[philso]

This past year, we used #25 chain to link the motors to the ball shooter wheel. We found that some of the sprockets that appeared to have irregular/non-standard tooth pitch. The large (28-32 tooth range) and small (10-16 tooth) sprockets were aligned so that they were co-planar. When rotated slowly, by hand, the chain can be seen to "climb" on top of one of the teeth of the large sprocket. This would always occur at the same spot on the sprocket regardless of which part of the chain was wrapped around it. We did not get significant wear on the sprockets or chain stretch. All the sprockets we had trouble with were stamped from sheet aluminum. On some of them, we noticed teeth that had "notches" in them, when new. It looked like the tooth pattern was "wrapped" around a circle that was slightly too large. We had to file the notch away to make the chain seat properly around that tooth.

I posted about this problem on a thread about #25 chain earlier this year. I seem to recall that some other teams ha no problems and some had similar problems and that it may be dependent on the supplier or even the batch of the sprockets.

Phil