Part 9

In the same year that Peter Cooper built his engine, the South Carolina Railway Company had a locomotive, called the "Best Friend," built at the West Point Foundry for its line. In 1831 this company had another engine, the "South Carolina" (Fig. 5), which was designed by Mr. Horatio Allen, built at the same shop. It was remarkable in having eight wheels, which were arranged in two trucks. One pair of driving-wheels, _D D_ and _D′ D′_, and a pair of leading-wheels, _L L_ and _L′ L′_, were attached to frames, _c d e f_ and _g h i j_, which were connected to the boiler by kingbolts, _K K′_, about which the trucks could turn. Each pair of driving-wheels had one cylinder, _C C′_. These were in the middle of the engine and were connected to cranks on the axles _A_ and _B_.

The "De Witt Clinton" (Fig. 6) was built for the Mohawk & Hudson Railroad, and was the third locomotive made by the West Point Foundry Association. The first excursion trip was made with passengers from Albany to Schenectady, August 9, 1831. This is the engine shown in the silhouette engraving of the "first[10] railroad train in America" which in recent years has been so widely distributed as an advertisement.

In 1831 the Baltimore & Ohio Railroad Company offered a premium of $4,000 "for the most approved engine which shall be delivered for trial upon the road on or before the 1st of June, 1831; and $3,500 for the engine which shall be adjudged the next best." The requirements were as follows:

The engine, when in operation, must not exceed three and one-half tons weight, and must, on a level road, be capable of drawing day by day fifteen tons, inclusive of the weight of wagons, fifteen miles per hour.

In pursuance of this call upon American genius, three locomotives were produced, but only one of these was made to answer any useful purpose. This engine, the "York," was built at York, Pa., and was brought to Baltimore over the turnpike on wagons. It was built by Davis & Gartner, and was designed by Phineas Davis, of that firm, whose trade and business was that of a watch and clock maker. After undergoing certain modifications, it was found capable of performing what was required by the company. After thoroughly testing this engine, Mr. Davis built others, which were the progenitors of the "grasshopper" engines (Fig. 7) which were used for so many years on the Baltimore & Ohio Railroad. It is a remarkable fact that three of these are still in use on that road, and have been in continuous service for over fifty years. Probably there is no locomotive in existence which has had so long an _active_ life.

In August, 1831, the locomotive "John Bull," which was built by George & Robert Stephenson & Company, of Newcastle-upon-Tyne, was received in Philadelphia, for the Camden & Amboy Railroad & Transportation Company. This is the old engine which was exhibited by the Pennsylvania Railroad Company at the Centennial Exhibition in 1876. After the arrival of the "John Bull" a very considerable number of locomotives which were built by the Stephensons were imported from England. Most of them were probably of what was known as the "Planet" class (Fig. 8), which was a form of engine that succeeded the famous "Rocket."

The following quotation is from "The Early History of Locomotives in this Country," issued by the Rogers Locomotive & Machine Works:

These locomotives, which were imported from England, doubtless to a very considerable extent, furnished the types and patterns from which those which were afterward built here were fashioned. But American designs very soon began to depart from their British prototypes, and a process of adaptation to the existing conditions of the railroads in this country followed, which afterward "differentiated" the American locomotives more and more from those built in Great Britain. A marked feature of difference between American and English locomotives has been the use of a "truck" under the former.

In all of the locomotives which have been illustrated, excepting the "South Carolina," the axles were held by the frames so that the former were always parallel to each other. In going around curves, therefore, there was somewhat the same difficulty that there would be in turning a corner with an ordinary wagon if both its axles were held parallel, and the front one could not turn on the kingbolt. The plan of the wheels and running gear of the "South Carolina" shows the position that they assumed on a curved track (Fig. 5). It will be seen that, by reason of their connection to the boiler by kingbolts, _K K′_, the two pairs of wheels could adjust themselves to the curvature of the rails. This principle was afterward applied to cars, and nearly all the rolling-stock in this country is now constructed on this plan, which was proposed by Mr. Allen in a report dated May 16, 1831, made to the South Carolina Canal & Railroad Company; and an engine constructed on this principle was completed the same year.

In the latter part of the year 1831 the late John B. Jervis invented what he called "a new plan of frame, with a bearing-carriage for a locomotive engine," for the use of the Mohawk & Hudson Railroad. Jervis's engine is shown by Figure 9. In a letter published in the _American Railroad Journal_ of July 27, 1833, he described the objects aimed at in the use of the truck as follows:

The leading objects I had in view, in the general arrangement of the plan of the engine, did not contemplate any improvement in the power over those heretofore constructed by Stephenson & Company,[11] but to make an engine that would be better adapted to railroads of less strength than are common in England; that would travel with more ease to itself and to the rail on curved roads; that would be less affected by inequalities of the rail, than is attained by the arrangement in the most approved engines.

