Model engine construction, with practical instructions to artificers and amateurs

Front matter

I KB I lliill

Mr

MODEL ENGINE CONSTRUCTION.

Preface

Having had some experience in the construction of model steam-engines, I publish this work for the purpose of giving a few practical instructions to Artificers, but more especially to Amateurs who wish to make a working model steam-engine, provided they be supplied with the proper tools, and only know how to set about it. I commence by enumerating the necessary tools, giving the average price of a few of them, take up the boilers and their fittings, with engine details, show how to work up the separate parts from their castings, fit these together, and erect a horizontal engine and test it under steam. All this is minutely described, as it forms the groundwork for the construction of all the other engines. I next give examples of the different types of engines, Stationary, Locomotive, and Marine, as well as how to make a carriage and a model railway. After giving a few notes on pattern-making, proportions of engines, property of steam, etc., I conclude with vi PREFACE.

a hot-air engine, which is easily fitted up. I have omitted oscillating cylinder engines, such as are sold in large numbers in the shops of the model-makers for boys to play with, as these are really models of no existing type of engine, merely toys ; the making of them serves no educational purpose, and when made they are not at all satisfactory as regards their steaming powers. All the engines here have double-acting fixed slide-valve cylinders, and approximate in construction to those in actual practice. If carefully made according to instructions, none of them will fail to work, and it would be possible to demonstrate the action of the steam-engine to a class from any one of them, which really makes a model engine of some use after being made, as well as a source of pleasure to the maker.

The locomotive boiler described on page 37 will raise plenty of steam, as it maintains a good draught of air through the fire-box and fire-tube when at work. I have omitted the marine engine (as made at the present day) with circulating-pumps, air-pumps, and surface condenser, as being too complicated, but give two different types of compound non-condensing engines, which will afford some scope for the amateur's ability.

As regards the working drawings, these have all been carefully re-drawn by a competent draughtsman from original sketches drawn by me. Four of

PREFACE. vii

the sheets contain drawings of engines designed and constructed by myself, viz. the locomotive and tender, the bogie-tank locomotive, the centre crank horizontal, and the traction engines.

All these drawings may be thoroughly relied upon as being correct, and in one or two instances, by doubling the dimensions over all, a larger and more powerful working engine can be made.

Certain people maintain that model engine-making, like some other " hobbies," is simply a waste of time, and nothing more. Such persons, I am sure, are ignorant of what they are talking about, and I feel certain that most of my readers will agree with me "that there are few pastimes better fitted to give such good training to the mind, the eye, and the hand at one and the same time as model-making." For young Mechanical Engineers, during their apprenticeship, it is invaluable. All who can afford it should have a small workshop of their own, fitted with a set of tools, including a good lathe, so that they can devote their spare time to this pastime. For the same class who cannot afford to erect a workshop and procure tools, it might be advantageous if the Heads of large engineering establishments were to allow their apprentices and young engineers the use of the tools in the workshop (subject to certain regulations) during evenings and spare hours, for them to keep their hands in by viii PREFACE.

making small engines, and perhaps supplement this by giving prizes for the best constructed and the best working engine under steam, made by their apprentices. By so doing, many lads would be kept out of mischief and temptation, be encouraged to follow their profession or trade, become dexterous in the use of different kinds of tools, get intimately acquainted with the mechanism of the several parts of the steam-engine, and acquire knowledge that would not be easily forgotten, and which would be of great service during after-life.

It has been suggested to me that if a Postal Amateur Mechanics' Society was started, on the same lines as the Postal Photographic Society, for the interchange of patterns, ideas, etc., between amateurs living at a distance from the large centres, such society would bring persons of kindred tastes into communication with each other.

