ABC Dragon Fly Mk II, 320 hp, 9-cylinder British WWI aero engine, 1919
Object No. B2538
This is a Dragon Fly Mk II British WWI aero engine designed in England by ABC Motors Ltd and made by the Sheffield Simplex Motor Works at Tinsley, Sheffield, in 1919. More than 11,000 Dragonfly engines were ordered by the authorities to power British aircraft in World War I from seventeen manufacturers who were to produce the engines under licence from ABC Motors Ltd. A few were flown in aircraft but were close to disintegration after only a few hours running. The engine was not a success as it developed insufficient power, overheated and vibrated badly. The vibration was attributed to coincidence of the running speed with the critical torsional oscillation frequency of the crankshaft. This phenomenon had not been fully recognised at the time and helped focus attention on an important aspect of radial engine development. After only 1,147 engines had been delivered, the balance of the order for the Dragon Fly Mk 11's was cancelled due to continuing problems with its performance and the end of the war. The aircraft engine is part of the Museum's Barraclough Collection. Sir Henry Barraclough was Professor of Mechanical Engineering at the University of Sydney and was interested in military engineering. He made trips to Europe to acquire stationary engines for the University, and several rare and significant examples have been preserved by the Museum since they became outdated for teaching purposes. During World War I Barraclough supervised a large contingent of Australian ammunition workers in Britain, and at the end of the war he had the foresight to acquire a group of aero engines made in several countries that had been parties to the conflict. This group, which includes this Dragonfly, was later donated to the Museum and is significant as a record of the diversity of engine designs in the early days of powered flight. Prepared by N.L. Svensson July 2006, edited by Judith Campbell, MAAS volunteer, March 2017
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Summary
Object Statement
Aircraft engine, Dragon Fly Mk II, WWI, single-row, radial, air cooled, nine cylinder, 320 hp, 1750 rpm, steel, designed by ABC Motors Ltd, made under licence by Sheffield Simplex Motor Works Ltd, Tinsley, Sheffield, England, 1919
Physical Description
The Dragonfly aero engine comprises a nine-cylinder, single-row, air-cooled, radial engine designed to provide 320 hp at 1750 rpm. The cylinder assemblage was fixed relative to the aircraft fuselage while the propeller rotated with the crankshaft. Cam-driven push rods protruded from the crankcase in the front of the engine and actuated the inlet and exhaust valves in the cylinder head through rocker levers. Each cylinder has one large inlet valve and two smaller exhaust valves. The spring loaded inlet valve rod passed through the mixture transfer pipes at the back of the engine. The spiral spring-loaded rocker arm for the exhaust valves acts on a cross piece which connects with the valve rods to either side of each cylinder head. Exhaust pipes joined to the ports conveyed the products of combustion through the engine cowling. The cylinders are steel forgings with integral heads and the cooling fins are coated with copper in an attempt to improve cooling. The pistons are of aluminium alloy. Two Claudel-Hobson H.C.8 carburettors and two Thompson Binnel Magnetos (Type AK9 Nos 418/420, made in Birmingham) are fitted. The magnetos fired two spark plugs mounted on the side of each cylinder. As in all radial engines, one of the connecting rods connects with the crankshaft in a conventional manner. This rod is designated the 'master rod' and other connecting rods articulate with it. The engine operated on the four-stroke cycle where the air was first drawn through a carburettor then through a circular manifold to the engine cylinders. Ignition occurred in alternate cylinders during each engine revolution. Specifications Height: 1240 mm Width: 1240 mm Depth: 1215 mm Cylinder diameter: 139.7 mm Piston stroke: 165.1 mm Weight: 299 kg Compression ratio: 4.42:1 Engine plate details: ABC Engine Type: Dragonfly Mk II No. 5000 Manufactured by Sheffield Simplex Motor Works Tinsley, Sheffield, England Previously L734
DIMENSIONS
Height
1300 mm
Depth
900 mm
SOURCE
Credit Line
Presented by the University of Sydney, 1983
Acquisition Date
16 August 1983
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