pic: Butterfly Drive V2

[Greg Woelki]

Originally Posted by GeeTwo

Today was the day (though I used a sheet of paper rather than a board). I'll follow up later (probably over the weekend) with a diagram, but the bottom line is that if the module has a short pendulum arm (vertical distance between the drive axle and the CoG), and ignoring bearing friction, wheel slippage can be avoided by ensuring that

• cos(θ-φ) > r cos(φ)/μR

I'm having trouble trying to derive this so I'd love to see your analysis.

Edit: As far as the design itself goes, I have a couple of comments. First, I'd highly recommend that you extend the hex shaft that goes through the vex clamping gearbox so that it supports the other side of the module as well. This will not only improve serviceability by making it far easier to access the e-clip but also make the module more stable against twisting. It isn't critical for the module to be solid against twisting because it won't see much of any load in those directions, but there's no downside to improving it and, at the very least, it will make the meshing between the 48T gears nicer. Finally, if you could put a standoff in the bottom corners of the side rails it would significantly improve the rigidity where you have the giant cutouts, though they still make me uneasy.