[sanddrag]

I'm wondering if a laser machine would be able to burn out some lexan (0r acrylic) gears without melting it. It doesn't have to be super precise, just functional enough for a demo box. If not, maybe a waterjet? Do you have access to either of those? With proper indexing equipment and a gear cutter you could even cut your own gears on a mill.

I'm not totally going for the friction wheel thing. I think gears would be way cooler, even if some extra work is involved.