In Jervis's locomotive the main driving-axle, _A_, shown in the plan of the wheels and running gear, was rigidly attached to the engine-frame, _a b c d_, and only one truck, or "bearing-carriage," _e f g h_, consisting of the two pairs of small wheels attached to a frame, was used. This was connected to the main engine-frame by a kingbolt, _K_, as in Allen's engine.

The position of its wheels on a curve, and the capacity of the truck, or "bearing-carriage," to adapt itself to the sinuosities of the track are shown in the plan. The effectiveness of the single truck for locomotives, in accomplishing what Mr. Jervis intended it for, was at once recognized, and its almost general adoption on American locomotives followed.

In 1834, Ross Winans, of Baltimore, patented the application of the principle which Mr. Allen had proposed and adopted for locomotives "to passenger and other cars." He afterward brought a number of actions at law against railroads for infringement of his patent, which was a subject of legal controversy for twenty years. Winans claimed that his invention originated as far back as 1831, and was completed and reduced to practice in 1834. The dispute was finally carried to the Supreme Court of the United States, and was decided against the plaintiff, after an expenditure of as much as $200,000 by both sides. It involved the principle on which nearly all cars in this country are now and were then built; and, as one of the counsel for the defendants has said, "It was at one time a question of millions, to be assured by a verdict of a jury."

In 1836, Henry R. Campbell, of Philadelphia, patented the use of two pairs of driving-wheels and a truck, as shown in Figure 10. The driving-wheels were coupled by rods, as may be seen below. This plan has since been so generally adopted in this country that it is now known as the "American type" of locomotive, and is the one almost universally used here for passenger, and to a considerable extent for freight, service. An example of a modern locomotive of this type is represented by Figure 11.

From these comparatively small beginnings, the magnificent equipment of our railroads has grown. From Peter Cooper's locomotive, which weighed less than a ton, with a boiler the size of a flour-barrel, and which had difficulty in beating a gray horse, we now have locomotives which will easily run sixty and can exceed seventy miles an hour, and others which weigh seventy-five tons and over. A comparison of the engraving of Peter Cooper's engine with that of the modern standard express passenger locomotive (Fig. 11) shows vividly the progress which has been made since that first experiment was tried--little more than half a century ago. In that period there have been many modifications in the design of locomotives to adapt them to the changed conditions of the various kinds of traffic of to-day. An express train travelling at a high rate of speed requires a locomotive very different from one which is designed for handling heavy freight trains up steep mountain grades. A special class of engines is built for light trains making frequent stops, as on the elevated railroads in New York, and those provided for suburban traffic (Fig. 12)--and still others for street railroads (Fig. 13), for switching cars at stations (Fig. 14), etc. [Pp. 110 and 113]. The process of differentiation has gone on until there are now as many different kinds of these machines as there are breeds of dogs or horses.

Nearly all the early locomotives had only four wheels. In some cases one pair alone was used to drive the engine, and in others the two pairs were coupled together, so that the adhesion of all four could be utilized to draw loads. The four-wheeled type is still used a great deal for moving cars at stations, and other purposes where the speed is comparatively slow. But to run around sharp curves the wheels of such engines must be placed near together, just as they are under an ordinary street-car. This makes the wheel-base very short, and such engines are therefore very unsteady at high speeds, so that they are unsuited for any excepting slow service. They have the advantage, though, that the whole weight of the machine may be carried on the driving-wheels, and can thus be useful for increasing their friction, or adhesion to the rails. This gives such engines an advantage for starting and moving heavy trains, at stations or elsewhere, which is the kind of service in which they are usually employed.

If the front end of the engine is carried on a truck, as in Campbell's plan (Fig. 10)--which is the one that has been very generally adopted in this country--the wheel-base can be extended and at the same time the front wheels can adjust themselves to the curvature of the track. This gives the running-gear lateral flexibility. But as the tractive power of a locomotive is dependent upon the friction, or adhesion of the wheels to the rails, it is of the utmost importance that the pressure of the wheels on the rails should be uniform. For this reason the wheels must be able to adjust themselves to the vertical as well as the horizontal inequalities of the track.

