Chapter XI: The Boy’s Own Model Locomotive, and How to Build It

BY H. F. HOBDEN.

Those who class model engines as mere toys, and fit only to amuse the very youngest members of the human family, entirely forget the important place they hold in the estimation of inventors and those interested in mechanism as a means by which they can practically carry out their ideas, because models not only have the advantage of cheapness in construction as compared with the full-sized machine, but also the still greater advantage of being, from the small size and light weights of their parts, capable of construction by the inventor himself without having to employ strangers.

I suppose there is no taste more universal amongst boys, old as well as young, than that for mechanism and engineering. What boy does not feel interested in the models displayed in the various shop windows in our large towns, and what lad with any mechanical bent but has a longing to make one for himself and feels an intense pleasure in being able to do so? And it is with the intention of helping those who would like to build one, but have not the necessary knowledge, that I purpose to explain, as simply as possible, the best method of building model locomotives.

In previous pages of this volume, practical instructions by skilled writers have been given on model stationary engines of a simple make, and also on engines for steamboats, but of all models the locomotive has the greatest charm for most boys, and not unjustly so, as when well finished and carefully painted it has a very handsome appearance, and moreover has the additional charm of its locomotive power.

Those of my readers who have practically carried out the instructions in the previous chapters just referred to, have become, I have no doubt, by this time quite _au fait_ in handling their tools and feel at home in their workshop; but for the benefit of those boys who have had no practical experience, let me give a word or two of advice before we begin our locomotive.

First then, with all engineering work, either large or small, great care must be taken to get the measurements perfectly correct in spacing out the various parts to be joined together, and do not think, because it is only a model you are making, that any off-hand way will do, because you will find before the engine is half finished that great accuracy is necessary if you wish your model to be a working one.

A slight mistake in the measurements of a large engine will cause so much friction as to take half its power to overcome, and the same thing occurring in a model would stop it entirely.

Then with respect to any part you may require to solder, be careful always to make the brass or other metal you wish to unite quite hot. You will then get a good firm joint.

Do not just touch the metal with the soldering iron and then take it away. You might certainly stick the parts together slightly in that way, but they would be sure to come apart the first time they received a blow or any pressure was put on them.

Soldering on the best work should be used very seldom, and all the fastenings should be either done by riveting, screwing, or brazing; and I need hardly remark that no part of a boiler should be soldered which comes in direct contact with the flame of the lamp or furnace.

Brazing, with the exception of very small articles, is beyond the ordinary powers of an amateur.

Even to braze the seams of a model boiler requires a forge fire or very powerful gas-blast, which is too expensive for most boys to get; but small things, such as a broken slide, valve rod, etc., can be easily brazed by using a gas blow-pipe, and as it will cost you very little to make and will prove a useful tool for sweating in solder as well as brazing, I will briefly explain.

Fig. 1 is a section of the blow-pipe complete.

To make it, first get a small piece of brass tube (A) of about half an inch diameter and five inches long; drill a hole at two inches from one end, and insert a piece of gas tube (B) and solder it in place.

Next take a piece of glass tubing a quarter of an inch diameter and about seven inches long, hold one end in a gas flame, and when red-hot draw it out to a fine point, then file round and break off the tip, leaving a small hole.

Next squeeze a sound cork into the tube A as at C, and drill a quarter of an inch hole through its centre and insert the glass tube D, and the blow-pipe is finished. To use it you connect the pipe B with a gas bracket by a rubber tube, and the glass tube D must be fastened to a pair of bellows by means of another piece of rubber tubing; the bellows should have an air-bag attached, to enable you to keep a constant pressure up and prevent having a jerky flame.

When requiring to braze any article, bind the parts together with some very fine brass wire and cover it up with a little powdered borax and water, then lay the article on a piece of charcoal, and if it is necessary to preserve the temper of the steel you are about brazing, cut a potato in half and push each end of the steel rod into the halves, which will prevent the temperature of the rod getting too high.

When you have it all nicely fixed, turn on the gas and light your blow-pipe, immediately work the bellows with your foot, and by either pushing in the glass tube D, or drawing it slightly out, you can regulate the shape of the flame as required.

Then bring the flame to bear on the joint, well supplied with the borax, and soon you will find the brass wire melt and run into the joint like water. It must then be neatly filed up, and the join will be scarcely visible.

Having made this useful tool, I will mention a few others you should get before commencing work; they will not cost much.

A centre punch or pointed steel spike for marking metal for drilling, etc., and a small riveting hammer, three or four files of different degrees of fineness, a screw plate and taps, and also a small hand-drill with a set of drills to fit, will be most useful; and of course very little can be done without a good firm vice.

If you have a lathe, so much the better; it will enable you to save lots of odd coppers for turning various parts. Curves for bending metal on you can easily make from pieces of bar iron, holding them in the vice when working on them.

