Section II.—Portable and Locomotive Engines

Engines and boilers, when of small size, are now often combined in one structure which may be readily transported. Where they have a common base-plate simply, as in Fig. 114, they are called, usually, “semi-portable engines.” These little engines have some decided advantages. Being attached to one base, the combined engine and boiler is easily transported, occupies little space, and may very readily be mounted upon wheels, rendering it peculiarly well adapted for agricultural purposes.

Fig. 114.—Semi-Portable Engine, 1878.

The example here shown differs in its design from those usually seen in the market. The engine is not fastened to or upon the boiler, and is therefore not affected by expansion, nor are the bearings overheated by conduction or by ascending heat from the boiler. The fly-wheel is at the base, which arrangement secures steadiness at the high speed which is a requisite for economy of fuel. The boilers are of the upright tubular style, with internal fire-box,[349] and are intended to be worked at 150 pounds pressure per inch. They are fitted with a baffle-plate and circulating-pipe, to prevent priming, and also with a fusible plug, which will melt and prevent the crown-sheet of the boiler burning, if the water gets low.

Another illustration of this form of engine, as built in small sizes, is seen below. The peculiarity of this engine is, that the cylinder is placed in the top of the boiler, which is upright. By this arrangement the engine is constantly drawing from the boiler the hottest and driest steam, and there is thus no liability of serious loss by condensation, which is rapid, even in a short pipe, when the engine is separate from the boiler.

Fig. 115.—Semi-Portable Engine, 1878.

The engine illustrated is rated at 10 horse-power, and makers are always expected to guarantee their machines to[350] work up to the rated power. The cylinder is 7 by 7 inches, and the main shaft is directly over it. On this shaft are three eccentrics, one working the pump, one moving the valves, and the third one operating the cut-off. The driving-pulley is 20 inches in diameter, and the balance-wheel 30 inches. The boiler has 15 11∕4-inch flues. It is furnished with a heater in its lower portion. The boiler of this engine is tested up to 200 pounds, and is calculated to carry 100 pounds working pressure, though that is not necessary to develop the full power of the engine. The compactness of the whole machine is exceptional. It can be set up in a space 5 feet square and 8 feet high. The weight of the 10 horse-power engine is 1,540 pounds, and of the whole machine 4,890 pounds, boxed for shipment. Every part of the mechanism usually fits and works with the exactness of a gun-lock, as each piece is carefully made to gauge.

Portable engines are those which are especially intended to be moved conveniently from place to place. The engine is usually attached to the boiler, and the feed-pump is generally attached to the engine. The whole machine is carried on wheels, and is moved from one place to another, usually by horses, but sometimes by its own engine, which is coupled by an engaging and disengaging apparatus to the rear-wheels. English builders have usually excelled in the construction of this class of steam-engine, although it is probable that the best American engines are fully equal to them in design, material, and construction.

The later work of the best-known English builders has given economical results that have surprised engineers. The annual “shows” of the Royal Agricultural Society have elicited good evidence of skill in management as well as of excellence of design and construction. Some little portable engines have exhibited an economical efficiency superior to that of the largest marine engines of any but the compound type, and even closely competing with that form. The causes of this remarkable economy are readily[351] learned by an inspection of these engines, and by observation of the method of managing them at the test-trial. The engines are usually very carefully designed. The cylinders are nicely proportioned to their work, and their pistons travel at high speed. Their valve-gear consists usually of a plain slide-valve, supplemented by a separate expansion-slide, driven by an independent eccentric, and capable of considerable variation in the point of cut-off. This form of expansion-gear is very effective—almost as much so as a drop cut-off—at the usual grade of expansion, which is not far from four times. The governor is usually attached to a throttle-valve in the steam-pipe, an arrangement which is not the best possible under variable loads, but which produces no serious loss of efficiency when the engine is driven, as at competitive trials, under the very uniform load of a Prony strap-brake and at very nearly the maximum capacity of the machine. The most successful engines have had steam-jacketed cylinders—always an essential to maximum economy—with high steam and a considerable expansion. The boilers are strongly made, and are, as are also all other heated surfaces, carefully clothed with non-conducting material, and well lagged over all. The details are carefully proportioned, the rods and frames are strong and well secured together, and the bearings have large rubbing-surfaces. The connecting-rods are long and easy-working, and every part is capable of doing its work without straining and with the least friction.

