Engineers and Mechanics Encyclopedia 1839: Railways: Robert Stephenson

The extraordinary friction and resistance between the flanges of the wheels of a locomotive engine, and the edges of the rails, in passing round curves, unless the radii be very considerable, struck forcibly the attention of Robert Stephenson, who succeeded in devising a very ingenious mode of obviating it, which he patented on the 25d of January, 1826.

The following description of it is extracted from the Register of Arts:-

"Instead of two wheels, used as usual to the extremities of one axletree, Mr. Stephenson's plan is to have a separate axletree to each wheel, so that they may revolve independently, and at different velocities, as circumstances may require. The outer wheels of a four-wheeled carriage (or those which are on the longest of two curved parallel lines) will therefore be at liberty to run faster than those on the inner side (or on the shortest line), thereby preventing that sliding motion, and its destructive effects, when passing round curves, which, on extensive lines of road, are generally found unavoidable.

Mr. Stephenson's improvements in axles likewise embrace another object of more momentous importance, that of providing a remedy for the unequal strain to which a carriage is subjected in passing over those parts of a railway that lie hollow, or below the level of the contiguous parts, owing to the sleeper, or other supports having sunk or given way, which causes the carriage and its load sometimes to rest upon three wheels instead of four, producing undue strains or fractures, and at other times causing the carriage to pass off the rails.

To provide against these circumstances, the axletree of each wheel turns, in a fixed bearing, which is bolted to the frame of a carriage: this bearing, instead of having a circular aperture for the axle to turn in, has a long vertical slot, in which the axle can rise tip and down, as may suit the undulations or imperfections of the line of rail. This, however, could not take place, unless the opposite . extremity of the axletree moved upon a universal joint, which Mr. Stephenson has adopted, giving the preference to the ball and socket for that purpose, on account of its strength and simplicity.

Fig. 1 exhibits a plan of a carriage-frame, with its wheels and axletrees; and Fig. 2 a side elevation or section, as seen from the interior of the frame. Similar letters of reference in each figure indicate corresponding parts: a-a shows the frame of the carriage; b-c-b-c the four tapered axletrees, having at the small end of each a globular knob, revolving in a hollow spherical socket, as seen at e-e-e-e.

In Fig. 2 the bearings f-f are shown bolted to the carriage-frame a; at g, the axletree is seen. in the upper part of the bearing; and at h, the axletree is shown to have fallen down the slot, allowing the wheel to accommodate itself to the sunken part of the rail i.

In this last contrivance the wheel alone is supported, and the carriage has still to sustain the unequal pressure, owing to its resting upon three wheels. The chief advantage that results from it, is in keeping the wheel always on the rail; because, if the hollow was so great as to allow the flanch to rise above the surface of the rail, the carriage might in its progress be thrown over, producing very serious consequences. An accident of this kind recently occurred to the new locomotive carriage of Braithwaite and Ericsson (the "William the Fourth"), on the Liverpool and Manchester Railway, by which it was very nearly thrown down a deep precipice; proving the necessity of some contrivance to effect the object aimed at by Mr. Stephenson's arrangement.

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We have already described, at page 477, a patented improvement by Robert Stephenson on the axletrees of railway carriages. At the period we are now treating of, another invention, from the same celebrated engineer, presents itself to our notice; it is dated the 11th of March 1831, and is entitled, “Improvement in the axles and parts which form the bearings at the centres of wheels, which are to travel upon edge railways."

In order to produce rotation in the wheels, and consequently progression of locomotive carriages, it is necessary to fix the wheels on the ends of the axles, and when this fixture is effected in the usual manner, the weight of the carriage and its contents is supported by concave bearings resting on the upper surfaces of the cylindrical ends of the axles, and hence arises a difficulty in keeping the rubbing parts constantly lubricated, as the oil supplied to the parts in contact will have a tendency to escape by its gravity to a more open space on the looser sides of the axles; and the consequence of this is, considerable waste of oil, with an imperfect lubrication.

