the eccentric forward, and mark the rod opposite centre of valve pin. + +Bore hole for pin, and insert pin. + +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. + +Solder eccentric and disc to shaft. + +Solder steam pipe to cylinder, and a brass disc to the rear end of the +cylinder. + +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. + + +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. + +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. + +(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. + +(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. + + + +XV. A HORIZONTAL SLIDE-VALVE ENGINE. + +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. + +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. + +[Illustration: Fig. 53.--Elevation of a large horizontal engine.] + + +The principal dimensions of the engine are as follows: + +Bedplate (sheet zinc), 13-1/2 inches long; 4-1/2 inches wide; 1/8 inch +thick. + +Support of bedplate (1/20 inch zinc), 3 inches high from wooden base to +underside of bedplate. + +Cylinder (mandrel-drawn brass tubing), 1-1/2 inches internal diameter; +2-13/16 inches long over all. + +Piston, 1-1/2 inches diameter; 1/2 inch long. + +Stroke of piston, 2-1/4 inches. + +Connecting rod, 5 inches long between centres; 5/16 inch diameter. + +Piston rod, 5-1/8 inches long; 1/4 inch diameter. + +Valve rod, 4-1/8 inches long; 3/16 inch diameter. + +Crank shaft, 5 inches long; 1/2 inch diameter. + +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. + +Centre line of crank shaft, 10-3/8 inches from cross centre line of +cylinder. + +Bearings, 1 inch long. + +Eccentric, 9/32-inch throw. + +Fly wheel, diameter, 7-1/2 inches; width, 1 inch; weight, 6 lbs. + +Pump, 3/8-inch bore; 3/8-inch stroke; plunger, 2 inches long. + +[Illustration: Fig. 54.--Plan of a large horizontal engine.] + +Other dimensions will be gathered from the various diagrams of details. + + +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. + +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. + +[Illustration: Fig. 55.--Standards of Bedplate.] + +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. + +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. + +[Illustration: FIG. 56.-Cylinder standard before being bent.] + +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. + +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. + +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. + +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. + +Bore a 1/4-inch hole in the centre of one cover--be sure that it is the +right one--for the piston rod. + +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. + +[Illustration: FIG. 57.--Vertical section of cylinder.] + +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. + +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. + +[Illustration: FIG. 68.-Wall-piece for steam chest, with gland and valve +rod in position.] + +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. + +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. + +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. + +[Illustration: FIG. 69.--Valve plate.] + +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. + +[Illustration: FIG. 60.--Piece for steam ways.] + +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. + +[Illustration: FIG. 61.--Valve plate and steam ways in section.] + +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. + +In the assembling of these parts a blowpipe spirit lamp or a little "Tinol" +soldering lamp will prove very helpful. + +The following order should be observed: + +(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. + +(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. + +(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. + +(4.) Solder in pieces bb. These should be a tight fit, as it is difficult +to hold them in place while soldering is done. + +(5.) Bore a 5/16-inch hole in the lower side of the central division and +solder on the exhaust pipe. + +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). + +[Illustration: FIG. 63.-Parts of slide valve.] + +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. + +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. + +Each bearing is shown with two standards. The doubling increases rigidity, +and enables an oil cup to be fixed centrally. + +The shape of the standards will be gathered from Fig. 53, their outline +being dotted in behind the crank. + +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. + +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.) + +Bore holes in the bearings for the oil cups, which may be merely forced in +after the engine is complete. + +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. + +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. + +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. + +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. + +The standards and bed should have matching marks made on them. + +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. + +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. + +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. + +[Illustration: FIG. 64.--Cross section of crosshead and guide.] + +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. + +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. + +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. + +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] + +[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.] + +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. + +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. + + +OTHER DETAILS. + +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. + +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. + +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. + +[Illustration: FIG. 66.-Vertical section of force pump driven by engine.] + +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. + +Lubrication.--When the engine is first put under steam, lubrication +should be very liberal, to assure the parts "settling down" without undue +wear. + +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. + +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. + +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. + + +Making a Governor. + +[Illustration: FIG. 66.--Elevation of governor for horizontal engine. +Above is plan of valve and rod gear.] + +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. + +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. + +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. + +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. + +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. + +The two weights WW are pieces of brass bar slotted for driving on to DD, +which taper gently towards the outer edge. + +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. + +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. + +Regulation of the speed may be effected either + +(1) by driving the governor faster or slower relatively to the speed of the +crank shaft; + +(2) by altering the position of W on D; + +(3) by altering the compression of the spring by shifting F; + +(4) by a combination of two or more of the above. + +Generally speaking, (3) is to be preferred, as the simplest. + +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. + + +FINAL HINTS. + +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. + +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. + +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. + + + +XVI. MODEL STEAM TURBINES. + +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.) + +The turbines to be described work on the De Laval principle, which has been +selected as the easier for the beginner to follow. + +A Very Simple Turbine. + +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. + +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. + +[Illustration: FIG. 67.--Simple steam turbine.] + +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. + +[Illustration: FIG. 68.