This year my team has a variable-angle elevator, and we were wondering how teams improved the stability of a mechanism like this. We were thinking of using a constant force spring in order to prevent it from jumping back and forth from jolts when driving
Is the movement mostly from slop (backlash), flex in the system, or the motor being overpowered ?
its from backlash… we are using webbing to move it up and allowing gravity to pull it down. We are trying to make it smoother… I can post a picture if that helps !
And what range of motion needs to be covered? 90degrees?
Yes, a constant force spring or two pulling down will help stabilize it. You should be able to get away with a pretty strong one. You DO need to watch that the spring doesn’t pull your winch down before the match starts! If you had a way to add some damping to the spring that could help further. Either draggy spool or a rubber suspended spool or end mount might help too. Or some felt pads pressed against the spring itself. Maybe make the spring slide over a felt covered curve? I think just getting the hold-down in place will help quite a bit. Probably 80% of the value right there!
You should add some shrouding to keep the strap from jumping off your drum; that would be catastrophic!
so should we have a spring that is going up and the other pulling down?
No, all down fighting your winch.
We’ve found that using vex components for a mechanism like this introduces a ton of slop from their tolerances on the hubs and gears, so if that is how your mechanism is attached I would get some shim stock and shim whatever is attached to the shaft it rotates on. Also helps to make sure your belt/chain/whatever is spinning this is properly tensioned.