To remedy this, Mr. Stephenson employs for each pair of wheels, a double axle, consisting of a hollow casing, on the extremities of which the wheels are firmly fixed, and a solid axis passing through the hollow casing, and supporting on its ends the weight of the carriage, through the medium of hollow bearings attached to springs of the usual construction, which connects the bearings with the side rails of the carriage, placed necessarily on the outside of the wheels. Thus the supporters or wheels being fixed to the concave parts of the bearings, and the supported weight or carriage being connected with the convex or solid part of the bearings, the oil will have a tendency by its gravity to accumulate on the rubbing parts, and thus combine a perfect lubrication with an economical supply of lubricating material.

The solid axles are made thickest near their extremities, so that the parts which pass through those portions of the hollow axles which are fixed into the naves of the wheels, and at the same time the apertures of the corresponding parts of the hollow axles, are diminished, both being turned perfectly cylindrical, that they may be fitted together with facility, and come into contact only where the bearings are intended to take place.

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Until recently the locomotive engines upon the Liverpool and Manchester Railway, were usually constructed with a double cranked axis upon the two main wheels of the carriage, which wheels were provided with flanges on their peripheries to keep the engine on the rails. But this mode of construction has been found to be defective, owing to the liability of the crank axis becoming strained or broken, by the excessive friction of the flanges of the wheels against the rails, when the locomotive is entering sidings, turnings, or crossings of the rails, or passing along curvatures in the line. For it will be evident that the carriage has a tendency at these places to run off the rail sideways; which tendency is counteracted by the flanges on the wheels bearing laterally against the inside edges of the rails, on the concave side of the curvature; and, when it is considered that the great weight and momentum of the moving body onsets with a sudden inflexible resistance at the extreme end of the lever, or periphery of a large wheel, we may readily conceive its liability to be broken, or at least strained.

It is evident that any lateral bending of the cranked axle, although far short of a fracture, will, by putting the wheels out of square, produce a violent surging motion of the whole engine sideways in its further progress along the rails; and such violent action most be very liable to break the cranked axle, or run the engine off the rails. To obviate these disadvantages, Mr. Robert Stevenson (under his patent dated 7th October, 1833), divests the tires of the main impelled wheels of their flanges, and in lieu thereof, employs two small additional wheels with flanges behind the former. These additional wheels are applied beneath the fireplace end of the boiler, for keeping the engine straight on the rails in its progress forwards; and the axles of these wheels being straight, and, consequently, stronger than the cranked, are not liable to be broken or bent, as experience has proved with respect to the axles of the fore wheels, which are precisely the same.

In the following cuts are exhibited a side elevation, an end elevation, and an end section of one of Mr. R. Stevenson's improved engines, in all of which figures the same letters of reference indicate corresponding parts, though differently viewed. K-K are the main impelled wheels on the cranked axle, without any projecting flanges on the tires, which run on the edge rails L. M-M are the additional small wheels with flanges, applied beneath the hinder or furnace end of the boiler; and 0 are the ordinary small wheels with flanges beneath the chimney end of the boiler, where the working steam cylinders are situated.

The small wheels, 0 and M, with flanges, as before observed, keep the engine straight upon the rails; and the large impelled wheels K, have only to advance the engine forwards, and to bear a due proportion of the weight, without having any thing to do with keeping the engine on the rails; therefore the cranked axle is liberated from all lateral strains, which is wholly transferred to the small wheels 0 and M, with flanges, which, having a straight axle, are capable of sustaining it.

It is often of essential importance to be able to arrest the progress of a carriage upon a railway with great promptitude; and the breaks in ordinary use for this purpose, have not always been found sufficiently potent for that purpose. As a remedy for this inconvenience, Robert Stephenson, under the same patent, proposes to employ the force of steam acting upon pistons or plungers in small cylinders; so that when it is required to stop the train, it is only necessary to turn a small cock, which allows the steam to flow instantaneously through a pipe into the cylinder, and by its pressure on the piston, give motion to a system of levers, which cause two brakes or clogs to be forced against the peripheries with great energy, and to arrest the motion of the vehicles very quickly.

