Pobjoy P

The Pobjoy P was a British seven-cylinder, air-cooled, aircraft engine designed by Douglas Rudolf Pobjoy and built by Pobjoy Airmotors. It became the progenitor of the Pobjoy R/Niagara/Cataract family of small radial engines. A notable feature of the Pobjoy P was the propeller reduction gear which allowed the small engine to operate at more desirable higher speeds.[1]

'P'
Type Piston radial aero-engine
National origin United Kingdom
Manufacturer Pobjoy Airmotors
Designed by Douglas Rudolf Pobjoy
First run ca.1926
Developed into Pobjoy R

Applications

Specifications (Pobjoy P)

Data from Jane's all the World's Aircraft 1928[2]

General characteristics

  • Type: 7-cylinder air-cooled, radial, left-hand tractor
  • Bore: 2.83 in (72 mm)
  • Stroke: 3.43 in (87 mm)
  • Displacement: 151.05 cu in (2.48 l)
  • Diameter: 25 in (640 mm)
  • Dry weight: 115 lb (52.16 kg)
  • Designer: Douglas Rudolf Pobjoy

Components

  • Valvetrain: overhead valves operated by rockers, push-rods and tappets driven by a cam-plate at the rear of the engine
  • Fuel system: One Zenith carburetor
  • Fuel type: 80% Petrol, 20% Benzol
  • Oil system: Dry sump, pressure system at 45 psi (310 kPa)
  • Cooling system: Air-cooled
  • Reduction gear: Double-helical spur gear 0.524:1

Performance

  • Power output: 60 hp (45 kW) at 3,000 rpm rated output; 67.5 hp (50.3 kW) at 3,300 rpm maximum
  • Specific power: 0.397 hp/cu in (18.1 kW/l)
  • Specific fuel consumption: 0.57 lb/hp/h (0.35 kg/kW/h)
  • Oil consumption: 0.023 imp pt/hp/h (0.018 l/kW/h)
  • Power-to-weight ratio: 0.522 hp/lb (0.858 kW/kg)

References
  1. Lumsden, Alec S.C. (1994). British piston aero-engines and their aircraft (1. publ. in the UK. ed.). Shrewsbury: Airlife Publ. pp. 178–179. ISBN 1-85310-294-6.
  2. Grey, C.G., ed. (1928). Jane's all the World's Aircraft 1928. London: Sampson Low, Marston & company, ltd. pp. 18d–19d.
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