Dynohub
The
Dynohub was Sturmey-Archer's
hub dynamo for bicycles. The Dynohub was designed to generate electrical lighting power for bicycles during the Second World War. The initial
GH12 12-volt model was introduced in 1936 followed several years later by the
GH8. This 8-volt unit was in turn supplanted in the 1950s by the lighter-weight
GH6 6-volt version, which remained in production through the early 1980s. The term "dynohub" is sometimes
applied generically to bicycle hub dynamos, but it originates as a trademark.
The GH6 version produced a rated output of 6 V, 0.33 A (2 W) from a 20-pole ring magnet with a stator having a continuous winding. Original
headlamp bulbs are 6 V, 0.25 A (1.5 W) (e.g., CRY5) and a rear bulb of 6 V 0.04A (0.24W) (e.g., CRY8). This is different from a modern standard bicycle dynamo, though replacements can still be had.
[5] Common substitutions are the modern standard 2.4 W
headlamp bulb and a
tail lamp bulb of 0.6 W. One rider reports much more light with a 6.3 V, 0.25 A (1.6 W) type 40 bulb.
[6]
Rated output was reached at around 20 km/h (12 mph), a
rotational speed of approximately 60 rpm. The name dynamo implies
DC output, but as usual with bicycle dynamos (known as
generators in North America), output was in fact
alternating current.
Dynohubs were offered as front hubs and as rear geared hubs. The
AG was an AW three-speed rear hub with inbuilt dynamo, while the
FG was a dynamo similarly combined with an FW four-speed.
Hub generators were absent from Sturmey-Archer's product range from the 1980s until the 2006 introduction of the
X-FDD front hub, which combines a 6v, 0.4 A (2.4 W) or 0.5 A (3 W) dynamo with a 70 mm
drum brake.
[7]
