Alright, so it’s been recommended frequently that arms get some counterbalance going. It may be overkill for a CIM-powered arm, but we’ve got a few pounds to play with at Palmetto; I’d rather make it beneficial rather than just bolting junk onto the robot.
The one problem is that our particular arm (photo) has to start down in order to fit in the box. Seems like we could rig up some form of latch to pop the arm free during the autonomous period, but I’m sure there has to be some other means that I don’t know about.
Are there any Thursday-at-the-regional tricks that’ve worked in the past?
If the arm pivot were more substantial, and you didn’t need ballast, I’d recommend the surgical tubing tied to the back end of the arm trick…as has been mentioned by a few others in various threads…
If you use constant force springs, you can more easily tune the force to an extent so that it will basically stay in whatever position you choose to put it in. Or, in the same respect, though not as effective, you could tune any sort of regular spring balance so that it still assisted the arm, but would no have enough force to swing the arm out of place at start.
Search for constant force in Mcmaster.
If you just want a latch to hold the arm down at the beginning of the match, you could try a leaf spring pressed against the side of the arm. Any arm would be able to simply pull past it if you wanted to deploy.
We use gas springs from McMaster.com to counterballance our arm (like the ones you find holding up a car hood or liftgate). They’re light and not too pricy at ~$15. The most common are compression, so it makes them pretty easy to mount too.
We found that a small bungee kept our arm pretty balanced. We had to make some modifications to make sure that it was not too tight. If you’ve ever been hit by a bungee, you can understand.
