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Locomotive Accessories

Auxiliary Equipment of a Modern Engine


THE man who owns and drives a motor car knows that his car would be useless without certain important accessories. It is not generally realized that a steam locomotive similarly needs accessories. Every engine, for instance, must have a reliable means of feeding its boiler with water. An apparatus must exist to apply sand to the rails when they are too slippery to provide sufficient “bite” to start a heavy train. A whistle or hooter must be provided to give “audible warning of approach”; and so on.

Steam Injectors

One of the most interesting auxiliaries possessed by a locomotive is its injector, an instrument which apparently defies all the laws of nature by forcing water into the boiler by the direct action of its own steam pressure - a seeming impossibility to the uninitiated.

The injector was invented by a Frenchman, Henri Giffard, in 1859. Escaping the fate of many inventions, it was immediately adopted by many railway companies and locomotive building firms. The patent rights were taken up by Sharp, Stewart and Co. in 1860, and various inventors devised improvements, so that to-day the injector is practically supreme as a locomotive boiler feeder. It is easy to realize why injectors were favoured as soon as they appeared, for the terrific pressure in the feed pipes of a pump-fed locomotive running at speed (sometimes as much as 3,500 lb per sq in) caused burst pipes and leaky joints, defective clacks, and other troubles, while freezing in cold weather was another source of failure.

The seeming paradox of an injector utilizing steam from a boiler to feed water into that boiler, thus overcoming its own pressure, may be simply explained. Let us suppose steam to be cold, so that a person might stand in a jet of it without being scalded. Now imagine two hose nozzles, from one of which steam at, say, 30 lb pressure is issuing, and from the other, a jet of water at the same pressure. Now, if anyone walked past these nozzles in the “line of fire”, he would pass the

steam jet with very little discomfort; but, on encountering the stream of water, he would probably be knocked over, or at least made to stagger. The steam, being unstable, and merely gas or vapour, can be resisted; not so the solid jet of water, which, though issuing from the nozzle at the same pressure as the steam, has a far greater power, by virtue of its being a “solid” body having a certain amount of momentum.

Carrying the illustration a step farther, let us imagine a jet of steam issuing from a nozzle attached to a boiler. Suppose we have a means of transferring to a jet of water the speed at which the steam issues from the nozzle. The water, having more “punch” behind it than the steam, as mentioned above, would force up the check valve and enter the boiler against the original steam pressure. The injector is the means by which this is carried out, and the operations are performed in the following manner.

The diagram shows the component parts of an injector in its simplest form, and this consists of a body, three cones, and a valve. The first cone is called the steam cone, and receives steam direct from the boiler via screw-down valve and pipe. Water from the tender or tank is admitted between the first cone and the second, or combining cone. This cone has a vent half-way along it, which is normally kept closed by the valve. The third, or delivery cone, is placed the other way round, with its nozzle and that of the second cone a short distance apart. The large end of the delivery cone is connected to the boiler by a check valve and pipe.

Injector diagram

INJECTOR DIAGRAM. The above drawing illustrates the arrangement of the cones in

a steam injector. These may be arranged either horizontally or vertically, the principle

of operation remaining the same. Steam from the boiler enters the steam cone and

condenses in the water entering the injector through the inlet shown. The condensed

steam and water pass through the combining cone, enters the delivery cone and is forced

by its own velocity into the boiler. Excess water escapes through the overflow pipe.

The injector works as follows. When the steam is turned on, it issues from the cone at considerable velocity and enters the combining cone. As the nozzle of this is smaller than the steam nozzle, it cannot all get out, so lifts the valve and escapes there. Meanwhile the action has formed a partial vacuum in the space between the two cones, and water at once starts to rush in from the tank, as this space is connected to the water supply. Immediately the water enters the space, the steam strikes it and condenses in it, and a vacuum is formed in the combining cone, pulling the valve down tightly on its seat.

In condensing, the steam gives up its velocity to the water, and this is further accelerated by the vacuum in the combining cone, so that a stream of water flies from the nozzle of this cone at high speed. For a second or two after the action begins the jet will fluctuate a little in intensity, and some of it will go down the overflow pipe; but as soon as the jet is “fully established”, it shoots across the intervening space, enters the delivery cone, and proceeds up the delivery pipe, through the check valve, and so into the boiler. Should water continue to run from the overflow after the injector has begun to feed, too much water is being drawn in between the steam and combining cones. This can be regulated by a cock on the feed pipe, so that the overflow is “dry” all the time the injector is worked.

