Jacob Ellehammer

Jacob Christian Hansen Ellehammer
Born	June 14, 1871 Bakkebølle
Died	May 20, 1946 (1946-05-21) (aged 74) Copenhagen
Nationality	Danish
Education	Watchmaker, mechanic
Occupation	Engineer
Engineering career
Discipline	Aviation
Significant design	Ellehammer semi-biplane

Jacob Christian Hansen Ellehammer (June 14, 1871 – May 20, 1946) was a Danish watchmaker and inventor born in Bakkebølle, Denmark. He is remembered chiefly for his contributions to powered flight.

1914 photo of Ellehammer's coaxial helicopter hovering

Following the end of his apprenticeship as a watchmaker he moved to Copenhagen where he worked as an electronics mechanic before establishing his own company in 1898. In the beginning he produced cigarette machines, beverage machines and other electronic machinery. In 1904 he produced his first motorcycle, the Elleham motorcycle.

In 1903–1904 Jacob Ellehammer used his experience constructing motorcycles to build the world's first air-cooled radial engine, a three-cylinder engine which he used as the basis for a more powerful five-cylinder model in 1907. This was installed in his triplane and made a number of short free-flight hops as mentioned below.

In 1905, he constructed a monoplane, and in the following year a "semi-biplane". In this latter machine, he made a tethered flight on 12 September 1906.

1935 photo of Ellehammer's disc-rotor compound helicopter model

Ellehammer's later inventions included a successful triplane and helicopter. His helicopter was a coaxial machine. A famous photo shows it hovering in 1914, though there is no evidence that it was successful in achieving translational flight. Ellehammer later studied a disc-rotor configuration - a compound helicopter with coaxial blades that extended from the hub for hover, and retracted for high speed vertical flight. Although a wind tunnel model was constructed, there's no evidence that anything more was studied.

In 1986, Ellehammer was inducted into the International Air & Space Hall of Fame at the San Diego Air & Space Museum.

See also

• Early flying machines

References

• The Early Years (Aviation Century), 2003, Ron Dick, Amanda Wright Lane, Dan Patterson, Boston Mills Press, ISBN 1-55046-407-8
• Wings: A History of Aviation from Kites to the Space Age, 2004, Tom D. Crouch, W. W. Norton & Company, ISBN 0-393-32620-9
• 100 Years of Flight: A Chronology of Aerospace History, 1903-2003 (Library of Flight Series), 2003, Frank H. Winter, F. Robert Van Der Linden, AIAA, ISBN 1-56347-562-6

External links

• Ellehammer A/S founded by J.C.H. Ellehammer in 1904 - Today producing ejectors and pumpsystems for the maritime industry