Quote:
Originally Posted by asid61
How close is close? If you measure your belt around the pulley and it's less than the tube, then you should be okay even if it's very close.
I know 192 did a 2x2 Belt-in-tube drivetrain in 2014.
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See the spreadsheet he linked. 192 has traditionally run 22 tooth pulleys. 24 tooth pulleys have a 1.654" OD, which inside a 1.75" tube interior leaves no room for even a 0.1" drop. And you want some breathing room for the belt.
The numbers tell me 18 tooth pulleys are risky. You are definitely beyond the torque rating at stall, and would probably see ratcheting and serious wear under full forward to full reverse or other high load conditions. See page 18 of
this document. 22-24 tooth pulleys are only ~50% better, but maybe that's enough. 192 seems to have success with 22.
This may also be of interest. That's a 2"x1.5" tube but it looks like the belts are only 9mm wide and the pulley looks like 24 teeth. Looks like they get away with this by clearing away the top and bottom wall of the tube. 1625 went on to field a
similar drive (plus some sweet drop down "lobster" modules to drive sideways) for competition in 2011.