Pobjoy Niagara

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.

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

Variants

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

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

Niagara

• Aeroput MMS-3
• Airspeed Fleet Shadower
• CLW Curlew
• Comper Kite
• Comper Swift
• General Aircraft Monospar ST-25
• General Aircraft Fleet Shadower
• Gribovsky G-25
• Lambach HL.I
• Moss M.A.1
• Pobjoy Pirate
• Saro Shrimp
• Shapley Kittiwake
• Short Scion Senior
• Short Scion
• Short S.31 (half scale Stirling)
• Spartan Clipper
• Westland CL.20

Cataract

• British Klemm Swallow
• Hafner A.R.III Gyroplane
• Hendy Hobo
• Pitcairn PA-22

Cascade

• Autogiro AC-35

Survivors

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

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

Specifications (Pobjoy Niagara IV)

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

See also

Related development

• Pobjoy R

Comparable engines

• Rotec R2800
• Warner Scarab

Related lists

• List of aircraft engines