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Aviation History
1917
1917 - 1276.PDF
HTl operates the machine gun interrupter gear and the tachometer drive. t-'~ Constructional Details. Cylinders.—Except for the steel water jackets, the cylinders are made entirely of cast iron. The water- jacketed heads, including the twin inlet and exhaust valve passages, are cast integral with the cylinder castings. The bore of the cylinders is 145 mm. and the thick- ness of the cylinder walls tapers from 5.5 mm. at the Pig. 7.—Sketch of propeller thrust race, showing split collar which secures the races in position. DECEMBER 6, 1917. • Three rings are provided above the gudgeon pin, the lower one being a scraper ring. The width of each ring is 8 mm., and the width of gap in cylinder equals 0.45 mm. The space between the two top rings is 4.25 mm., whilst the scraper ring is 10 mm. below the middle ring ; 4-mm. pegs are provided to locate the radial position of each ring, and six 2-mm. holes are drilled in the piston below the scraper ring. The slightly domed head of each piston is supported by a hollow conical pillar, which is machined from a steel forging and is riveted on to the underside of the piston, as shown in the sectional drawing of the piston (Fig. 5). The lower end of the conical pillar, which is machined at the same time as the holes'in the gudgeon pin bosses are bored, bears on the centre part of the gudgeon pin, and to allow for this the centre portion of the top of the connecting-rod small end and gudgeon pin bush is cut away. By this construction the greater part of the force of the explosion is transmitted from the head of the piston directly to the connecting-rod. The gudgeon pins are 38 mm. diameter, and are bored1 30 mm. inside diameter. The centre portion of the gudgeon pin is 25 mm. bore for a length of 20 mm., where the conical piston head support bears on the centre of the gudgeon pin. The piston ring side clearance equals 0.004 m- Tb-e diameter at the top of the piston equals 144.15 mm. The diameter at the bottom of the piston equals 144.67 mm. Connecting-rods.—The very clean design of the tubular, connecting-rods is apparent in the photo- graphic views, and the details of their constructionbase flanges to 6.5 mm. at the top of the cylinder barrels. The water jackets are of die-pressed sheet steel, are clearly shown in the sectional drawing (Fig. 6).built up from half sections and welded both at the vertical joints and at the bottom of the water jackets to flanges machined on the outside of the cylinder barrels. The water jackets are exceptionally long, extending to within 45 mm. of the cylinder base flanges. Seven annular corrugations are formed in the water jackets to allow for expansion, and three transversely in the sheet steel crown of the water jackets. The water spaces formed in the cylinder-heads and the cooling of the valve pockets is well carried out. Dished plates are welded in position in the water space above the crown of each cylinder to deflect the flow of water on to the exhaust valve pockets. The diameter of the cylinder-head water connections is 60 mm. The cylinder registers extend 10 mm. below the base flanges into the crank chamber, and are held down by four 12 mm. studs, and also by dogs at four points. The dogs are secured by long studs which pass through the top half of the crank chamber and are screwed into the bottom halves of the main bearing housings, which are cast integral with the bottom half of the base chamber. The parts of the holding- down studs which screw into the aluminium are of larger diameter and of coarser pitch. The nuts which secure the cylinder holding-down clamps are of interesting design, being of circular cupped forma- tion and drilled radially with four 12-mm. holes for screwing up with a " Tommy Bar." The total weight of each cylinder complete with valves, valve springs and valve rocker-supports equals 44.25 lbs. Pistons.—The pistons, with the exception of the small conical pillars, are made entirely of cast iron, The whole of the connecting-rod, including the lugs for the four bolts securing the halves of the big end, is machined all over from a steel forging. The outside diameter of the tubular rod is 36 mm. and the inside is bored with a 30-mm. hole from the crankpin end to 1 ••••;• : Fig. 8.—Details of valves and valve springs. within 6 mm. of the gudgeon pin bush—the bottom end of the bore being fitted with a screwed plug. A 6-mm. steel pipe, for lubricating the gudgeon pin, is fixed inside the centre of the connecting-rod, and the pipe is supported in the centre by two flanged discs, as shown in the drawing. The weight of the big end is lightened by four 12-mm. holes and one 30-mm. hole drilled radially through the big end. Two semi-circular oil grooves are machined in the white metal of the big end bearing caps, and one lateral groove is cut in the top portion of the big end bearing. The total weight of the complete con- lbs. 1 oz.; the big end weighingf necting-rod is 7 lbs. 1 oz. and weigh 7.62 lbs! each, complete with rings and 4 lbs. 12 ozs. and the small end 2 lbs. 5 ozs gudgeon pin. Total big end side clearance equals 0.15 mm 1276 and 7*
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