TechShop San Jose's
Thumler's Tumbler had a couple of issues: The center shaft that held the cover on had come loose, and it made a odd noise when running. Time for some exploratory surgery!
Take the bowl off the top. Flip the unit over, remove the four screws that hold the base on.
Turn it over again and peel the neoprene sheet off.
There it is! The shaft broke out of the base, and the motor cracked the mounting plate.
There wasn't enough clearance to weld a plate on top of or below the existing plate, so I opted to cut out the broken part and weld in a fresh piece of metal.