All injectors work on the above principle, but the types are many and varied. The original Giffard injector was similar to the above, except that the steam cone was made adjustable, and the water was regulated by sliding the steam cone in and out of the combining cone. Adjustable cones are not necessary in most types of modern injectors; and instead of the combining cone having a valve in it, a part of the wall of the cone itself is hinged, and lifts to allow surplus steam to escape when the injector starts. This type of cone is known as the flap nozzle. Another arrangement is to divide the combining cone into two parts, the front part sliding in the injector body. On starting, steam pushes the front part forward and escapes between the sections; but, on the injector beginning to feed, the vacuum in the cone draws the two parts together and presents an unbroken surface to the water.

A MODERN INJECTOR is shown here, and the compact design of this important auxiliary to a locomotive is clearly indicated. Steam is taken to the top of the long casting at the right. On the left of the steam inlet is the cock controlling the water supply. Beneath the water cock is the flange to

which is bolted the overflow pipe. The flange at the bottom of the main casting, on the right, is bolted to a pipe delivering feed water to the boiler.

Present-day live steam injectors are mainly of two classes - lifting and non-lifting. The former are again sub-divided into horizontal, vertical, combination, and other types. Combination lifting injectors are usually fitted on the boiler backhead, inside the cab, and are entirely self-contained, having all steam and water valves, check valves, and regulators integral, so that in the event of overhaul or repair being needed, the whole apparatus can be removed bodily and replaced by a fresh one without delaying the engine unduly. Non-lifting injectors are fitted below the level of the bottom of the tank, generally on the framing below the cab, so that water flows to them by gravity. They are usually of the horizontal type.

Exhaust Steam Injectors

Everybody who hears a locomotive “puff” must realize that the exhaust steam leaves the cylinders at considerable pressure. Engineers soon began to give attention to the problem of utilizing some of this pressure to work a special type of injector. The feat was accomplished, and the exhaust steam injector has now reached such a degree of perfection that a Davies and Metcalfe product has put water into a boiler, against 150 lb steam pressure, with exhaust steam at a pressure of 1 lb only. In principle, the exhaust injector is the same as the live steam injector, but the steam cones are duplicated; exhaust steam first enters the injector by a very large cone and “picks up” the water. A little live steam is then admitted by a supplementary cone, and gives the added impetus necessary to overcome the modern high boiler pressures. The feed water, after the two lots of steam have condensed in it, is usually at a temperature above that of boiling water at atmospheric pressure; and therefore some means of closing the overflow, after the injector has started working, has to

be fitted. If this were not done, the water would “flash” into steam as it passed the overflow chamber. A valve is fitted to the overflow outlet, and this is kept closed by a small piston connected with the delivery pipe, all the time the injector is working.

Donkey Pumps

Although the eccentric - or crosshead - driven pump has long since been discontinued in locomotive practice, the separate donkey-pump still finds favour, as it will feed water into a boiler after the water has been heated up by exhaust steam and rendered too hot for an injector to deal with. The chief types of pump at present used are the Weir and Worthington pumps, and have either one or two steam and pump cylinders.

Briefly, the donkey pump consists of a steam cylinder and a pump cylinder arranged in line, the piston-rod being common to both. Steam is admitted above and below the piston in the steam cylinder by a slide valve, which in turn is operated by a reversing valve worked from a trip gear on the piston rod. The trip gear could not be directly connected to the slide valve;

otherwise, as soon as the slide valve covered both ports of the steam cylinder, the pump would stop.  The pump cylinder is double-acting, suction and delivery valves being provided at both top and bottom of the cylinder.

Feed Water Heaters

A common form of feed-water heater bears a strong resemblance to the barrel of a locomotive boiler. The barrel of the heater has a tube plate fixed at a little distance from either end. Through the barrel passes a large number of small diameter thin gauge tubes, the ends of the barrel being covered by ordinary flat or dished caps. The space around the tubes, between the tube plates, is connected to the water supply, so that all feed water going from the tank to the boiler has to pass through it. A connexion is made to the lower part of the blast-pipe, and a pipe led from it to one end of the heater barrel. When the engine is working, a part of the exhaust steam is shunted through this pipe and passes through all the tubes in the heater barrel, giving up its heat to the feed water surrounding them.