When you have your tools ready, the materials are required you intend working on, which will consist of several sheets of brass and copper, the castings and various-sized screws and bolts; and having got these all together, we can set to work on our locomotive.

I think it would be better to first give you directions for making a simple one of about fifteen inches, and then to proceed to a more perfect model after.

In a previous article you will find a description of the action of the steam in the cylinder, and although that is in a marine engine, the action is precisely the same in the cylinders of a locomotive, and you should therefore read the description carefully and thoroughly understand it; there is also given a method of turning the cylinders, and hence I shall not describe the process again, but consider that you already know sufficient about it, should you wish to make your cylinders in preference to buying them ready finished.

At the commencement of this chapter is a drawing of the model we are about to build in its finished condition, and Fig. 2 is a side view of the same, of which A is the boiler, B the chimney, C a screw head to fill boiler with water, D the steam chest with safety valve on top, E the whistle, F the steam tap to start the engine with, HH are the leading and trailing wheels, and I the driving ditto, K the cylinders, L the frame, M the buffers, N a set thumb-screw to fasten a tender on by, O is the lamp, and P is a small tap, used to ascertain the quantity of water in the boiler. The handrails R and S complete it; and I think this is sufficiently clear for you to perfectly understand the general working arrangements of the model.

Locomotives, whether real or only model ones, can all be divided into three principal parts, viz., the carriage or framework, the engine or cylinders and parts connected with them, and the boiler, and we will now proceed to make each part in turn, beginning with the framework.

First take a sheet of brass for the bed-plate, about one-sixteenth of an inch thick, and cut it to an oblong shape, four inches wide by fourteen inches long, as in Fig. 3, and be very careful that the corners are right angles. This is to be hammered out quite flat and filed up smooth, and finished with emery cloth held round a flat piece of wood; you must also cut a hole in it for the boiler to rest in as at C, beginning half an inch from B and making the hole eleven inches long by one inch and a half wide, taking care it is quite central on the line AB, or you would get your engine lopsided, and you must take the same care in setting the chimney, steam dome, etc., as when not exactly central it gives a bad unsightly look to an otherwise well-finished model.

The next step is to cut out the side frames (Fig. 4), drilling holes at A B C for the axles to work in; you can finish both sides in the same way, and, turning the bed-plate upside down, fasten the frames on at a quarter of an inch from either side by small angle pieces, as in Fig. 5, or by soldering, which is much quicker. Then fasten by the same means a piece across each end about half an inch deep, and the frame is ready for the wheels.

These can be had ready finished, but if you have the castings, they must be chucked in the lathe and the tires turned up to the form shown in Fig. 6. The small wheels should be about two and a half inches diameter and the driving wheels four inches. The rim B should project a little over one-sixteenth of an inch, and the rest of the edge should be bevelled off slightly as at A.

The spokes may then be filed up smooth, previously drilling out the centre hole for axle before removing it from the lathe.

Great care must be taken to turn both the driving-wheels to exactly the same diameter, or one wheel would travel farther in a revolution than the other, and as they ought to be both fixed rigidly on to the crank shaft, the engine would never travel in a straight line, but would always run in a circle. You will require some steel wire for the axles, and can fasten them to the wheels by soldering or by cutting a slot with a fine file in the centre of wheel, as at A, Fig. 7; then filing a small portion of the ends of the axle flat, drive in a brass wedge made from a piece of wire, which will hold them together firmly.

The crank shaft or axle must be hammered up to shape, making it hot occasionally in the gas flame whilst working it.

The cranks should be at right angles to each other, and the throw of the crank is to be half the distance of the cylinder stroke. For instance, say the cylinders are an inch and a half in stroke, the distance between A B (Fig. 8) will be three-quarters of an inch; you must then ease the size of crank at A, to prevent the piston knocking the cylinder ends.

The cylinders require such extreme care in turning that it is by far the best plan to buy them ready to put on your framework; and if you get a pair of oscillating ones three-quarters of an inch bore and about an inch and a half stroke, you will get sufficient power to drive your locomotive several miles an hour.

Fig. 9 shows you an underneath view of the framework and the position to place the cylinders in, which should be supported by a couple of lugs (A A) screwed to the bed-plate B which must have a piece cut out on either side to allow the driving-wheels (C) to work in, as at D, because, being larger than the others, they project beyond the top of the bed-plate, as shown in Fig. 2. You can now screw on by means of the hook F the buffer-beam, previously cut from a piece of mahogany, five inches long, half an inch thick, and one inch deep, nicely squared and sand-papered.

Drill a hole at G and pass the shank of hook through the beam and piece of brass in front of frame, and screw up tight with nut H.

