I worked on a small Renault in the early seventies that used a air gap
clutch with electromagnets. It was an interesting affair with radio tubes
in the control box.
All kinds of devices have been designed using eddy currents including
tachs as mentioned.... even dynomometers.
Lots of new designs using old ideas. Also old ideas like perpetual
motion/zero energy loss in new designs.
Randy

"GMasterman" wrote in message
...
At a recent OTC show in Houston, SWACO, a oilfield services contractor,
was
showing off a mud centrifuge with a unique drive system. It consisted of a
flywheel with rare earth magnets mounted on it and a solid copper flywheel
opposite it. The closer the rotating magnetic flywheel gets to the copper
flywheel, the more rotational energy is transfered. With the two flywheels
close together, both would spin at the same speed. As they were seperated
the
driven flywheel would slow down, and with enough gap, completely stop. No
energy comsumed to operare as a variable speed tranny and clutch. Picture
the
implications of this in the auto industry future. Never realized that a
magnetic field would affect copper. I'm talking about a 100hp(?)motor
rotating
a 1000#(?) centrifuge bowl and rotor