Extending a climber's arm

[Cash4587]

I have been questioning the engineering behind climbers and linear lifts recently. I have no clue how any of them are powered both up and down. I can only seem to engineer one that pulls one way and free spins the other and is powered by springs or surgical tube. Any help/ideas?

[Madison]

This is a great place to start -- http://www.chiefdelphi.com/media/papers/1322

[Thad House]

If you have a pulley at both the top and the bottom, you can wind up the top cable to pull it up and the bottom cable to pull it down.

[Mike Marandola]

Teams also do this with long lengths of timing belt. I learn the best by watching videos. A few videos that gave me ideas are:

Robonauts 2011 robot (http://www.youtube.com/watch?v=8lRtC8wBUa0)
Cheesy poofs 2011 robot (http://www.youtube.com/watch?v=HJVGgaAJefo)
2013 simbotics robot tour (http://www.youtube.com/watch?v=CIBaWdIZX7k)

Also check out some pictures of this year's robots here (https://www.dropbox.com/sh/3fxabc28nvvkcr8/A2tQie9tgK)
Specifically 67, 254, and 1114

Do some research of the 2011 robot designs. Many had linear slide type mechanisms.

[apples000]

Lead screws.
http://en.wikipedia.org/wiki/Leadscrew

[R1ffSurf3r]

Our main stage is just a loop of chain with a drive and idler sprocket on the bottom stage, where part of the chain is fixed to the second stage. It's then rigged with more chain so the last stage extends at the same time.

Our only arm that used plastic bearings, and used bungee to extend (power retract for hanging) was 2010. And honestly this thing was such a huge pain in the butt