Bristol Pegasus
From Wikipedia, the free encyclopedia
- For the vectored thrust engine, see Rolls-Royce Pegasus
- Bristol Pegasus is also a motor-racing club in Bristol, England.
The Bristol Pegasus was a British 9-cylinder single-row air-cooled radial engine used in the 1930s and 1940s. Confusingly, Bristol chose to reuse the name many years later for the engine used in the Hawker Siddeley Harrier; that engine later became known as the Rolls-Royce Pegasus.
Contents |
[edit] History
The Pegasus was designed by Sir Roy Fedden as the follow-on to the Bristol Aeroplane Company's very successful Bristol Jupiter, following lessons learned in the Mercury effort. The Mercury was a small engine that produced about as much power as the Jupiter, through a combination of supercharging that improved the "charge", and various changes to improve the operating RPM. Power of a piston engine can be calculated by multiplying the charge per cylinder by the number of cycles per second; the Mercury improved both and thereby produced more power for a given size. The primary advantage was a much improved power-to-weight ratio.
The Pegasus was the same size, displacement and general steel/aluminum construction as the Jupiter, but other improvements allowed the maximum engine speed to be increased from 1,950 to 2,600 rpm for take-off power. This improved performance considerably from the Jupiter's 580 hp (430 kW), to the first Pegasus II with 635 hp (474 kW), to 690 hp (515 kW) in the first production model Pegasus III, and eventually to the late-model Pegasus XXII with 1,010 hp (750 kW) thanks to the two-speed supercharger (introduced on the Pegasus XVIII) and 100-octane fuel. This gave rise to the claim "one pound per horsepower" reflecting the excellent power-to-weight ratio.
Some famous users of the Pegasus were the Fairey Swordfish, Vickers Wellington, and Short Sunderland. It was also used on the Anbo 41, Bristol Bombay, Saro London, Short Empire, Vickers Wellesley and the Westland Wallace. Like the Jupiter before it, the Pegasus was also licensed by the PZL company in Poland. It was used it on PZL.23 Karaś and PZL.37 Łoś bombers. In Italy Alfa Romeo built both the Jupiter (126-RC35) and the Pegasus under licence, with the engine based on the Pegasus designated as Alfa Romeo 126-RC34 and civil version as the 126-RC10.[1]
Over 17,000 Pegasus engines were built.
[edit] Specifications (Pegasus XVIII)
General characteristics
- Type: 9-cylinder supercharged air-cooled radial engine
- Bore: 5.75 in (146 mm)
- Stroke: 7.5 in (191 mm)
- Displacement: 1,753 in³ (28.7 L)
- Diameter: 55.3 in (1,405 mm)
- Dry weight: 1,180 lb (535 kg)
Components
- Valvetrain: Four pushrod-actuated valves per cylinder, two inlet and two sodium-cooled exhaust valves
- Supercharger: High-speed centrifugal, single-stage two-speed
- Fuel system: Claudel-Hobson carburetor with automatic boost and mixture control
- Oil system: Dry sump with one combination pressure/scavenge pump
- Cooling system: Air-cooled
Performance
- Power output:
- 1,000 hp (745 kW) at 2,600 rpm at 3,000 ft (915 m) with 87-octane fuel
- 885 hp (660 kW) at 2,600 rpm at 15,500 ft (4,730 m) with 87-octane fuel
- 1,065 hp (795 kW) at 2,600 rpm at 1,250 ft (380 m) with 100-octane fuel
- 965 hp (720 kW) at 2,600 rpm at 13,000 ft (3,965 m) with 100-octane fuel
- Specific power: 0.60 hp/in³ (27.7 kW/L) at 1,250 ft (380 m) with 100-octane fuel
- Compression ratio: 7:1
- Power-to-weight ratio: 0.90 hp/lb (1.49 kW/kg)
[edit] Applications
- Blackburn Baffin
- Boulton Paul Overstrand
- Bristol Bombay
- Handley Page Hampden
- Handley Page Harrow
- Saro London
- Short Empire
- Short Mayo Composite
- Supermarine Stranraer
- Supermarine Walrus
- Vickers Vespa
- Vickers Victoria
- Vickers Vildebeest
- Vickers Vincent
- Vickers Valentia
- Vickers Wellington
- Vickers Wellesley
- Westland Wallace
[edit] References
- Bridgman, L, (ed.) (1998) Jane's fighting aircraft of World War II. Crescent. ISBN 0-517-67964-7
[edit] Notes
- ^ Alfa Aero Engines. aroca-qld.com. Retrieved on 2007-08-25.
[edit] See also
|
|||||
|
||||||||||||||
