Fig. 12 shows more fully the arrangement and location of the machinery. The engine used in these vehicles is made with four cylinders of the single action type; that is, they take steam at one end only. By using this construction, while the number of cylinders is increased, the other parts are greatly simplified, as the piston rods, crossheads and guides can he dispensed with. In addition, the whole engine can be made very compact.
The boiler is of the flash type; that is, it carries no water ordinarily, but when the engine is in operation, a pump injects into the boiler at each stroke of the engine as much water as may be required to generate the steam necessary-to propel the vehicle; the instant the water enters the boiler it is converted into steam. As the amount of steam is proportional to the amount of water, it can be seen that by regulating the water supply, the power of the engine and thereby the speed of the
Fig. 13. Showing Details of the Boiler of the Serpollet Carriage.
carriage, can be controlled. This is the method actually employed to control the speed. In starting, a handle is moved which connects the engine, the boiler and the pump in the proper relation; and while under way the velocity is varied by the manipulation of a lever which controls the amount of water injected into the boiler. The fuel used is kerosene, which is vaporized and then fed into a properly constructed burner. The amount of oil supplied to the burner is regulated by the same lever that regulates the supply of water, so that both are increased or reduced in the proper proportion. The boiler is constructed of a number of steel tubes, which are about two and a half inches in diameter, and from three eighths to half an inch thick. These tubes are pressed into the form shown in Fig. 13, the dark line in the section marked A representing the interior space. A number of tubes collapsed in this form and bent into the shape B, are assembled as shown