Figure 15 shows the driving-wheels, axles, journal-boxes, and part of the frame and springs of an American type of engine--the circumference of the wheels only being shown. The axles _A A_ each have journal-boxes or bearings, _B B_, in which they turn. These boxes are held between the jaws _J J J J_ of the frames, and can slide vertically in the spaces _c c c c_ between the jaws. The frames are suspended on springs, _S S_, which bear on the boxes _B B_. The vertical motion of the boxes and the flexibility of the springs allow the wheels to adjust themselves to some extent to the unevenness of the track. But, in order to distribute the weight equally on the two wheels, the springs _S S_ on each side of the engine are connected together by an equalizing lever, _E E_. These levers each have a fulcrum, _F_, in the middle, and are connected by iron straps or hangers, _h h_, to the springs. It is evident that any strain or tension on one spring is transferred by the equalizing lever to the other spring, and thus the weight is equalized on both wheels.

But to give perfect vertical adjustment of such an engine to the track, still another provision must be made. Everyone has observed that a three-legged stool will always stand firm on any surface, no matter how irregular, but one with four legs will not. Now if the back end of a locomotive should rest on the fulcrums of the equalizing levers, as shown in Figure 15, and the front end should rest on the two sides of the truck, it would be in the condition of the four legged stool. Therefore, instead of resting on the two sides of the truck, locomotives are made to bear on the centre of it, so that they are carried on it and on the two fulcrums of the equalizing levers, which gives the machine the adjustability due to the three-legged principle. When more than four driving-wheels are used the springs are connected together by equalizing levers, as shown in Figure 29 (p. 124), which represents a consolidation engine as it appears before the wheels are put under it.

Having a vehicle which is adapted to running on a railroad track, it remains to supply the motive power. This, in all but some very few exceptional cases, is the expansive power of steam. What the infant electricity has in store for us it would be rash to predict, but for locomotives its steps have been thus far weak and uncertain, and when we want a giant of steel or a race-horse of iron our only sure reliance is steam. This is the breath of life to the locomotive, which is inhaled and exhaled to and from the cylinders, which act as lungs, while the boiler fulfils functions analogous to the digestive organs of an animal. A locomotive is as dependent on the action of its boiler for its capacity for doing work as a human being on that of his stomach. The mechanical appliances of the one and the mental and physical equipment of the other are nugatory without a good digestive apparatus.

A locomotive boiler consists of a rectangular fireplace or fire-box, as shown at _A_, in Figure 16, which is a longitudinal section, and Figure 17 a transverse section through the fire-box. The fire-box is connected with the smoke-box _B_ by a large number of small tubes, _a a_, through which the smoke and products of combustion pass from the fire-box to the smoke-box, and from the latter they escape up the chimney _D_. The fire-box and tubes are all surrounded with water, so that as much surface as possible is exposed to the action of the fire. This is essential on account of the large amount of water which must be evaporated in such boilers. To create a strong draught, the steam which is exhausted from the cylinders is discharged up the chimney through pipes, and escapes at _e_. This produces a partial vacuum in the smoke-box, which causes a current of air to flow through the fire on the grate, into the fire-box, through the tubes, and thence to the smoke-box and up the chimney. Probably many readers have noticed, that of late years the smoke-boxes of locomotives have been extended forward in front of the chimneys. This has been done to give room for deflectors and wire netting inside to arrest sparks and cinders, which are collected in the extended front and are removed by a door or spout, _L_, below.

To get the water into the boiler against the pressure of steam a very curious instrument, called an injector, has been devised. Formerly force-pumps were used, but these are now being abandoned. The illustration (Fig. 18) shows what may be called a rudimentary injector. _B_ is a boiler and _E_ a conical tube open at its lower end--and connected to a water-supply tank by a pipe, _C_. A pipe, _A_, is connected with the steam-space of the boiler and terminates in a contracted mouth, _F_, inside of the cone _E_. If steam is admitted to _A_, it flows through the pipe and escapes at _F_. In doing so it produces a partial vacuum in _E_, and water is consequently drawn up the pipe _C_ from the tank. The current of steam now carries with it the water, and they escape at _G_. After flowing for a few seconds the water has a high velocity and the steam, mingling with the water, is condensed. The momentum of the water soon becomes sufficient to force the valve _H_ down against the pressure below it, and the jet of water then flows continuously into the boiler. A very curious phenomenon of this somewhat mysterious instrument is that if steam of a low pressure is taken from one boiler it will force water into another against a higher pressure. Figure 19 is a section of an actual injector used on locomotives.

Having explained how the steam is generated, it remains to show how it propels a locomotive. It does this very much as a person on a bicycle propels it--that is, by means of two cranks the wheels are made to revolve, and the latter must then either slip or the vehicle will move. In a locomotive the driving-wheels are turned by means of two cylinders and pistons, which are connected by rods to the cranks attached to the driving-wheels or axles. These cranks are placed at right angles to each other, so that when one of them is at the "dead-point" the piston connected with the other can exert its maximum power to rotate the wheels. This enables the locomotive to start with the pistons in any position; whereas, if one cylinder only was used it would be impossible to turn the wheels if the crank should stop at one of its dead-points.

