Ellehammer, Jacob Christian Hansen

SUBJECT AREA: Aerospace

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b. 14 June 1871 South Zealand, Denmark

d. b. 20 May 1946 Copenhagen, Denmark

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Danish inventor who took out some four hundred patents for his inventions, including aircraft.

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Flying kites as a boy aroused Ellehammer's interest in aeronautics, and he developed a kite that could lift him off the ground. After completing an apprenticeship, he started his own manufacturing business, whose products included motor cycles. He experimented with model aircraft as a sideline and used his mo tor-cycle experience to build an aero engine during 1903–4. It had three cylinders radiating from the crankshaft, making it, in all probability, the world's first air-cooled radial engine. Ellehammer built his first full-size aircraft in 1905 and tested it in January 1906. It ran round a circular track, was tethered to a central mast and was unmanned. A more powerful engine was needed, and by September Ellehammer had improved his engine so that it was capable of lifting him for a tethered flight. In 1907 Ellehammer produced a new five-cylinder radial engine and installed it in the first manned tri-plane, which made a number of free-flight hops. Various wing designs were tested and during 1908–9 Ellehammer developed yet another radial engine, which had six cylinders arranged in two rows of three. Ellehammer's engines had a very good power-to-weight ratio, but his aircraft designs lacked an understanding of control; consequently, he never progressed beyond short hops in a straight line. In 1912 he built a helicopter with contra-rotating rotors that was a limited success. Ellehammer turned his attention to his other interests, but if he had concentrated on his excellent engines he might have become a major aero engine manufacturer.

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Bibliography

1931, Jeg fløj [I Flew], Copenhagen (Ellehammer's memoirs).

Further Reading

C.H.Gibbs-Smith, 1965, The Invention of the Aeroplane 1799–1909, London (contains concise information on Ellehammer's aircraft and their performance).

J.H.Parkin, 1964, Bell and Baldwin, Toronto (provides more detailed descriptions).

JDS