The buffers can be properly turned up and fitted with springs, but that I will explain when making our more perfect model, and content ourselves now with a couple of brass flat-headed screws, such as are used in connections of electric batteries, and which form capital imitation buffers, one having to simply screw them into the beam about one inch from either end, leaving them projecting about half an inch.

The framework is now sufficiently complete to be lacquered. First polish every part intended to be bright, carefully removing all traces of file-marks and any grease that may be on the work by a little acid; and after drying it place it on a sheet of iron held over the gas--or fire, if clear--until it is moderately warm. You can then apply the lacquer with a small brush, taking care not to go over any part more than once. The lacquer can be had at most model shops, and is cheaper to buy ready-made than to prepare yourself.

The spokes of the wheels should be painted; black-lined on green looks very well, and the ordinary tube oil-paint, mixed with a little mastic varnish, is the best to use.

The buffer-beam should be varnished, and the cylinders ought to have a coat of paint, leaving the cylinder-covers and the flanges bright.

The frame may now be put aside to dry, covered up from dust by a paper box, whilst we proceed to make the boiler (Fig. 10).

This is a most important part of the locomotive, and is the cause of a great many failures and unsatisfactory working, even amongst the professionally-built models. I well remember how, when a lad at school, I fell deeply in love with a beautiful highly-polished brass locomotive of about the size we are now building, which was displayed in an optician’s window. Having made inquiries about the price, and got it reduced from to £5 to £4, with a promise to keep it for me, I set to work to save my pocket-money, and for some months rigidly abstained from all kinds of tarts and toys; and when finally the last shilling was saved which completed the amount, and I carried it--my first model--home in triumph, no boy was ever happier. But, oh! the bitter disappointment when, after getting up the steam and trying to start the engine, I found it would not work.

I was too young then to find out the reason, and the man who kept the shop, not being a practical mechanic, could give me no help, and although, after we had tried it together, he offered to take it back, I decided to keep it with a view to remedy the defect, if possible; but it was a long time before I found out that the fault lay in the boiler not being able to supply sufficient steam for the cylinders, in consequence of not having enough heating surface acted on by the lamp.

Since that day I have made numerous models, and have always taken precautions to avert such a difficulty, and although the method I am about to describe entails a little extra work, you will feel well repaid for the trouble when you find what a splendid head of steam can be kept up.

The boiler should be eleven inches long by three inches and a half in diameter, and you can buy copper tubing of that size which is very suitable for the job, or you can form it from a sheet of copper or brass bent to shape round a wooden roller, and either riveted or soldered together. You must then turn two circles of brass about an eighth of an inch thick for the ends, and polish the outside of each nicely.

Then push them into either end of the boiler about an eighth of an inch from the edge, as in A (Fig. 11); they can now be soldered in place, and you will find your gas blow-pipe very useful here. The projecting flange should be hammered down all round, like B (Fig. 11), which can also be sweated afterwards with solder, and finished off with a half-round file.

When filing solder or lead, only use an old worn file, as the soft metal soon fills up and spoils a good one, and although it can be melted out by heat, it is not advisable to do so.

You will now require to drill a hole at A (Fig. 10) for the chimney, which should be three-quarters of an inch in diameter. Then cut a slot in the bottom of the boiler six inches long by an inch and a half wide, commencing a quarter of an inch from the forward end of the boiler.

Now take a sheet of copper and cut a piece about six inches and a quarter long by six inches broad, and bend it over a wooden roller to the shape shown at Fig. 12, keeping it an inch and a half apart between A B. Cut also two other pieces of copper to the shape of your bent sheet (Fig. 12), and make it long enough to reach to the dotted line. These form the two ends, which may be placed an eighth of an inch from the edges, as in Fig. 13, and soldered in place, and the projecting rims turned over and sweated with solder from the outside in the same manner as you did to the boiler-ends in Fig. 11. Then drill a three-quarter-inch hole at B (Fig. 13) for the bottom of chimney-tube to go into, and cut a piece of three-quarter-inch brass tubing of sufficient length to pass out at top of boiler about half an inch, as shown at A (Fig. 10). You can then hammer out a rim or flange on the bottom end of chimney-tube, and push it up through the hole in the copper box and solder it in place from the top, as at A (Fig. 14).

Now drill a couple of small holes at each end of the box B C (Fig. 14); these should be rather more than an eighth of an inch in diameter, to allow an eighth of an inch tube to pass through.

Get two twelve-inch lengths of hard-drawn steam-piping of an eighth of an inch in diameter, and with your screw-plate put a thread on each end of about half an inch in length, then drill some holes in any odd piece of brass plate, and with the screw-taps form eight nuts to fit the threads on the piping, and finish them up to shape with a file.

Then take the piping and bend it very gently, to prevent it cracking, round a bar of iron or handle of some tool held in the vice until it is of the form shown at Fig. 15. Do each one the same, and then mix a little turps with some white lead and smear each end where you have formed the screws, taking care not to get any into the tubes, and they might have a plug of paper put in temporarily to prevent it.

