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 one of the deadliest global conflicts in history. Belligerents included much of Europe, the Russian Empire, the United States, and the Ottoman Empire, with fig ...

. 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 ABC Motors Limited ("All British (Engine) Company") of Hersham, Surrey, England was a manufacturer of cars, aircraft, motor scooters, and engines for road and air. Established by Ronald Charteris in Hersham, Surrey in 1912, its chief designe ...

was founded in 1911 by

Granville Bradshaw Granville Eastwood Bradshaw OBE, AFRAeS (1887–1969) was an English engineer and inventor who designed motorcycle, auto, and aero-engines. History Bradshaw was born in Preston, Lancashire in 1887 as the son of William and Annie Bradshaw. His ...

, who was also the company's chief designer. In 1917, after initial promising tests of the

ABC Wasp The ABC Wasp was an experimental 170 hp (127 kW) seven-cylinder radial engine designed by the noted British engineer Granville Bradshaw, and primarily built by ABC Motors, ABC Motors Limited. An order for twelve experimental 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 pinkish ...

-plated

cooling fin In the study of heat transfer, fins are surfaces that extend from an object to increase the rate of heat transfer to or from the environment by increasing convection. The amount of conduction, convection, or radiation of an object determines the ...

s, 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 The Royal Air Force (RAF) is the United Kingdom's air and space force. It was formed towards the end of the First World War on 1 April 1918, becoming the first independent air force in the world, by regrouping the Royal Flying Corps (RFC) an ...

aircraft would be powered by the Dragonfly in 1919. Types designed to be powered by the big nine cylinder included the

Sopwith Dragon The Sopwith Dragon was a British single-seat fighter biplane developed from the Sopwith Snipe. Design and development In April 1918, the sixth Snipe prototype was fitted with a 320 hp (239 kW) ABC Dragonfly I radial engine.Mason 19 ...

(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 a n ...

), 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 di ...

, 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 Bill Gunston (1 March 1927 – 1 June 2013) was a British aviation and military author. He flew with Britain's Royal Air Force from 1945 to 1948, and after pilot training became a flying instructor. He spent most of his adult life doing research ...

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 Resonance describes the phenomenon of increased amplitude that occurs when the frequency of an applied periodic force (or a Fourier component of it) is equal or close to a natural frequency of the system on which it acts. When an oscillati ...

of its own crankshaft, 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 The Rolls-Royce Eagle was the first aircraft engine to be developed by Rolls-Royce Limited. Introduced in 1915 to meet British military requirements during World War I, it was used to power the Handley Page Type O bombers and a number of o ...

; 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 * Austin Greyhound * Avro 533 Manchester * BAT Basilisk * Boulton Paul Bourges * Bristol Badger *

de Havilland DH.11 Oxford The Airco DH.11 Oxford (later de Havilland) was a British twin-engined biplane bomber which was designed to replace the earlier Airco DH.10 Amiens. It was designed to use the unsuccessful ABC Dragonfly engine and was abandoned after the first ...

* Nieuport London * Siddeley Siskin * Sopwith Bulldog * Sopwith Cobham * Sopwith Rainbow *

* Sopwith Snark *

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 en ...

* 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 threate ...

Aircraft air-cooled radial piston engines