pic: First Sheet Metal Drivetrain CAD

[z_beeblebrox]

Here's version 2 that incorporates AustinSchuh's advice and adds other improvements including:
-Easily removable gearbox connected via gear to the axle (like 971's recent robots). Increases belly pan space and simplifies belt mounting.
-Outer wheel bearings are in sliding blocks tensioned with cams, allowing for better belt performance.
-WCD-style pulley mounting allows for belt changes without removing wheels.
-1.8lbs lighter

Closeup of cam and bearing block. There's an identical block and cam on the outside. Anyone see problems with this setup?

[Joe G.]

The gearbox as you have it looks pretty difficult to manufacture. Extremely deep and narrow U-channels like that are hard to make with a press brake without some specially designed tooling.

Or is that two pieces? It's a little hard to tell.

Either way, I'd suggest using a flat panel that bolts to the outside of the chassis rail instead. Laser cut bolt holes hold much better tolerances than bends, and you have to keep things pretty tight when center-center gear distances are concerned.

[z_beeblebrox]

As per Joe G.'s advice, the gearbox is now two plates. The lightening pattern is improved and an access hole for the outer tensioners is added.

[AustinSchuh]

Originally Posted by z_beeblebrox

As per Joe G.'s advice, the gearbox is now two plates. The lightening pattern is improved and an access hole for the outer tensioners is added.

What tolerances can your shop hold on bends? I'm not sure your gearbox is going to mesh with your wheel correctly. You have the bend tolerance of the frame + the bend tolerance of the gearbox. For our shops, I would realistically say that that is +- 20 thou. For a gearbox, you want to hold +- 1 thou on c-c. 971 does this with a dowel pin and a tight tolerance slot in the gearbox plates. That makes it so the laser ends up holding all the tolerances, giving us essentially +- 1 thou on the c-c for the wheels.

I've found it really nice to have a square cutout above our wheels, and cutouts in the frame big enough for hands. That makes it really easy to see how your wheels are wearing, and to get your hands inside if you need to do something.