In handling the engines at the competitive trial, most experienced and skillful drivers are selected. The difference between the performances of the same engine in different hands has been found to amount to from 10 to 15 per cent., even where the competitors were both considered exceptionally skillful men. In manipulating the engine, the fires are attended to with the utmost care; coal is thrown upon them at regular and frequent intervals, and a uniform depth of fuel and a perfectly clean fire are secured. The sides[352] and corners of the fire are looked after with especial care. The fire-doors are kept open the least possible time; not a square inch of grate-surface is left unutilized, and every pound of coal gives out its maximum of calorific power, and in precisely the place where it is needed. Feed-water is supplied as nearly as possible continuously, and with the utmost regularity. In some cases the engine-driver stands by his engine constantly, feeding the fire with coal in handfuls, and supplying the water to the heater by hand by means of a cup. Heaters are invariably used in such cases. The exhaust is contracted no more than is absolutely necessary for draught. The brake is watched carefully, lest irregularity of lubrication should cause oscillation of speed with the changing resistance. The load is made the maximum which the engine is designed to drive with economy. Thus all conditions are made as favorable as possible to economy, and they are preserved as invariable as the utmost care on the part of the attendant can make them.

These trials are usually of only three or five hours’ duration, and thus terminate before it becomes necessary to clean fires. The following are results obtained at the trial of engines which took place in July, 1870, at the Oxford Agricultural Fair:

With all these engines steam-jackets were used; the feed-water was highly and uniformly heated by exhaust-steam; the coal was selected, finely broken, and thrown on the fire with the greatest care; the velocity of the engines, the steam-pressure, and the amount of feed-water, were very carefully regulated, and all bearings were run quite loose; the engine-drivers were usually expert “jockeys.”

The next illustration represents the portable steam-engine as built by one of the oldest and most experienced manufacturers of such engines in the United States.

Fig. 116.—The Portable Steam-Engine, 1878.

In the boilers of these engines the heating-surface is given less extent than in the stationary engine-boiler, but much greater than in the locomotive, and varies from 10 to 20 square feet per horse-power. The boilers are made very strong, to enable them to withstand the strains due to the attached engine, which are estimated as equivalent to from one-tenth to one-fifth that due to the steam-pressure. The[354] boiler is sometimes given even double the strength usual with stationary boilers of similar capacity. The engine is mounted, in this example, directly over the boiler, and all parts are in sight and readily accessible to the engineer.

One of these engines, of 20 horse-power, has a steam-cylinder 10 inches in diameter and 18 inches stroke of piston,[355] making 125 revolutions per minute, and has 9 square feet of grate-surface and 288 feet of heating-surface. It weighs about 41∕2 tons. Steam is carried at 125 pounds.

In the class of engines just described, the draught is obtained by the blast of the exhaust-steam which is led into the chimney. Such engines are now sold at from $120 to $150 per horse-power, according to size and quality, the smaller engines costing most. The usual consumption of fuel is from 4 to 6 pounds per hour and per horse-power, burning from 15 to 20 pounds on each square foot of grate, and each pound evaporating about 8 pounds of water. A usual weight is, for the larger sizes, 500 pounds per horse-power.

Fig. 117.—The Thrashers’ Road-Engine, 1878.

These engines are sometimes arranged to propel themselves,[356] as in the Mills “Thrashers’” road-engine or locomotive, of which the accompanying engraving is a good representation. This engine is proportioned for hauling a tank containing 10 barrels, or more, of water and a grain-separator over all ordinary roads, and to drive a thrashing-machine or saw-mill, developing 20 or 25 horse-power. This example of the road-engine has a boiler built to work at 250 pounds of steam; the engine is designed for a maximum power of 30 horses.

