Hub dynamo
From Wikipedia, the free encyclopedia
A hub dynamo is a small electrical generator built into the hub of a bicycle wheel to power lights. Modern hub dynamos are regulated to 6V 3W, although the best will drive 0.5A at up to 12V.
The market was largely pioneered by Sturmey-Archer with their Dynohub product of the 1950s-1970s, which competed effectively with contemporary sidewall (bottle) and (later) bottom-bracket units. The Sturmey product was heavy, having a steel case, and like all bicycle dynamos of the time tended to overdrive the lamps at high speeds. Modern hub dynamos are greatly more sophisticated. Their electrical design is largely self-regulating, and lamp failure due to overvolting is now rare.
Shimano make a variety of hub dynamos under the Nexus brand. These are regarded as sound value, being considerably cheaper than the Schmidt Original Nabendynamo (SON), which is generally regarded as the best on the market, but which generates more drag. The Shimano units come with an automatic light-sensitive switch. The SON can be used to power two 6V lamps in series at speeds above about 12mph, and Schmidt manufacture lamps designed to facilitate this. These lamps have optics based on the Bisy FL, a very highly regarded light for road use.
