The ABC Dragonfly was a British radial engine developed towards the end of the 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]
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 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), the Nieuport Nighthawk, and the Siddeley Siskin. Of this order 1,147 engines were built, but only nine or ten actually flew.[4]
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, causing severe vibration, a little known condition at the time.[2] 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 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.
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. ISBN1-85170-347-0.
Gunston, Bill. World Encyclopedia of Aero Engines. London: Guild Publishing, 1986.
Lumsden, Alec. British Piston Engines and their Aircraft. Marlborough, Wiltshire: Airlife Publishing, 2003. ISBN1-85310-294-6.
January 05, 2023
dragonfly, british, radial, engine, developed, towards, first, world, expected, deliver, excellent, performance, time, ordered, very, large, numbers, proved, however, extremely, unreliable, abandoned, when, faults, were, unable, corrected, dragonfly, science, . The ABC Dragonfly was a British radial engine developed towards the end of the 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 DragonflyABC Dragonfly at the Science Museum London Type Radial aero engineNational origin United KingdomManufacturer ABC MotorsDesigner Granville BradshawFirst run 1920Number built 1 147 Contents 1 Design and development 2 Variants 3 Applications 4 Specifications Dragonfly IA 4 1 General characteristics 4 2 Components 4 3 Performance 5 See also 6 References 6 1 Notes 6 2 BibliographyDesign and development EditABC 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 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 the Nieuport Nighthawk and the Siddeley Siskin Of this order 1 147 engines were built but only nine or ten actually flew 4 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 causing severe vibration a little known condition at the time 2 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 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 EditDragonfly I 1918 320 hp 239 kW Dragonfly IA 360 hp 268 kW revised pistons and cylinder heads revised oil system Applications EditArmstrong Whitworth Ara Austin Greyhound Avro 533 Manchester BAT Basilisk Boulton Paul Bourges Bristol Badger de Havilland DH 11 Oxford Nieuport Nighthawk Nieuport London Siddeley Siskin Sopwith Bulldog Sopwith Cobham Sopwith Rainbow Sopwith Dragon Sopwith Snark Sopwith Snapper Westland WeaselSpecifications Dragonfly IA EditData from Jane s Fighting Aircraft of World War I 5 General characteristics Type nine cylinder air cooled radial engine Bore 5 in 139 7 mm Stroke 6 in 165 1 mm Displacement 1 389 86 in 22 78 L 2 Dry weight 600 lb 273 kg Components Valvetrain 3 overhead valves 2 inlet and 1 outlet per cylinder Fuel system Twin carburettors Oil system 2 oil pumps Cooling system Air cooledPerformance Power output 340 hp 254 kW at 1 650 rpm Specific power 0 24 hp in 11 kW L Specific fuel consumption 0 56 pints per bhp hour 0 32 L kW Oil consumption 7 pints per hour 3 97 L hr Power to weight ratio 0 56 hp lb 0 93 kW kg See also EditLawrance J 1 contemporary American nine cylinder radial 1921 direct ancestor of the Wright Whirlwind series of golden age American aviation radials References Edit Wikimedia Commons has media related to ABC Dragonfly Notes Edit Lumsden 2003 p 52 a b c d e Gunston 1986 p 8 a b Bruce 1974 p 292 Lumsden 2003 p 53 Grey 1990 p 256 Bibliography Edit 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 ISBN 1 85170 347 0 Gunston Bill World Encyclopedia of Aero Engines London Guild Publishing 1986 Lumsden Alec British Piston Engines and their Aircraft Marlborough Wiltshire Airlife Publishing 2003 ISBN 1 85310 294 6 Retrieved from https en wikipedia org w index php title ABC Dragonfly amp oldid 1087947631, wikipedia, wiki, book, books, library,