The working of a feed water heater


is illustrated by this drawing. Water from

Injector or feed pump enters through flange A,

passes clack valve B, and enters nozzle C, imparting a velocity that creates a slight vacuum around cone D. Steam is drawn in; this condenses and heats the water. Similar action takes place in cone E, which delivers the feed-water at a temperature approaching that of the steam.

In some of the older locomotives, notably Beattie’s engines on the London and South Western Railway, and Stroudley’s on the London, Brighton and South Coast Railway, part of the exhaust steam was passed back into tender or tanks, and so heated up the whole body of feed water direct. This arrangement worked so long as no oil or grease went back with the exhaust steam, and eventually found its way to the boiler.

The ideal feed-water temperature is one within a few degrees of the temperature of the boiler itself at working pressure. Engineers have long striven to avoid the ill-effects of introducing feed water at low temperature, which sets up all kinds of stresses in the material of the boiler and causes leakage of tubes, joints, and stays. The feed from an injector, especially an exhaust injector, is hot, and so is the feed from a donkey-pump taking its supply from a tubular or other form of feed-water heater. But even if the feed is at atmospheric boiling point - 212 degrees - it falls far short of the ideal, as steam at 200 lb pressure has a temperature of 388 degrees.

A Gresham and Craven feed water heater

FEED WATER is heated by means of this apparatus, which is bolted in

duplicate to the top of a locomotive boiler shell. The flange on the left

is bolted to the water supply pipe from the injector or pump. On top of the fitting can be seen the adjusting screw which controls the lift of

the clack valve. The right-hand flange is bolted to the boiler barrel, and

immediately beneath this can be seen the openings to the two cones C and D indicated in the drawing above. The feed water is delivered to the boiler

through the out-turned opening shown.

To obviate this trouble, a British firm, Messrs Gresham and Craven, Ltd, have introduced a top-feed fitting which puts the water in the boiler with a kind of injector action, and obtains extra heat from a small amount of live steam. The fitting has a self-contained check valve, and is attached to the top of the barrel near the crown. Feed from injector or pump goes first through the check valve, and then through two small cones, around which are annular spaces directly connected with the steam space of the boiler. Steam is drawn through these, and mixed with the feed water, heating it up so that, at final discharge into the boiler, it is within 30 degrees of the steam temperature.

Soot Blowers

Passing from the water to the fire side of the boiler, it is imperative that as much of the heat as possible should be transmitted to the water. This is to be accomplished only by keeping the firebox sheets and the tubes clean and free from soot. The firebox is practically self-cleaning, as any soot deposit :accumulating from the combustion of “flary” coal is generally burnt away when the fire becomes clear; but a certain amount remains in the tubes.

The old-fashioned method, still used on many British locomotives, is for the fireman to sweep the tubes by hand, using a long steel rod with a bunch of flax on the end, operated from the smoke-box end; but practically all modern engines, especially in America and the Dominions, are now equipped with steam-operated soot-blowers. These can be used while the engine is running, and are of especial benefit to those engines having a large nest of superheater flues. A small deposit of soot on superheater elements materially reduces their efficiency.

A "Clyde" type of soot blower

CLEANING THE FLUES on a locomotive is accomplished by means of a steam soot-blower, The above picture shows the “Clyde” type of apparatus fitted to the back of a firebox. When steam is turned on, nozzle A is carried forward and revolved by the movement of hand-wheel H. A jet of steam impinging on the boiler tube plate is thus blown through all the boiler flues in turn, clearing away all soot and ashes. The lower picture illustrates the form of soot blower which is attached to either side of the firebox where boiler design renders this position necessary. This type of blower is operated through gearing contained in the casing, marked T (below)  and worked by a long rod from the cab.

Deatils of the soot blower

DETAILS OF THE SOOT-BLOWER (see both illustrations). A nozzle, B flange, C nut, D tailpiece, E steam spindle, F chest, G sleeve, H handwheel, J triple screw, K triple nut, L instruction plate, M automatic drain, N patent piston rings, P gland, Q gland bolts, R guide pin, S cover, T gear casing, U universal joint.