J. A.

Part I. Boiler And Engine Details, With Tools

CHAP. PAGR

I. TOOLS USED IN MODEL ENGINE-MAKING ... 3

II. THE BOILERS AND THEIR FITTINGS ... ... 31

III. THE STEAM-ENGINE ... ... ... ... 78

IV. FITTING UP THE ENGINE, ETC. ... ... 124

Part II. Different Types Of Engines: Stationary, Locomotive, Marine

VI. BEAM, HORIZONTAL, AND VERTICAL ENGINES 157 VII. TRACTION, PORTABLE, AND SEMI-PORTABLE

VIII. LOCOMOTIVE ENGINE AND TENDER ... ... 200

IX. LOCOMOTIVE ENGINES ... ... ... 231

X. CARRIAGES AND RAILWAYS ... ... ... 253

XI. COMPOUND MARINE ENGINES... ... ... 281

XII. PROPORTIONS OF ENGINES, ETC., PATTERN- MAKING, CASTINGS, ETC. ... ... ... 296

XIII. HOT-AIR ENGINE, SMALL POWER ENGINE, AND

LIST OF ILLUSTRATIONS.

FIG.

PAGE

FIG.

1. Bench lathe ...

2. Driver-cbuck ...

3. Wood-chuck

4. Drill-chuck

5. Lathe-carrier ...

6. Bell-chuck

7. Lathe-dog

8. Face-plate

9. Chisels for turning . . .

10. Soldering bolts

11a. Boiler for kitchen fire ...

11b. Safety - valve with weight

12. Spring safety-valve ...

13. Direct - acting springvalve

14, 15. Pressure-gauge

16. Water-gauge

18. Gauge-cock

19. Whistle

20. Simple whistle

21. Clack-valve ...

22. Wheel- valve

23. Pump

24. Injector

25. The cylinder

26. Cylinder valve face ...

27. Cover for chucking in lathe

28. Stuffing-box and gland

29. Piston with ring surrounding it ...

30. Connecting-rod

31. Bearings and plurnmer- block

32. Standard for vertical engine

33. Crank-axle

Crank-axle with centre crank ... ... 105

The slide - valve, and

section of steam-chest 107 The eccentric-strap ... Ill The eccentric - pulley

and strap finished ... 112 Sheet-brass eccentric-strap ... ... 118

Throttling-governor ... 119

Loose eccentric ... 135

The ordinary link

The slot-link marked

out on a piece of metal 140 The slot-link after being finished ... ... 141

Lifting- links ... ... 142

Expansion-valve ... 145 Joy's valve-gear ... 153

Action of steam in the

cylinder, &c. facing 154 Beam engine ... ... 158

The ' ' Parallel Motion " 159 Perspective view of

traction engine ... 169 Perspective view of

portable engine ... 190 Perspective view of

underneath engine ... 195 Bogie-tank locomotive 232

The train 252

Railway, elevation of . . . 268 Railway, transverse section of ... ... 268

Patterns for making a

cylinder 303

Elevation and plan of pattern for chairs ... 307

LIST OF WORKING DRAWING SHEETS.

Locomotive boiler ,

.. Sheet No.

Vertical boiler

Beam engine

Horizontal engine ...

Vertical engine

Inverted vertical engine ...

5»

Semi-portable engine

Locomotive engine and tender ...

i)

55 55 55 55 "• •••

Bogie-tank locomotive

Single locomotive

Six-coupled tank locomotive

Eail way carriage ...

Railway wagon and van ...

Railway

Railway signal

Compound marine engine

Compound tandem engine

•• 55

Hot-air engine

The above are also published in a sep

%r ale form

PART I.

BOILER AND ENGINE DETAILS, WITH

TOOLS.

B

MODEL ENGINE CONSTRUCTION.

Chapter I. Tools Required In Model Engine-making

The lathe is an indispensable tool, and cannot be done without ; but it requires some little practice to be able to use it properly. Let the amateur purchase a 3 J" centre bench lathe from any of the makers, but without back gear, as very often this is not used. The price varies, but we think that a good one may be had from £3 10s. up to £6, according to finish, and the number of chucks, etc. that go with it. Along with each lathe is usually supplied a drill- and driver-chuck, a hand-rest, and two tees. A face-plate and slide-rest are extras, and must be ordered if required, though we propose to do without them here. A 3J" centre lathe is a suitable size to purchase, as it is fairly strong, and will turn tolerably heavy work, and fine work quite as well, i. e. if the lathe is well made, the centres truly in line, and properly hardened, so as not to wear away rapidly. A lathe (Fig. 1) consists of two supports, firmly connected at their base, and fastened at right angles to the iron bed (which is 30" long, and planed quite true along the top) by means of screws, A. The outer poppet-head is bored for the screw, and the inner one is fitted with a collar, within which the mandrel that carries the speed pulleys turns ; the left end of the mandrel is concave, so as to allow of the steel point of the screw being tightened up and fit closely. C is called a T-rest ; this slides along the slot in the bed, and can be clamped at any point, as well as elevated or depressed, when required. This is used for leaning the cutting tool upon, in order to afford greater steadiness when working. B is the right-hand poppet-head or tail-stock, which is also movable along the slot in the bed, and capable of being fastened anywhere, to suit the length of work

