Hactar expressed precisely :
I was told this might be a good place to ask.

I'm looking for a slipring or commutator to go around the axle to my
wheelchair wheels. The catches are, it needs a 1" center hole (to go
around the axle nut), nothing can break if the wheel's removed (that's
easy, just push a button) and the body's put in a car trunk, and it only
has about 10mm clearance axially. On the plus side, it only needs to
carry a hundred mA, its radial clearance is something close to two feet,
and my maximum speed is around 75 RPM. Four conductors would be nice,
but I can live with two. Does such a thing exist for a reasonable amount
of money, perhaps in the model-making or robotics communities?

I have an idea about making one (per side) out of a CD-R, some
alternator brushes, and some sheet metal, if a pre-made one can't be
found. I figure I'll put the CD part on the wheel, to keep its angular
momentum down.

Many childrens scooters come with flashing lights in the small wheels.

http://shop.kmart.com.au/wcsstore/Km...40935607-f.jpg
The lights are only on when the scooter is moving.
I have no idea how they work but I would be looking for some clues
there.
At 77 I have no use for scooters but I am always on the lookout for odd
ways of doing things as I build helpful devices dor disabled people of
all ages.

--
John G