On May 5, 8:30*am, (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. *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.

--
-eben * * * * *royalty.mine.nu:81
* * *If you need someone to blame
* * *Throw a rock in the air
* * *You'll hit someone guilty -- U2, _Zooropa_, "Dirty Day"

On May 5, 8:30*am, (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. *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.

--
-eben * * * * *royalty.mine.nu:81
* * *If you need someone to blame
* * *Throw a rock in the air
* * *You'll hit someone guilty -- U2, _Zooropa_, "Dirty Day"

If you have pneumatic tires and you can dismount the rims from the
spokes you can make up little insulators to fit around the spokes to
electrically isolate the rim from the spokes. Now all you would have
to do is make a spring loaded brush to contact the rim and one to make
contact with the hub and then you would be in business. (Just stay out
of deep puddles of salt water) one side of the lighting could then be
attached to any spoke, and you could tun a thin strip of copper
through the valve stem hole and make that your second connection.

I think if you went this way it would be best to do one spoke at a
time and that way your wheel would not get too far out of whack as you
can re-tighten one at a time. Alternatively you could just take a
spare set of rims to a bike shop and let the wizards do it and true
the wheels. (Probably better than they come from the factory.)

Of course if the rims are anodized aluminum that might not conduct
very well and you would have to get below the anodizing for it to
work.

How much space is there between the spokes at the hub? If you had
enough room you could slip a soft battery case using either AA or C
cells that were sewn into a strap that could be fastened around the
inside hub with Velcro. Out of this a small switch, plug for the
lights and and a charging jack would come out to hook everything up.
You might also build in the switch that could detect motion and if
static for more than a minute or horizontal it would shut off. Or you
could mount the batteries parallel with the spokes fastened between
plastic disks. What I am thinking about here is two flexible plastic
disks 6 to 10 inches in diameter. Each disk would have a hole in it
the same size as the wheel hub and a slit from the hole to the outside
edge. The batteries could be attached with zip ties through slits in
the plastic and then you could feed one side of the slit in between
the spokes and wind it around so that it would be between the spokes.
A couple more zip ties to fasten this assembly to the spokes and you
are in business.

I like the plastic disk idea the best as it would be cheap and easy to
make. You might skip the switch altogether and just use a plug that
you could either plug your lights into or unplug the lights to shut it
off or to plug in the charger.

Good luck with the project.

Roger Shoaf