The Pobjoy Niagara is a British seven-cylinder, air-cooled, radial, aero-engine first produced in 1934. The design ran at higher speeds than conventional engines, and used reduction gearing to lower the speed of the propeller. This led to a noticeable off-centre mounting for the propeller. The Niagara was a popular engine for light and experimental aircraft, well regarded due to its small diameter, smooth operation, low noise and innovative engineering.
Niagara IBore/stroke 77 x 87 mm (3.03 x 3.43 in), swept volume 2,835 cc (173 cu in). Compression 6.25:1, gearing 0.47:1. Normal continuous power 84 hp (63 kW) at 3,200 rpm at sea level.
Niagara IIBore/stroke 77 x 87 mm (3.03x3.43 in), swept volume 2,835 cc (173 cu in). Compression 6.0:1, gearing 0.39:1. Normal continuous power 84 hp (63 kW) at 3,200 rpm at sea level.
Niagara IIIBore/stroke 77 x 87 mm (3.03x3.43 in), swept volume 2,835 cc (173 cu in). Gearing 0.47:1. Normal continuous power 88 hp (66 kW) at 3,300 rpm at sea level.
Niagara IVSimilar to Niagara III but with a higher operating rpm. Normal continuous power 98 hp (73 kW) at 3,500 rpm at sea level.
Niagara VLarger version of the basic Niagara. Bore/stroke 81 x 87 mm (3.19 x 3.43 in), swept volume 3,138 cc (191.5 cu in). Compression 8.0:1, gearing 0.47:1. Normal continuous power 125 hp (93 kW) at 4,000 rpm at sea level.
Cataract I-IIIDe-rated, uncowled versions of Niagara I-III with simple inter-cylinder baffles for cooling and trickle-down lubrication for lower exhaust rockers. Compression 5.7:1, gearing 0.47:1.
CascadeDirect drive version of Cataract I. Normal continuous power 66 hp (49 kW) at 2,100 rpm.
Aeroput MMS-3Airspeed Fleet ShadowerCLW CurlewComper KiteComper SwiftGeneral Aircraft Monospar ST-25General Aircraft Fleet ShadowerGribovsky G-25Lambach HL.IMoss M.A.1Pobjoy PirateSaro ShrimpShapley KittiwakeShort Scion SeniorShort ScionShort Stirling (half scale prototype)Spartan ClipperWestland CL.20British Klemm SwallowHafner A.R.III GyroplaneHendy HoboAutogiro AC-35A Pobjoy Niagara powered Comper Swift G-ACTF that is owned and operated by The Shuttleworth Collection, Old Warden remains airworthy in 2017 and displays to the public at home airshows during the flying season.
A preserved Pobjoy Niagara engine is on public display at the Science Museum (London).
Data from Lumsden.
Type: 7-cylinder, air-cooled, radial engineBore: 3.03 in (77 mm)Stroke: 3.43 in (87 mm)Displacement: 173 cu in (2.8 L)Diameter: 26.5 in (673 mm)Dry weight: 130 lb (59 kg)Valvetrain: 1 inlet and 1 exhaust valve per cylinderFuel system: 1 Claudel-Hobson carburettorFuel type: 70 octaneCooling system: Air-cooledPower output: 98 hp at 3,625 rpm max at sea levelCompression ratio: 6:1Power-to-weight ratio: 0.75 hp/lb