[*BCM*] Fwd: [phonography] Cycling recordists

Thomas John Vitolo tjvitolo at bu.edu
Sat Jan 7 08:39:40 EST 2006


I stumbled on this while looking up ways to
> generate power.    http://www.freelights.co.uk/   it seems to be a
> nice way to make your bike visible without making it more difficult
> to
> ride (friction and so on).  The key is the magnet tumbles past one
> of
> the magnets on the spokes and thereby creates electrical current. 
> No
> physical turbine gets cranked, which seems amazing to me not being
> much of an electrician.

It still makes it more difficult to ride.  After all, you've now got to (1) work
harder because you've added weight to your wheel and have to "lift" it, and (2)
the magnetic force of when the moving magnet approaches the generator results in
resistance.  Think of pushing a magnet toward another like magnet.  Sure, it's
not much resistance in either case, and you get the added bonus of recovering
nearly all of the force when (1) the magnets get to "fall" and (2) the generator
pushes the magnet away once it's past.

But, no machine is perfectly efficient, so there is a 100% chance that this
frictionless dynamo system makes it harder to pedal than no dynamo system at
all.  How much harder to pedal?  Probably not much.

 - stomv

P.S.  Since your cycle will have more mass with the dynamo system on, you will
face more rolling friction when you ride, it's just that the friction isn't on
the dynamo, it's between your wheels and the road.
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