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The Oberursel U III is a so called rotary engine. The engine rotates around the stationary crankshaft.

The propeller is connected to the rotating engine housing. Rotary  engines were very popular in the early days of aviation because their advantages over static engines with fixed housing: the construction was simpler and weight was reduced, they ran more smoothly because of the large inertial mass of the revolving cylinders and liquid-cooling was not necessary.

With increasing engine power and thus increasing weight the centrifugal forces which occurred became greater and greater and control of the aircraft was thus made increasingly difficult. In addition, the consumption of fuel and lubricant was considerably greater than that with static engines. Construction of revolving cylinder engines ceased in 1918.

The U III was a copy of the French Gnome Lamda engine.

Technical specifications:

  • Manufacturer: Motorenfabrik Oberursel AG, Oberursel, 1915
  • Aircooled, 14 cylinder twin row, four stroke rotary engine
  • Power rating: 118 kW (160HP)
  • Engine speed: 1200 min-1
  • Displacement:  23.7 l
  • Bore: 124 mm
  • Stroke: 140 mm
  • Weight: 193 kg