The ABC Dragonfly was a British

radial engine The radial engine is a reciprocating type internal combustion engine configuration in which the cylinders "radiate" outward from a central crankcase like the spokes of a wheel. It resembles a stylized star when viewed from the front, and is ...

developed towards the end of the

First World War World War I (28 July 1914 11 November 1918), often abbreviated as WWI, was List of wars and anthropogenic disasters by death toll, one of the deadliest global conflicts in history. Belligerents included much of Europe, the Russian Empire, ...

. 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.

Design and development

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. 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). One distinctive feature was the use of

copper Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pink ...

-plated cooling fins, which were claimed by Bradshaw to be so effective that water would not boil on the surface of the radiators.Bruce 1974, p.292 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, with 11,500 engines having been ordered from 13 suppliers by June 1918. It was planned that the bulk of RAF aircraft would be powered by the Dragonfly in 1919. Types designed to be powered by the big nine cylinder included the Sopwith Dragon (a derivative of the existing

Snipe A snipe is any of about 26 wading bird species in three genera in the family Scolopacidae. They are characterized by a very long, slender bill, eyes placed high on the head, and cryptic/ camouflaging plumage. The '' Gallinago'' snipes have ...

), the

Nieuport Nighthawk The Nieuport Nighthawk was a British fighter aircraft developed by the Nieuport & General Aircraft company for the Royal Air Force towards the end of the First World War. Although ordered into production before the aircraft first flew, it did ...

, and the Siddeley Siskin. Of this order 1,147 engines were built, but only nine or ten actually flew.Lumsden 2003, p.53. The engine was described in brief by aviation journalist Bill Gunston in his book, 'Plane Speaking' in the chapter headed, 'Cancel the Others...' In this he suggested that Bradshaw had proved to be a better salesman than a designer, and had proved non-committal when asked about initial testing which was ultimately to reveal severe problems with the much-vaunted engine. Already 30 kg over its designed weight as built, Dragonfly was subject to severe overheating. Gunston referred to it as the worst cooled aero engine ever made. The copper-plated cooling fins proved useless; the cylinder heads tended to glow a dull red at operational speeds, and in extreme cases caused heat damage and even charring to the propeller. Developed power fell far short of estimates even when the engine was run at 15 percent over-speed (producing only 315 hp ) and it showed much poorer fuel consumption than expected. Attempts to improve cooling with cylinder redesign were marginally successful, but the death blow fell when it was realized that the engine was designed to run at the torsional resonance frequency of its own

crankshaft A crankshaft is a mechanical component used in a piston engine to convert the reciprocating motion into rotational motion. The crankshaft is a rotating shaft containing one or more crankpins, that are driven by the pistons via the connecti ...

, causing severe vibration, a little known condition at the time. These problems proved unsolvable, resulting in an absurdly low service life (around 30 to 35 hours per engine), and the Dragonfly was eventually abandoned. Gunston's observations suggested that it had been as well that the

Armistice An armistice is a formal agreement of warring parties to stop fighting. It is not necessarily the end of a war, as it may constitute only a cessation of hostilities while an attempt is made to negotiate a lasting peace. It is derived from the ...

had been signed in 1918, as the only other aero engine still in production at that time was the Rolls-Royce Eagle; all other types having been cancelled in favour of the untested Dragonfly.

Variants

;Dragonfly I :1918, 320 hp (239 kW) ;Dragonfly IA :360 hp (268 kW), revised pistons and cylinder heads, revised oil system.

Applications

Armstrong Whitworth Ara The Armstrong Whitworth Ara was an unsuccessful British single-seat biplane fighter aircraft of the First World War built by Armstrong Whitworth. Design and development In early 1918, the British Air Ministry wrote RAF Specification Type 1 f ...

Austin Greyhound The Austin Greyhound was a British two-seat biplane fighter aircraft of World War I built by car manufacturer Austin. Owing to the end of the War and an unreliable engine, it was unsuccessful, only three being built. Development and design I ...

Avro 533 Manchester The Avro 533 Manchester was a First World War-era twin-engine biplane photo-reconnaissance and bomber aircraft designed and manufactured by Avro. Design and development Designed as a twin-engine bomber and photo-reconnaissance aircraft, the ...

BAT Basilisk The BAT F.K.25 Basilisk was a prototype British fighter aircraft of the First World War. A single engined biplane intended to meet a requirement to replace the Sopwith Snipe, the Basilisk was unsuccessful, only three being built. Development an ...

Boulton Paul Bourges The Boulton & Paul P.7 Bourges was a prototype British twin-engined biplane day bomber built by Boulton & Paul to replace the Airco DH.10 Amiens. Despite demonstrating excellent performance and manoeuvrability, only three prototypes were buil ...

* Bristol Badger * de Havilland DH.11 Oxford *

Nieuport London The Nieuport London was a British night bomber aircraft designed in the First World War. A twin-engined triplane, the London was dogged by the unavailability and unreliability of its engines, and did not fly until 1920. Only two were built. De ...

* Siddeley Siskin *

Sopwith Bulldog The Sopwith 2FR.2 Bulldog was a prototype British two-seat fighter of the First World War. A single-engined biplane, the Bulldog was a fighter/reconnaissance aircraft intended to replace the Bristol F.2 Fighter, but was unsuccessful, with no r ...

* Sopwith Cobham * Sopwith Rainbow * Sopwith Dragon *

Sopwith Snark The Sopwith Snark was a British prototype fighter aircraft designed and built towards the end of the First World War to replace the RAF's Sopwith Snipes. A single engined triplane, the Snark did not fly until after the end of the war, only ...

Sopwith Snapper The Sopwith Snapper was a prototype British fighter aircraft of the First World War. A single-engined biplane designed by the Sopwith Aviation Company to replace the Sopwith Snipe fighter, it first flew after the end of the war, but did not ...

* Westland Weasel

Specifications (Dragonfly IA)

References

Notes

Bibliography

* Bruce, J.M. "Sopwith Snipe...:...the RAF's First Fighter. (Part 2). " '' Air Enthusiast International'' Volume 6 Number 6, June 1974. Bromley, UK: Fine Scroll. * Grey, C.G. (ed.). ''Jane's Fighting Aircraft of World War I''. London, Studio, 1990. . * Gunston, Bill. ''World Encyclopedia of Aero Engines''. London: Guild Publishing, 1986. * Lumsden, Alec. ''British Piston Engines and their Aircraft''. Marlborough, Wiltshire: Airlife Publishing, 2003. . {{DEFAULTSORT:ABC Dragonfly 1910s aircraft piston engines

Dragonfly A dragonfly is a flying insect belonging to the infraorder Anisoptera below the order Odonata. About 3,000 extant species of true dragonfly are known. Most are tropical, with fewer species in temperate regions. Loss of wetland habitat thre ...

Aircraft air-cooled radial piston engines