My Wife (Brenda) has a SSpin on her droid and we found away to make a

nice drive for it.

We used a small 24v. motor (which is available in 12v. also)

http://www.superdroidrobots.com/shop/item.asp?itemid=374&catid=7

Sorry I don't know how to do the tiny Url thing.

We used 2- 4" drive wheels (They come as a set)

We just used a longer screw and a nut between the 2 wheels.

http://www.servocity.com/html/precision_disk_wheels.html

And this .250 adapter for the motor.

http://www.servocity.com/html/set_screw_hubs.html

The hardest part was prepping the SSpin.

Her SSpin is mounted as if a kid was going to ride it.

I noticed some people mount it upside down. (I hope yours is not)

Under the SSpin there is a area where the marbles and the spacers ride

and there's a lip from the top half of the SSpin that rides on each side of the

marble bearing.

There is 4 heavier ribs on the top half that have to be cut down and this

will give you a smooth area for the drive wheel to turn the dome.

Looking at the bottom you have 4 large holes and you can use 1 of the rear holes

to insert the dome wheel/motor combo.

I made a real simple version of Atomic Pickles dome motor holders and it all

works perfectly.

On Brenda's blog you can see it working and if your interested I can get some

pics of how it fits and works.