The boiler in all its details has been designed to meet the requirements peculiar to the fire service and needs a full explanation with illustrations.
The auxiliary appliances found necessary for the operation of the modern steam fire engine are large in number; this is owing to the fact that the machine combines within itself so complete a system for extinguishing fires. The supplies needed for its maintenance and use are also in proportion, as to quantity and variety, to its complex make up.
The boiler, which is generally of the upright semi-water tube type, is combined with the engine by means of a strong iron frame, which carries all the appliances as well as the driver’s seat, and also forms the body of the truck.
Vertical Section.
Fig. 395.
The pumps may be of the reciprocating or rotary type, and are generally placed in front of the boiler. If of the reciprocating type, two pumps are placed alongside each other, and are operated either by a double slide valve or piston valve engine.
The piston rods connect directly with the plunger rods and are also connected to a crank shaft by means of either connecting rods or yokes, the cranks being set at right angles, so that one pump is always acting, while the other passes the dead center, thus giving a practically steady stream.
The engine exhausts into the stack, which gives the necessary draft. Some engines are equipped with a boiler feed pump, others only depend upon an injector, or feed directly from the main pump. The coal box, which also forms a platform for the engineer to stand upon while under way, is placed back of the boiler.
All engines are equipped with two suctions and two discharge openings, so that either side may be connected up. The tool box and driver’s seat are in front of the engine. The frame rests upon springs, to make the machine easy running.