Fig. 1. — Bench Lathe.

A, outer poppet-head and speed pulleys ; B, tail-stock or live-head ; C, T-rest ; D, crank-axle and fly-wheel j E, treadle ; F, gut-band.

between the centres ; its point can. be advanced or drawn back, as required, by means of the screw and hand- wheel. D is the crank-axle which is connected with the treadle E by means of a rod, and so turns the fly-wheel, and this by means of a chain, or gut-band F, connects with the speed pulleys communicating motion to the mandrel. The pulleys on the spindle and mandrel are three or four in number, of different sizes, and so arranged that when the band is placed on the left-hand pulley a very rapid motion is given to the mandrel, as when turning wood. This motion is reduced more and more as the band is transferred to the right, till, at the extreme right, the rotatory motion is much slower than that of the spindle, and is used for iron-turning. There is generally a three-speed fly-wheel on the driving-axle as well. When the lathe is used for turning, and work must be centred in it, certain contrivances made of iron called " chucks " are fixed to the mandrel on which the speed pulleys are placed, and are for the purpose of centering the work, and making it revolve when the lathe is driven. Castings for making lathes are sold, but we advise the amateur to purchase his lathe ready made, for unless this tool is well made, with a perfectly flat bed, the points properly hardened, and standing in line facing each other, it will never turn out good work, even with the most experienced workman.

For metal-turning, a driver-chuck is used. This screws by one end on to the mandrel, and carries

Fig. 2.

a steel centre-point at the other ; a steel rod which is generally bent at right angles outside, so as to be parallel to the line of centres, passes through the bore of the mandrel, and is fixed in position by a set-screw. Against this rod, the shank of the lathe-carrier (attached to the work) rests, and is taken round with it when the lathe revolves (see Kg. 2).

A wood-chuck is similar to the above, but carries a three-pronged fork at one end. This is held in the chuck with a set-screw, the fork can be driven tightly into a piece of wood before placing it in the lathe ; the prongs grip the wood, when the movable head is screwed up tight, and cause it to revolve with the lathe (see Fig. 3).

A drill-chuck is much the same as the last, having a hole at one end with a set-screw into which

Fig. 3.

different-sized drills can be inserted; some chucks have an extra plug for taking very fine drills. The wood-chuck can be made to act as a drill-chuck, by removing the fork, inserting the stem of a drill instead, and tightening it up with the set-screw (see Fig. 4).

Lathe-carriers are made of steel or iron ; the head has a slot into which work must be firmly driven after centering, and tightened up by the set-screw. The stem, when the work is in the lathe, rests against the crank of the driver-chuck, and revolves, taking the work round with it. It is best to have two or three different sizes of lathe-carriers, and any blacksmith will make them (see Fig. 5).

A bell-chuck (see Fig. 6) is necessary for centering work to be drilled, as when boring out a cylinder. It is screwed on to the lathe, and the work, having been previously centre-punched, is put in the lathe, and retained in position by means of half-a-dozen set-screws, which are tightened up equally all round the work, so as to keep its centres in line with those of the lathe. The advantage of this tool is that, having a bell shape, the drill can be sent completely through the work and out at the other end, which cannot be done so well with a face-plate. The accurate centering of work in a bell-chuck is very difficult, and takes some practice to do it properly. Price 14s. to 30s.

A lathe-dog is a contrivance which is useful for gripping fine work, and holding it in the lathe. The work is gripped between the two halves, the

Fig. 6.

screws serving to draw them together ; the tail can be bent, or left straight at one end to catch against the driver-chuck ; if bent, it can be passed through a hole in the face-plate when chucked (see Fig. 7).

