Tank tread bumpers?

[MaGiC_PiKaChU]

Originally Posted by AndyBare

Not necessarily, you're mixing two rules together.. As long as you have a rigid surface in the same plane as the treads, and your bumpers covered at least 8 inches of each corner, you'd be in compliance. An example would be if the bumper was fastened to 2 L brackets attached to some 80-20.

R19 ROBOTS are required to use BUMPERS to protect all outside corners of the FRAME PERIMETER. For adequate protection, at least 8 in. of BUMPER must be placed on each side of each outside corner...
and
R21 section G. must attach to the FRAME PERIMETER of the ROBOT with a rigid fastening system to form a tight, robust connection to the main structure/frame

that's right but your drawings above put the bumpers over the threads. The plywood backing have to start beyond the threads