Rolls-Royce Hawk
# 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)