The slide-rest is a very expensive addition to a lathe (costing fully £3 for a 3^-" centre lathe), and we will dispense with it for our work; with a little practice it can readily be done without.

MODEL ENGINE CONSTRUCTION.

A face-plate (Fig. 8) is a very useful adjunct to the lathe (costs 10s. to 15.5.). It is an iron disc, planed quite flat on one side, and screws on to the mandrel by the other. Slots radiate outwards from the centre; through these screws or clamps "lathe dogs," as they are called, pass, and by them work is clamped to the face-plate, and properly centred in the lathe. The face-plate revolves and carries

Fig. 8.

the work round with it, which should be so placed as to turn in line with the lathe-centres. Remove the steel point from the movable head, insert a suitable sized drill. Feed the drill forwards, by gradually pushing it up against the work by turning the hand-wheel, and it will soon cut its way through, if kept from revolving. This is done by clamping to the drill-stem, at right angles, a small iron bar, forked, or with a ring at one end, through which the drill passes ; there is a set-screw for tightening up. The bar rests by its opposite end on the top of the T-rest, along which it slides with the drill. In this method, the work revolves and the drill "is stationary, which gives the best results, but it is a little difficult to chuck the work properly at first. Work must always be first correctly centred, and then centre-punched, before attempting to chuck it in a lathe.

A rose-cutter is useful for finishing a cylinder. After boring out the cylinder, while it is still chucked, fix this tool to the mandrel and feed by the hand-wheel. When it has gone through the cylinder, this latter will be found to be quite circular inside, and as smooth as glass. Different-sized cutters are required for different-sized cylinders.

To drill a hole through a piece of brass.

Besides the above method, we have found the following plan give satisfaction. In this method, the drill revolves and the work is kept stationary, and is used in all cases where a hole is required to be drilled through the metal, but the keeping exactly between the true centres is not of the same vital importance as when boring-out a cylinder. Screw the wood-chuck on to the poppet-head, remove the fork, and insert a drill, punch a centre hole at both ends of the work before chucking, remove the point from the movable head, keep the work from revolving, by gripping it with a pair of gas-fitters' pliers, or if larger, by clamping on a lathe-carrier, which will slide along the T-rest. Run the mandrel up against the work, and push the metal forwards on to the revolving drill by turning the hand-wheel. The drill will soon cut through the metal. The end of the work that rests against the mandrel must be filed flat before chucking, and be at right angles to the hole that is to be drilled.

Note. — A 3 1" centre lathe will take the finest drills up to -J", for boring out brass or gun-metal.

A set of wire-chucks, capable of taking varioussized drills, from T V up to -§-", will be found very useful, especially if they are self-centering.

When turning metal, take care to chuck the work firmly ; it can then be turned down accurately to the required form (using a pair of callipers properly adjusted, to give the correct size in diameter) with a graver or steel chisel, and, finished with a fine file and oil, or emery cloth and oil, while still revolving in the lathe.

After the metal is chucked, it is first "roughed down" with a graver to the required form; second, smoothed with a chisel ; third, polished with emery cloth and oil, and then removed from the lathe.

Fig. 9.

Be careful always when turning to use wellsharpened chisels; a grindstone is necessary to keep a good edge upon them.

Chisels are of various shapes : some have a flat edge, others are bevelled, and others again taper to a sharp point at one end. Of the last variety, it is best to have a right, and left-hand tool. Chisels should be made of good square cast steel ; old files do fairly well for this purpose — any blacksmith can make one out of an old file (see Fig. 9).

A screw-cutting lathe is not required for our work, as all the screws we need can be made by hand, with a set of taps and a screw-plate.

Vices. These are for holding metal when it is being filed down to lines previously marked upon it. We advise a 4" jaw vice for holding heavy work, and a small 2£" jaw table- vice for fine work, which can be attached to a bench or table. A small hand-vice, with a thumb-screw for tightening up the jaws, is very useful for gripping small work when filing. The small sizes range from 6s. up to 10s. 6d., and the larger sizes from £1 10s. up to £5.

