Chief Delphi - Elevator counterweight / constant spring and ability to lift different number of tote

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Re: Elevator counterweight / constant spring and ability to lift different number of

Quote:

Originally Posted by Jared (Post 1424008)

Worm drives CAN backdrive- especially multi start worms. As they wear in, they can backdrive a vibrating and shaking robot.

This is certainly true.

As a note, if anyone is looking at the AM WormBox, we used it last year as the initial (and largest) reduction for the arm on our 2014 robot, Kaizen. The WormBox has a multi-start worm gear and was very much back-drivable by the 'reaction forces' of our robot accelerating and stopping. We counter-balanced this arm reasonably well using surgical tubing to enable us to gear the arm faster... with this counter-balance the arm wouldn't backdrive the WormBox when sitting statically (at least when not holding a ball), but could be backdriven if you pushed the arm to a desired position.

The WormBox worked pretty well for us (enabling us to have compact, lightweight, low-backlash gearing), but we did preemptively insert one or two thrust bearings axially on the worm-shaft, which I would recommend to anyone that uses it, particularly if they expect impact loading on the mechanism. We only got away with cantilevering the output gear for a while before we wore down the 7075 Aluminum gear that we mated to it and the press fit of a bearing on the output shaft of the WormBox. This was in issue with our implementation though, not the WormBox.

Re: Elevator counterweight / constant spring and ability to lift different number of

Quote:

Originally Posted by Jon Stratis (Post 1422031)

Instead of trying to counterbalance, think instead of applying a friction brake of some sort. Try thinking about how you brake a bicycle tire, and see if you can do something like that with your spool that lifts the elevator. Pneumatic would be a great way to generate that braking force without burning out a motor!

We opted for the KOP drive system, but we're equipping it with holonomic wheels, so we are considering "recycling" the 4" rubber tires as brakes. We'd build a clamp that fits around the wheel, probably with a brake lining of carpet, and open and close it pneumatically. Not sure how often we'd have to change the carpet - my guess is after a about 12-24 hours of practice, and between tournaments.

Re: Elevator counterweight / constant spring and ability to lift different number of

DeWalt, and other drill transmissions, have anti-back-drive pins in them that can work quite nicely for this purpose. As a bonus: they work in BOTH directions AND there's a white paper on how to interface them with FRC motors called "Nothing But DeWalts."