Soot-blowers are of two general types; those operated from the backhead, and those from the side of the firebox, but the general principle remains the same. One of the stays is replaced by a short tube through the water space, and this houses a fan-shaped nozzle which is supplied by steam through a valve easily accessible to the engineman. Every two hours or so steam is turned on to the nozzle, which shoots a powerful jet of steam across the firebox on to the nest of tubes. The nozzle can be moved by a hand wheel, and the whole tube area covered. The action of the steam jet and the pull of the engine’s own exhaust combined cause the steam to mix with the products of combustion, so that a considerable volume of very hot and dry gas passes through the tubes at a high velocity and effectually scours them out. The whole operation takes only a few minutes, all soot is blown into the smoke-box and passes out through the chimney, and the tubes, flues, and super-heater elements are left perfectly clean.

On many engines, especially those of the former London and North Western Railway, on which the engines were often loaded to capacity, the heavy blast puts an excess of small cinders in the smoke-box. Some of the older engines had a hopper with an open bottom in the smoke-box, through which any accumulation would fall when steam was shut off. But the general practice is to arrange two steam jets in the bottom of the smoke-box. This arrangement stirs up any accumulation and enables the blast to throw it out of the chimney. Anyone who has travelled in a train hauled by an old “Precursor” or “Experiment” class engine has experienced the intermittent rain of cinders on the tops of the coaches.


In the early days of the railways there were numerous level crossings - known as grade crossings in America - and, in the absence of proper signalling, accidents to farm carts and similar vehicles were trot infrequent, although the trains generally made so much noise that they heralded their approach from afar.

But, after a train had demolished a farm cart containing a load of eggs and butter at a crossing, and the farmer had obtained compensation, a Leicester musical instrument maker was commissioned to make a “steam trumpet”, which was fitted to a locomotive, and proved a success.

Further details of this innovation are given in "The Story of the LMS”, which begins on page 925. From the “steam trumpet” was evolved the modern whistle, which, from a single note as used in Great Britain, has developed into the well-known American “chime”.

Passengers on trains often hear a succession of long and short blasts, which cause children to wonder if the engine-driver is “having a game”; but these blasts are part of a signalling code which is used by drivers to give route indications, and other messages to signalmen and so on. For instance, if a signalman on one particular line hears two “crows”, he knows that “something has gone wrong with the works”, and that the driver is asking for another engine to be waiting at the first convenient change-point; so he telephones the necessary instructions, and this saves delay.

The Steam Blower

The long chimneys of the early engines provided sufficient natural draught to maintain the fire when the engine was standing; but, as boilers became bigger and chimneys shorter, it began to be difficult to maintain the fire and keep a full head of steam when waiting in a siding. One driver solved the problem by making a hole in the smoke-box and inserting the end of a piece of lead piping in it, the other end of which he connected to a cylinder cock. If his fire died down when waiting to take a train he would screw the tender brake hard on, and open the regulator a little. Steam from the cylinder cock blew up the chimney and livened up his fire, so that he soon had “feather” at the safety valves.

Combined pump and heater for the boiler feed water

A COMBINED PUMP AND HEATER for the boiler feed water fitted by Messrs J. Stone, Ltd, to a “Beyer-Garratt” locomotive on the Kenya-Uganda Railway. The water is heated by means of tubular heaters which are placed on top of the boiler. The pump, with its valves, is situated at the side of the boiler, and is controlled from the locomotive cab. To the left of the feed-water heater steam pump is shown a small steam turbine and electric generator for supplying current to the headlights at either end of the engine. To the left of the feed-water heater is seen the dome from which steam is taken to the cylinders, and to the left of this again are the clack valves through which water is supplied to the boiler. Against the smoke-box can be seen the Westinghouse pump for supplying compressed air to the brake system.

From this simple device the steam blower was evolved. It is merely a ring of tube, in most instances, or possibly a casting resembling a domestic gas ring with a number of small holes in it, and is located on the blast pipe. Steam is turned into it by a cock or wheel valve in the cab, and the jets go up the chimney and so keep the draught working.

If the blower is not opened when the regulator is shut, and the engine is running, flames will often beat back through the firehole door; and several enginemen have been burnt through absent-mindedness in not opening the blower valve before shutting off steam. The plan of interconnecting regulator and blower valves has been used, but it is not quite satisfactory -as, for instance, when the fire is being allowed to die out completely in the depot.

