RAF 3
The RAF 3 was a British liquid-cooled, V-12 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 Armstrong Whitworth and Napier & Son. The RAF 7 was a high compression version of the same engine.[1]
| RAF 3 | |
|---|---|
| Type | Piston inline aero engine | 
| National origin | United Kingdom | 
| Manufacturer | Royal Aircraft Factory | 
| First run | September 1914 | 
| Major applications | Royal Aircraft Factory R.E.7 | 
| Number built | 289 | 
| Developed from | RAF 1 | 
| Developed into | RAF 4 | 
Variants
    
- RAF 3
 - 1914 - Prototype engine, 200 horsepower (150 kW).
 - RAF 3a
 - 1914 - Main production variant, increased bore, 260 horsepower (194 kW). 29 built by Armstrong Whitworth, 260 built by Napier & Son.
 - RAF 7
 - 300 horsepower (224 kW) high compression version with high-lift camshafts.
 
Applications
    
    
Specifications (RAF 3a)
    
Data from Lumsden[2]
General characteristics
- Type: 12-cylinder, upright, 60-degree Vee engine
 - Bore: 4.5 in (114.3 mm)
 - Stroke: 5.5 in (140 mm)
 - Displacement: 1,049.4 cu in (17.24 L)
 - Dry weight: 780 lb (354 kg)
 
Components
- Valvetrain: Overhead valve, both valves operated by a single pushrod
 - Cooling system: Liquid-cooled
 - Reduction gear: 0.5:1, left-hand tractor
 
Performance
- Power output: 260 hp (194 kW) at 1,750 rpm (takeoff power)
 - Specific power: 0.25 hp/cu in (11.25 kW/L)
 - Compression ratio: 5.3:1
 - Power-to-weight ratio: 0.33 hp/lb (0.54 kW/kg)
 
See also
    
Related development
Comparable engines
Related lists
References
    
    Notes
    
- Gunston, 1989, p. 156.
 - Lumsden 2003, p. 223.
 
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