[MattB703]

Nice design concept. I think it is great that you are looking at different solutions. We all need to do some of that to get progress.

I have a couple of comments/critiques based on your sketch that I hope will be helpful;

1. You mentioned using timing belts. That usually means cogged or toothed belts. Is that what you intended? One potential problem is that you have your drive pulley contacting the outside surface of the belt while your wheel pulleys contact the inside surface of the belt. With this kind of arrangement you would need to use a belt that is cogged on both surfaces.

2. Your drive pulley is pretty small. You will lose a lot of efficiency trying to drive a belt around a radius that small.

3. This one is a little complicated. A cogged belt is like a chain. It has discreet positions that it contacts at (IE. if the belt is held still you can turn the pulley 1 tooth but not 1/2 of a tooth) The way your design is now you have the center wheel pulley contacting the belt in 2 discontinuous positions. Let's say that the teeth on the bottom of the middle pulley are meshed with the belt. Now we will trace along the belt around the drive pulley and the back pulley and get back to the contact point between the belt and the top of the middle pulley. What is the chance that the belt teeth will be "exactly" lined up with the pulley teeth?

Don't give up. I believe that high strength timing belts are quite viable for FIRST robot drive-trains (I haven't convinced my team yet).

Good luck.

Matt B

ps
here is a concept I have been batting around my head. It is very far from finished, but maybe it will start some thoughts.
[IMG]belt drive system.jpg[/IMG]