That's a pretty sweet idea, i have to say.
There are some simple ways to get up the vertical bars (for example, clamp onto it with a wheel on each side, and spin the wheels. They'll naturally tighten onto the bar while they pull you up) - the problem we saw with using them is the amount of precision needed to get your mechanism arranged on the bar. I'm sure some team or teams out there will figure out a great way to take care of the precision problem... but we wanted to keep it simpler and fool proof.
So like many others here, we're going with a winch - it's simple, strong, and automatically locks to prevent being back driven. The innovative, and really cool, part is getting the hook up to the horizontal bar - that part takes under 1 second and needs, at most, a servo (we may be able to get the winch motor to work with it, eliminating the servo) in our prototype. It'd be nice to improve that on the real robot