This engine has a balanced valve and automatic cut-off, and is fitted with a reversing-gear for use on the road. The driving-wheels are of wrought-iron, 56 inches diameter and 8 inches wide, with cast-iron driving-arms. Both wheels are drivers on curves as well as on straight lines. The engine is guided and fired by one man, and the total weight is so small that it will pass safely over any good country bridge. A brake is attached, to insure safety when going down-hill. Although designed to move at a speed of about three miles per hour, the velocity of the piston may be increased so that four miles per hour may be accomplished when necessary.

This is an excellent example of this kind of engine as constructed at the present time. The strongly-built boiler, with its heater, the jacketed cylinder, and light, strong frame of the engine, the steel running-gear, the carefully-covered[357] surfaces of cylinder and boiler, and excellent proportions of details, are illustrations of good modern engineering, and are in curious contrast with the first of the class, built a century earlier by Smeaton.

Fig. 118.—Fisher’s Steam-Carriage.

Steam-carriages for passengers are now rarely built. Fig. 118 represents that designed by Fisher about 1870 or earlier. It was only worked experimentally.

Fig. 119.—Road and Farm Locomotive.

The above is an engraving of a road and farm locomotive as built by one of the most successful among several British firms engaged in this work.

The capacity of these engines has been determined by experiment by the author in the United States, and abroad by several distinguished engineers.

The author made a trial of one of these engines at South Orange, N. J., to determine its power, speed, and convenience of working and manœuvring. The following were the principal dimensions:

The boiler was of the ordinary locomotive type, and the engine was mounted upon it, as is usual with portable engines.

The steam-cylinder was steam-jacketed, in accordance with the most advanced practice here and abroad. The crank-shaft and other wrought-iron parts subjected to heavy strains were strong and plainly finished. The gearing was of malleableized cast-iron, and all bearings, from crank-shaft to driving-wheel, on each side, were carried by a single sheet of half-inch plate, which also formed the sides of the fire-box exterior.

The following is a summary of the conclusions deduced by the author from the trial, and published in the Journal of the Franklin Institute: A traction-engine may be so constructed as to be easily and rapidly manœuvred on the common road; and an engine weighing over 5 tons may be turned continuously without difficulty on a circle of 18 feet radius, or even on a road but little wider than the length of the engine. A locomotive of 5 tons 4 hundredweight has been constructed, capable of drawing on a good road 23,000 pounds up a grade of 533 feet to the mile, at the rate of four miles an hour; and one might be constructed to draw more than 63,000 pounds up a grade of 225 feet to the mile, at the rate of two miles an hour.

It was further shown that the coefficient of traction[359] with heavily-laden wagons on a good macadamized road is not far from .04; the traction-power of this engine is equal to that of 20 horses; the weight, exclusive of the weight of the engine, that could be drawn on a level road, was 163,452 pounds; and the amount of fuel required is estimated at 500 pounds a day. The advantages claimed for the traction-engine over horse-power are: no necessity for a limitation of working-hours; a difference in first cost in favor of steam; and in heavy work on a common road the expense by steam is less than 25 per cent. of the average cost of horse-power, a traction-engine capable of doing the work of 25 horses being worked at as little expense as 6 or 8 horses. The cost of hauling heavy loads has been estimated at 7 cents per ton per mile.

Such engines are gradually becoming useful in steam-ploughing. Two systems are adopted. In the one the engine is stationary, and hauls a “gang” of ploughs by means of a windlass and wire rope; in the other the engine traverses a field, drawing behind it a plough or a gang of ploughs. The latter method has been proposed for breaking up prairie-land.

Thus, thirty years after the defeat of the intelligent, courageous, and persistent Hancock and his coworkers in the scheme of applying the steam-engine usefully on the common road, we find strong indications that, in a new form, the problem has been again attacked, and at least partially solved.

