Hactar wrote:

In article . com,
Pete C. wrote:

Hactar wrote:

In article . com,
Pete C. wrote:

Hactar wrote:

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.
...
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.

I'm afraid you won't find much for off the shelf slip ring assemblies,
and what there are will be $$$$. Give the small amount of power you need
to transmit, I'd consider using a rotary transformer coupling to
transmit the power as AC instead of DC.

What's a rotary transformer? I really need to minimize the "on wheel"
weight; it's especially important not to cause a torque in the wheel.

Basically just two coils of magnet wire, concentric with the rotary
axis, one mounted on the rotating part (wheel) and one on the fixed part
(chair/axle), AC voltage applied to one is coupled to the other with the
rotation of the moving part having essentially no effect on the
coupling. Also has the advantage of being non-contact and non-wear.

That sounds like it would work, if it were thin enough. I'd need a
rectifier/capacitor and voltage converter on each wheel, and an inverter
on the body. Where do I find one, or is it something I make?

You'd have to build it. Also, you wouldn't be running 120V 60Hz AC to
it, you'd be using something like 12V AC and probably a few KHz
frequency. This is similar to the setup used for waterproof non contact
charging stations as seen on some electric shavers.