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Aviation History
1914
1914 - 0979.PDF
THE NEW so H,P. DUPLEX GYRO ENGINE. one VALVE trouole has been, and in some cases, still is, „ of the most important factors, which place limits upon the endurance of aeronautical engines ; and the improved performance of modern engines is largely due to the attention which has been given by designers to the elimination of such defects. This has been especially so in the case of engines of the rotary type in which the inlet valve is located in the piston, as apart from difficulties associated with access to that part, the valve is, because of its position, very imperfectly cooled ; and it is not, therefore, surprising that certain well-known makers have discontinued the manufacture of models in which the valve is so placed. In the latest Gyro engine, manufactured by the Gyro Motor Co., of U.S.A., a special piston valve, which controls the exit of a part of the exhaust and the entrance • ; U| am I Kr f—i 1 1^^,-. ^ * 1 Jf\ *•* vA 5t ••:• * I r " \m ^ \1 Three-quarter view of the 80 h.p. Gyro Motor, showing valve operating mechanism. of the fresh carburetter air, is substituted for the valve in the piston, which, in the old model, was mechanically operated by a lever mounted upon the end of the connecting rod (see Flight, January 25th, 1913). Several of the old type of motors have been rendering excellent service at the Beatty School at Hendon during the past year. Otherwise than in valve gear, this engine embodies practically the same construction as its predecessor, and we can, therefore, confine our attention to the new features which have been introduced. The accompanying illustrations show the internal construction and the assembled arrangement of the motor. The main exhaust valve, D, is as previously fitted in the head of the cylinder, and is operated by an overhead rocking lever and push rod from a cam mounted in a separate compartment at the end of the crankcase. This cam is of the duplex type, one side operating the main exhaust valve, D, whilst the other side controls the movement of the piston valve, C. The latter moves within a casing, B, mounted in circumferential grooves formed on the wall of the cylinder in the vicinity of the ports, A, which function alternately as auxiliary exhaust ports and as gas intake ports. The casing, B, communicates at its outer end with the atmos phere or with the common exhaust muffle, if fitted, for which purpose a screwed connection is provided, while the inner end is enclosed, and from the side a lead through which the carburetted charge is drawn is taken to a casing on the opposite side of the crankcase. The mode of operation of the gear is extremely simple. On the power stroke the two pistons, P and C, move towards the crank-shaft, uncover both faces of the auxiliary ports, A, and thus permit the main portion of the burnt gases to escape into the atmosphere. The piston, P, continues to descend for a distance of about two inches, closes the auxiliary exhaust port and then returns, scavenging out the remaining gases through the main exhaust valve, D. On the next stroke of the engine, the induction stroke, the valve, D, is kept open until just before the upper edge of the piston reaches the auxiliary ports, A, thus admitting pure air into the cylinder. But in the meantime, the valve, C, has descended to its limit of travel, returned, and its lower edge has uncovered the A sectional view through the cylinder 80 h.p. Gyro Motor. jn duplex and valves of the outside of the ports, A; so that when the inner ends of the ports are uncovered by the piston, P, communication is made with the gas mixing chamber; and during the remainder of the induction stroke a rich mixture is drawn into the cylinder. The piston and the piston valve then move outwards, close the auxiliary ports, A, and the main piston performs the compression stroke. Two special advantages accrue from the adoption of 979
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