(pictures of how they work)
http://cvt.com.sapo.pt/reduce_axial_...al_sliding.htm
That's a really interesting site.

I've had some ideas about CVTs, especially when I rode a bicycle a lot,
and it's nice to see that they weren't totally crazy. I'd since
forgotten about them--thanks for (inadvertantly) reminding me. I
thought they'd be more efeccient, but I didn't think they'd be in the
~30% range.