Descending robot arm

[Robby Unruh]

Originally Posted by Brandon_L

We had a similar problem. Its all about the counterweight. We were using bungee cords, and when there were no forces holding the arm down, so it was free spinning, it would only sit about an inch from the floor. We then found a heavy duty spring, it started out at about 4" long. We swapped out the bungee cord for the spring and now when its free spinning it wants to stay almost perfectly horizontal out, stretching the spring to about 7". It made all the difference in the world.

Before: http://www.youtube.com/watch?v=a_yD4oc4j2g (doesn't actually show it coming down, as we were afraid to break...everything)

After: http://www.youtube.com/watch?v=KB1veyKNYQI

I don't know how this will help you with a double jointed arm, I don't know how exactly yours works.

We also had problems with the window motors locking up, switching to victors and putting them in break mode fixed that.

Our arm is incredibly similar to that, our second joint is pneumatic so it's only got two ranges of movement. So how do you think we'll do using surgicial tubing as our counter weight? I don't think we have time to get/order springs to use before shipment.

- edit -
is enabling Break Mode on the victors safe? I've never heard/seen anything about that.