These clogs or brakes, and their mode of action, are shown in the side elevation on the preceding page. a is the hollow cylinder into which a plunger is fitted, to act by a lever y, and an upright rod f, upon the two brakes d-d, which are suspended by pendulous links z from a centre pin or bolt e fixed to the frame. The brakes are caused to apply to the circumferences of the tires of the wheels K and M; by means of links, which are interposed between the two brakes, and which links, when put down into an angle, as shown in the figure, leave the brakes free of the wheels K and M; but when, by opening the cock C, the steam from the boiler is admitted through the pipe b-b, into the hollow cylinder a, it raises up the plunger therein; and the latter, by its lever y, and rod f, draws up the links towards a straight line, and then they force the two brakes apart from each other, against the wheels K and M, with an increased force beyond that which the plunger exerts; that increase of force being in consequence of the leverage at y, and the oblique direction of the links. When the handle of the cock c is turned the other way, it allows the steam to issue through an upright spout, and escape from the cylinders into the open air.

The following letters have reference to the other parts of the engine. At h is the fire-box; i the ash-grate; j is the boiler, cylindrical in shape, through the lower part of the transverse sectional area of which are passed longitudinally a great number of small brass tubes, proceeding from the furnace chamber, and serving as the hot-air flues, and conduct the some into the "smoke-box" 1, at the other end, whence the resulting gases from the combustion of the fuel ascend the chimney n; p is the steam-head; q a safety valve; another valve, the extremity of the lever of which is held down by the elastic force of a sitting steel-yard at s; t is a man hole; u the working peer; v the springs; w-w the iron brackets that connect the machinery to the wooden frame; s the fire-door; y, the throttle-cock, provided with a lever and graduated scale.

In the end elevation it will be observed that the axes of the running wheels M, like those at 0, are straight; the form of the axles to the wheels K, are represented in the annexed cut, and they are forged with great care from the roughest quality of iron, and are turned and centred as well as the running wheels in the lathe.

Locomotive engines, constructed according to the description of the foregoing, Mr. Stephenson says, have the effect of preventing the boilers being burnt out so soon as usual, by allowing them to be made of greater magnitude and strength; the additional wheels supporting the extra weights.

The bearing springs are used for the extra small wheels, the same as is now done for other wheels in ordinary engines; the six springs used causing all the six wheels to apply and bear fairly on the rails, and ease all jolts and concussions; the relative weights, or portions of the whole weight of the engine, which is to be borne by each of the six wheels, being regulated by the strength and setting of their respective bearing springs.

The main wheels, which are impelled by the power of the engine, are, in all cases, left loaded with as much of the weight of the engine as will cause sufficient adhesion of those wheels to the rails, to avoid slipping thereon.

The larger the entire capacity of a boiler is, the more metallic heating surface it will contain; and, consequently render unnecessary that extreme heat which is so prejudicial to the metal. And that diminution of the intensity of the combustion, the patentee considers to be advantageous in another point of view; because the jet of waste steam (which is thrown into the chimney to produce a rapid. draught therein, for exciting the combustion of the fuel) may be greatly diminished in its velocity, which will permit the waste steam to escape from the working cylinders with greater freedom than could be permitted with smaller boilers, wherein a greater heat and a more rapid generation of steam, are indispensable to furnish the requisite power.

The following cut exhibits another form of Mr. Stephenson's locomotive engine, such as is now in use, but with the foregoing improvement added thereto. The foremost wheels, at the chimney end of the boiler, are, in this however, impelled by means of outside cranks and connecting rods, as well as the two middle wheels K, which are on the cranked axle; in other respects, the improvement is the same as in the other engine. The brakes, or clogs, are, of course, applicable to this or any other engine, but they are left out in this instance, as being unnecessary to our illustration.

We have, in the previous parts of this article, alluded to the imperfections, which from time to time manifested themselves in the modes adopted for fastening the rails of edge railways to the chairs and sleepers. Owing to the effects of expansion and contraction, and the violent shocks and strains to which they are subjected, the task of perfecting these parts of the mechanism of railways has hitherto been found one of difficult accomplishment even to the most experienced and skilful.