One of the most important of the prerequisites to ultimate success in the substitution of steam for animal power on the highway is that our roads shall be well made. As the greatest care and judgment are exercised, and an immense outlay of capital is considered justifiable, in securing easy grades and a smooth track on our railroad routes, we may readily believe that similar precaution and outlay will be found advisable in adapting the common road to the road-locomotive. It would seem to the engineer that the[360] natural obstacles generally supposed to stand in the way have, after all, no real existence. The principal inconvenience that may be anticipated will probably arise from the carelessness or avarice of proprietors, which may sometimes cause them to appoint ignorant and inefficient engine-drivers, giving them charge of what are always excellent servants, but terrible masters. Nevertheless, as the transportation of passengers on railroads is found to be attended with less liability to loss of life or injury of person than their carriage by stage-coach, it will be found, very probably, that the general use of steam in transporting freight on common roads may be attended with less risk to life or property than to-day attends the use of horse-power.

The Steam Fire-Engine is still another form of portable engine. It is also one of the latest of all applications of steam-power. The steam fire-engine is peculiarly an American production. Although previously attempted, their permanently successful introduction has only occurred within the last fifteen years.

Fig. 120.—The Latta Steam Fire-Engine.

As early as 1830, Braithwaite and Ericsson, of London, England, built an engine with steam and pump cylinders of 7 and 61∕2 inches diameter, respectively, with 16 inches stroke of piston. This machine weighed 21∕2 tons, and is said to have thrown 150 gallons of water per minute to a height of between 80 and 100 feet. It was ready for work in about 20 minutes after lighting the fire. Braithwaite afterward supplied a more powerful engine to the King of Prussia, in 1832. The first attempt made in the United States to construct a steam fire-engine was probably that of Hodge, who built one in New York in 1841. It was a strong and very effective machine, but was far too heavy for rapid transportation. The late J. K. Fisher, who throughout his life persistently urged the use of steam-carriages and traction-engines, designing and building several, also planned a steam fire-engine. Two were built from his design by the Novelty Works, New York, about 1860, for Messrs. Lee & Larned.[361] They were “self-propellers,” and one of them, built for the city of Philadelphia, was sent to that city over the highway, driven by its own engines. The other was built for and used by the New York Fire Department, and did good service for several years. These engines were heavy, but very powerful, and were found to move at good speed under steam[362] and to manœuvre well. The Messrs. Latta, of Cincinnati, soon after succeeded in constructing comparatively light and very effective engines, and the fire department of that city was the first to adopt steam fire-engines definitely as their principal reliance. This change has now become general.

The steam fire-engine has now entirely displaced the old hand-engine in all large cities. It does its work at a fraction of the cost of the latter. It can force its water to a height of 225 feet, and to a distance of more than 300 feet horizontally, while the hand-engine can seldom throw it one-third these distances; and the “steamer” may be relied upon to work at full power many hours if necessary, while the men at the hand-engine soon become fatigued, and require frequent relief. The city of New York has 40 steam fire-engines. One engine to every 10,000 inhabitants is a proper proportion.

Fig. 121.—The Amoskeag Engine. Section.

In the standard steam fire-engine (Fig. 120) reciprocating engines and pumps are adopted, as seen in section in Fig. 121, in which A is the furnace, and B the set of closely-set vertical fire-tubes in the boiler. C is the combustion-chamber, D the smoke-pipe, and R the steam-space. E is the steam-cylinder, and F the pump, which is seen to be double-acting. There are two pairs of engines and pumps, working on cranks, set at right angles, and turning a balance-wheel seen behind them. G is the feed-pump which supplies water to the boiler, H the air-chamber which equalizes the water-pressure, which reaches it through the pipe, I J. K is the feed-water tank, under the driver’s seat, L, which, with the engines and boiler, are carried on the frame, M M. The fireman stands on the platform, N. When it is necessary to move the machine, an endless chain connects the crank-shaft with the rear-wheels, and the engine, with pumps shut off, is thus made to drive the wheels at any desired speed.

A self-propelling engine by the Amoskeag Company[363] had the following dimensions and performance: Weight, 4 tons; speed, 8 miles per hour; steam-pressure, 75 pounds per square inch; height of stream from 1 1∕4-inch nozzle, 225 feet; 1 3∕4-inch nozzle, 150 feet; distance horizontally, 1 1∕4-inch nozzle, 300 feet; 1 3∕4-inch, 250 feet—a performance which contrasts wonderfully with that of the hand-worked fire-engine which these engines have now superseded.

