Napier Saber

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Napier Saber aircraft engine

The Napier Saber is an aircraft engine from the British company Napier & Son with 24 cylinders and slide control (English: "sleeve valve"). The water-cooled H engine (two counter-rotating 180 ° V12 engines) developed in the late 1930s under the direction of Major Frank Halford was built until the late 1940s.

During World War II , the Saber powered British fighter planes such as the Hawker Typhoon and the Hawker Tempest . The engine was developed into one of the most powerful piston aircraft engines. In the first versions, its output was around 1800 hp (1320 kW). In later versions it delivered up to 3500 hp (2570 kW). The last prototypes even developed up to 4000 PS (2940 kW). Nevertheless, it was ultimately abandoned because of the development of jet engines .

history

Before the Saber , Napier had worked on large engines. Their best-known work was the Lion  - a water-cooled Y-motor with twelve cylinders (three rows with four cylinders each), which was used very successfully between the world wars and, in a modified form, powered seaplanes for the Schneider Trophy (1923 and 1927). At the end of the 1920s he was no longer competitive, so Napier was working on a replacement. This resulted in two air-cooled engines with an H-engine design: the H16 Napier Rapier and the H24 Napier Dagger . H-motors have the advantage of a very compact design and a vibration-free run, since their two 180 ° V-motor halves can rotate in opposite directions and thus balance out all orders of free inertia forces and torques. However, the air cooling caused thermal problems on the rear cylinders and the associated loss of reliability. Therefore, it was decided to use a water-cooled H24 - the Saber .

technical description

The Saber had as H-motor two crankshafts with six cranks as in an inline six cylinder around 0 °, 120 °, 240 °, 240 °, 120 °, 0 ° were added. In contrast to the Rolls-Royce Eagle 22 (also an H24 engine with slide valve control), the two crankshafts, offset by 180 ° to each other, did not run in opposite directions, but in the same direction. Even so, the Saber ran very smoothly. The firing intervals were even, but the cylinders directly one above the other fired at the same time. So it was not fired every 30 ° crank angle, but only every 60 °.

The engine had no valves and camshafts, but instead a "Burt-McCollum" valve control. The rotating slides were driven by shafts and small cranks in such a way that they opened the inlet and outlet slots at the right moment during the up and down movement of the piston. This made the engine very speed-stable. The cylinders on top of each other fired at the same time and their exhaust pipes led into a common exhaust. The engine was charged by a twin-flow centrifugal compressor , which was driven by the two crankshafts via a gearbox.

Technical specifications

Cutaway model of a Saber in the Royal Air Force Museum, London
  • Type: water-cooled 4-stroke H24 gasoline engine with slide control (Burt-McCollum) and supercharging
  • Stroke: 121 mm
  • Bore: 127 mm
  • Displacement: 36.8 liters
  • Compression: 7: 1
  • Power: 2570 kW (3500 PS ) at a speed of 4000 rpm
  • Weight: 1070 kg (dry)

Museum pieces

The Saber engine from a plane that crashed during World War II is on display in the Laatzen Aviation Museum near Hanover.

Web links

Commons : Napier Saber  - collection of images, videos and audio files