--Wheel for steam turbine, showing one vane +twisted into final position.] + +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. + +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. + +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. + +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. + +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. + +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. + +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. + +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. + + +A Practical Steam Turbine. + +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. + +[Illustration: FIG. 69.--Model steam turbine, showing vertical cross +section (left) and external steam pipe (right).] + +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. + +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. + +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. + +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. + +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. + +On the outside of D scribe two circles of 2-inch and 1-11/16-inch radius, +between which the steam pipe will lie. + +On the inside of D scribe a circle of 1-27/32-inch radius for the steam +ports. + +On the outside of E mark a 7/8-inch circle for the exhaust pipe. + +On the inside of both mark the circles between which the ring must lie. + +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. + +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. + +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. + +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.) + +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. + +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. + +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.) + +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. + +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.) + +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. + +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. + +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. + +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. + +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. + +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. + +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. + +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. + +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. + + +A More Elaborate Turbine. + +[Illustration: FIG. 70.--Vertical section of steam turbine with formed +blades (left); outside view of turbine, gear side (right).] + +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. + + +CONSTRUCTION. + +[Illustration: FIG. 71.--Plate marked out for turbine wheel blades. B is +blade as it appears before being curved.] + +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. + +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. + +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. + +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. + +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. + +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. + +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. + +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. + +[Illustration: FIG. 72.--Nozzle of turbine, showing its position +relatively to buckets.] + +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. + +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. + +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.) + +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. + +[Illustration: FIG. 73.--Perspective view of completed turbine.] + +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. + +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. + + + +XVIL. STEAM TOPS. + +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. + +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. + +A Small Top.--Fig. 74 shows a small specimen, which is of the +self-contained order, the boiler serving as support for the top. + +[Illustration: FIG. 74.-Simplest form of steam top.] [1] + +[Footnote 1: Spirit lamp shown for heating boiler.] + +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. + +[Illustration: FIG. 75.--Wheel of steam top, ready for blades to be bent. +A hole is drilled at the inner end of every slit to make bending easier.] + +Solder the plates into the tube, allowing an overlap of a quarter of an +inch beyond the lower one, to help retain the heat. + +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. + +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. + +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. + +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. + +[Illustration: FIG. 76. Steam port details.] + +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. + +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. + +A small brass filler should be affixed to the boiler halfway up. A filler +with ground joints costs about 6d. + +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. + +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. + +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. + +[Illustration: FIG. 77.---Large steam top and base.] + +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. + +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. + +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. + +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. + +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. + + + +XVIII. MODEL BOILERS. + +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. + +Therefore the following warnings:-- + +(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. + +(2.) If in doubt, make the boiler much more solid than is needed, rather +than run any risks. + +(3.) Fit a steam gauge, so that you may know what is happening. + +(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.) + +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. + +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. + +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. + +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. + +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. + +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. + +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. + +[Illustration: FIG. 78.] + + +Some Points in Design. + +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. + +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. + +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. + +[Illustration: FIG. 79--Side and end elevations of a small water-tube +boiler.] + +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. + + +A Vertical Boiler. + +[Illustration: FIG. 80.--Details of vertical boiler.] + +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. + +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. + +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. + +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. + +[Illustration: FIG. 81.--Perspective view of horizontal boiler mounted on +wooden base.] + +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. + +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. + +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. + + +A Horizontal Boiler. + +[Illustration: FIG. 82.--Longitudinal section of large water-tube +boiler.] + +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. + +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. + +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. + +[Illustration: FIG. 83.-End of horizontal boiler, showing position of holes +for stays and fittings.] + +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. + +[Illustration: FIG. 84.--Doubled cross tubes In horizontal boiler flue.] + +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. + +[Illustration: FIG. 85.--Showing how to mark out strengthening patch +round steam dome hole.] + +The positions of stays and gauges is shown in Fig. 83. + +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. + + +A Multitubular Boiler. + +[Illustration: FIG. 86.