Fig. 122.—The Silsby Rotary Steam Fire-Engine.

It has recently become common to construct the steam fire-engine with rotary engine and pump (Fig. 122). The superiority of a rotary motion for a steam-engine is apparently so evident that many attempts have been made to overcome the practical difficulties to which it is subject. One of these difficulties, and the principal one, has been the packing of the part which performs the office of the piston in the straight cylinder. Robert Stephenson once expressed the opinion that a rotary engine would never be made to work successfully, on account of this difficulty of packing. The most palpable of the advantages of the rotary engine are the reduction in the size of the engine, claimed to result from the great velocity of the piston; the avoidance of great accidental strains, especially noticed in propelling ships; and a great saving of the power which is asserted to be expended in the reciprocating engine in overcoming the inertia while changing the direction of the motions. These advantages adapt the rotary engine, in an especial manner, to the driving of a locomotive or steam fire-engine.

Fig. 123.—Rotary Steam-Engine.

Fig. 124.—Rotary Pump.

In the Holly rotary engine, seen in Fig. 123, eccentrics and sliding-cams, which are frequently used in rotary engines,[366] and which are objectionable on account of their great friction, are avoided. Corrugated pistons, or irregular cams, C D, are adopted, forming chambers within the cases. In the engine the steam enters at A, at the bottom of the case, and presses the cams apart. The only packing used is in the ends of the long metal cogs, which are ground to fit the case and are kept out by the momentum of the cams, assisted by a slight spring back of the packing-pieces. The friction on the pump (Fig. 124) is said to be less than in the engine. This is the reason given in support of the claim that the rotary engine forces water to a given distance with from one-fourth to one-third the steam-pressure necessary to drive all reciprocating engines. The smaller amount of power necessary to do the work, the less strain and consequent wear and tear upon the whole machine, are said to make it more durable and reliable. The pump being chambered, its liability to injury by the use of dirty or gritty water is lessened, and it is stated that it will last for years, pumping gritty water that would soon cut out a piston-pump. The pump used with this engine is, as shown in the above illustration, somewhat similar to the rotary engine driving it. Each of the revolving pistons has three long teeth bearing against the cylinder, and packed, to prevent leakage, like the engine-cams. They are carried on steel[367] shafts coupled to the engine-shafts. The water enters at E and is discharged at F, and the passages are purposely made large in order that sand, chips, and dirt, which may enter with the water, may pass through.

The rotary engine is gradually coming into use for various special purposes, where small power is called for, and where economy of fuel is not important; but it has never yet competed, and may perhaps never in the future compete, with the reciprocating-piston engine where large engines are required, or where even moderate economy of fuel is essential. This form of engine has assumed so little importance, in fact, in the application of the steam-engine, that comparatively little is known of its history. Watt invented a rotary engine, and Yule many years afterward (1836) constructed such engines at Glasgow. Lamb patented another in 1842, Behrens still another in 1847. Napier, Hall, Massey, Holly, La France, and others, have built engines of this class in later times. Nearly all consist either of cams rotating in gear, as in those above sketched, or of a piston set radially in a cylinder of small diameter, which turns on its axis within a much larger cylinder set eccentrically, the piston, as the former turns, sliding in and out of the smaller cylinder as its outer edge slides in contact with the inner surface of the larger. In some forms of rotary engine, a piston revolves on a central shaft, and a sliding abutment in the external cylinder serves to separate the steam from the exhaust side and to confine the steam expanding while doing work. Nearly all of these combinations are also used as pumps.

