Armstrong Siddeley Ounce

The Armstrong Siddeley Ounce was a small two-cylinder aero engine developed by Armstrong Siddeley in 1920.[1] 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.

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


Specifications (Ounce)

Data from Lumsden.[2]

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)


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


See also

Comparable engines

Related lists



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


  • 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.
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