Files are sold in different shapes, and degrees of fineness in cut. A rasp is a very coarse file for roughing down wood ; " rough " files are used for shaping, — " bastard " files may be purchased of any shape, — " smooth," " dead smooths," the finest of all, complete the various forms, along with the "triangular" and "round" files.

When using, fix the metal firmly in the vice, take the handle of the file in the right hand, press downwards with the left thumb on the tip of the file, pass it slowly and deliberately, but lightly, over the work, so as not to jump, and on the return stroke scarcely touch the work at all. The vice should be raised so high as to allow of the elbow passing over the vice when the arm is against the body, in order to use the file properly.

Surface-plate. This is a very expensive article, and is a block of iron the surface of which is planed perfectly flat, and is used for grinding the faces of cylinders, slide valves, etc., by the aid of emery powder and oil. It can be done without, and an iron for ironing clothes used instead. Get a perfectly flat smoothing-iron, cut off the handle, and fix it upside-down in a block of wood, and on the flat sole of the iron grind all the cylinders, valves, etc. ; this does very well. Another way is to use a part of the flat bed of the lathe to grind the metal upon. The price of a surface-plate is from 8s. to 10s., according to size.

Centre-punch. This is indispensable for metal-work, and consists of a piece of round steel tapering

c down to a point at one end, for marking out work, etc. ; price 10c?.

Broaches or rimers are useful for enlarging circular apertures, as in cylinder covers.

Screw-plate and taps. A watchmaker's plate and taps, from y 1 -^" to the finest sizes, are useful for delicate work. Another set of plate and taps, ^V' to yV'j is also required. These should be of the Whitworth Standard Gauge, and will be found quite sufficient for all our purposes. Prices run from 3s. 6d. up to 7s. 6d.

When it is desired to make a screw, take a piece of iron wire thicker than the size required, cut to the requisite length, leave a part longer than the full length of the screw for the head, grip the wire by one end in the hand-vice ; having separated the jaws of the large vice a little way, let the wire rest between the jaws, leaning on their upper surface ; take the hand-vice in the left hand and a file in the right hand, then gradually turn the hand-vice slowly round, keeping the wire resting on the upper surface of the vice ; file away, gradually passing round the wire, till it gets of a smaller diameter than the part held in the hand-vice — this part forms the head of the bolt. Continue filing until the stem is rather a tight fit in the hole of the screw-plate that is selected for use ; next grip the screw in the bench vice by the head ; take the screw-plate, oil the hole, and gradually force it on by turning from right to left, when it will be found that a screw-thread forms on the wire. If the screw-plate when turning feels a tight fit, it is best to unscrew it and file down the stem a little bit thinner, or it is apt to break in the screw-plate and give trouble. After the screw is made the requisite length, remove the bolt from the bench vice, then you can file the head square, and shorten it also.

To make a nut, take a piece of brass, file it square, centre punch, fix in the vice, and with the hand-drill, drill a hole through it, suitable for the size of tap corresponding to the hole in the screw-plate that was used for making the thread on the bolt; grip the nut in the vice, and if a small tap, fix it in the hand-vice, oil it, and force it through the nut, while rotating the hand-vice in the right hand. This forms a thread in the nut of the same size as that on the bolt. When done yon can file away the corners of the nnt and make it octagonal, if you choose. If properly made, the nnt will fit the screw on the little bolt. The above method applies to any size of bolt and nut it is desired to make ; but for taps of \" and larger sizes, instead of holding them in the hand-vice when using, tap wrenches with adjustable jaws, to suit different-sized taps (which give good leverage), are required to take them round ; brass wire is not good to make small-sized screws from, as the thread when made is very apt to give way or " strip," as it is called. A little practice will enable an amateur to make all the screws and nuts he requires. This plan we recommend, rather than buying them ready made.

Pliers. It is best to have one or two pairs of different sizes, as well as a sharp cutting-edged pair for dividing wire, and a watchmaker's pair for delicate work. These cost about Is. 6d. each.

Burnishers are highly-polished pieces of steel for polishing metal. They are rapidly moved over the part to be made bright ; a little weak beer facilitates this operation.