--Cross section of multitubular boiler.] + +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. + +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. + +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. + +[Illustration: FIG. 87.--Longitudinal section of multitubular boiler.] + + +CONSTRUCTION. + +[Illustration: FIG. 88.-Two arrangements for tube holes in multi tubular +boiler.] + +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. + +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. + +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. + +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. + +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." + + +Boiler Fittings. + +[Illustration: FIG. 89.-Safety valve.] + +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. + +[Illustration: FIG. 90.-Steam gauge and siphon.] + +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. + +[Illustration: FIG. 91.-Water gauge.] + +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. + +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. + +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. + +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. + +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. + +[Illustration: FIG. 92.--Steam cock.] + +Steam Cocks.-The screw-down type (Fig. 92) is very preferable to the "plug" +type, which is apt to leak and stick. + +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. + +[Illustration: FIG. 94.--Benzoline lamp for model central-flue boiler.] + +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. + +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. + +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. + +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. + +Do not increase your working pressure without first re-testing the boiler +to double the new pressure to be used. + +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.) + +[Illustration: FIG. 95.-Paraffin burner for vertical boiler.] + +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. + +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. + + + +XIX. QUICK BOILING KETTLES. + +[Transcriber's note: Do not use lead solder on articles associated with +human or animal consumption.] + +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. + +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. + +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. + + +Fire-tube Kettles. + +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. + +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. + +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. + +[Illustration: FIG. 96 (a).] + +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. + +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. + +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. + +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. + +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. + +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. + +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. + +[Illustration: FIG. 96--(b), (c), and (d).] + +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.) + +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. + +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. + +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. + + + +XX. A HOT-AIR ENGINE. + +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. + +[Illustration: FIG. 97.--Vertical section of hot-air engine.] + +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. + +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. + +[Illustration: FIG. 98.] + +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. + +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. + +[Illustration: FIG. 99.] + +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.) + +[Footnote 1: Thin iron plate has the disadvantage of soon corroding.] + +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. + +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. + +[Illustration: FIG. 100.--Exterior view of hot air engine.] + +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. + +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. + +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. + +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. + +[Illustration: FIG. 101.-Details of built-up crank.] + +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. + +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.) + +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. + +[Illustration: FIG. 102.] + +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. + +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. + +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. + +[Illustration: FIG. 103.--Plate for lamp chamber cut out ready for +bending.] + +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. + +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. + +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. + +[Illustration: FIG. l04.-Spirit lamp for hot-air engine, with regulating +tap.] + +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. + +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." + + + +XXI. A WATER MOTOR. + +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. + +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. + +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. + +[Illustration: FIG. l05.--Simple water turbine.] + +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. + +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. + +[Illustration: FIG. 106.--Water turbine, with pulley side of casing +removed.] + +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. + +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. + +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. + +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. + +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. + +[Illustration: FIG. 107.--Plan of water turbine, showing arrangement of +nozzle.] + +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. + +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. + +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. + +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. + +[Illustration: FIG. l08.-Water motor working a photographic dish-rocker.] + +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. + +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. + + + +XXII. MODEL PUMPS. + +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. + +[Illustration: FIG. l09.-Vertical section of force pump.] + +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. + +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. + +[Illustration: FIG. 110.] + +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. + +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. + +[Illustration: FIG. 111.--Details of lever for force pump.] + +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. + +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. + +[Illustration: FIG. 112--View of steam pump, showing details.] + +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. + +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. + +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. + + +CONSTRUCTION. + +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. + +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. + +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. + +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. + +[Illustration: FIG. 113.--End view of striking mechanism of steam pump.] + +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. + +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. + +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. + +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. + +The stops, T1 T2, are small, adjustable collars, kept tightly in place on +R1 by screws. + +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. + +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. + +Note.