Multiple radial engine

A double
radial engine with 2 × 7 cylinders U III rotary engine from the Oberursel engine factory from 1914/15; Displacement 23.6 l; Max. 115 kW / 160 hp at 1200 min ^-1
exhibit in the German Museum in Munich

A multiple radial engine is a multiple cylinder reciprocating piston engine in which, in contrast to an inline radial engine, the cylinders of several stars are not arranged in a line (linear) behind one another, but slightly offset (helical). This design feature arises from the fact that multiple radial engines are usually air-cooled and their valves (like a simple radial engine) are OHV bumper- controlled, while in-line radial engines are mostly liquid-cooled and their valves are controlled via overhead camshafts, like in an in-line engine ( OHC and DOHC ). In addition, multiple radial engines are made up of a few stars (maximum: four 7-stars in the Pratt & Whitney R-4360 Wasp Major and Schwezow ASch-2K ), as they otherwise have cooling problems that are otherwise difficult to control. With in-line radial engines, this is less critical due to the liquid cooling. Here the cooling can also be mastered by six, eight or even ten stars in a row.

Since multiple radial engines also accommodate a large number of cylinders in a very compact design, they also have high power densities (power related to the engine mass or engine volume) and are used wherever high power is to be concentrated, such as. B. in aircraft engines. Very large engines are, for example, the Soviet Schwezow ASch-2K, Schwezow ASch-73 and Schwezow ASch-82 , the American Pratt & Whitney R-4360, Pratt & Whitney R-2800 and Pratt & Whitney R-1830 , and the American Wright R. -4090 , Wright R-3350 and Wright R-2600 , the British Bristol Centaurus , Bristol Hercules and Bristol Taurus as well as the German BMW 803 , BMW 802 and BMW 801 .