Re: my mountain bike
I think that is going to have to be a GEBE type engine unless you can find a way of hanging a chengine off the front of the frame and chaining it to the rear wheel...
The problem with the GEBE set up as you have the bike will be wheels - they pretty much have to be spoked standard types or nothing - Trying to shoehorn a GEBE sheave onto those wheels would be pretty hard and is more likely to cause the wheel to fail mid ride..
I do have one thought however and that is using a roller type transmission rack mount either rear or front mounted or (and this is alot more complicated) using a chain fixed to the rim in some way meshing to a toothed gear off an automatic clutch direct from a mounted engine (similar to the cyclemaster idea)- but that would be a custom self-fabbed job and not for the faint hearted.
The problem with all rollers is that of slip - if its wet you loose speed unless you have the springs set very tight - but if you do that you get a bad case of fried and worn tires when its dry unless they are adjustable.
The belt drive is probably the most efficient and is fit and forget pretty much but it will need the spoked wheels (on the upside, if you choose that you can get a rear wheel set and trued with the sheave from GEBE for a reasonable price).
I love the style of the bike though but I do worry about strength a little - vibration can take its toll.. and it would be a shame if something terminal happened.. not to mention what might happen to it in a crash
Jemma xx