The Steam Sander

Though the “bite” of a smooth wheel on a steel rail is sufficient to haul a heavy load, the rails sometimes become wet and slippery, and the engine will slip badly unless sand is dropped. In early days there was no sanding gear, and firemen had to get down and shovel ballast under the wheels. Later, sand pipes were fitted, with funnel tops through which the fireman dropped sand from a receptacle on the engine. Later still, sand boxes, with pipes and valves, were fitted, so that sand could be dropped direct on the track rails; but this sometimes did not fall on the rails on a curve or in windy weather.

Sanding the rails

SANDING THE RAILS. This apparatus enables sand to be blown by means of a steam jet under the wheel of the locomotive, thus affording an adequate grip should the surface of the line be wet or grasy. Dry sand is carried in the box shown and falls by gravity to the bottom of the sand trap, where it piles up and so blocks its own outlet. When steam is turned on to the ejector a partial vacuum is created which draws in air from the opening shown to the left of the sand trap, so releasing the sand from the trap and forcing it under the wheel. On shutting off steam the sand again piles up in the trap, which is thus sealed until required again.

In 1886, Mr. Holt, Works Manager of the Midland Railway Works at Derby, designed an arrangement whereby sand could be blown under the wheels of a locomotive by compressed air; but, as this robbed the brake reservoirs of air, steam was substituted. The action of the steam and sand acts also as a cleaning agent on the rails. The bottom of the sand pipe has a small steam cone in it, resembling an ejector nozzle, which creates a partial vacuum in the sand pipe, drawing the sand over through a trap below the sand box, and then blows it directly under the wheels. The sand must be dry, so that it will flow freely. There is, however, another apparatus known as the Lambert wet sander, which uses water instead of steam, and delivers a kind of “sludge” under the wheels. With this type of sanding gear dried sand is not necessary.

Power Reversers

The weight of the motion on modern engines has become so great that it requires a substantial gear and a fair amount of physical strength on the part of the driver to operate the reverse. Power reversers, therefore, are often used, and are common in America, where big engines are the order of the day. The most common form embodies the principle of the “floating lever”. A cylinder is mounted at the side of the boiler and its piston is connected to the reverse or reach rod. This cylinder has a slide valve which is connected to the middle of a floating lever. The top of the lever is connected to a small handle in the driver’s cab; while the lower end is attached by a short rod to the crosshead of the reversing cylinder, or some convenient point on the reach rod.

Supposing the engine is in mid gear, the floating lever will be vertical, with the valve covering the ports on the reversing cylinder. On the driver pushing his lever to either end, the floating lever is tilted and steam is admitted to the reversing cylinder by the corresponding movement of the slide valve. But, as the other end of the floating lever is attached to the crosshead or reverse shaft, this end also moves in the opposite direction to the first movement, bringing the slide valve back to the original position, and cutting off steam from the cylinder after the desired movement has been accomplished. The floating levers are proportioned so that the slightest movement of the hand lever operates the valve and produces a corresponding movement of the power gear.

“Booster” Engines

We have already seen that it requires considerable power to move a train from a dead stand, but very little to keep it on the run once it is well away; and for most of a run a locomotive is working well under its maximum power output. It occurred to some engineers that if some means could be devised for temporarily increasing the power output, for starting purposes or for intermittent steep grade climbing, a much smaller engine could be used for a given load, with resulting operating economies. This led to the introduction of the “booster”, which is a small auxiliary engine driving one or more pairs of wheels on the engine or tender.

The idea is not new, for in 1863 one of the former Great Northern locomotive superintendents, Archibald Sturrock, designed some goods engines in which the tender wheels were coupled and driven by a pair of inside cylinders. They were not a success, because the boilers were not large enough to supply steam to what virtually amounted to two locomotives. They

differed from the modern booster-fitted engine in that the auxiliary cylinders were in action the whole of the time, whereas the booster is used only as required.

