The double-spool design keeps the tension constant as it unwinds, maintaining a steady rate of spin at the generator, producing 3 volts, the same current as if the radio had two AA batteries. Gears attached to the spindle transfer the spinning motion to a pulley that turns the generator. When the radio plays, the spring pulls itself back onto the first spindle. To wind the radio, the user turns a crank that pulls the spring onto a second spindle and coils it in the opposite direction, coiling it in a way the spring naturally resists. At rest, the spring is wound on a spindle. ![]() The Freeplay radio uses the same kind of spring that rewinds automobile seat belts - a steel strip about four inches wide and 30 feet long. He settled on a mechanism rather different from a watch spring. The biggest technical hurdle was the spring. The radio suddenly began playing, and Bayliss knew that such a device could be made practical. Spinning the axle causes the motor to become a generator, sending electricity into its wires. Such motors spin when electricity is supplied through their wires but can be run in reverse. The generator was essentially a small electric motor. Bayliss rushed to his home laboratory and wired an ordinary transistor radio to an off-the-shelf generator about the size of a 35mm film can. Bayliss says it suddenly occurred to him that the low voltage needed by transistor radios probably could be produced by a very small generator and that the generator could be turned by a metal spring wound periodically. ![]() Health education programs about the value of condoms, for example, were being broadcast on radio, but many people lacked access to electricity, even in battery form. The program explained that, because of poor mass communication, simple safe-sex information that could stop the spread of AIDS did not reach many of Africa's poorest people. The radio was developed by Trevor Bayliss, a British inventor inspired by watching a BBC television documentary on AIDS in Africa. The device has gained a small market among more affluent customers who like the idea of depending more on elbow grease than commercial power supplies. Although not widely known in this country, the radio has been available for about two years in some parts of the Third World, especially where there is no electricity and batteries are too expensive for ordinary people. About 60 turns of the handle will give you about 30 minutes of playing time. It has a built-in generator powered by a spring that you wind by hand. ![]() It's the BayGen Freeplay, a windup radio that can tune AM, FM and shortwave bands. Just turn the crank for about 20 seconds, and the radio is good for another half hour or so.
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