title: Rolls-Royce Hawk
text: # Rolls-Royce Hawk
  
  The Rolls-Royce Hawk was a British aero engine designed by Rolls-Royce in 1915. Derived from one bank of six cylinders of the Rolls-Royce Eagle, it produced 75 horsepower at 1,370 rpm. Power was progressively increased to 91 hp by February 1916, and 105 hp by October 1918.
  
  After Rolls-Royce made the prototypes, the Hawk was manufactured under licence by Brazil Straker in Bristol between 1915 and 1918. During this period 204 engines were built, and the Hawk earned a reputation for high reliability.
  
  Many engines of this type were used to power the SSZ class coastal patrol airships of which 76 were built.
  
  ## Applications
  
  * Avro 504F
  * Farman MF.7
  * Royal Aircraft Factory B.E.2
  * SS class blimp (1 example)
  * SSP class blimp
  * SSZ class blimp
  * SST class blimp
  
  Post war one engine (serial number 332) was fitted into a specially built hull and launched on Windermere in 1922 with the name Canfly. With a flywheel added it was directly connected to the boat's propeller without a gearbox. Capable of reaching speeds of 26 knots (30 mph; 48 km/h) Canfly was used as the official's boat at several world speed record attempts during the 1920s and 1930s. The boat and engine are now displayed in a working but non-operational state at the Windermere Jetty museum.
  
  ## Specifications (Hawk I)
  
  Data from Lumsden
  
  ### General characteristics
  
  * Type: 6-cylinder liquid-cooled inline aircraft piston engine
  * Bore: 4 in (101.6 mm)
  * Stroke: 6 in (152.4 mm)
  * Displacement: 452.3 in³ (7.41 L)
  * Length: 46.85 in (1190 mm)
  * Width: 23.5 in (597 mm)
  * Height: 35.5 in (902 mm)
  * Dry weight: 387 lb (175.5 kg)
  
  ### Components
  
  * Valvetrain: OHC – Overhead camshaft
  * Fuel system: Twin Claudel-Hobson FZR carburettors
  * Fuel type: Petrol
  * Cooling system: Liquid-cooled
  
  ### Performance
  
  * Power output: 75 hp (56 kW) at 1,350 rpm
  * Compression ratio: 5.1:1
  * Power-to-weight ratio: 0.2 hp/lb (0.3 kW/kg)
  