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— 16 MARINE REVIEW. EVANS MULTIPHASE ROTARY ENGINE. A RIVAL OF THE RECIPROCATING ENGINE THAT IS TO BE BACKED BY A STRONG CORPORATION OF LARGE CAPITAL—DETAILS OF CONSTRUCTION. The accompanying illustrations show the general appearance and de- tails of construction of an engine patented August 25, 1900, by James M. Evans, 805, No. 84 La Salle street, Chicago. It is the final outcome of nearly eighteen years of thought on the subject of rotary engines in gen- eral, during which time the inventor has ben alternately stationary engt- neer, shop mechanic and designer. He has therefore given the subject close consideration from all three sides and the engine now under con- sideration has received praise from skilled engineers who have heretofore stated openly that they did not believe an effective rival of the recipro- cating engine would be produced. The engine shown is the fourth in construction after the general design had been produced, and is of 100 H.P., with 600 revolutions, 100 lbs. of steam, one-third cut-off, running non-condensing. The outside dimensions are 22x22x16 in. and. weight 1,000 Ibs.; diameter of steam cylinder 17 in.; of rolling piston, 12 in.; width of cylinder 5 in.; speed of rolling piston, 567 ft.; crank throw, 2% in., ., making stroke of about 16 in.; diameter of crank shaft, 3% in. Fig. 1. Evans Rotary Engine, external view. Fig. 1 is an external view, showing the central cylinder, with steam chests bolted to it on either side, so that the engine may run either way, taking steam from one side and exhausting on the other, the necessary difference in size of steam valve openings being easily and simply adjusted when changing from one to the other. ‘abe Fig. 2. Evans Rotary Engine, steam chest cover removed, showing steam valve and ports. Fig. 2 shows the cover of the steam chest removed and the steam ‘valve pulled out on the shaft, revealing two of the three steam ports, in the head, a central hub containing roller bearings for the main shaft, and the central cup-shaped part of the steam valve necessary to fit over this hub. The valve consists of two parts, the disc as shown and a sliding annular ring, containing the same number of openings as the disc upon which it is carried, and adapted to be automatically rotated by a governor, [January 3, SS eB re RD ne ee ee Ce or to remain constantly at a predetermined angle of cut-off as desired. In the latter case the cut-off may be varied while the engine is in motion, ranging from the full opening of 120°, as shown, to a point where all but two of the openings are closed. : : Fig. 3 shows the valve and cylinder head. removed, revealing the working parts within the cylinder. These consist of the crank shaft A, which is built-up, to allow of easily removing the working parts; the roll- ing piston B,:journaled upon the crank pin and revolving upon the pin. Fig. 3. Evans Rotary Engine, interior of steam cylinders. with the outer circumference rolling in contact with the wall of the cylin- der. Three division walls C, separate the cylinder into three 120° compart- ments, each of which has separate steam entry and exhaust ports. In the view the exhaust port shows an angular opening and the plug on the right side of the upper pocket shows the position of the steam entry port. These ports are similar, each being plugged on alternate sides, The divi- sion walls are held in position by shoes in grooves of the sides of the rolling piston and move in and out of the pockets in the cylinder as the piston rolls about the cylinder. They are supported on both sides for their whole length by grooves in the cylinder heads and also by the whole width of the pockets, one-third of the length of the slides always remain- ing within the pockets. A rocking shoe, Fig. 4,.is provided at the inner end of each slide. which maintains a steam-tight joint between the circum- ference of the rolling piston and the inner end of its division wall. A balance plate of ordinary construction is used on the steam side of the division walls, to maintain tight pockets for the slides. The outer ends of pockets are cored to form pneumatic chambers to receive and return the - divisions, the pressure of air being calculated to receive and overcome the momentum of the slides and return them without undue force. ‘The piston is a disc of cast iron, bored to receive the crank’pin and covered by two thin annular: shells, serrated in the center of their circum- ference so as to move out against the cylinder heads without allowing a steam to leak under the ends Z4 UI of the division walls or slides. Fig, 5. Packing at end of division walls. They are turned down over the sides of the piston, so as to carry the grooves for the shoes of the slides,- and are fastened to the piston by flat annular rings of copper, the outer ee rings being anchored to the inside of the movable shells and the inner circumference clamped to the piston by clamping rings and screws. This gives a steam-tight joint of great flexibility and allows the sides of the shells to be held against the cylinder heads by the steam pressure in the chamber. As the steam and friction surfaces may be readily proportioned to each other on the prin- ciple of a balanced valve, it will be seen that the packings on all points of wear are steam-controlled and that they will remain tight to the limits of wear; also that these limits may be much greater than in the ordinary engine. The motion of the rolling piston is epicycloidal in all its parts, so that there is no wear on the cylinder wall, very little on the crank pin, which is fitted either plain or with roller bearings, and the motion of the shells rubbing on the cylinder heads will keep both shells and heads flat to the limits of wear. The packing on the ends of the slides rubs against the circumference of the piston shells, but owing to the shape of the shoe. Fig. 4, it is steam controlled, and the great latitude of motion in the pocket will keep it tight until worn to the point where renewal is neces- sary. New packings are cheap and easily inserted. All curves are circular and all planes flat and right-angled, making them easy of renewal with limited facilities, as would be the case on ship board, or in small ports with poor machine shops. -- The piston speed is slow—much slower than is the case in many re- ciprocating engines—and slower than most experts would believe until they had calculated the epicycloid curves with due reference to the diam- eters of cylinder and piston in relation to the crank-throw. By placing an actual crank in the engine, the side pressure of the steam is taken off the shaft and utilized in holding the piston against the cylinder wall, while any wear on the crank pin will not affect the working parts of the engine, as the piston is entirely controlled by the steam and the cylinder wall. The wear on the crank-shaft boxes is, therefore, less than in the recipro- circumference of the