design and make one of these

not sure how it is driven as there is no chain.

If you expand the information at the top of the video there's loads more detail.

Hydraulic drive apparently!!

www.eyetohand.com
Worth keeping an eye on for his progress

Shame he rushed to get the video out- as it raises question and doubt
(crank/cabling/drive etc missing in vid)

Good luck to him, hope he sorts it all out and makes a go of it

Regards
Rob

Mmmm, hydraulic drive is interesting! Looks like the way forward once efficiency problems have been overcome. Two-wheel-drive mountain bikes!

Wikipedia linky

[Edited on 16/8/09 by AdamR]

I posted my comment, a toothed belt would work and you could tension it as the frame is assembled and take the belt of and store it when it is folded. Don't get too technical or overengineered as hydraulics would need to be transmitted through the joint in the frame and involve it being oil tight as well.