pic: Modular Gearbox

[GeeTwo]

Originally Posted by Ari423

The tubes there are actually 1.5" wide. Inside each tube needs to fit one gear (.5"), one shaft collar (.25"), and two bearing flanges (.0625" ea). 1" tube with a .100" wall gives .8" of inside width, which is .075" too small to fit everything. I was able to reduce the outside tube width to 1.125". I could further reduce it by removing the shaft collar and replacing it with two retaining rings, but that would require the shafts to be machines which I didn't want to do.

I agree that you would not want retaining rings, even if machining were not an issue - they're a high-stress point.

Did you consider using thunder hex stock? Not because it's rounded, but because it has a bore. You could retain the shafts with self-tapping screws and washers (or tap the hole and use elevator bolts) and save a few tenths relative to shaft collars. There may be other pre-bored hex stock out there as well. Churros would work for demonstration purposes, but are not good for transferring the torque you'll need in a drive train, much less an arm.