I Informal cost analysis after using the tumbler a while concluded that it had easily paid for itself in the first year. This was based on the fact that I had probably saved 250 hours of labor and saved over $300 in abrasives such as flap discs and knotted cup brushes.
The timer is an Intermatic FF30MC 30-Minute, Spring Wound Wall Switch type, with Brushed Metal finish. My usual run time is around 20 minutes.
I made a latching tool to assist opening and closing the doors. I feel it is desirable to require this force so opening and closing is a very intentional operation and never an accidental one. I started with a straight piece of pipe and in several steps modified it to it's current shape. The socket end fits over both the handle and spring lever of the draw latch and the slot end fits over the wall of the door. The lazy S shape seems to give the best leverage.