Pobjoy_Niagara Knowpia

Niagara
	Pobjoy Niagara on display at the Science Museum, London
Type	Piston radial aero engine
Manufacturer	Pobjoy Airmotors
First run	1934

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,^[1] well regarded due to its small diameter, smooth operation, low noise and innovative engineering.

Variants edit

Niagara I: Bore/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.^[2]

Niagara II: Bore/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.^[2]

Niagara III: Bore/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.^[2]

Niagara IV: Similar to Niagara III but with a higher operating rpm. Normal continuous power 98 hp (73 kW) at 3,500 rpm at sea level.^[2]

Niagara V: Larger 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.^[2]^[3]

Cataract I-III: De-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.^[2]^[3]^[4]

Cascade: Direct drive version of Cataract I. Normal continuous power 66 hp (49 kW) at 2,100 rpm.^[4]

Applications edit

Airworthy Pobjoy Niagara installed in a Comper Swift at the Shuttleworth Collection

Niagara edit

Cataract edit

Cascade edit

Autogiro AC-35

Survivors edit

A 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.^[5]

Engines on display edit

A preserved Pobjoy Niagara engine is on public display at the Science Museum (London).

Specifications (Pobjoy Niagara IV) edit

Data from Lumsden.^[2]

General characteristics

Type: 7-cylinder, air-cooled, radial engine
Bore: 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)

Components

Valvetrain: 1 inlet and 1 exhaust valve per cylinder
Fuel system: 1 Claudel-Hobson carburettor
Fuel type: 70 octane
Cooling system: Air-cooled

Performance

Power output: 98 hp at 3,625 rpm max at sea level
Compression ratio: 6:1
Power-to-weight ratio: 0.75 hp/lb

References edit

Notes edit

^ Gunston 1989, p.111.
^ ^a ^b ^c ^d ^e ^f ^g Lumsden 2003, p.179.
^ ^a ^b Jane's All the World's Aircraft p.26d
^ ^a ^b Ord-Hume p.589
^ www.shuttleworth.org Retrieved: 28 February 2017.

Bibliography edit

Grey, C.G. (1972). Jane's All the World's Aircraft 1938. London: David & Charles. ISBN 0-7153-5734-4.
Gunston, Bill. World Encyclopedia of Aero Engines. Cambridge, England. Patrick Stephens Limited, 1989. ISBN 1-85260-163-9
Lumsden, Alec. British Piston Engines and their Aircraft. Marlborough, Wiltshire: Airlife Publishing, 2003. ISBN 1-85310-294-6.
Ord-Hume, Arthur W.J.G. (2000). British Light Aeroplanes. Peterborough: GMS Enterprises. ISBN 978-1-870384-76-6.