History of aicraft piston engines

Cylinder d esign was similar to that of t he wright j

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Unformatted text preview: with the cylinder used o n the W r i g h t t u r b o - c o m p o u n d engine, the most highly developed aircooled radial. 46 F igure 4 1.—Pratt & W hitney W asp air-cooled radial engine, 1 9 2 6 ; 4 25 hp at 1900 r p m , 6 5 0 l b. T he first such United States e ngine of over 4 0 0 hp to go i nto general service, it pioneered many technical features w hich became standard practice for this type. Cylinder d esign was similar to that of t he Wright J-5 (fig. 36e) except t hat rocker-arm supports and h ousing were cast integral w ith the cylinder h ead—an i m p o r t a n t innovation. (Photo A-3087) F igure 4 2.—Forged a l u m i n u m crankcase of P ratt & Whitney Wasp engine. Left, complete c rankcase. Right, forging of one half before m a c h i n i n g . (Photo A-3105) F igure 4 3.—Divided c rankshaft, from Pratt & W hitney Wasp engine. The Gnome (see f i g . 20) p ioneered this design for radial aircraft engines. (Photo A-3106) 47 F igure 4 4.—Pratt & W htney D ouble Wasp R - 2 8 0 0 - C B - 1 6 1 8-cylinder a ir-cooled 2-row r adial engine, 1 9 4 6 ; 2 8 0 0 hp a t 2800 r p m , 2 3 2 7 lb. Earlier m odels were extensively used i n World War I I , and t h i s model w as widely used in commercial a nd military aircraft. (Photo A-3103) F igure 4 5.—Pratt & W hitney Wasp Major R -4360 2 8-cylinder 4 -row radial engine, 1948 (cutaway); 3 5 0 0 hp at 2 9 0 0 r p m , 3842 lb. A post-World War II military and commercial engine. (Photo A-4132) 48 Figure 46.—Wright Cyclone R-1820 1 425-hp9-cylinderengine, 1953. When t his engine first came into use in 1933, it was rated at 525 hp at 1900 rpm. It was used in the Douglas DC-3 and Boeing B-17, among others. (Photo A-3090) Figure 47.—Wright Turbo-Cyclone R-3350 18-cylinder 2-row radial engine, 1955 (cutaway); 3700 hp at 2900 rpm, about 3000 lb. This post-war engine had three exhaust-driven turbines geared to the crankshaft, and it was the latest and most highly developed piston type to be widely used in large military and commercial airplanes. (Photo A-3089) i rV> .JH m T he following comparison illustrates the development of air-cooled engines from 1922 t o the present time: 1922 1955 Engine . . .,..'.'. Lawrance J - l Wright TurboCompound Number of cylinders 9 18 Bore and stroke, in 4.5x5.5 6.125x6.3125 Maximum hp 200 3, 700 R pm . . 1,800 2,900 Brake mean effective pressure, psi . . 112 302 Mean piston speed, ft/min . . . 1, 650 3, 070 H p per sq in. piston area . . ... . 1.4 7. 0 Weight, lb, per hp, dry (without oil and oil radiators) . . 2.38 0.96 As had been true of liquid-cooled engines, improvements in fuels, s upercharging, and cooling systems as well as great improvements in detail design, were important factors in this development. T he subject of the air-cooled engine should not be left without mention of the remarkable development of the light-airplane engine, beginning w ith the small British 4-cylinder v ertical Cirrus and DeHavilland Gypsy engines of 1927, and of the 4-cylinder Continental A-40 (fig. 48). Introduced in 1931, this 38-h...
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