Now put a nut on at either end as far as the thread will allow it, and smearing a little white lead round the holes drilled in ends of box B C (Fig. 14), push the tubes in from the inside and screw up firmly with the remaining nuts in the position shown at Fig. 16. The inside nuts can then be tightened up with a spanner, and if you have carefully done this you will never be troubled with any leakage, no matter what pressure you may get in the boiler.

These tubes are immensely strong, and from their small size the water in them is raised quickly to a higher temperature than that contained in the rest of the boiler, causing a continual circulation to take place and a constant supply of steam to be formed.

The box can now be placed in the boiler through the slot cut in the bottom, taking care that the top of box is not more than half way up the boiler, as in B (Fig. 10). This will leave a portion projecting below the lower edge of boiler, like C. This part protects the flame of the lamp from being blown away by the draught caused by travelling along, which would cause you to lose steam. Solder it firmly in position from the outside, to prevent the flame touching any soldered portion. Also solder neatly round A (Fig. 10).

The chimney can be made from another piece of three-quarter brass tube. Chuck it in the lathe, and turn it up bright, and put a collar on it at A (Fig. 17) to allow it to push on to the piece of tube left projecting at A (Fig. 10).

The top of chimney, or bell-mouth, B (Fig. 17), will require turning in the lathe also, and fitting on neatly.

The steam-chest D (Fig. 10) is a brass casting you can turn up also, and after cutting a circular hole in top of boiler of about an inch in diameter it can be either screwed or soldered on, previously putting the steam-pipe E in position by drilling a hole at F, and after bending it as shown, pass it through at F and solder in place.

The top of pipe E should be about a quarter of an inch from top of inside of steam-chest.

Before soldering on the steam chest drill a couple of holes, as at G H (Fig. 10), one for the small lug G to be screwed into, which holds one end of the lever of the safety valve, and that at H should be drilled conical with a rhymer, and the valve H can be turned in the lathe, and afterwards ground to fit the hole with a little emery and water, by means of a slot cut across the top and worked round with a screw-driver.

The spring-case of safety-valve is easily made from a piece of the one-eighth of an inch brass tubing, and using some small, hard brass wire to form the spring of. When finished it should be hooked to the eye screwed into boiler at V.

The manhole, or screwhead, K, is used to refill the boiler by when it has steamed low, and will require to be turned up to shape; and the bed L it screws into can be firmly soldered on the boiler, having first drilled a hole slightly larger than the diameter of the screw itself, which should be sufficiently large to allow an ordinary tin funnel to be used to refill by, and the screw ought to be large enough to hold a leather washer under the head to keep it steam-tight.

The whistle M will require a hole drilled for it to be screwed into, and that, as also the steam-tap N and water-tap O, can be bought cheap ready to put on, and is more satisfactory than making them yourself. But should you wish to do so, the method I have already described in Chapter X. of making an oil-cup applies equally to these.

The tap O should be screwed in at a slightly higher level than the top of box B, and when working the engine, should steam issue from it when turned on instead of water, you ought to immediately blow off steam by safety-valve H. Then unscrew K, and refill the boiler with water.

By this time the framework will no doubt be quite dry, and you can then clean and polish the boiler and attach it to the frame by a screw or solder at the forward end, and the steam-pipe N can be screwed on to the projecting piece of tube left at F, whilst you also screw a short length of pipe into the steam-box of engine through a hole in the bed-plate. Then bend it up to the steam-tap and solder them carefully in position; this will hold the after end of boiler firmly.

Go over every soldered joint to see if any small hole is left, and re-solder where necessary, as a hole in the boiler not larger than a pin’s point would prevent you getting any adequate pressure of steam, as the water would all blow out.

When so far complete, you can either lacquer or paint the boiler as suits your fancy, and whilst it is drying there will be time to make the lamp (Fig. 18).

It is simply an oblong box made of tin or any piece of thin metal you may have, and should be one inch and a quarter wide by five inches long, and about three-quarters of an inch deep. To make it, cut say a piece of tin four and a half inches by five inches, and bend it to shape, then solder the two edges together and cut two ends to fit. Push them in and solder in place.

Then cut three pieces of brass quarter-inch tubing into three quarter-inch lengths, drill holes in top of lamp and insert them, allowing about a quarter of an inch to project, as at A (Fig. 18); then solder them on four pieces of bent wire (C C C C), by which to hang the lamp by means of two wire pins run through them and small holes drilled in sides of projecting piece C (Fig. 10).

The screw-filler B (Fig. 18) will have to be soldered in also, and when complete the tubes A may be filled with cotton wick, and the lamp about three parts full of methylated spirit, which will give a clear smokeless flame.

