[DampRobot]

Worm gears all the way!

Worm gears are great. They're nonbackdrivable, and lend themselves to both manual and closed loop control. Basically, where you put them they stay, which means that you can have a much simpler and less finicky control loop. I think we just had a P loop on our worm powered claw tilt this year, and had it not been for the precise angle requirements, open loop control would have worked just fine.

12 DP seems like a reasonable pitch based on my experience, but you could probably get away with as high as 20 DP.

Realistically, whenever I've seen large shock loads running through a worm gearbox, either the spacers around the worm or the thrust bearings on the worm are what get damaged. When the worm gear teeth are 3/16" of hardened steel, and your washers on your thrust bearing are 3/64" of unevenly supported stainless, it's not hard to see what will fail first. Of course, you can bump up the bearings to angular contact bearings, and make all your spacers steel, but at that point, you're likely going to see other things break before the worm gear. We ran a worm gear setup as our claw tilt this year, and shock loads (like stopping the claw suddenly) caused the screw holes holding the sprocket to the claw and the hex on the worm gearbox sprocket to round out before the worm and worm gear were damaged.

If you do go worm, you're going to want to throw a lot of power at it. I'd guess (without having run any numbers) that you'd need at the very least a CIM to power whatever you're describing. We ran a 2 CIM, 1 lead worm + 2 spur reductions gearbox this year, and observed efficiencies in the 6-7% range. That gearbox was the result of a lot of institutional knowledge too, I doubt our earlier versions were even that efficient. Worm gears are great, but they do dump a lot of power.

We've been doing worm gearboxes for about four years now. Let me know if you'd like to see some of our gearbox CAD. I'd be happy to share designs and experience.