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Ounce
Type	Piston engine
National origin	United Kingdom
Manufacturer	Armstrong Siddeley
First run	1920

The Armstrong Siddeley Ounce was a small two-cylinder aero engine developed by Armstrong Siddeley in 1920. The engine was originally conceived as a test piece but ran very well and was put into production for early ultralight aircraft and use in target drones. The Ounce used two cylinders from the preceding Jaguar I radial engine.

Applications

• Bristol Babe
• 1920 redesigns of the '1917 Type Aerial Target'

Specifications (Ounce)

Data from Lumsden.

General characteristics

• Type: Two cylinder, horizontally-opposed air cooled piston engine
• Bore: 5.0 in (127 mm)
• Stroke: 5.0 in (127 mm)
• Displacement: 196 cu in (3.2 L)
• Length: 20.5 in (521 mm)
• Width: 39.5 in (1003 mm)
• Height: 24.5 in (622 mm)
• Dry weight: 170 lb (77 kg)

Components

• Valvetrain: Overhead valve
• Fuel system: Carburettor
• Cooling system: Air cooled

Performance

• Power output: 45 hp (33.5 kW) at 1,500 rpm
• Compression ratio: 5:1
• Power-to-weight ratio: 0.26 hp/lb (0.43 kW/kg)

See also

Comparable engines

• ABC Scorpion
• Aeronca E-113
• Bristol Cherub
• Walter Atom

Related lists

• List of aircraft engines

References

Notes

1. Gunston 1989, p.18.
2. Lumsden 2003, p.66.

Bibliography

• Gunston, Bill. World Encyclopedia of Aero Engines. Cambridge, England. Patrick Stephens Limited, 1989. ISBN 1-85260-163-9
• Lumsden, Alec. British Piston Engines and their Aircraft. Marlborough, Wiltshire: Airlife Publishing, 2003. ISBN 1-85310-294-6.

External links

• AS Ounce information and images at the Power House Museum, Sydney, Australia

• Armstrong Siddeley aircraft engines
• 1920s aircraft piston engines