With the view of remedying these defects, Robert Stephenson, jun. obtained letters patent in December 1833, in which he says that the object of his improvement is to provide firm and secure bearings at the bottoms of the notches in the chairs for the rails to rest upon, those bearings being capable of self-adjustment, in order that they may adapt themselves correctly to the under parts of the rails; and the making of adequate provisions for fastening the iron rails securely downwards upon such self-adjusting bearings, as well as for confining the rails laterally within the notches in the chairs, but in such manner that the self-adjusting bearings will not be subject to be deranged, nor the fastenings to be loosened, by the effect of any such slight tilting or inclination of the chairs in the direction of the length of the rails, as may result from partial or unequal subsidence of the ground beneath the stone blocks or wood sleepers upon which the chairs are fastened, nor by the effects of any such slight elongations and contractions in the length of the rails as they are usually liable to from ordinary changes of temperature.

Mr. Stephenson's mode of effecting this, is by the application of a self-adjusting segmental bearing piece into a suitably-formed concavity, made below the level of the bottom of the notch of each chair; the flat or chord side of the segmental piece being uppermost, and forming the bearing-surface at the bottom of the notch in the chair. Upon that flat bearing-surface the under side of the iron rail is to rest, so that the bearing-surface will always accommodate itself to the under side of the rail, and form an even contact therewith, in consequence of the circular side of the segmental piece adapting itself to the required position, by turning in its concave cell.

The specification of this patent describes the action of these parts, and all the subordinate pieces by which the connexions are formed, with great minuteness. It will however be sufficient, for the generality of our readers, to describe the illustrative drawings that accompany the specification.

Fig.1 is a perspective view, and Fig. 2 a lateral elevation; Fig. 3 is a transverse section, and Fig. 4 a horizontal plan of a chair, for supporting and uniting the extremities of the lengths of iron rails for edge-railways. A-A is the flat bottom or base of the chair, which is to be bedded upon the stone block or wooden sleeper, and firmly fastened thereto by spikes driven down through the holes a-a. B-B are the cheeks of the notch in the chair, that notch being the parallel space which is left between the cheeks, for the reception of the rails C-c D-d, which may join together with a half lap-joint, as is shown in perspective at Fig. 1, and in the plan Fig. 4, the overlapping parts c-d being of the same size, or nearly of the same size, as the other parts of the rails, and those poets are included within the notch of the chair.

The bottom of this notch is deeper than is necessary for receiving the rails, and is depressed into a concavity of a suitable form, for receiving the segmental bearing-piece which is shown on the next page, at 4-4-4, in plan, elevation, and perspective: the under edges of the rails rest upon the uppermost flat surface of this bearing-piece.

The small figures 5 and 6 are cylindrical pins, which are fitted into cylindrical sockets, through each of the cheeks or sides B-B; and 8 and 9 are tapering or wedge-like keys, which are inserted through suitable mortices in the cheeks and across the pins 5 and 6, for the purpose of forcing forward those pins, so that their pointed extremities may press obliquely ripen the lower part of the grooved recesses in the rails, with a bearing-down action, to confine the rails downwards upon the bearing-piece, and laterally in the chair.

The cylindrical pins are shown detached, in order to explain the manner in which the pointed extremity applies into the grooved recess in the rails, so as to exert a searing-down action thereon. Fig. 5 represents perspective views, and Fig. 6 a transverse section of a chair for supporting the iron rails at intermediate distances between the extremities or junctions of their several lengths; it has only one cylindrical pin 5, fitted through one of its cheeks B, the opposite cheek K being a flat vertical surface, against which the flat side of the rail is pressed and held firm, by the keying up of the cylindrical pin 5, no as to confine the rail laterally at the same time, that the oblique action of the point of the cylindrical pin 5, in the grooved recess of the rail may produce a bearing-down action, which confines the rail down upon the segmental bearing-piece.

The chairs are made of cast iron; the sockets for the cylindrical pins, the mortices for the wedge- like keys, and the cells for the segmental bearing-pieces, being formed in the casting, as well as the holes for the holding-down spikes; the wedge-like cross keys, the cylindrical pins, and the segmental bearing-pieces, are made of wrought iron.

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