| Dragonfly | |
|---|---|
| ABC Dragonfly at the Science Museum (London) | |
| Type | Radial aero engine |
| National origin | England |
| Manufacturer | ABC Motors Limited |
| Designed by | Granville Bradshaw |
| First run | 1920 |
| Number built | 1,147 |
The ABC Dragonfly was a British radial engine developed towards the end of First World War. It was expected to deliver excellent performance for the time and was ordered in very large numbers. It proved, however, to be extremely unreliable and was abandoned when its faults were unable to be corrected.[1]
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ABC Motors was founded in 1911 by Granville Bradshaw, who was also the company's chief designer. In 1917, after initial promising tests of the ABC Wasp air-cooled radial, Bradshaw produced a design for a larger and more powerful engine, the nine-cylinder Dragonfly.[2] The engine was simple and easy to produce, and was predicted to give 340 hp (254 kW) for a weight of 600 lb (273 kg).[2] One distinctive feature was the use of copper-plated cooling fins, which were claimed by Bradshaw to be so effective that water would not boil on the surface of the radiators.[3]
On the basis of the promised performance, Sir William Weir, the Director of Aeronautical Supplies, made the decision to place large orders for the Dragonfly,[2] with 11,500 engines having been ordered from 13 suppliers by June 1918.[3] It was planned that a large proportion of RAF aircraft would be powered by the Dragonfly in 1919. Types designed to be powered by the Dragonfly included the Sopwith Dragon (a derivative of the existing Snipe), the Nieuport Nighthawk, and the Siddeley Siskin. Of this order 1,147 engines were built but only nine or ten actually flew.[4]
Testing showed severe problems with the much vaunted engine. It was subject to extreme overheating, the copper-plated cooling fins proving useless; showed much poorer fuel consumption than expected; and suffered severe vibration, running at the resonance frequency of the crankshaft.[2] These problems proved unsolvable, and the Dragonfly was eventually abandoned.
Data from Jane's Fighting Aircraft of World War I [5]
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