You can now start your locomotive by filling the boiler about three parts full of hot water, and then hooking the lamp underneath; you will soon get a good pressure of steam up.

See that all the taps are turned off; and if there is no leakage from careless workmanship, you will find, on turning the steam-tap on, the locomotive will run beautifully, and will travel at great speed either on a smooth oil-cloth or wood floor.

I will presently explain how to make a set of rails, on which she would run much quicker still; but for this engine, if you make a small tender of the shape shown at Fig. 19, and fasten it at any angle by the set-screw on the foot-plate of the engine shown at N (Fig. 2), the model will run in any sized circle you may wish, without lines, according to the angle at which you fix the tender to the engine.

Wooden coal trucks, etc., you can easily make to complete the train if you wish; but of course each one is an extra load for the engine to draw, and will prevent it going as quickly as when alone.

Tin is the best material to use for the tender, as no great strength is required; indeed, it should be made as light as possible. The wheels and axles you must finish in the same manner as those on the engine; and it could be made into a tank, to hold an extra supply of spirit, by soldering a piece of tin round the inside, and covering it in with another piece cut to shape, and fitted with a screw-nut to fill by, as shown in Fig. 18.

If you have carefully followed these simple directions, and also practically carried them out, you will be able, and no doubt anxious to try your constructive powers on a more complete model, and I will therefore endeavour to help you to do so.

A MORE FINISHED MODEL.

Should you be able to draw, you will find it a great help if you carefully sketch out on a sheet of cartridge paper the locomotive to the exact size you intend building it.

You can then take all the measurements from it, which will prove to be a saving in time and trouble. Of course the larger you make the engine, the more expensive the castings and materials will be; but if you persevere in making the locomotive I am about to describe, you will have a model of real value to you, and which would probably cost fifty pounds to buy ready finished; and if you turn the wooden models for the castings yourself, and use sheet-iron for the framework, etc., where possible, the total expense will not be so very great.

Fig. 20 is a side view of the locomotive in its finished state, and we will begin to work at it in the same manner as in the former model, viz., with the framework; but as some of my readers may have a preference for some special type of engine other than the one drawn, they can easily build it from the following directions, and keeping the same proportion in size as in Fig. 20, which is drawn to 1/8-inch scale.

The entire length should be about three feet two inches, and the bed-plate thirty-five inches by nine inches wide. The driving-wheels are eight and a quarter inches in diameter, and the leading wheels five and a quarter inches, and about six and a half inch gauge, viz., the space between the lines on which the wheels run.

The cylinders should be one and three-quarter inch bore by two and a half inch stroke, which will give sufficient power to drive the engine at a high rate of speed, with 30 lb. to 50 lb. of steam. The boiler is twenty-eight inches long, including smoke-box, by five inches diameter.

In Fig. 20 I have lettered the various parts, and it will be well to look over them carefully, as this engine differs materially from the previous model in its arrangement, being constructed exactly similar to a real engine.

A is the chimney, B steam-blast used to increase the intensity of the fire, and is worked by rod C running through the hollow handrail D, and ending in handle F. G the steam-dome and safety-valve is the same pattern as previously used, H extra safety-valve, worked from foot-plate; I steam-whistle, K wind-guard, L starting-lever, M smoke-box (with door), N O spring-buffers; P is the line-clearer, or wheel-guard; Q leading wheels, and R R driving ditto; S one of the cylinders, with piston-rod and guides bolted to frame, and showing double connecting rod at T T; U U are the springs which support the weight of the boiler, etc., on the axle-bearings; the spring on rear wheel does not show, being inside the safety-guard and handrail V. W is the back-pressure valve, through which the water is thrown by the force-pump into the boiler; and X is the blow-off tap to clear the model from all water after having used it; and Y shows the side of ash-pan.

Now to commence making the framework. This should be made of one-eighth of an inch sheet-iron, squared up perfectly true and flat, and cut out as shown in Fig. 21, commencing four inches and a half from A, and leaving six inches at B, and cutting it six inches wide there by eight inches long, and continuing it four inches wide for the rest of the distance. Be careful to keep it quite central on the line A B, and leave two connecting strips one inch wide, as at C C.

The side-frames come next. These must be much stronger, and quite different from those used in our previous model, and should be cut from the same eighth of an inch plate-iron to the shape shown in Fig. 22.

The centre of slot B is seventeen inches from one end, the centre of A ten inches from B, and centre of C thirteen inches from B.

In marking out work always measure from a fixed centre, for if you add one measurement to another any slight inaccuracy gets increased with each fresh measurement, and you might finally get the different portions out of place.

The slots are each an inch and a quarter wide by two inches deep, leaving one inch of iron at top as shown. The ornamental spaces can then be cut out, which lightens it considerably without weakening it much.

