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Unread 29-08-2012, 18:38
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AKA: Scott Meredith
FRC #5895 (Peddie School Robotics)
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Re: pic: 2012 frc971 transmission

Quote:
Originally Posted by Jared341 View Post
Having a number of teeth that is evenly divisible by 3 lets you hold a pulley with a standard 3-jaw chuck more easily, just in case you want to do something to the bore.
The tentative CAD design for now has us running a 6WD Franken-WCD with the two 15mm belts running inside a 2"x2"x0.125" tube. Not really ideal from a maintenance standpoint, but I'm hoping the belts will reliable enough.

I'm also fond of the divisible by 3 trick, but I think the 18T is the minimum Gates recommends for the 5mm profile, and bigger pulleys have higher load capacity. The 20T is about the biggest pulley size that fits comfortably inside the side rail tube, accounting for the center drop. The next pulley divisible by 3 is the 24T, which is too big. Setting up the 4-jaw isn't too big of a hassle, but I would probably just make a fixture plate for 8 pulleys, probe the existing bores and have the mill drill the bores to 0.5" before broaching them.
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