Quote:
Originally Posted by asid61
From what I've read, you should put in tensioners regardless because of the tolerances required for belt engagement. Adding a cam tensioner is less than 0.1lbs anyway, so there's no reason not to have one.
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If you put in tensioners, you could mess it up. If you don't, you can't. A very minor tradeoff, I know, but it's worth noting. It's surprisingly easy to overtension a belt.
You absolutely definitely do
not need tensioners for a belt driven WCD, provided you can machine bearing holes in your drive tube with reasonably good accuracy. Our past three years of robots will attest to that.
Quote:
Originally Posted by M. Mellott
I know that this system uses two 3-CIM transmissions but with only 2 motors each. Do you think that with the back-and-forth, high impact motion that a typical FIRST drive train will go through, the 9mm belts might not be strong enough? Would 15mm belts be a better choice for a drive train, especially for those who want to add on that third motor to each side?
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We have had poor experiences with 9mm wide belts in the drivetrain using pulleys about this small. Last year several teams had belt failures doing this, though manufacturing issues at Vex may have contributed in addition to undersizing.
To me there's basically no benefit to not going 15mm, and the reliability is *much* higher. Even if it does work, why would you want to gamble on the edge of a safety factor with your drivetrain? All of our 15mm setups have been rock solid.
By the way, a good calculator for belt center distance is here.
http://www.wcproducts.net/how-to-belts/ We have had good results with zero center distance added. Your mileage may vary based on your tolerances.