The frames, after being smoothed up, can be fastened to the bed-plate in the manner described before by angle-irons or knees riveted on. Two end-pieces must also be prepared an inch deep, and the ends hammered square at right angles, and then riveted to the bed-plate and side-frames, as shown by the rivets in Fig. 20.

Then drill three holes in them about an inch and a half from either end, and one in centre by which to bolt on the buffer-beams by means of a couple of screws put in from the back.

The buffer-beams should be mahogany, one inch wide, two inches deep, and ten inches long, squared nicely and sand-papered. A hook can then be made (Fig. 23), and, a hole being drilled in the centre of beam, you can pass the hook-stem through and into central hole of framework, and screw up tightly with nut at back, which will hold all firmly in place.

The buffers for this model must be made properly with springs to take the pressure, should you let it run into anything.

Turn out a wooden mould in the lathe and get four castings in brass made from it. Fig. 24 is an ordinary kind of buffer in general use, and, being in section, shows you the working arrangement of the spring, A is cast with a square base-plate two inches square, as in front view B, and is secured to buffer-beam by four flat-headed screws. The piece C must be turned true, and just the size to slide in and out A easily. Each part must be finished up in the lathe. A should be about an inch and a half long.

Drill a hole in beam to allow the head of pin to work in freely, and another hole in base-plate of buffer the size of pin, whose head prevents the spring forcing C entirely away from A.

The spring should be made of thick steel wire; the buffers can then be screwed on as just mentioned. The wheel-guard, or line-clearer P (Fig. 20), can next be cut out to shape and bolted on to frame, and should just clear the line by a quarter of an inch.

We will now proceed with the axle-bearings and springs U (Fig. 20). The wheels can be finished up in the same manner as previously described, so I need not say anything further about them.

Make a wooden model like Fig. 25 and get six castings in brass made from it. They then must be filed up square and smooth and fitted into the slots cut at A B C (Fig. 22), and either screwed or riveted on by the side holes.

Before finally fixing them prepare six brass bearings (B, Fig. 25). They must fit exactly, and slide easily in the inner surface of A, and a hole is to be drilled centrally through each five-eighths of an inch in diameter. These take the axles, which in this model are all straight, and three-quarters of an inch in diameter, shouldered off to five-eighths for the bearings.

The springs next require attention. Four pieces of either sheet iron or brass are wanted in each support an inch and a half long by a quarter wide. A hole is to be drilled at either end, as shown at C in Fig. 26. A should be three-eighths of an inch wide, drilled through and a pin put in, and all riveted together loosely.

The spring is best made from clock-spring, and cut to shape as at D. The top-piece requires to be made hot with your blowpipe, and then the ends turned over to hold the pin B. Each piece of spring must be slightly shorter than the upper, and the ends nicely graduated off, and when ready held together by the brass band F, which has a small hole drilled at F to hold the end of pin by which the pressure is directed on to the axle-boxes, as shown in Fig. 20. A hole is also to be drilled in bed-plate over centre of each axle-box to allow pin to pass through, and also a smaller one an inch and a half on each side for the support A (Fig. 26) to screw into. They can all be fitted into position.

The cylinders come next, and should be, as previously mentioned, an inch and three-quarters bore by two and a half inch stroke. These should be of the fixed slide-valve pattern, with double eccentrics fitted on middle axle-shaft, and reversing-lever brought to quadrant on foot-plate, as I will show presently, and for the method of making them I will again refer you to my article on the Model Launch Engine, and will simply give you in Fig. 27 the modified form necessary to suit a locomotive, in which A A are the eccentrics, B slide valve-rod, with guide G attached; C C the bed-plate, D the balance-weight, and F the rod leading to quadrant and lever on foot-plate. The cranks are put on outside the wheels and fastened by keys, as in Fig. 20.

The connecting rods T should be cut to the form shown in Fig. 28, and the ends squared out and a brass bush filled in with a hole drilled from top (A) to oil by, and a set-screw B fitted to adjust the bearings perfectly.

Although these little things give extra work in fitting a model, they add considerably to its finish and lessen the friction.

If you wish to fit a force-pump, it should be placed centrally between the cylinders, and be worked by an eccentric on main shaft, but a pump on a model locomotive is of very slight use unless it is arranged to work by hand also.

In Fig. 29 I have given a practical method of arranging one to be worked either way as desired. A is the pump, B the eccentric on main-shaft to work it by steam power; but when requiring to work the pump by hand, you have only to push up hook connection at C, which disconnects it from eccentric, and then by working the handle D, which is screwed into bottom of plunger C, the water is forced into boiler.

This pump is a little more troublesome to make, as it requires an extra stuffing-box at F, but it is very neat and useful, and the handle lying quite out of the way, does not spoil the appearance of the model.

