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.

Applications

• Comper C.L.A.7 Swift
• Parnall Imp

Specifications (Pobjoy P)

Data from Jane's all the World's Aircraft 1928

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: 0.35 kg/kWh (0.57 lb/(hp⋅h))
• Oil consumption: 0.018 L/kWh (0.023 imp pt/(hp⋅h))
• Power-to-weight ratio: 0.858 kW/kg (0.522 hp/lb)