steam acts expansively on the high-pressure piston in the usual Way. By the time the piston has reached the bottom of its stroke the piston-valve has passed above the ports, and a way is opened from above into the space below the piston, or first receiver. During the up-stroke (effected by the momentum of the fly-wheel only) the steam is merely trans ferred, practically without change of volume or pressure, into the receiver. At the beginning of the succeeding down-stroke steam passes front the receiver by holes below the upper piston into the hollow rod again, and out by holes above the second piston into the intermediate cylinder. On the next- up-stroke the steam ex hausts. just as described before, into the second receiver ; in the next down-stroke it passes into the low-pressure cylinder ; in the next up-stroke it is transferred into the "exhaust chamber," which is in communication with the atmosphere ; but it is not until the third revo lution after that in which the steam enters the high-pressure cylinder that it is finally expelled from the engine. The full pressure in the steam-chest is constantly acting upon the valve-pis ton. This insures that the eccentric-rod shall be kept constantly pressed against the eccen tric, as well on the up as on the down stroke. With the steam-pistons the case is different. They are much heavier, and they are all in egniHtu io during the up-stroke, fur there is at t hat time communication existing between the upper and lower sides of all of them. Special means, therefore, are required for checking their momentum on the up-stroke, so as to keep the connecting-roil brasses truly in "constant thrust." The upward movement of the guide piston compresses the air contained in the guide-cylinder. until at the top of the stroke a con siderable pressure is reached. sufficient to stop the line of pistons, etc., without shock, and without allowing the upper brass to leave the crank-pin. In fact, an air-cushion is substi tuted for the usual steam-eushion.
A test of the Willans engine, by Prof. A. IL W. Kennedy, showed a water-eonsmnption of 19.11 lbs. per indicated horse-power per hour, the engine developing horse-power.
The Allis Rolling-Jfill Reversing-Engine (Pig.. shows a pair of rolling-mill engines built by the E. P. Allis Co. for Carnegie, Phipps Co.'s Armor Mill in Pittsburg, Pa. The engines are driving a two-roll high train, and are reversed at every pass of the plate in the rolls. The steam cylinders are 10-in. diameter by 5.1-in. stroke, wit It Ileynolds' Corliss valve-gear with out the drop emit-ott mechanism ; the speed of the engines is cont rolled by the operator, and is varied in every-day practice from 5 revolutions to 120 revolutions per min. The reversing gear is handled by a counterbalanced reversing mechanism, operated by steam, which is con I rolled by a lever on the engineer's platforms: from this position he has :111 unobstructed view of all parts of t he engliie ;Ind roll-train. The jmirnals for the roll-shaft and engine crank shaft are formed in the same pillow-block, each one having !proper moans of taking up wear and adjustment. Power from the engine crank-shaft is transmitted to the roll-shaft by
means of apair of shrouded helical toot lm steel gears.
The Willard Cantleasing Engine, made by C. P. Willard & Co., is shown in Fig.
GE It differs from erdinary steam-engine in the feet that while steam is made in the generator, which is a part of the machine, the only function of the steam is to create, by con densation, a vacuum, which is the motive-power. The engine is double-acting, a vacuum being created alternately at each end of the cylinder. There is no greater than atmospheric pressure in the generator, and there conse quently is no danger of explosion. The con densation of the low-pressure steam, by which a vacuum is created, is effected by means of a surface-condenser, which is kept cool by water. Where the engine is to be used in a city or town public water service, the condens er is placed in the upright iron pocket shown at the back of the engine, and a small stream of water—for the 2-horse-power, pipe ; for the 4 horse-power, Fin. pipe—furnishes an abundant water-supply to keep the condenser cool. The water is admitted at the bottom, and rises to the top, and passes off through an overflow-pipe. Where there is no public service, the engine itself operates a small pump, which causes a circulation of water.
The cylinder does not require oiling or lu brication, as the low steam used, being very moist, is a sufficient lubricant. The engine requires no attention beyond simply keeping up the fire, and giving the wheel two or three turns when ready to begin operations. There are no exhaust, no steam-gauge, no gauge cocks, no boiler feed-pump or injector, nor any of these adjuncts of an ordinary steam-boiler. It is practically noiseless, and there is no escape of burned oil or noxious odors. Where power is needed in offices and buildings heated by steam, for running ventilating-fans, printing presses, or other machinery, the engine may be connected by a pipe with the steam-coil in the room, and run in this way without any generator with the machine ; consequently there will be no ashes or dust, and the engine may be started or stopped by opening or closing the valve connecting with the steam coil.
The Acme Aulonwhe Safety Engine and Boiler, wade by the Rochester Machine-Tool Works, Rochester, N. Y., is shown in Figs. 65 and 66.
The engine (Fig. 65) is an upright double-cylinder, single-acting engine, with cranks 180° to each other. The pistons being 1,1, times the stroke in length, form their own guides, the wrist-pins being slightly below the center of the pistons, and the steam-rings above and below the wrist-pins. The valve is of the balanced rocking type, and is placed on the top of the cylinders, the valve-case forming the cylinder-heads. The fly-wheel contains the automatic governor, which regulates the admission of steam to suit the varying loads, by changing the throw of the eccentric that actuates the valve. Lubrication is accomplished by carrying in the erank-case a mixture of oil and water, into which the cranks dip at every revolu tion.