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Originally Posted by sanddrag
I'm not sure how or why you broke your chains but we ran a 6 motor 2 speed with #25 13T sprockets without a problem. While you are correct in saying you can easily exceed the working load, the breaking point is over 1000lbs. Also, it is not about the force the motors produce, it is about the force the wheels can hold on the floor. But yes, larger is safer.
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I think a lot of it had to do with the style of play in 2003, versus this year. You mentioned elsewhere that your 2005 robot didn't have much pushing and shoving to do; by contrast, there were plenty of abrupt starts and stops in the 2003 game, not to mention outright collisions, where closing speeds could top 20 ft/s. Those represent shock loads not accounted-for in the 1050 lbf
static breaking load (actually, for cheap #25 chain, it can be as low as 780 lbf, per the ANSI spec.). Add to this the fact that the three-motor transmissions would accelerate the robot very quickly, and reverse direction just as abruptly, and it's clear that the chains were doomed. But even with a much more relaxed driving style, and better chain tensioners than we had in 2003, 5.3 times the working load doesn't seem too safe.