--To steady the flow and prevent "water hammer," a small air-chamber +should be attached to the delivery pipe. + +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. + +[Illustration: Fig. 114.--Plan of steam pump with fly wheel.] + + +A SUGGESTION. + +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. + + + +XXIII. KITES. + +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. + +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. + +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. + + +CONSTRUCTION. + +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. + +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. + +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. + +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). + +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. + +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. + +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. + +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. + +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. + +[Illustration: FIG. 115.--Details of stretcher attachment for +diamond-shaped box kites.] + +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. + +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. + +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. + +[Illustration: FIG. 116.--Plan of diamond box kite, showing arrangement +of stretchers.] + +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. + +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. + +[Illustration: FIG. 117.--Diamond box kite in perspective. Ties are +indicated by fine dotted lines.] + +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. + +The stretchers are tied together at the crossing points to give support to +the longer of the pair. + +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. + +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. + +[Illustration: FIG. 118.--Box kite with rear wings.] + +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. + +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. + +The materials required for the comparatively small example with which the +reader may content himself in the first instance are: + +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. + +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. + +Double-stitch tape along the edges of each piece. + +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.) + +Remove the rod and stitch the row. + +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. + +[Illustration: FIG. 119.--Plan of box kite with rear wings.] + +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.] + +[Illustration: FIG. 120.--Wing for box kite.] + +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. + +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. + +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. + +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. + +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. + +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. + +[Illustration: FIG. 121.--Box kite with front and back wings.] + +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. + +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. + +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. + +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. + +[Illustration: FIG. 122.--Simple string winder for kite.] + +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. + +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. + +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. + +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. + +[Illustration: FIG. 123.--Plan of string-winding drum, frame, and brake.] + +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. + +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: + +[Illustration: FIG. 124.--End view of string winder, showing brake and +lever.] + +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. + +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. + +[Illustration: FIG. 125.--String winder in operation.] + +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. + +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. + + + +XXIV. PAPER GLIDERS. + +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. + +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. + +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. + +[Illustration: FIG. 126.--Paper glider: Model "A."] + +[Illustration: FIG. 127.--How to launch Model "A."] + +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. + +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. + +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. + +[Illustration: FIG. 128.--Details of paper gliders: Model "B" above, +Model "C" below.] + +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. + +Note that if the leading edges of the front wings are bent slightly +downwards the glider may fly much better than before. + +A good specimen of this type is so stable that if launched upside down it +will right itself immediately and make a normal flight. + +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. + +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. + +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. + +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. + +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. + + + +XXV. A SELF-LAUNCHING MODEL AEROPLANE. +By V. E. Johnson, M.A. + +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." + +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. + +Before entering into special details we may note some broad principles +which must be taken into account if success is to attend our efforts. + +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. + + +Details.--To pass now to details, we have four distinct parts to deal +with:-- + +1. The framework, or fuselage. + +2. The supporting surfaces, consisting of the main plane, or aerofoil, +behind, and the elevator in front. + +3. The propellers. + +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. + +[Illustration: FIG. 129.-Sections of backbone for model aeroplane.] + + +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. + + +If you find the construction of the T-shaped rod too difficult, two +courses are open-- + +(l) To get a carpenter to do the job for you, or + +(2) To give the rod the triangular section shown in Fig. 129, each side of +the equilateral triangle being half an inch long. + +[Illustration: FIG. 150--Side elevation of model aeroplane.] + + +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. + +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. + +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. + +[Illustration: FIG. 131.--Front elevation of chassis.] + +[Illustration: FIG. l32.-Wheel for model aeroplane chassis.] + +[Illustration: FIG. 133.--Plan of model aeroplane.] + +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. + +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. + +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. + +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.) + +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. + +[Illustration: FIG. 134.--Front skid and attachment to backbone.] + +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. + +[Illustration: FIG. 135--"Centrale" wooden propeller.] + +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. + +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. + +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. + +[Illustration: FIG. 136.