Fire-engines, made by the best-known American builders of engines, with reciprocating engines and pumps, such as are in general use in the United States, have become standard in general plan and arrangement of details. These are probably the best illustrations of extreme lightness, combined with strength of parts and working power, which have ever been produced in any branch of mechanical engineering.[368] By using a small boiler crowded with heating-surface, very carefully proportioned and arranged, and with small water-spaces; by adopting steel for running-gear and working parts wherever possible; by working at high piston-speed and with high steam-pressure; by selecting fuel with extreme care—by all these expedients, the steam fire-engine has been brought, in this country, to a state of efficiency far superior to anything seen elsewhere. Steam is raised with wonderful promptness, even from cold water, and water is thrown from the nozzle at the end of long lines of hose to great distances. But this combination of lightness with power is only attained at the expense of a certain regularity of action which can only be secured by greater water and steam capacity in the boiler. The small quantity of water contained within the boiler makes it necessary to give constant attention to the feed, and the tendency, almost invariably observed, to serious foaming and priming not only compels unintermitted care while running, but even introduces an element of danger which is not to be despised, even though the machine be in charge of the most experienced and skillful attendants. Even the greatest care, directed by the utmost skill, would not avail to prevent frequent explosions, were it not for the fact that it rarely, if ever, happens that accidents to such boilers occur from low water, unless the boiler is actually completely emptied of water. In driving them at fires, they frequently foam so violently that it is utterly impossible to obtain any clew to the amount of water present, and the attendant usually keeps his feed-pump on and allows the foaming to go on. As long as water is passing into the boiler it is very unlikely that any portion will become overheated and that accident will occur. Such management appears very reckless, and yet accident from such a cause is exceedingly rare.

Fig. 125.—Tank-Engine, New York Elevated Railroad.

The changes which have been made in Locomotive-Construction during the past few years have also been in the direction of the refinement of the earlier designs, and[369] have been accompanied by corresponding changes in all branches of railroad-work. The adjustment of parts to each other and proportioning them to their work, the modification of the minor details to suit changes of general dimensions, the improvement of workmanship, and the use of better material, have signalized this latest period. Special forms of engine have been devised for special kinds of work. Small, light tank-engines (Fig. 125), carrying their own fuel and water without “tenders,” are used for moving cars about terminal stations and for making up trains; powerful, heavy, slow-moving engines, of large boiler-capacity and with small wheels, are used on steep gradients and for hauling long trains laden with coal and heavy merchandise; and hardly less powerful but quite differently proportioned “express”-engines are used for passenger and mail service.

Fig. 126.—Forney’s Tank-Locomotive.

A peculiar form of engine (Fig. 126) has been designed by Forney, in which the whole weight of engine, tender, coal, and water, is carried by one frame and on one set of wheels, the permanent weight falling on the driving-wheels and the variable load on the truck. These engines have also a comparatively short wheel-base and high pulling-power. The lightest tank-engines of the first class mentioned weigh 8 or 10 tons; but engines much lighter than these,[370] even, are built for mines, where they are sent into the galleries to bring out the coal-laden wagons. The heaviest engines of this class attain weights of 20 or 30 tons. The heaviest engine yet constructed in the United States is said to be one in use on the Philadelphia & Reading Railroad,[371] having a weight of about 100,000 pounds, which is carried on 12 driving-wheels.

Fig. 127.—British Express Engine.

Fig. 128.—The Baldwin Locomotive. Section.

