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Unread 17-02-2014, 04:09
AlecS AlecS is offline
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Re: Advice About Slipping / Breaking Timing Belts

Quote:
Originally Posted by Madison View Post
The pulleys are all on the same part, though it's probably flexible enough to explain where some of the slack is coming from; but we're seeing more slack than I would've expected, even then. Tomorrow, we'll try to laser cut a piece to force the versaplanetary shaft and larger pulley to the correct center-center distance and see what that looks like.

What am I missing with respect to the maximum loading?
RS-775-12 has a stall torque of .4315 N*m and free speed of 7300 RPM. 70:1 gearbox reduction followed by a 24:42 pulley reduction is 122.5:1 overall. Stall torque is 52.86 N*m or 467.85 in*lbf. Twice that is 935.7, but that is distributed over two 9mm belts (one on each side). There's one motor/gearbox/belt per side. Sorry if that was unclear. Only one of the belts failed.

It's pretty clear that the belt failed due to tension -- but the tension we put onto the belt was the only thing we could do to prevent it from ratcheting; that's what is most frustrating.

Thanks for the insight. Hopefully chain will be a bit more forgiving in our design and we can worry about more interesting problems.
Oh you did say you had two belts, my bad, completely missed that.
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Alec S.
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MadTown Robotics Team 1323