A frame-saw is used for cutting metal, and is furnished with a thumb-screw to give varying degrees of rigidity, according to the nature of the work done. A good steel " tenon " saw does very well for cutting brass. Prices vary from 4s. to 5s. 6d. Saws for the above cost from 6d. to lOd.

Grindstone. A hand one is best for the amateur. Always use it with water, to prevent softening of the tool when sharpening chisels. These can be purchased. 15" x 2" is a suitable size.

Oil-stones are required for sharpening the tools after grinding their edges.

Iron block. A big block of iron, which can be firmly gripped in the bench vice, will be found useful for finishing off flat work, as bed -plates, locomotive frames, etc. Instead of this, an anvil would do.

Callipers. A pair of these is required for getting the correct dimensions of work when turning ; those for outside measurement are the most useful. Price of a pair, about Is.

Steel chisels, suitable for making steam-ports in small-sized engines, can be obtained at the modelmaker's, or made from a steel bar, 1|" long and T V' broad at cutting edge; this size is useful for fine work, but it is well also to have a larger size, at least 2" long and T V' wide at cutting edge.

A pair of compasses with a set-screw are required, price Is. 8d.

A 36" foot-rule is a convenient size to have.

Metal shears are required for cutting sheet brass and copper, price 2s.

A small hammer for riveting is useful, price Is. 3d.

A metal square called an " engineer's " square is necessary, price Is. 6d.

A set of turning chisels and gouges are required for wood-work and metal-work. Sets of these can be purchased in blocks, at prices from 10s. to 17s. 6d.

A lacquering plate is a plate of iron to be heated over the fire. Work to be warmed for lacquering is laid upon it.

Lacquering. Bright brass when finished must be lacquered to prevent its getting tarnished. Brass lacquer can be purchased, and is applied with a small brush ; the metal having been previously heated in the spirit-lamp just hot enough for the hand to bear.

Brazing is rather too difficult for an amateur, and we will not describe the method here. For the engines given in this work no brazing is required, except for the internal fire-box and fire-tube ; but it is best to have the fire-box made by a coppersmith, as will be shown further on.

r? c c3

CO

Soldering-bolts (see Fig. 10). Soldering is required for model-making. This can be easily done and joints made perfectly steam-tight, after a little practice. We recommend two light copper bolts : a straight one, and one bent at right angles to the handle; and for a flux do not use resin but spirits of salt, made by saturating hydrochloric acid with strips of metallic zinc, till no more hydrogen is evolved ; this forms zinc chloride. Keep the solution in a well-corked bottle. By means of a wire touch the parts over with the solution before soldering, after having scraped them clean.

Method of soldering. Take the soldering-iron, warm it in the fire, with a file clean it thoroughly near the point on both sides, and if at the proper heat, after rubbing a little spirits of salt upon it, and touching it with a stick of soft solder, the solder will stick to the iron, and make it appear bright. This operation can be done at the proper heat (which is found out after a little practice), and is called " tinning the bolt," and must be done before soldering. After being used much, the " tinning will come off, and must be again renewed by the same process. After "tinning," warm the soldering-bolt in the fire; never let it arrive at a bright red heat, as this is too hot for use. Before beginning to solder, lay a stick of solder at one side, and a bottle with spirits of salt at the other. If you are going to solder two pieces of brass together, first clean both pieces by filing all round, where they are to join ; sprinkle a little spirits of salt on as a flux, to remove the tarnish ; then, with the soldering-bolt touch the stick of solder lightly, when a piece will adhere to it. Put the bolt with the solder upon the brass over the joint, and hold it on for a second or two, when the solder, if all tarnish be removed, will adhere to each piece, and they will become tinned over like the bolt. After tinning, bring the two pieces together, put on more spirits of salt, touch the solder-stick again with the bolt, and hold it over the pieces of brass for a little time to "sweat" in the solder; when cool, the two pieces will be found to adhere firmly together. At first, one is apt to make a clumsy job, and put on too much solder, but a little practice will enable the amateur to make a neat job and ( a first-rate joint. Brass, as well as iron and copper, must be tinned before attempting to solder two pieces together. Tin plate does not require tinning. Iron is more difficult to solder than brass, and for copper, the soldering-bolt must be made a little hotter than for brass.