A locomotive has two steam-cylinders, either side by side within the frame, and immediately beneath the forward end of the boiler, or on each side and exterior to the frame. The engines are non-condensing, and of the simplest possible construction. The whole machine is carried upon strong but flexible steel springs. The steam-pressure is usually more than 100 pounds. The pulling-power is generally about one-fifth the weight under most favorable conditions, and becomes as low as one-tenth on wet rails. The fuel employed is wood in new countries, coke in bituminous coal districts, and anthracite coal in the eastern part of the United States. The general arrangement and the proportions of locomotives differ somewhat in different localities. In Fig. 127, a British express-engine, O is the boiler, N the fire-box, X the grate, G the smoke-box, and P the chimney. S is a spring and R a lever safety-valve, T is the whistle, L the throttle or regulator valve, E the steam-cylinder, and W the driving-wheel. The force-pump, B C, is driven from the cross-head, D. The frame is the base of the whole system, and all other parts are firmly secured to it. The boiler is made fast at one end, and provision is made for its expansion when heated. Adhesion is secured by throwing a proper[372] proportion of the weight upon the driving-wheel, W. This is from about 6,000 pounds on standard freight-engines,[373] having several pairs of drivers, to 10,000 pounds on passenger-engines, per axle. The peculiarities of the American type (Fig. 128) are the truck, I J, or bogie, supporting the forward part of the engine, the system of equalizers, or beams which distribute the weight of the machine equally over the several axles, and minor differences of detail. The cab or house, r, protecting the engine-driver and fireman, is an American device, which is gradually coming into use abroad also. The American locomotive is distinguished by its flexibility and ease of action upon even roughly-laid roads. In the sketch, which shows a standard American engine in section, A B is the boiler, C one of the steam-cylinders, D the piston, E the cross-head, connected to the crank-shaft, F, by the connecting-rod, G H the driving-wheels, I J the truck-wheels, carrying the truck, K L; N N is the fire-box, O O the tubes, of which but four are shown. The steam-pipe, R S, leads the steam to the valve-chest, T, in which is seen the valve, moved by the valve-gear, U V, and the link, W. The link is raised or depressed by a lever, X, moved from the cab. The safety-valve is seen at the top of the dome, at Y, and the spring-balance by which the load is adjusted is shown at Z. At a is the cone-shaped exhaust-pipe, by which a good draught is secured. The attachments b, c, d, e, f, g—whistle, steam-gauge, sand-box, bell, head-light, and “cow-catcher”—are nearly all peculiar, either in construction or location, to the American locomotive. The cost of passenger-locomotives of ordinary size is about $12,000; heavier engines sometimes cost $20,000. The locomotive is usually furnished with a tender, which carries its fuel and water. The standard passenger-engine on the Pennsylvania Railroad has four driving-wheels, 51∕2 feet diameter; steam-cylinders, 17 inches diameter and 2 feet stroke; grate-surface 151∕2 square feet, and heating-surface 1,058 square feet. It weighs 63,100 pounds, of which 39,000 pounds are on the drivers and 24,100 on the truck. The freight-engine has six driving-wheels,[374] 545∕8 inches in diameter. The steam-cylinders are 18 inches in diameter, stroke 22 inches, grate-surface 14.8 square feet, heating-surface 1,096 feet. It weighs 68,500 pounds, of which 48,000 are on the drivers and 20,500 on the truck. The former takes a train of five cars up an average grade of 90 feet to the mile. The latter is attached[375] to a train of 11 cars. On a grade of 50 feet to the mile, the former takes 7 and the latter 17 cars. Tank-engines for very heavy work, such as on grades of 320 feet to the mile, which are found on some of the mountain lines of road, are made with five pairs of driving-wheels, and with no truck. The steam-cylinders are 201∕8 inches in diameter, 2 feet stroke; grate-area, 153∕4 feet; heating-surface, 1,380 feet; weight with tank full, and full supply of wood, 112,000 pounds; average weight, 108,000 pounds. Such an engine has hauled 110 tons up this grade at the speed of 5 miles an hour, the steam-pressure being 145 pounds. The adhesion was about 23 per cent. of the weight.

Fig. 129.—The American Type of Express-Engine, 1878.

In checking a train in motion, the inertia of the engine itself absorbs a seriously large portion of the work of the brakes. This is sometimes reduced by reversing the engine and allowing the steam-pressure to act in aid of the brakes. To avoid injury by abrasion of the surfaces of piston, cylinder, and the valves and valve-seats, M. Le Chatelier introduces a jet of steam into the exhaust-passages when reversing, and thus prevents the ingress of dust-laden air and the drying of the rubbing surfaces. This method of checking a train is rarely resorted to, however, except in case of danger. The introduction of the “continuous” or “air” brake, which can be thrown into action in an instant on every car of the train by the engine-driver, is so efficient that it is now almost universally adopted. It is one of the most important safeguards which American ingenuity has yet devised. In drawing a train weighing 150 tons at the rate of 60 miles an hour, about 800 effective horse-power is required. A speed of 80 miles an hour has been often attained, and 100 miles has probably been reached.

