Ok, so maybe we cheated a little bit. Maybe these will clear it up …
Basically, we took a solid aluminum rod, turned the outsides down enough to fit into the holes we drilled into the frame, and drilled out the center of the rod (all this was done on a mill and a lathe). Stick the 2 frame rails together, and it lines up perfectly. Clamp and weld. Once we welded the 4 2x1 braces in (you can see them in the top picture), we cut out tubes. Milled it down so 1/16" is outside the frame (so we didn’t cut the entire weld off). Our wheels are going to be driven off the hub on the wheel, so the shaft doesn’t have to spin. It took alot of machining, and work to get it right, but the final result is something that is dead on straight. Nothing worse than a robot that doesnt drive straight.