RAF 4

The RAF 4 is a British air-cooled, V12 engine developed for aircraft use during World War I. Based on the eight–cylinder RAF 1 it was designed by the Royal Aircraft Factory but produced by the two British companies of Daimler and Siddeley-Deasy. The RAF 5 was a pusher version of the same engine.[1]

RAF 4
Preserved RAF 4a engine at the Science Museum (London)
Type Piston inline aero engine
Manufacturer Royal Aircraft Factory
Designer A.J. Rowledge
First run December 1914
Major applications Royal Aircraft Factory R.E.8
Number built >3,600
Developed from RAF 1

Turbocharger

A turbocharged experimental version of the RAF 4, the RAF 4d, was developed using a Rateau exhaust-driven turbocharger. The engine was test-flown in a R.E.8, but the turbocharging experiments were abandoned after the turbine failed on 4 May 1918.[2]

Variants
RAF 4
1914 - Prototype engine, 140 horsepower (104 kW).
RAF 4a
1917 - Main production variant, 150 horsepower (112 kW). 3,608 built.
RAF 4d
1916 - 180 horsepower (134 kW), experimental supercharger installation. 16 built.
RAF 4e
1917 - 240 horsepower (180 kW), strengthened cylinders and enlarged valves.
RAF 5
1915 - 150 horsepower (112 kW), pusher version with fan-cooling.
RAF 5b
170 horsepower (127 kW), increased bore version of RAF 5.

Applications

RAF 4
The Royal Aircraft Factory R.E.8

RAF 5

Engines on display

A preserved RAF 4a engine is on public display at the Science Museum (London).

Specifications (RAF 4a)

Data from Lumsden[3]

General characteristics
  • Type: 12-cylinder, upright, 60-degree Vee engine
  • Bore: 3.94 in (100 mm)
  • Stroke: 5.51 in (140 mm)
  • Displacement: 806.15 cu in (13.2 L)
  • Dry weight: 680 lb (308 kg)

Components
  • Valvetrain: EOI (side-valve inlet, exhaust overhead)
  • Fuel system: Twin Claudel-Hobson Mk.1A carburettors
  • Cooling system: Air-cooled
  • Reduction gear: 0.5:1, Left-hand tractor

Performance

See also

Related development

Comparable engines

Related lists

References
Wikimedia Commons has media related to RAF 4.

Notes
  1. Gunston, 1989, p. 156.
  2. Hare 1990, p. 265
  3. Lumsden 2003, p. 224.

Bibliography
  • Gunston, Bill. World Encyclopaedia of Aero Engines. Cambridge, England. Patrick Stephens Limited, 1989. ISBN 1-85260-163-9
  • Hare, Paul R. The Royal Aircraft Factory. London: Putnam, 1990. ISBN 0-85177-843-7
  • Lumsden, Alec. British Piston Engines and their Aircraft. Marlborough, Wiltshire: Airlife Publishing, 2003. ISBN 1-85310-294-6.
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