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Aviation History
1915
1915 - 0619.PDF
AUGUST 20, 1915. each, and, therefore, the pis-tons have passed through four strokes, completing the whole cycle for one revolution of the cylinders. As regards the valves, these, it will be seen, are both situated in the cylinder heads and are operated direct by cams on the circular engine plates, shoes pivoted at one end being interposed between the valve stems and the cams. By suitably arranging the position and length of these the most suitable valve timing may be obtained. Short induction pipes lead to the inlet valve casings from drums round the central hollow shaft, the drum for the set of cylinders surrounding the revolving portion of the central shaft being a tight fit on the shaft, while the other drum revolves round the fixed portion of the shaft. From the carburettor the mixture is drawn through the I/IIGHT[ occur at regular intervals of 30°, the order of tiring being, when numbering as previously the one set of cylinders I, 3, Si 7,9. Hi and the other 2, 4, 6, 8, to, 12, where firing and exhaust together in opposing cylinders: 1-12-3-2-5-4-7-6-9-8-11-10-1. For firing and exhaust together in corresponding cylinders, the order of firing would be 1-6-3-8-5-10-7-18-9-2-11-4-1. Lubrication is by forced feed, the oil pa-sing from the pump through copper tubes contained in the hollow shaft to a swelling in the central gunmetal bush, whence it passes through an opening in the wall of the bush and in the shaft into the oil channels of the respective crank shafts as they pass the opening. From there the oil runs through passages in the crank shafts, crank webs and crank Sectional view of the " Maude" rotary engine. hollow shaft to the two sets 01 cylinders, admission to which is gained through openings in the walls of the shaft, and through the short induction pipes. The exhaust gases are either passed directly out into the open or a tubular ring fitted with baffle plates or narrow slots to form a silencer may be fitted so that it connects the exhaust ports of one set of cylinders. The order of firing will, of course, depend upon the number of cylinders, and will also be determined by the placing, relatively, of the two sets of cams. In the experimental engine now under going tests, only six cylinders are fitted, two sets of three each, pins to the big end bearings and hence through channels in tin- connecting rods up to the cylinder walls viA the hollow gudgeon pins. Although the cooling problem does not appear to give any trouble in the experimental engine, it would seem that when the full number of cylinders were fitted the inner half of all cylinders would get very little air and distortion might result. It is even a question whether for large high-powered engines of this type it would not be better to reiort to water cooling. This would, of course, necessitate considerable alterations, and among others the cylinders would have Diagrammatic view of the "Maude" rotary engine. and the two sets of cams are placed 90' apart, so that when one piston is making its power stroke the corresponding piston in the opposing cylinder is compressing. The firing order for this arrange ment and number of cylinders, numbering the one set 1, 3, 5, and the other 2, 4, 6, is as follows: 1-2-3-4-5-6. If it were desired to have firing-exhaust and induction-compression together in opposing cylinders instead of firing-compression and induction- exhaust, the two sets of cams would, of course, also be placed 90° apart, but in the opposite direction. In the experimental engine the firing does not occur at regular intervals but at 90°-30% orj°-30°, &c. In the 12-cylinder engine, however, all the impulses to be held stationary while the central shaft was allowed to revolve, but the alterations should rot offer any great difficulties. The objection might be raised that as there is a considerable distance between the bearings, and the central hollow shaft is unsupported in the middle where the drive is taken, there must be a considerable amount of " whip," but in this connection it should be remembered that as the cylinders are held at both ends they in themselves form a rigid structure and thus help to take part of the load ofi the shaft, which must, however, take the torsional stresses or torque. As we have already pointed out, the engine that has been built and is now being tested is only an experimental one, and no 619
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