G is the exhaust water-pipe bent up to the back pressure-valve on boiler, and H the supply-pipe carried on to rear of engine.

You will find two small blow-off cocks on each cylinder very handy to get rid of the condensed steam when starting the engine with cold cylinders, as without them the cylinders get choked, and you stand a good chance of getting scalded by the hot water being thrown up the chimney with considerable force.

The blow-off cocks can be connected with a tye-rod, and both worked from the foot-plate by a single handle.

The parts being all finished to your satisfaction, you should paint the bed-plate black, and side frames red, and when dry carefully line them black and white, and also pick out the rivets with black.

Of course individual taste has a great deal to do with the finish of a model, so I will leave it to you, merely suggesting you should get a fine lining tool to finish with, and when all is complete put it aside to dry whilst we proceed to build the boiler.

This will require the greatest care, but with due attention you will be able to turn it out well. Some sheet copper will be required one-eighth of an inch thick, and although this is more expensive than iron, it does not rust, and is more suitable for the work in hand.

First cut a piece nineteen inches long by sixteen wide, and bend it round, forming a cylinder five inches in diameter; the lap must be closely riveted, and then the two ends hammered out into a flange outwards, leaving the body of boiler seventeen inches long, as in Fig. 30; B is the shape of piece to be next riveted on at after end, then take another sheet nine inches wide, and hammer a half-inch flange round it so as to fit over the dotted line in A.

Then rivet them firmly together, and also another piece in after end.

It will now have the appearance of Fig. 31, and should be four and a half inches deep from A to B, and forming a copper box six inches wide from B to C, and eight inches from C to D.

Then rivet together another box to form the inner casing four and a half inches wide by six and a half inches long and nine inches deep.

The bottom of this must be hammered outwards to the dimensions of BC CD, as shown in section Fig. 32 at AA. A hole is next to be cut out in the centre of rear plate, and also the rear part of inner casing which comes opposite to it, and one three-quarter inches by two and a half, forming an elliptical opening for the furnace door.

A casting of that shape and three-quarters of an inch thick, which is the distance between the inner and outer casing BC, must be procured and drilled with holes every three-eighths of an inch, and firmly riveted in position, as shown in section at D.

Two pins or lugs (FF) should project on either side of the inner surface to support the fire-bars and ash-pan, and the bars should be made of cast-iron, and small enough to be got out easily by tilting up one side, and the bars ought to run lengthways of the engine.

You next require some hard-drawn brass tubing three-quarters of an inch diameter, and must cut the pieces slightly over seventeen inches long, then drill ten holes in the inner plate as at E (Fig. 32), and in the position and arrangement shown in Fig. 33. These tubes should have a wire ring brazed on about a quarter of an inch from either end, and then being placed in their respective holes in tube plate, the projecting portion is to be beaded back with a flange, or you can fit them in as described previously (Fig. 16) by each being double-screwed and nutted. These tubes allow the smoke and flame to pass through from the furnace to the smoke-box (M Fig. 20), and so away up the chimney, and by the large surface they expose to the fire, help to raise steam very quickly.

If you just add together the combined surfaces of these tubes, you will find there is more than two square feet of surface exposed and acted on by the fire, which enables the boiler, although small, to make steam rapidly. In some large engines three hundred tubes are fitted. The steam supply-pipe and regulating lever-handle should now be made and placed in position, and Fig. 34 shows the shape to make it.

A B are the front and rear plates of boiler, C is the supply pipe, bent with a screw end downwards after passing plate A, and then upwards into steam-dome, where it should be securely fastened by a cross-piece; D is the tap or valve, which can be turned on or off from the foot plate by means of the long rod F, ending in lever-handle G.

The rod must be fitted with a stuffing-box, the same as those used on the cylinders, and packed with cotton to prevent loss of steam by leakage; and when this is all firmly fixed, the forward end of the boiler can be furnished with tube-plate, riveted on and the tubes flanged over.

You should now take the boiler to a practical brazier and have it properly hard-brazed in every join and round each tube, and you might cut the hole for steam-dome and have it brazed on at the same time. If this is properly done you never need be in fear when the water runs low, as the boiler might get almost red-hot without injuring it much. Of course it is not advisable, as it would blister and spoil the appearance of the paint outside. This is a good opportunity to test the boiler before fitting it up, and you should fill it with water through a hole drilled in top of dome, and then fix on the test-pump, which you could borrow from any engineering-shop. If too far away from town to do that, you must make use of the force-pump attached to your model, and work it by hand, watching the pressure-gauge in the meanwhile. Test it to 100 lb. per square inch, which will be sufficient, as 50 lb. will be a fair working pressure. Should you have to test it with your own pump, the pressure-gauge will have to be bought then, as that is an article you cannot make yourself. A small gauge of Bourdon’s make, of an inch and a half diameter, will cost about twenty-five shillings, and although it may seem a rather high price for such a small thing, it is absolutely necessary to have it, as you could not tell what dangerous pressure you had raised in the boiler without it.

