this thing is a bit of a test\research exercise. i am not going to build a full size device right away of this.. more like a 1/5th scale model.. ive worked a bit more at it.. trying to develop pseudo code for each of 4 states ive identified...

currently i am assuming the hardware will be:

DC motor with encoder
linear encoder
pneumatic damper or spring
a reel, some rope, a 18f4550 with usb setup
check this out:

www.robertguyser.com/tugofwar.gif