Quote:
Originally Posted by Mike Marandola
I agree that chain may be better in this design, but what about the AM14U? It has no active tensioning.
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My statement is colored by our experience, which was with small pulleys (22T I think) with 9mm wide 5mm GT3 belts. We know that we are running these belts out of spec, and it shows because we do have belts break. Previous years we used the same set of belts until practice for off-seasons, but last year we went through some belts during season practice due we think to the higher CG design. I would not feel comfortable running our current setup without a tension. For this year, we are looking at moving to 15mm belts so we are not as under the rated specs (we are currently running ~2X the rated load for the belts based on my memory of the calculations we did).
I see that the AM14U runs 42T pulleys and 15mm belts. This is should be 3X better on the loading than what we are doing (not including the rating difference of HTD vs GT3), but without running the life numbers, I still bet the belts are still close to the rating for this application. If you want to run belts without tensioners, I would follow with this pattern (looking back at your pictures, it appears like this is what you are doing).
Based on quick calculations from AM's listed weights, it looks like a AM14U has under 0.4lb of belts, and would require about 1lb of chain. I don't see that as a huge weight difference, particularly to pay for drivetrain reliability. Last year I saw a few WCD that chose to run belts with small pulleys, and were running competitions without wheels powered because the belts broke and it is very difficult to replace the belts. My opinion is that if you don't have a good plan for how to change a belt mid competition if it breaks (and preferably a way to tension the belts properly to help keep them from breaking), then you are probably better off with chain. This doesn't mean belts aren't working for teams, I just caution the mass movement to put belt drive trains.