1894, when the period of modern development
began. What may be called a second period of
development occurred, however, about I860, when
Thomas Riekett, A. F. Yarrow, A. Pattison, H.
P. Holt, and others, built several steam vehicles.
Quite generally these vehicles approached the
traction engine in cliaracter, having heavy boilers
and engines and large water and fuel space, but
room for only a few, usually tor not more than
four, passengers. They were, in fact, hardly
more than self-moving boilers and engines with
a few seats attached.
JloDERX Period of DE-5L0PirE?JT. Turning now to the modern period of development, there are first a few inventions to notice, and then the motor-carriage as it existed in its various types in U102 can be considered. In 1884 Gottlieb Daimler invented his small high-speed gas-en- gine, followed in 188.5 by his invention of a single-cylinder, inelosed-crank and flj-wheel en- gine. In 1885 the latter engine was applied to a bicycle. In 1880 Carl Benz invented his single horizontal cylinder, water-jacketed engine, which he aj^plied to a tliree-wheel carriage. In 1889, M. Leon Serpollet invented his water-tube boiler, which he applied to a motor vehicle in 1894. About this same time electric vehicles began to be developed in France and America. Modern automobiles, therefore, may be classified, according to the motive power used, into : ( 1 ) Steam vehicles, in which steam is generated in a boiler burning coal, coke, or compressed fuels, or some form of oil, and is supplied to a steam- engine; (2) oil vehicles, using internal-combus- tion engines with petroleum, gasoline, or naph- tha; (3) electric vehicles, using electric motors supplied with current from a storage battery. Otiier forms of motive power, such as liquid air and com])ressed gases, have been suggested, but they are not practically employed.
Ste.m Vehicles. Modern steam automobiles may be divided into two classes : ( 1 ) Light vehicles for passenger service and (2) heavy vehicles for trucking freight. In Europe, and particularly in Franc"e, the most notable work in light steam vehicles has been done by 51. Leon Serpollet, who has applied his instantaneous generator, or boiler, invented in 1889, to motor- vehicle propulsion. The Serpollet boiler is of the water-tube type, the tubes being inclosed in a rectangvilar shell of two thicknesses of iron, packed between with asbestos. Immediately above and surrounding the burner is a coil of round pipe. These coils receive the water and pass it into a series of tubes, which zigzag back and forth across the space inside the shell. From these tubes the steam and water pass into twisted flat tubes, which deliver superheated steam to the engine. The fuel used with the Serpollet boiler is vaporized oil. Two forms of engines are used in modern Serpollet vehicles, both four-cylinder engines with the cylinders arranged in pairs. .In one engine the two pairs of cylinders are placed diagonally, like the arms of a letter V, so as to make an angle of 45 de- grees with each other and with the crank-shaft at the apex of the angle; in the other engine the two pairs of cylinders are placed on the opposite sides of the crank-shaft in the same horizontal plane. The power is conveyed from the crank- shaft to a countershaft parallel to the rear axle by chain and from the counter-shaft to the driv- ing-axle by gearing.
Aside from the Serpollet and one or two otner European vehicles, the chief development of the light steam automobile has been in America, where about a dozen makers are turning out such vehicles in considerable numbers. American builders use, to a great extent, the fire- tube boiler, but certain makers prefer water- tube boilers for their carriages. The standard American automobile boiler is a cylindrical upright-shell boiler with vertical fire-tubes. The tubes are either copper or steel, and run from 300 to 350 in number. The shell is of steel plate throughout or has steel-plate ends and cop- per-plate barrels. One prominent maker uses steel ends and a copper barrel, wrapped with two layers of piano wire. The fuel used is some form of mineral oil, usually gasoline, which is burned in special burners which vaporize the oil. The pressure for feeding the oil to the burners is obtained by compressed air, supplied by either a hand-pump or a power-pump, operated from the moving parts of the engine. Automatic feed- pumps, o])erated from the engine, supply water to the boiler. The boiler is usually arranged to blow off at about 225 pounds pressure, and there is provided an automatic valve arrange- ment for shutting off the fuel when the boiler pressure reaches a certain amount. The operating steam pressure usually runs from 120 to 180 pounds. The engine commonly used is a doublecylinder, double-acting engine, set vertically, the cylinder diameter varying from 2^4 to 3 inches, and the stroke from 3 to 3^2 inches. A few vehicles have been provided with vertical com- pound engines with a by-pass arrangement for turning live steam into the low-pressvire cylin- der. The exhaust is usually at the rear of the vehicle through a funnel-shaped aperture, in- closed in the water-tank. In one type of vehicle, however, the steam from the engine passes through the hollow tubes of the running frame into a transverse tube, located at the front, and having numerous small orifices to dissipate the steam vapor. Usually the vehicle is driven by a chain from the engine-shaft to the rear driving- axle, b«t in a few cases an intermediate counter- shaft is used.
Considering now heavier vehicles, both for pas- sengers and freight, it is seen that considerable progress has been made, though such wagons and carriages are not in so wide use as the lighter ones. In America one of the heaviest steam vehicles ever constructed was the 20-passenger omnibus exhibited at New York in 1900. This vehicle is peculiar in having its running gear in two parts, one carrying the rear, or driving wheels, and the other carrying the front, or steering wheels. The wheels are of wood with a steel felly, carrying a 4-inch solid tire, and are mounted on cold-drawn solid- steel axles with roller bearings. The motive mechanism consists ofa4X5X7X 5-inch com- pound engine, arranged with a by-pass to permit live steam to be turned into the low-pressure cylinder. This engine, which with the boiler is placed nearly directly over the front wheels, has a chain-drive to a countershaft, located about midway of the vehicle. Two chain-drives run from this counter-shaft to the roar wheels. The boiler used is the 25 horse-power water- tube boiler of the climax type. Among steam omnibuses of European make those of De Dion and Bouton, and Scotte, of France, and of the
