pic: CGX-115, cam-counterweighted cycloidal drive

[asid61]

Originally Posted by Scott Kozutsky

As I understand this mechanism, the cyclodial gear nearest the cim drives against the mounting plate of the cim, which would be fixed against the main structure of the bot. The other cyclodial gear is driving against another plate which is mounted to the arm.

Because both cyclodial gears advance in the same direction, wouldn't this gearbox just provide a powered zero output?

BTW, great work, it's actually because of you that I know that these gearboxes exist at all.

That's an interesting way to look at it. You would be correct if both cycloidal gears had the same tooth count. However, because the second stage gear is actually minus one tooth, the result is a little different.
This is the order of motion:
1. The miniCIM drives the camshaft
2. The wobble gear rotates around the CIM axis, but it itself turns once for every 30 rotations (the first 30:1 reduction)
3. The second wobble gear, bolted to the first one, rotates once for every 30 rotations as well.
4. Due to the eccentric nature of that rotation, the arm is pushed 1/30th of a rotation for each rotation of the second gear about its axis, creating the second 30:1 reduction.

It's a bit easier to see if you have the cad model working. The arm is forced to rotate, essentially.

Don't thank me, thank s_forbes! He provided the CAD model for the first cycloidal gears and the spreadsheet to calculate the gear ratio and dimensions.