[Thad House]

Originally Posted by Chris is me

It's really worth noting that specs are pretty conservative numbers based on thousands of hours of runtime. FRC robots run for a tiny fraction of that, hence why hundreds of teams each year run 25 chain or HTD belts without any failures. 35 chain may not be a bad choice, but I think nearly any robotics team who can keep sprockets in line with each other and chain in reasonable tension can handle #25. It's really not as finicky as people make it out to be. If you can mill exact centers, 15mm belts are a good solution; I haven't personally heard of any failures of wide belts yet.

Something else is that wheel sizes, gearing and sprocket/pulley size affects the load number dramatically. Our 2013 robot used 2 CIM's, 6 in wheels, and 22 tooth sprockets with a 12.75:1 reduction. That results is 623lbs of stall force being able to be applied to the chain. Our 2014 robot used 3 CIMs, 4 in wheels and 28 tooth sprockets with a 7.44:1 ratio. This results in 665 lbs of stall force being able to be applied. These numbers are very similar, and shows that forces are based on much more then just # of CIMs.

#25 chain is rated for about 800 lbs, so we were within spec, especially since the wheels slip before you can get close to stalling the motors.

Originally our 2014 robot used 9mm vex belts on 24 tooth pulleys, and we snapped alot of belts because the pulleys were too small and we overloaded the belts.