The American locomotive-engine has a maximum life which may be stated at about 30 years. The annual cost of repairs is from 10 to 15 per cent. of its first cost. On moderately level roads, the engine requires a pint of oil to each 25 miles, and a ton of coal to each 40 or 50 miles run.[376] One of the best-managed railroads in the United States reports expenses as follows for one month:

Although the above sketch and description represent the construction and performance of the standard locomotive of the present time, there are indications that the compound arrangement of engines will ultimately be adopted. This will involve a considerable change of proportions, greatly increasing the volume and weight of steam-cylinders, but enabling the designer to more than proportionally decrease the weight of boiler and the quantity of fuel carried. There is no serious objection to their use, however, and no insuperable difficulty in the construction of the “double-cylinder” type of engine for the locomotive. A few such engines have already been put in service. In these engines the high-pressure cylinder is placed on one side and the larger low-pressure cylinder on the other side of the locomotive, thus having but two cylinders, as in the older plan. The valve-gear is the Stephenson link, as in the ordinary engine. At starting, the steam is allowed to act on both pistons; but after a few revolutions the course of the steam is changed, and the exhaust from the smaller cylinder, instead of passing into the chimney, is sent to the larger cylinder, which is at the same time cut off from the main steam-pipe. When the engine is ascending a steep gradient the steam may, if necessary, be taken from the boiler into both cylinders, as when starting.[377] Compound engines of this kind have been used on the French line of railroad from Bayonne to Biarritz. They were designed by Mallet and built at Le Creuzot. The steam-cylinders are of 91∕2 and 153∕4 inches diameter, and of 173∕4 inches stroke of piston. The four driving-wheels are 4 feet in diameter, and the total weight of engine is 20 tons. The boiler has 4841∕2 square feet of heating-surface, and is built to carry 10 atmospheres pressure. When hauling trains of 50 tons at 25 miles an hour, these engines require about 15 pounds of good coal per mile.

The total length of the railways in operation in the United States on the 1st day of January, 1877, was 76,640 miles,[93] being an average of one mile of railway for every 600 inhabitants. The railways are as follows:

In 1873 came the great financial crisis, with its terrible results of interrupted production, poverty, and starvation, and an almost total cessation of the work of building new railroads. The largest number of miles ever built in any one year were constructed in 1872. The greatest mileage is in Illinois, reaching 6,589; the smallest in Rhode Island, 136, and in Washington Territory, 110. The State of Massachusetts has one mile of railroad to 4.86[378] miles of territory, this ratio being the greatest in the country. The longest road in operation is the Chicago & Northwestern, extending 1,500 miles; the shortest, the Little Saw-Mill Run Road in Pennsylvania, which is but three miles in length. The total capital of railways in the country is $6,000,000,000, or an average of $100,000 per mile. The earnings for the year 1872 amounted to $454,969,000, or $7,500 per mile. The largest net earnings recorded as made on any road were gained by the New York Central & Hudson River, $8,260,827; the smallest on several roads which not only earned nothing, but incurred a loss.

The catastrophe of 1873-’74 revealed the fact that the latter condition of railroad finances was vastly more common than had been suspected; and it is still doubtful whether the existing immense network of railroads which covers the United States can be made, as a whole, to pay even a moderate return on the money invested in their construction. At the period of maximum rate of extension of railroads in the United States—1873—the reported lengths of the railroads of Europe and America were as follows:

The railroads in Great Britain comprise over 15,000 miles of track now being worked in the United Kingdom, on which have been expended $2,800,000,000. This sum is equal to five times the amount of the annual value of all the real property in Great Britain, and two-thirds of the national debt. After deducting all the working expenses, the gross net annual revenue of all the roads exceeds by $110,000,000 the total revenue from all sources of Belgium, Holland, Portugal, Denmark, Sweden and Norway. An army of 100,000 officers and servants is in the employ of the companies, and the value of the rolling-stock exceeds $150,000,000.