Locomotive cab fittings


The numbers are explained in the following key:

1. Train heating steam valve.

2. Auxiliary steam valve for exhaust injector.

3. Steam valve for live injector.

4. Vacuum brake gauge.

5. Boiler steam gauge.

6. Train heating steam gauge.

7. Water gauge (blow-down cock at foot).

8. Water test cocks.

9. Main regulator with drifting valve attachment

10. Vacuum brake handle and valve.

11. Steam ejector handle.

12. Blower valve.

13. Hydrostatic cylinder lubricator.

14. Firehole door lever.

15. Axlebox lubricator.

16. Exhaust injector water cock handle.

17. Coal watering hose cock.

18. Damper handles.

19. Reversing screw and handle.

20. Front and back sanders.

21. Cylinder drain cock lever.

22. Live steam injector water valve handle.

23. Automatic train control apparatus.

X. Washout plugs.

The normal arrangement of the booster, as applied to the trailing wheels of an “Atlantic” or “Pacific” locomotive, or any other type having uncoupled wheels under the cab, is merely the provision of a small two-cylinder engine, about 10 in bore and 12 in stroke, complete with crossheads, connecting rods and crankshaft, and piston valves operated by return cranks, the whole being mounted on a frame attached to the trailing truck. The engine is set to run ahead only, and has a pinion wheel on the crankshaft. On the trailing axle a gear wheel is mounted, and between them is an idler gear that can be put into mesh with wheel and pinion by an air or vacuum cylinder.

The booster engine receives steam from the boiler direct or from the super-heater header. The idler gear control is so arranged that when the reverse lever is pushed into full gear the idler is engaged, and the booster helps the locomotive to get away with its load by turning the trailing wheels and temporarily converting them into extra driving wheels. When the driver notches up to a certain predetermined point of cut-off the idler wheel is disengaged, steam is cut off from the booster, which then ceases to operate, and the trailing axle runs free, acting merely as a carrying axle.

When the booster is applied to a tender truck the action is just the same, but the wheels of the truck are sometimes coupled, as on the Sturrock steam tender, thus allowing the booster to exert more power than when driving a single axle.

Boiler Washing

In the chapter on “Driving a Locomotive” mention was made of boiler washing. In early days this was accomplished by connecting two hoses to hydrants in the engine shed alongside the pits, and squirting cold water at high pressure through holes in the smoke-box tube-plate and backhead. Both straight and bent nozzles were used on the hoses, so that every part of the inside of the boiler was cleaned, especially round the stays and over the firebox crown. The holes were normally closed by bronze taper plugs, known as “washout plugs”.

In some instances very large plugs of similar type were used to close the mudholes around the foundation ring, instead of the oval plate with “bridge” fastening. Modern boiler washing is done in a similar manner, but hot water is used, supplied either by a special hot main or by a portable boiler with injectors of a special type to suit the work.


The cylinders and valves of a locomotive need an unfailing supply of oil while running, and this is provided either by a mechanical or hydrostatic lubricator. The mechanical lubricator consists of a metal box, usually fixed on the running board, and containing four or more small pumps which are operated either by eccentrics or by a slide crank. Motion is given to the eccentric-shaft or crankshaft by a ratchet gear driven by a lever similar in action to the well-known engineers’ ratchet-brace, but arranged vertically. The end of the lever is oscillated by being attached by a connecting link to any part of the motion which may be suitable. Each pump draws oil from a supply carried in the box, and delivers it to cylinder or valve chest as required.

The hydrostatic lubricator has no working parts at all, oil being fed to the cylinders by the direct action of the steam. It consists of a box, on the front of which are four or more glass tubes. Each has a screwdown valve at the bottom, and a union at the top for connecting up the oil pipes leading to the cylinders and steam chests. Steam enters the oil box via a pipe and regulating valve connected to the boiler, and condenses. The water so formed raises the level of the oil and causes it to flow down pipes to the bottom of the sight-feed glasses, through which it passes as visible “beads”, and then proceeds through the oil pipes to the cylinders and valves.

Feed-water pump fitted to a Tanganyika metre-gauge locomotive

FEED-WATER PUMP fitted to a Tanganyika metre-gauge locomotive. This pump is worked by steam and forces water into the boiler through the clack valves mounted on top of the boiler to the left of the chimney. To the right of the smoke-box can be seen part of a feed water heater, and

immediately behind the lamp on the buffer beam can be seen equipment which is often carried on locomotives overseas - a screwjack for use in the event of derailment. Note the large electric headlight on top of the smoke-box, current for which is supplied by means of a steam-drive turbo-generator.

You can read more on “Development of the Fire-Box”, “Firing the Locomotive Mechanically” and “The Locomotive Booster” on this website.