It will probably interest a good many readers to know how the steam gets into the cylinders and moves the pistons and then gets out again, and how a locomotive is made to run either backward or forward at pleasure.

Figure 20 (p. 118) shows a section of a cylinder, _A A′_, with the piston _B_ and piston rod _R_. The cylinder has two passages, _c c_ and _d d_, which connect its ends with a box, _U_, called a steam-chest, to which steam is admitted from the boiler by a pipe, _J_. The two passages _c_ and _d_ have another one, _g_, between them, which is connected with the chimney. These passages are covered by a slide-valve, _V_, which moves back and forth in the steam-chest, alternately uncovering the openings _c_ and _d_. When the valve is in the position shown in Figure 20, obviously steam can flow into the front end _A_ of the cylinder through the passage _c_, as indicated by the darts. The valve has a cavity, _H_, underneath it. When this cavity is over the passage _d_ and _g_, it is plain that the steam in the back end _A′_ of the cylinder can flow through _d_ and _g_ and then escape up the chimney. Under these circumstances the steam in the front end _A_ of the cylinder will force the piston _B_ to the back end. When it reaches the back end of the cylinder the valve is moved into the position shown in Figure 21, and steam can then enter _d_ and will fill the back end _A′_ while that in the front end escapes through _c_ and _g_. The piston is then forced to the front end by the pressure of the steam behind it. It will thus be seen that the steam enters and escapes to and from the cylinder through the same openings.

From what has been said it is obvious, too, that every time the piston moves from one end of the cylinder to the other the valve must also be moved back and forth in the steam-chest. This is done by what is called an eccentric.

An "eccentric" is a disk or wheel (Fig. 22) with a hole, _S_, the size of the axle of the locomotive to which it is attached. The centre _n_ of the outside periphery of the eccentric is some distance from _S_, the centre of the shaft. A metal ring, _K K_ (Fig. 23), made in two halves, embraces the eccentric, and the latter revolves inside of this ring. A rod, _L_, is attached to the strap, and is connected with the valve so that the motion of the eccentric is communicated to it. It is obvious that if the eccentric revolves it will impart a reciprocating motion to the rod _L_, which is communicated to the valve.

If properly adjusted on the axle the eccentric will run the engine in one direction. To run the opposite way another eccentric must be provided. Therefore locomotives always have two eccentrics for each cylinder. These, _J_ and _K_, are shown in Figure 24, which represents the "valve-gear" of a locomotive. _S_ is a section of the main driving-axle, to which the eccentrics are attached by keys or screws. _C_ is the eccentric rod of the forward-motion eccentric and _D_ that of the one for running backward. As a locomotive must be run either backward or forward, and, as the one eccentric moves the valve to run forward and the other to run backward, we must be able to connect or disconnect the rods to and from the valve at will. The eccentric rods of the early locomotives had hooks on the ends by which they were attached to or detached from suitable pins connected with the valves. But these hooks were very uncertain in their action and therefore were abandoned, and now what is known as the "link-motion" is almost universally used for the valve-gear of locomotives. It consists of a "link" (_a b_, Fig. 24) which has a curved opening or slot, _k_, in it in which a block, _B_, fits accurately, so that it can slide from end to end of the link. This block has a hole bored in the middle which receives a pin, _c_, which is attached to the end of the arm _N_ of the "rocker" _M O N_. The rocker has a shaft, _O_, which can turn in a suitable bearing, and two arms, _M_ and _N_; the latter, as explained, is connected to the link by the pin _c_ and block _B_. The upper arm _M_ has another pin, _V_, on its end, which is connected by a rod, _v V_, to the main slide-valve _V_. The rocker-arms, as will be seen, can vibrate about the shaft _O_.

The link is hung by a pendulous bar, _g h_, to the end _g_ of the arm _E_, attached to the shaft _A_. This shaft has another upright arm, _F_, which is connected by a rod or bar, _G G′_, to a lever, _H I_, called a reverse lever, whose fulcrum is at _I_. To save room, in the engraving this lever and the cylinder _G_ are drawn nearer to the main axle _S_ than they would be on an engine. The lever is located inside the cab of the locomotive, and is indicated by the numbers 17 17′ in Figure 36 on p. 133, which is a view looking from the tender at the back end of a locomotive. The lever has a trigger (_t_, Fig. 24) which is connected by a rod, _r_, to a latch, _l_, which engages in the notches of the sector _S S′_. This latch holds the lever in any desired position and can be disengaged from the notches by grasping the upper end of the lever and the trigger.