--Axle and hook for propeller.] + +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. + +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. + +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. + + + +XXVI. APPARATUS FOR SIMPLE SCIENTIFIC EXPERIMENTS. + +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. + +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. + +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. + +[Illustration: FIG. 137.] + +[Illustration: FIG. 138.] + +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. + +[Illustration: FIG. 139.] + +[Illustration: FIG. 140.] + +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. + +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. + +[Illustration: FIG. 141.] + +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. + +[Illustration: FIG. 142.] + +[Illustration: FIG. 143.] + +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. + +The substitution of a long narrow slit for a circular hole gives other +effects. + +[Illustration: FIG. 144.] + +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. + +[Illustration: FIG. 145.] + +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. + +[Illustration: FIG. 146.] + +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. + +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. + +[Illustration: FIG. 147.--Apparatus for illustrating an apparent +scientific paradox.] + +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. + +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. + +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. + +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. + +[Illustration: FIG. 148.-Magic pendulums.] + +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. + +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. + +With two equally long and equally weighted pendulums, the three following +experiments may be carried out:-- + +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. + +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. + +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. + +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. + +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. + +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. + +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). + +[Illustration: FIG. 149.--Smoke-ring apparatus.] + +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. + +[Illustration: FIG. 150.--Smoke-making apparatus.] + +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. + +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. + +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. + + + +XXVII. A RAIN-GAUGE. + +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. + +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. + +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. + +[Illustration: FIG. 151.--Standard rain-gauge.] + +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. + +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. + +[Illustration: FIG. 152.--Section of homemade rain-gauge.] + +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. + +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. + +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. + +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. + +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). + +All tinned iron surfaces should be given a couple of thin coats or paint. + +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. + +[Illustration: FIG. 153.--Self-measuring gauge.] + +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. + +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. + +[Illustration: FIG. 154.--Gauge in case.] + +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). + + + +XXVIII. WIND VANES WITH DIALS. + +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. + +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. + +[Illustration: FIG. 165--Wind vane with dial.] + +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. + +[Illustration: FIG. 156.--Elevation and plan of vane.] + +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. + +[Illustration: FIG. 157.--Details of bevel gear and arrow.] + +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. + +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. + +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. + +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. + +Note.--In the vicinity of London true north is 15 degrees east of the +magnetic north. + +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. + +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. + +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. + +[Illustration: FIG. 158.--Plan and elevation of electric contact on vane +post.] + +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. + +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. + +[Illustration: FIG. 159.--Magnetic recording dial.] + +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). + +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). + +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. + +[Illustration: FIG. 160.--Another type of electric dial with compass +needle for pointer.] + +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. + +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. + +[Illustration: FIG. 161.--General arrangement of electric wind recorder.] + +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. + +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. + + + +XXIX. A STRENGTH-TESTING MACHINE. + +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. + +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. + +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. + +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. + +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. + + +CONSTRUCTION. + +[Illustration: FIG. 162.--Plan of strength tester.] + +[Illustration: FIG. 163.--Grips of strength tester.] + +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. + +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. + +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. + +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. + +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. + +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. + +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. + +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. + +[Illustration: FIG. 164.--Handle for twisting test.] + +To prevent the handle bending over, solder round the pivot hole 3/4 inch of +brass tubing, fitting the pivot closely. + +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. + +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. + +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. + + + +XXX. LUNG-TESTING APPARATUS. + +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. + +Air Volume Measuring.--The air which the lungs deal with is +scientifically classified under four heads: + +1. Tidal air, which passes into and out of the lungs in natural breathing. +About 30 cubic inches in an adult (average). + +2. Reserve air, which can be expelled after a normal expiration. About 100 +cubic inches. + +3. Complemental air, which can be drawn in after a normal inspiration. +About 100 cubic inches. + +4. Residual air, which cannot be removed from the lungs under any +conditions by voluntary effort. About 120 cubic inches. + +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. + +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. + +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. + +[Illustration: FIG. 166.--Section of lung-capacity tester.] + +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. + +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. + +[Illustration: FIG. 166.--Perspective view of lung-capacity tester.] + +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. + +The wire sliding in the tube will counteract any tendency of the container +to tilt over as it rises. + +A nozzle, D, for the air tube is soldered into the side of A, as shown. + +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. + +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. + +[Illustration: FIG. 167.