Back to basics.
Look at this link from Andy at AndyMark. It has a nice diagram of how a telescoping system works.
http://d1pytrrjwm20z9.cloudfront.net...atorDesign.pdf
You can put the tubes inside each other or slide them along side each other, either way will work.
Here is an old CD thread that might help, also,
http://www.chiefdelphi.com/forums/sh...t=manipulators
Finally, many pop-up campers use cable lift systems. Here is a link to how they work.
ttp://www.customcylindersintinc.com/understanding_camping_trailers_roof_lift_systems.h tm
Dr. Bob
Chairman's Award is not about building the robot. Every team builds a robot.