Beam pumping-engines are now almost invariably built with crank and fly-wheel, and very frequently are compound engines. The accompanying [illustration] represents an engine of the latter form.
Fig. 105.—Double-Cylinder Pumping-Engine, 1878.
A and B are the two steam-cylinders, connected by links and parallel motion, C D, to the great cast-iron beam, E F. At the opposite end of the beam, the connecting-rod, G, turns a crank, H, and fly-wheel, L M, which regulates the motion of the engine and controls the length of stroke, averting all danger of accident occurring in consequence of the piston striking either cylinder-head. The beam is carried on handsomely-shaped iron columns, which, with cylinders, pump, and fly-wheel, are supported by a substantial stone foundation. The pump-rod, I, works a double-acting pump, J, and the resistance to the issuing water is rendered uniform by an air-chamber, K, within which the water rises and falls when pressures tend to vary greatly. A revolving shaft, N, driven from the fly-wheel shaft, carries cams, O P, which move the lifting-rods seen directly over them and the valves which they actuate. Between the steam-cylinders and the columns which carry the beams is a well, in which are placed the condenser and air-pump. Steam is carried at 60 or 80 pounds pressure, and expanded from 6 to 10 times.
Fig. 106.—The Lawrence Water-Works Engine.
