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Aviation History
1917
1917 - 1277.PDF
."'•"•.._• DECEMBER 6, 1917. Fitted to the rear end of the crankshaft is a friction clutch for operating the wireless drive, which is designed so that the driving brake-shoes of the clutch can be thrown in orTmr of engagement with the driving pulley from the pilot's seat, through the action of two wedges, which operate the friction shoes through ball-ended levers. ^ Fig. 9.—Valves and valve gear parts. Fig. 10.—View of cylinder, showing valverockers and formation of water jacket. the float of the small end bush between the gudgeon pin bosses equals 14 mm. Crankshaft.—The six-throw crankshaft runs on seven plain bearings, and weighs 109.25 lbs., including the propeller boss. The cranks are, of course, set at 1200, and the diameter of all the journals is 62 mm., whilst that of the crankpins is 60 mm. The length of the front journal bearing (propeller end) equals 79 mm., and the length of the other journal bearings equals 54 mm.,v with the exception of the rear end bearing, which is 55 mm- The crankshaft journals and crankpins are bored for lubrication, the webs being drilled with com- municating holes in the usual manner. The internal diameter of the holes bored in both the crankpins and journals is 27 mm. The ends of the holes are plugged with sheet steel discs sweated into the recessed ends of holes, and all the discs which plug the rear ends of the holes in both the crankpins and journals are drilled with a central 5-mm. hole, presumably with the idea of lubricating the camshafts with the oil thrown out by the cianks. A double-thrust ball race, 120 mm. diameter, is fitted at the front end of the crankshaft behind the front flange, to which the propeller hub is bolted. The thrust races are large enough to be assembled over the cranks, and are secured in position by a split collar which is screwed on to the crankshaft. The halves of the split collar are held together on the screw thread on the shaft by a recess cut in the split collar. This recess holds a corresponding flange turned on the crankshaft. Details of this construction are shown in the sketch in Fig. 7. The propeller boss is attached to the crankshaft by a flange which is bolted to a corresponding flange on the end of the crankshaft by eight 14-mm. bolts. Full details of the propeller boss are given in the sectional drawing (Fig. 21). Valves and valve gear.—The twin inlet and exhaust valves work vertically in the cylinder heads, and are operated as previously mentioned by rockers mounted on ball-bearings, carried by supports screwed into the cylinder head. The general design of the valves and valve springs is shown in Figs. 8 and 9. The rocker levers operate the valve stems through hardened steel rollers which are mounted on eccentric bolts. These, in conjunction with adjustable Fig. 11.—Arrangement of exhaust camshaft and half-compression gear. spherical joints screwed into the top ends of the vertical push rods on each side of the cylinders, give a fine adjustment for the tappet clearances. The spherical joints on the valve rockers are evidently provided to simplify the alignment of the valve rocker supports which are screwed into the cylinder heads. Semi-spherical joints are also provided at the 1277
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