Rolls-Royce Exe

Exe
Type	Piston X-24 aero-engine
National origin	United Kingdom
Manufacturer	Rolls-Royce Limited
First run	September 1936
Major applications	Fairey Battle
Developed into	Rolls-Royce Pennine

The Rolls-Royce Exe, or Boreas,^[1] was a 24-cylinder air-cooled X block sleeve valve aircraft engine intended primarily for the new Fairey Fleet Air Arm aircraft, particularly the Fairey Barracuda. The Exe was relatively powerful for its era, producing about 1,100 hp (820 kW). This is notable given the relatively small 1,300 cubic inches (22 L) displacement, the Merlin requiring 1,600 cubic inches (27 L) for approximately the same power level. The X-24 layout made this quite a compact engine.

The Exe was named after the River Exe, although Rolls-Royce later transferred the use of river names to its gas turbine engines.

Design and development

The Exe was under development in 1939, having been started in the 1930s, along with the Peregrine and Vulture. Work on the Exe was suspended in August 1939,^[2] and stopped about August 1940.^[3] Ernest Hives, head of the Rolls-Royce aero engine division, wanted to stop work on the Exe, Peregrine, and Vulture to concentrate on the Merlin and Griffon engines. An enlarged version, the Rolls-Royce Pennine, was built later in the war, but cancelled as jet engines became the company's focus.

Originally intended for the Supermarine Type 322 and Fairey Barracuda the Exe was only test flown in a Fairey Battle, the first flight taking place on 30 November 1938. This aircraft continued in use for some time as a communications aircraft where the Exe was noted to be quite reliable in service.^[4]

Applications

Fairey Barracuda (intended)
Fairey Battle (testbed)
Supermarine Type 322 (intended)

Specifications (Exe)

Data from Gunston and Lumsden.^[5]^[6]

General characteristics

Type: 24-cylinder supercharged air-cooled 90-degree X layout aircraft piston engine
Bore: 4.225 in (107.3 mm)
Stroke: 4.0 in (100 mm)
Displacement: 1,348 in³ (22.09 L)
Dry weight: 1,530 lb (690 kg)

Components

Valvetrain: Sleeve valve
Supercharger: Gear-driven centrifugal type supercharger, single stage
Fuel type: Petrol
Cooling system: Pressure air-cooled
Reduction gear: 0.358:1, left hand tractor

Performance

Power output: 1,150 hp (860 kW) at 4,200 rpm, +4.5 psi boost at sea level
Compression ratio: 8:1
Power-to-weight ratio: 0.75 hp/lb (1.23 kW/kg)

References

Notes

^ This name was dropped due to conflict with the Bristol Aeroplane Company's series of Greek mythology named engines, Lumsden 2003, p.201.
^ Lloyd 1978, p4-5.
^ Pugh 2000, p.263-265.
^ Rubbra 1990, p.148.
^ Gunston 1989, p. 142.
^ Lumsden 2003, p.201.

Bibliography

Gunston, Bill. World Encyclopaedia of Aero Engines. Cambridge, England. Patrick Stephens Limited, 1989. ISBN 1-85260-163-9
Lloyd, Ian Rolls-Royce: The Merlin at War (1978, Macmillan London) ISBN 0-333-24016-2
Lumsden, Alec. British Piston Engines and their Aircraft. Marlborough, Wiltshire: Airlife Publishing, 2003. ISBN 1-85310-294-6.
Pugh, Peter.The Magic of a Name: The Rolls-Royce Story, The first 40 Years (2000, Icon Books Cambridge) ISBN 1-84046-151-9
Rubbra, A.A. Rolls-Royce Piston Aero Engines - a designer remembers: Historical Series no 16 :Rolls-Royce Heritage Trust, 1990. ISBN 1-872922-00-7

External links

Photo of the Rolls-Royce Exe
The Exe-engined Fairey Battle (top picture) in a 1948 issue of Flight

[1] This name was dropped due to conflict with the Bristol Aeroplane Company's series of Greek mythology named engines, Lumsden 2003, p.201.

[2] Lloyd 1978, p4-5.

[3] Pugh 2000, p.263-265.

[4] Rubbra 1990, p.148.

[5] Gunston 1989, p. 142.

[6] Lumsden 2003, p.201.

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