In [Fig. 3391a], one engine and pump is shown in side elevation, and the other in section, the cranks being at a right angle, one to the other. A yoke from the piston rod spans the crank, so that the steam and pump pistons are in line and directly connected. From the lower end of this yoke, a rod connects to the crank shaft upon which are the two fly wheels and the eccentrics for the steam valves.
It will be seen in the longitudinal section, [Fig. 3390a], that the steam valve face is a segment of a circle and therefore answers, so far as the distribution of the steam is concerned, to a simple D slide valve, which exhausts through the pipes m, p. The steam pipe n enters the bottom of the steam chest at n′.
The two main pumps a are made in one piece, entirely of composition; one of them is shown in section. The piston is a solid piece of brass, as well as the cylinder in which it works, but are made of different composition, one hard, the other soft, to prevent cutting. The valves are of India rubber; the discharge valve is a ring, one for each end of the pump, as shown at b, [Fig. 3391a]. One is shown open, while the other is closed. They are held in place by grooved rings of brass; these rings fit in grooves in the rubber, which, when they are put in the pump, and their set screws are in, with their points in the grooves in the brass rings spoken of above, the discharge valves are complete for work.
The suction valves are shown at k on [Fig. 3391a], and will be easily understood. They are of a design for this special use and place, which is around the pump cylinder in a circular chamber. The water ways covered by these valves are long and narrow, one valve covering two of these openings, they being held in place by two studs that go through the centre part of the valve, a wire going through these studs, and close to the back of the valve which keeps it up to the seat, the only spring to either of these valves being the elasticity of the rubber. The opening and connection d, d is the inlet to the pump, and where the suction hose goes on, there being a pipe or chamber with branches for the two air chambers, and at each end is a discharge gate and a connection for the leading hose. The part d is the feed pump for the boiler supply, e is the air chamber on the pipe that leads to the boiler to ease off the shocks caused by the plunger striking the water, when the pump does not fill. It is drawn broken off to show the upper part of the pump barrel and stuffing box. The pipe f is the feed water pipe from the pump to boiler, shown from different points in [Figs. 3390a] and [3391a]. g is what we call the suction pipe to the feed pump. It connects to the main pump in the discharge part of it.
A piece of hose pipe connects to the boiler at a point just above the water line, so that hot water or steam (according to the height of the water in the boiler) may be applied to any part that may have become frozen.
Heaters are almost universally used in connection with steam fire engines to keep the water hot, and in many cases to keep a few pounds pressure to shorten the time of going to work should the fire be close at hand. This boiler has an advantage for this kind of heating; the circulation is so perfect and free that all the water in it is heated alike; so when the fire is lighted the steam starts immediately up, instead of having to wait till some cold water has been heated that had not been reached by the very limited circulation in them, there being some parts that the circulation produced by the heater does not reach, leaving, of course, this water cold.
The arrows k′′ ([Fig. 3391]), show the direction of the circulation when working with fire in the fire box; those marked l′′ show the direction of it when on the heater which is directly opposite.
The outside pipe connected at about the water line is the outlet from the heater, and the inlet to the boiler, which carries the heated water over the crown sheet, where, as it gets cooler, it enters the coils, descends into the leg, and from there to the pipe near the bottom of the boiler; this pipe leads to the heater, so that the water is kept moving just in proportion to the heat given it; any kind of a heater can be used with the same result.