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diff --git a/14664-0.txt b/14664-0.txt new file mode 100644 index 0000000..a573d91 --- /dev/null +++ b/14664-0.txt @@ -0,0 +1,8222 @@ +The Project Gutenberg eBook of Things To Make, by Archibald Williams + +This eBook is for the use of anyone anywhere in the United States and +most other parts of the world at no cost and with almost no restrictions +whatsoever. You may copy it, give it away or re-use it under the terms +of the Project Gutenberg License included with this eBook or online at +www.gutenberg.org. If you are not located in the United States, you +will have to check the laws of the country where you are located before +using this eBook. + +Title: Things To Make + +Author: Archibald Williams + +Release Date: January 11, 2005 [eBook #14664] +[Most recently updated: February 21, 2021] + +Language: English + +Character set encoding: UTF-8 + +Produced by: Don Kostuch + +*** START OF THE PROJECT GUTENBERG EBOOK THINGS TO MAKE *** + + + + +[Illustration] + +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. + + + + +XVII. +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. + + + + +XXXVII. +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 THINGS TO MAKE *** + +***** This file should be named 14664-0.txt or 14664-0.zip ***** +This and all associated files of various formats will be found in: + https://www.gutenberg.org/1/4/6/6/14664/ + +Updated editions will replace the previous one--the old editions will +be renamed. + +Creating the works from print editions not protected by U.S. copyright +law means that no one owns a United States copyright in these works, +so the Foundation (and you!) can copy and distribute it in the +United States without permission and without paying copyright +royalties. 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