Sturmey-Archer Dynohub
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The Dynohub was an early form of hub dynamo for bicycles made by the Sturmey-Archer company from the 1950s to the 1970s. The term dynohub is sometimes applied generically to bicycle hub dynamos, but, like hoover, it originates as a trademark.
The Sturmey Archer GH6 Dynohub was designed as a means of generating electrical lighting power for bicycles during the second world war. It was in production for almost four decades, first making an appearance in 1943. The standard version produced a rated output of 6V, 3W from a 20 pole ring magnet with a stator having a continuous winding. 12 and 8 volt versions were produced but were heavier and were withdrawn from production.
Rated output was reached at around 20 km/h (12mph), a rotational speed of approximately 60rpm. The name dynamo implies DC output, but as usual with bicycle dynamos (known as generators in the United States), output was alternating current.