Gearbox problem?

[Kevin Ray]

Has anyone else had a problem with gear alignment when using the AndyMark modification enabling the large and small CIM's to be mated into the same gearbox? We completed the drive train weeks ago (Everything was to spec and ran well for the first few hours). Last week, however, we noticed a clanging from the gearboxes and looked into the "viewing hole" and noticed that the large CIM gear was barely touching its mate. There was no wallowing of any holes--so we can't explain why there's a space. Panic hit because the whole bot is built around the gearbox. We did pull it apart and found that we could pivot the large CIM on the 6mm bolt over nearly 1/4 inch (at the two top mounting bracket holes) to more fully engage the mating 50 tooth gear.
Oh, for those who want to know how we corrected the problem, we drilled through the gearbox plate and into the mounting plate on the large CIM and tapped the hole. We then realigned the capture bar onto the motor mounting plate and drilled new holes. Problem solved

It now hums when it runs and hasn't moved at all since.

BTW we had no problems until we stressed the drivetrain under extreme conditions. Thankfully it was discovered early and not at the competition.