[Chris is me]

Originally Posted by jimbo493

2 Wheels allow for more traction and less stress on the bevel gears, plus its just helps with overall stability, we are using the new 4in vex wheels

We will probably use .125 in

2 wheels doesn't inherently equal more traction. It would result in pretty much the same stress on the bevel gear as well - how do you figure that it would result in less?

Originally Posted by Bryce Paputa

With a rough top tread I would think you would get more friction, but probably not with a smooth vex wheel, but this is just a guess.

Please don't guess.

The edge case I know about that seems to affect pushing force based on wheel width is roughtop tread on 4" wheels. I remember reading data somewhere (but not experimenting myself, something to do in the fall) which showed a negligible difference in traction for 6" and 8" wheels of different widths as well as wedgetop tread. Specifically 4" roughtop tread wheels have noticeably better traction in a 2" wide configuration as opposed to 1" wide.

I have never seen any data on Colson wheels or Vex wheels with regard to width versus traction. Based on purely subjective experience, I think people are somewhat overstating the benefits of a wider wheel in terms of carpet traction. We would have to do testing to be sure though, perhaps in the fall.

The increase in turning torque is correct though and if more surface area was beneficial I'd just have a single thicker wheel to take advantage of the low torque required to turn near the axis of rotation.

Yes, definitely a factor here. Your turning torque is a function of the size of your moment arm when spinning the wheel, so the farther from the center the tread is in contact with the ground the greater the torque needed to turn the module.

Also, getting the holes on the two 1/8th inch pieces of aluminium to line up is going to be very challenging, I would recommend making it out of a single piece of extrusion or two flat plates with standoffs.

Alternately they could leave the bends in, with a bit more clearance away from each other, and use standoffs to actually hold the plates together to ensure alignment. This keeps the rigidity benefits of the bends.

OP: Have you thought about how to mount this to a frame? A popular idea on the west coast is to make a 2x1 frame and mount the gearbox to each side of the 2x1, using the existing frame as a big spacer. Also, what are your gear ratios?

Thinking about it more, It would also be pretty difficult to make this design with a single wheel. I still think we will have enough torque to turn the wheel with adequate speed. There really is only one way to find out..to test it.

Not at all, you can easily do some math to get an approximation of how much torque it takes to turn a wheel and whether or not your system has enough reduction to do so.