STEAM ENGINE. 528 STEAM ENGINE. engraving the different parts are designated by letters as follows : The engine frame, A ; the cylinder, B ; the piston rod, C ; the crosshead, D; the connecting rod, E; the ciank, F; the fly wheel, G; and the governor, H. The first practical use of importance to which Fig. 10. CONNECTING ROD. Top and Bide views. steam engines were put was the pumping of water, and the pumping engine still remains one of the principal forms of the steam engine. The various tyjjes of pumping engines are de- scribed in the article on Pumps and Pumping Machinery. The next important use of the stationary steam engine was for driving the machinery of factories, mills, and workshops, and such establishments still consume an enor- mous aggregate of steam-engine power. The mill engines are not infrequent. A horizontal simple engine of comparatively small size which can be used for dynamo driving or other high-speed work, is shown by Fig. 11. A third type of .stationary engine is the hoisting engine, which in its smaller sizes combines a vertical steam boiler and a duplex hori- zontal or vertical en- gine in one machine. Such engines do not have a fly wheel, but connect directly with a crank shaft which drives the d r u m upon which the hoist- ing rope is wound. Hoisting engines of larger size have sep- arate boilers and often operate as many as eight separate drums. Tile largest sizes of hoisting engines are those used in raising ore from deep mine shafts. These mine hoists have capacities of from 2000 to 5000 horse power. Like the smaller sizes, they are either duplex vertical or duplex liorizontal engines. A duplex engine consists of a right-hand and a left-hand engine, both of which couple to the same crank shaft. They are to be distinguished from cross-compound engines, which have a WG Fig. 11. SMALL HIGH-BPEED HORIZONTAL ENGINE. modern form of mill engine is the horizontal di- rect-acting fly wheel engine, in which the power is taken from the fly wheel and transmitted to sliafting by means of belts. ( See Belts and Power, Transmission of.) For mill engines of large size present practice favors compound en- gines; simple engines are used when the unit of power -which is required is small. Generally tandem compound and cross compound engines are preferred to engines using steam with tliree or four expansions, although multiple-expansion similar appearance structurally, by the impor- tant fact that each half of the machine is dis- tinct from the other half so far as the use of the steam is concerned. In direct-acting mine hoists the drum or drums are mounted directly on the crank shaft: in general hoists the crank shaft drives a separate drum shaft by means of gear- ing. A fourth form of stationary engine is the rolling-mill engine, used for driving the trains of roils in rolling mills. (See Rolling Mill.) This is usually a horizontal simple engine of