--Apparatus for showing lung power.] + +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. + + +A Pressure Recorder. + +[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.] + +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. + +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. + + +CONSTRUCTION. + +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. + +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. + +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. + +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. + +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. + +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. + +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. + +Caution.--Don't ask people with weak lungs to try experiments with the +apparatus described in this chapter. + + + +XXXI. HOME-MADE HARMONOGRAPHS. + +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. + +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. + +[Illustration: FIG. 168.--Simple Rectilinear Harmonograph.] + +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. + +[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.] + +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. + +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. + +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. + +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. + +[Illustration: FIG. 169.--Goold's Twin Elliptic Pendulum Hamonograph.] + +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. + +[Illustration: FIG. 170.--Benham's miniature Twin Elliptic Pendulum +Harmonograph.] + +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. + +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. + +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. + +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. + + +Practical Instructions for making Harmonographs. + +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. + +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. + +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. + +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. + +[Illustration: FIG. 171.--Gimbal giving universal movement: point +suspension.] + +Points should rest in cup-shaped depressions in a metal plate; knife-edges +in V-shaped grooves in a metal ring. + +[Illustration: FIG. 172.--Knife-edge universal-motion gimbal.] + +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. + +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. + +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. + +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. + +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. + +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. + +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.) + +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. + +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. + +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.) + +[Illustration: FIG. 173.] + +[Illustration: FIG. 174.--Pivot for pen lever.] + +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. + +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. + +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. + +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. + +[Illustration: FIG. 175.--End of pen lever.] + +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.) + +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. + +[Illustration: FIG. 176.--Clip to hold glass pen.] + +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. + +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. + +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. + +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. + +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. + +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. + +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. + +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. + +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. + +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. + +Inks.--I have found Stephens's coloured inks very satisfactory, and can +recommend them. + +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. + +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. + + +Details of Harmonographs. + +The reader may be interested in details of the apparatus shown in Figs. 168 +and 170, made by the writer. + +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. + +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. + +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. + +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. + +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. + +[Illustration: FIG. 177.--Suspension for lower weight of Twin Elliptic +Harmonograph.] + +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. + +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. + +[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.] + +[Illustration: FIG. 177a.--Harmonograms of 3:4 ratio (antagonistically). +(Reproduced with kind permission of Mr. C. E. Benham.)] + +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. + +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. + +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. + +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. + +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. + +1. Every ratio has two forms. + +(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. + +(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.) + +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.) + +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. + +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. + +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. + +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. + + + +XXXII. A SELF-SUPPLYING MATCHBOX. + +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. + +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. + +[Illustration: FIG. 178.--Self-supplying matchbox, with match in position +for removal by fingers.] + +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. + +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. + +[Illustration: FIG. 179.--Details of self suplying matchbox.] + +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. + +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. + +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. + +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. + +Pierce a small hole through DD, in line with the slot, and insert a pin. +Draw the box fully up, and see if the top of A sinks to the proper place. +If it projects a little, lengthen the slot a trifle. + +Cut out the supports EE, finish them neatly, and glue them to A. Make sure +that the pin lets the box touch them. + +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. + +Note that the lid must not be opened when the box is down, as it would be +wrenched off its pivots. + + + +XXXIII. A WOODEN WORKBOX. + +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. + +[Illustration: FIG. 180.--Showing how to draw an ellipse.] + +[Illustration: FIG. 181.--Norwegian workbox.] + +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. + +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. + +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. + +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. + +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. + +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. + +The exterior may be decorated by a design in poker-work, or be stained and +varnished. This is left to the maker's discretion. + + + +XXXIV. WRESTLING PUPPETS. + +[Illustration: FIG. 182.--Peg marked for cutting and drilling.] + +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. + +The clothes pegs used must be of the shape shown in Fig. 182, with a round +top. They cost one penny per dozen. + +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. + +To get the best results the two arms and the four legs should be paired off +to exactly the same length. + +[Illustration: FIG. 183.