Originally Posted by cannonball2
... your system I can see is a larger slower turning roller and the possible use of a cent. clutch. The rest is complexity that adds weight and failure points-belts, bearings etc...
When I use the term FD, I mean Friction Drive without any other qualifications. Consequently, a FD with a centrifugal clutch and one with a movable-roller clutch are two different systems.
I mean this arrangement to be a FD, and the roller will be on a frame (not the bike frame) that is moveable.
The diagram is a top view. The purple pieces form the movable frame that pivots on the outside bearings (swinging above and below the page).
The motor will be mid-frame somewhere I've yet to decide. I haven't even picked a bike yet.
My existing ICEmotor-bike works, and it's what I'm using, but main thing I learned with its construction is that its design needs improvement. So, I want to start afresh.
I'll use the 79cc HF 4 stroke. No centrifugal clutch.
Yes, I certainly want a larger roller (perhaps around 150 mm, 6") because I want sufficient engagement to allow the braked tire to kill the engine as a precautionary feature.
Regarding simplicity, using the roller as both the clutch and a drive member is the mechanical simplification I'm using. (The belt to the roller shaft doesn't need to grow or shrink with a change in position of the roller shaft.) I reckon the additional failure rate of additional bearings will impact only trivially on reliability.
Regarding weight, the idea of using this system of moving the roller is to avoid weight on the clutch. The overall weight seem tolerable to me.