[asid61]

Thank you for all the advice!

On bevel gear meshing, I'm using the 12 pitch 15 tooth miter gears from Vex, so I thought that they might be okay with 0.01" tolerances. Your experiences tell otherwise, so I'll design a non-coaxial version as well.

Thank you Tyler for the advice. That's exactly what Iw as looking for here.
Thrust loads from the miter gears are acting on the bearings, but the bearings face outwards such that the flange side of the miter gear is taking the loads.

Box deformation was something I though would be minimized by the use of 1/8" tubing over 1/16", but I want to test the deformation first before upgrading to 3/16" wall or 1/4" wall tubing. Perhaps the lightening on yours affected it in unforseen ways.

The bottom module can be made into 1/4" wall tubing with hardly any effects, so I'll do that.

The weight is low because I'm used to optimizing weight in my designs; as a result I have thinner wall tubing here. If this was more than 9lbs, I would have scrapped it. That's just too much, even for something made on a drill press.