These were horizontal engines, attached to locomotive boilers.

At a similar exhibition held at Bury, in 1867, considerably better results even than these were reported, as below, from engines of similar size and styles:

KEY: A: Number.

B: Diameter.

C: Stroke.

D: Nominal.

E: Dynamometric.

F: Point of cut off.

G: Revolutions per minute.

H: Pounds coal per horse-power per hour.

---------------+-------------+-----+--------------+------+------+---- MAKERS' NAME | CYLINDERS. | | HORSE-POWER. | | | AND +-----+-------+ +-------+------+ | | RESIDENCE. | A | B | C | D | E | F | G | H ---------------+-----+-------+-----+-------+------+------+------+---- | |Inches.| In. | | | | | Clayton, | | | | | | | | Shuttleworth | 1 |10 | 20 | 10 | 11.00| 3.10 | 71.5 | 4.13 & Co., Lincoln | | | | | | | | | | | | | | | | Reading Iron- | | | | | | | | Works Company, | 1 | 8-5/8 | 20 | 10 | 10.43| 1.4 |109.4 | 4.22 Reading | | | | | | | | ---------------+-----+-------+-----+-------+------+------+------+----

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 ill.u.s.tration represents the portable steam-engine as built by one of the oldest and most experienced manufacturers of such engines in the United States.

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 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.

[Ill.u.s.tration: FIG. 116.--The Portable Steam-Engine, 1878.]

One of these engines, of 20 horse-power, has a steam-cylinder 10 inches in diameter and 18 inches stroke of piston, making 125 revolutions per minute, and has 9 square feet of grate-surface and 288 feet of heating-surface. It weighs about 4-1/2 tons. Steam is carried at 125 pounds.

In the cla.s.s 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.

[Ill.u.s.tration: FIG. 117.--The Thrashers' Road-Engine, 1878.]

These engines are sometimes arranged to propel themselves, 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 pa.s.s 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.

[Ill.u.s.tration: FIG. 118.--Fisher's Steam-Carriage.]

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 surfaces of cylinder and boiler, and excellent proportions of details, are ill.u.s.trations of good modern engineering, and are in curious contrast with the first of the cla.s.s, built a century earlier by Smeaton.

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

[Ill.u.s.tration: 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 man[oe]uvring. The following were the princ.i.p.al dimensions:

Weight of engine, complete, 5 tons 4 cwt. 11,648 pounds.

Steam-cylinder--diameter 7-3/4 inches.

Stroke of piston 10 inches.

Revolution of crank to one of driving-wheels 17 Driving-wheels--diameter 60 inches.

" breadth of tire 10 inches.

" weight, each 450 pounds.

Boiler--length over all 8 feet.

" diameter of sh.e.l.l 30 feet.

" thickness of sh.e.l.l 7/16 inch.

" fire-box sheets, outside, thickness 1/2 inch.

Load on driving-wheels, 4 tons 10 cwt. 10,080 pounds.

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 Inst.i.tute_: A traction-engine may be so constructed as to be easily and rapidly man[oe]uvred 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 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 windla.s.s 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 Hanc.o.c.k 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 subst.i.tution 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 natural obstacles generally supposed to stand in the way have, after all, no real existence. The princ.i.p.al inconvenience that may be antic.i.p.ated 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 pa.s.sengers 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.

[Ill.u.s.tration: 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 6-1/2 inches diameter, respectively, with 16 inches stroke of piston. This machine weighed 2-1/2 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. 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 and to man[oe]uvre 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 princ.i.p.al 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.

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-s.p.a.ce. _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.

[Ill.u.s.tration: FIG. 121.--The Amoskeag Engine. Section.]

[Ill.u.s.tration: FIG. 122.--The Silsby Rotary Steam Fire-Engine.]

A self-propelling engine by the Amoskeag Company 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.

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 princ.i.p.al 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 a.s.serted 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.

[Ill.u.s.tration: FIG. 123.--Rotary Steam-Engine.]

[Ill.u.s.tration: FIG. 124.--Rotary Pump.]

In the Holly rotary engine, seen in Fig. 123, eccentrics and sliding-cams, which are frequently used in rotary engines, and which are objectionable on account of their great friction, are avoided.