This being done, proceed to make the smoke-box, which should be three inches deep, and of the same shape and dimensions shown in Fig. 35. This and the chimney can be made of iron, hammered up to shape and finished with a brass ring. The smoke-box can be screwed to the forward flange on boiler. The door is drawn open to show the amount of bulge it should be hammered to.

In the centre a hole should be drilled through which to pass the screw used to close it, which is attached to the loose bar A. The handle B is then screwed up tight.

The door is circular and must be large enough to overlap the opening about half an inch, and have a couple of bright iron or brass eyes (C) riveted on to form the hinge.

We can now make the back pressure-valve (Fig. 36). A is a front view, with plate by which it is bolted on to boiler, as at W (Fig. 20).

It is very simple to make, and consists of the casting A with the top and bottom covers, and the ball-valve B, which ought to be ground with a little emery-and-oil to fit perfectly. It acts in this manner. The water being forced up C from the pump, raises B and passes into the boiler. On the up-stroke of pump the pressure is removed from under B, and pressure of steam in boiler causes it to fall back and close opening entirely, preventing any water passing away from boiler. A small flange can be put on each outer side of boiler near furnace to support it on bed-plate level with smoke-box.

The boiler should now have a coating of flannel, cut to shape and wrapped round the body part, and a casing of sheet tin put over it and secured by brass bands, and small nuts underneath, as shown in Fig. 20.

The steam supply-pipe can now be connected with the cylinders, and it should be made forked, as in Fig. 37. A leads from steam-pipe, and branches off to each cylinder, where it must be screwed up with white lead.

The exhaust-pipes (B B) should be of larger tubing, and bent round up the sides of smoke-box, so as to be out of the way when you require to clean the tubes. A small brass pipe (C) must also be passed through chimney, and bent upwards and fitted with tap, which should take steam from top of boiler, and be used as shown at D and F (Fig. 20). This helps to raise steam very quickly.

Fig. 38 is a rear view of the foot-plate, and shows the necessary fittings you must either make or buy to complete the model. The cocks you can manage easily, but the water-gauge is beyond most amateurs’ skill to turn out satisfactorily. A is the furnace-door, B two gauge-taps, C starting lever-handle, D spring-balance safety-valve, F wind-guard (with two look-out hobs), G steam-whistle handle, H pressure-gauge, K steam-blast handle, M glass water-gauge, N the quadrant and-lever for reversing the engine, O the rear buffer beam (with buffers), P the wheels showing axle, R R the springs for same, and V is the safety-guard rail on either side.

When these fittings are made, holes must be drilled in rear-plate for each, and then firmly screwed in place with white-lead: and the glass tube in water-gauge and the stuffing-box in gland of starting-lever should be packed with tallow and cotton wick.

The entire engine can now have another coat of paint.

The smoke-box chimney and rear-plate should be black, and the body any colour, according to fancy, leaving the brass bands bright.

When lined and quite dry it should have a coat of the best hard, clear varnish, and again be allowed to dry thoroughly before using it, which by this time, I have no doubt, you are anxious to do. Whilst it is drying you will have time to make the lines for it. And you should get some square bar-iron, cut it into six-foot lengths, if you wish the lines to be portable, and drill a hole in each end half an inch deep. They then can be joined end to end by a wire, pin, or plug.

The lines must be kept at a proper distance apart by being secured to pieces of wood placed transversely underneath by screws passing through holes drilled in the rails at about every six inches. You can then lay them down end to end and form a long line. If you want a circular line, each section must be bent to a portion of a circle; one of about thirty feet diameter is suitable for this model.

When finished, place the locomotive on them and get up steam. Fill the boiler with water by means of a funnel until you see it rise up three parts of the way in the glass water-gauge. Then see that all taps are turned off and light the fire. Charcoal forms the best fuel to use, as it gives a clear, hot fire, without smoke.

Try occasionally if you have any steam by lifting safety-valve, and when there is any turn on the blast-tap, which will soon draw up the fire, and you will presently see the pressure rise, and be indicated in the pressure-gauge.

When showing 30 lbs. of steam you might start her, turning on the cocks on cylinders until no more condensed steam issues from them. Then shut them off and turn on steam full power, and watch your model travel, gradually increasing its speed; and I hope you will have many pleasant hours’ enjoyment in running your locomotive and showing its action to your friends, which will well repay you for the time spent in building it.

[Here is a new use for eggs! All that is needed are a pen or pencil, a few eggs or egg-shells, a little artistic talent, with a few ‘ideas’ and there you are! If also furnished with a gum-pot, pair of scissors, and some paper, there need be no difficulty about the frills, etc.]]