When heading off on a lengthy bike tour, the weight of equipment carried is a big factor to consider. Obviously the lighter your load is, the easier a time you will have of it. Installing a dynamo hub eradicates the need to carry batteries for your bike lights and even lets you charge your mobile phone or GPS from electricity you yourself have generated whilst cycling. Although the amount of electricity generated is fairly small, dynamo hubs provide more than enough power to keep your bike well lit at all times, and a special adapter means you can put the extra power to good use as well.
The very first tyre-powered dynamo lamp for a bicycle was pioneered by Sturmey-Archer in 1934. This revolutionary product, called the Dynolamp, featured a dynamo, lamp and switch in one complete unit that fitted onto the front wheel and sat just in front of the steering column. For over forty years this model was really the only viable option on the market for those who wished to cycle at night without using battery operated lighting. However, it was unwieldy and heavy, and was discontinued in the 1980’s. Since then many companies have competed to design smaller, lighter yet more efficient dynamo hubs. Today, cyclists can purchase hubs that are fitted inside the wheel rims and cause very little drag.
How Dynamos Work
Dynamos use magnetic power to convert the power generated by the turning of a wheel into electrical power. They consist of a number of permanent magnets with a copper coil that rotates inside their poles. When the mechanical rotation (wheel turning) causes the wire to turn, it varies the magnetic flux, which in turn creates an electric field. This then drives charge carriers through the coil, creating an electrical current which can be fed into whatever device it is designed to power. A typical dynamo will produce around 6v of power when the cyclist travels at 10mph.
The New Generation
Previously, dynamo hubs were not widely used amongst serious cyclists for three main reasons: one; they cause drag which slows you down; two; they are very noisy and three; the lights go out as soon as you stop pedalling. With the new generation of dynamo hubs, these problems have been all but eliminated. The new hubs are tiny, fit inside your wheel rims and are completely silent. The drag effect cannot yet be eradicated completely, but it is virtually unnoticeable unless you are a professional road racer. The lights have additional LEDs which store up unused power and will remain lit for around five minutes while standing. The one downside to the new hubs is that you do have to have your wheel rebuilt to fit them, but next time you do, think about getting some popped in.
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