[Greg Perkins]

I'm having a hard time seeing what the benefits are with this design, all I can tell and assume is your going to have an issue with keeping those gearboxes safe. I also can tell that if you are rotating your wheels those gearboxes are going to rotate outside of the robot too, and thats just asking for trouble.

If I was designing this, I would mount 2 andymark or a custom shifter (or not) gearbox vertically inside the robot, and then run chains to each corner. Each module would have a shaft that ran down the tube, and mated bevel gears to the wheel shaft, then have just the wheels exposed

Other than that, the chassis and arm design looks good!