--Clothes-peg wrestlers.] + +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. + +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. + +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. + +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. + +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. + +[Illustration: FIG. 184.--Large wrestlers made of stout wood.] + +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. + + + +XXXV. DOUBLE BELLOWS. + +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. + +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. + +[Illustration: FIG. 185.--Double-acting bellows. Two methods of coupling +shown.] + +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. + +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. + + + +XXXVI. A HOME-MADE PANTOGRAPH. + +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. + +[Illustration: FIG. 186.--Details of simple pantograph.] + +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. + +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. + +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. + +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. + +If proportions other than those given are required, a very little +calculation will locate the necessary holes. + +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. + +[Illustration: FIG. 187.--Diagram showing how to mark off pantograph +rods. The dotted lines above rod give distances of holes from ends.] + +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. + +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. + +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. + +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. + +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. + + + +XXXVII. A SILHOUETTE DRAWING MACHINE. + +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. + +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. + +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. + +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. + +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. + +[Illustration: FIG. 188.--Silhouettograph in use.] + +[Illustration: FIG. 188a.--Group of silhouettes drawn with the machine +described.] + +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. + +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. + +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. + +A thread attached to the pencil will enable you to keep the pencil off the +paper until you wish to begin drawing the profile. + +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. + +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. + +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. + + + +XXXVIII. A SIGNALLING LAMP. + +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. + +The stand for the lamp is admirably supplied by the ordinary camera tripod. +For the illuminant we may select any good acetylene cycle lamp. + +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. + +[Illustration: FIG. 189.--Signalling lamp with quick-moving shutter.] + +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. + +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. + +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. + +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. + +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. + +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. + +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. + +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. + +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. + +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. + +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. + +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. + +The tension of the spring must be just sufficient to close the shutter +smartly and prevent it rebounding far enough to pass any light. + + + +XXXIX. A MINIATURE GASWORKS. + +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. + +[Illustration: FIG. 190.--General view of gas-making apparatus.] + +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-- + +(l) The formation of gas in a retort; + +(2) The condensation of the tar; + +(3) The condensation of steam; + +(4) The removal of the ammonia gas; + +(5) The removal of the sulphuretted hydrogen and carbonic acid. + +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. + +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. + +[Illustration: FIG. 191.--Vertical section of condenser.] + +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. + +[Illustration: FIG. 192.--Plan of condenser.] + +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. + +[Illustration: FIG. 193.--Vertical section of purifier.] + +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. + +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. + +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. + +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. + +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. + +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. + +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. + +[Transcribers note: Premature lighting of the burner may cause the flame to +propagate into the system and explode. I speak from experience.] + + +INDEX. + +Aeroplane, model, self-launching. +Bedplate for engine. +Bellows, double. +Bench, joiner's. +Benham's harmonograph. +Bicycle shed. +Boilers, model. +Bookstand. +Box kites. + +Cabinets, cardboard, cigar-box, match-box, tool. +Circles, rolling. +Clock, electric alarm. +Colour top. +Cylinder, double-acting steam. + +Developing sink. +Doors for shed. +Double-acting horizontal steam engine. +Double bellows. + +Eccentrics. +Electric alarm clock. +Electric motor, reciprocating. +Electric railway. +Engine, hot-air. +Experiments, apparatus for simple scientific. + +Fuels for model boilers. + +Gasworks, miniature. +Ganges, rain, water, +Gimbals, or universal joints. +Gliders, paper. +Goold's harmonograph. +Governor for engine. + +Harmonographs. +Hot-air engines. +House ladder. + +Joiner's bench. + +Kettles, quick-boiling. +Kites, box. +Kite winders. + +Ladder, house. +Lamp, signalling. +Locomotive, electric. +Lung-testing apparatus. +Magic swingers. +windmill. +Match-boarding. +Match-box, self-supplying. +Morse code. +Morse sounder. +Motor, electric. +Motor, water. + +Nozzle for steam turbine. + +Pantograph. +Pendulums for harmonograph. +Pens for harmonograph. +Pneumatic puzzle. +Poultry house. +Propellers for aeroplane. +Pumps. +Puppets, wrestling. +Puzzle, pneumatic. + +Railway, electric. +Rain gauges. +Reciprocating steam engine, simple. +Resistance, adjustable, for electric railway. +Reversing switch for electric railway. +Riveting. + +Safety Valves. +Sawing trestle. +Shed for bicycle. +Signalling lamp. +Silhouette drawing machine. +Simple scientific experiments. +Sink, developing. +Slide valve. +Smoke-ring apparatus. +Soldering. +Spokes, magic. +Steam cocks. +Steam engines. +Steam gauge. +Steam pump. +Steam tops. +Steam turbines. +Strength. testing machines. +Swingers, magic. +Switch, multiple battery. +Switch, reversing. + +Target apparatus. +Telegraphic apparatus. +Testing boilers. +Tool cabinet. +Top, colour. +Tops, steam. +Track for model railway. +Trestle, sawing. +Turbines, model steam. + +Vanishing spiral. +Vice for Joiner's bench. + +Water gauge. +Water motor. +Weights for harmonograph pendulums. +Windmill, magic. +Wind vanes; electric. +Workbox, Norwegian. +Wrestling puppets. +Wriggling line. + + +THE END. + +PRINTED IN GREAT BRITAIN AT THE PRESS OF THE PUBLISHERS. + + + + + +End of the Project Gutenberg EBook of Things To Make, by Archibald Williams + +*** END OF THIS PROJECT GUTENBERG EBOOK THINGS TO MAKE *** + +***** This file should be named 14664.txt or 14664.zip ***** +This and all associated files of various formats will be found in: + https://www.gutenberg.org/1/4/6/6/14664/ + +Produced by Don Kostuch + +Updated editions will replace the previous one--the old editions +will be renamed. + +Creating the works from public domain print editions 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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