Lycoming XR-7755

Lycoming XR- 7755 is the name of an engine, which was developed between 1943 and 1945 by the U.S. manufacturer Lycoming.

The XR- 7755 marked the culmination of the development of radial engines as aircraft engines. It was a 36 -cylinder radial engine with liquid cooling, in which four 9-cylinder stars were arranged behind one another ( in series). Each cylinder bank had an overhead camshaft ( OHC ) with two separate cams per cylinder - a cam for the fuel-saving travel mode, the second for the performance- intensive start-up mode. For this switching the cam timing the camshafts could be adjusted axially.

The one-piece crankshaft was bent four times - once for each of the four stars. The offset angle of the individual offsets be as in -line four- cylinder 0 °, 180 °, 180 °, 0 °. So even firing intervals are achieved ( each 20 ° of crankshaft rotation ignition ).

For a high output per liter he had a compressor. Compressors allow a delay-free, fast revving of an engine without a so-called turbo lag. To compensate for the decline in high altitudes by decreasing air pressure filling ratio and thus avoid loss of power, possessed of the XR- 7755 is also an additional turbocharger.

The intended goal of the development vierventiligen four-stroke engine were 7000 hp ( 5150 kW). Also great was also the fuel consumption: at 2600 rpm, where horsepower 5000 were produced, consumed the XR- 7755, approximately 2,200 liters per hour AvGas. As with all large and very powerful aircraft engines he drove to a pair of counter-rotating propellers, because a conventional single propeller needed otherwise an impractically large diameter in order to realize the great power still can.

With the end of the Second World War, the development of the engine due to lack of demand of the military has been discontinued.

The XR- 7755 is the largest and most powerful ever built aircraft piston engine in the world. Just as a ship's engines were manufactured by Maschinenfabrik Zvezda from Saint Petersburg larger radial engines: the Zvezda M503 ( a 42 -cylinder radial engine ) and the Zvezda M520 ( a 56 -cylinder radial engine ).

Specifications

  • Type: vierventiliger, water-cooled 36 - cylinder four -stroke petrol engine (144 valves, OHC - controlled)
  • Stroke: 171 mm
  • Bore: 162 mm
  • Capacity: 126.9 liters
  • Power: 3680 kW ( 5000 hp) at 2600 rpm
  • Maximum speed: 2700/min
  • Length: 3050 mm
  • Diameter: 1525 mm
  • Mass: 2744 kg (dry)
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