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Aviation History
1916
1916 - 0259.PDF
MA»CH 3C> J9l6- \ftJGHf] THE, 135 H.P. THOMAS AEROMOTOR. IN producing what is known as the Model 8 Aeromotor, the main objectives of the Thomas Aeromotor Co., of Ithaca, N.V., U.S.A., have been reliability, brake horse power developed, and rate of production. By a judicious selection of materials, and an efficient combination of system and the use of up-to-date tools, it has been possible to achieve not only these desirable qualities, but also to secure that the various parts are interchangeable—a point of considerable importance at all times. One of the principal features of this motor, which is of the 8-cylinder V water-cooled type, is that the propeller or tractor screw is driven through a reduction gear, the speed of the latter being 1,200 r.p.m. and that of the engine 2,000 r.p.m., at which speed a brake horse-power at the propeller shaft of 135 is guaranteed. The cylinders of 4 ins. bore and 5! ins. stroke are of the " L" head type, cast in pairs from a special, hard, close-grained iron, the water jackets being cast integral and providing ample space around all parts of the cylinder, including the valve caps, which are easily reached by the removal of an aluminium cover plate. Each pair of cylinders is held down on to the crankcase by six studs located close to the cylinder walls. Made of Tungsten steel, the valves are in one piece without welding, and give a clear opening of 2 J ins.; the valve springs are made of a special alloy steel in order to stand up under the most severe conditions of continuous service. The valve push rods, which pass through guides held in the cylinder-base flanges, are made of hardened tool steel, and are operated directly by the cams without intervening cam rockers. Means is provided whereby the tappet clearances may readily be adjusted, and great care has been taken to prevent oil leakage at the push rods. The camshaft is located in the crankcase between the two banks of cylinders, and the sixteen cams are formed integral with the shaft, hardened and ground to size. Drilled for lightness, the shaft itself is of large proportions, thereby insuring rigidity and long life to its three phosphor-bronze bear ings, which are lubricated by high pressure force feed directly from the main oil duct. A flange to receive the timing gear is formed on the driven end of the camshaft. The timing gears have spur cut teetK and are made of chrome nickel steel, heat treated. Lubrication of the gears is effected by overflow of oil through the pressure regulating relief valve, which is situated adjacent to the An end view of the Made! 8 Thomas aeromotor, showing the propeller reduction'.gearbox. Two side views o! the Model 8 Thomas aeromotor. 259
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