Gearbox problem?
 

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.

Re: Gearbox problem?
 

A few teams had this same issue.

The solution is that there is an inside and an outside to the mounting plate. Our plan was to label the plates so it was easy to tell this, but that did not get done. If the motor was mounted exactly shown on the document posted on this page, then the gears would mesh much closer together.

Some teams have responded that the gear mesh was a bit too tight when they assembled the Upgrade kit as shown on the assembly instruction document. To fix this, teams made either the 6mm stud hole larger (by 0.020") or by making the the capture bar holes larger (by 0.020"). These larger holes let the Mini-Bike motor gear move away from it's mate.

Andy B.