[ChrisH]

For the past several years the BeachBots have used a cascading lift. Last year our "sliding" gear box, which enabled us to slide sdieways on the bar, weighed as much as a tetra. So the lift we used last year should work for what you want easily. I don't have the numbers handy here at work so I can't tell you the calculations we used. But I can tell you about the winch.

We used two stock FP motors and gearboxes. We used the "jeep driver" plastic parts to connect to a drum of slightly larger diameter. The winch was somewhat over powered as we made it strong enough to lift a second robot should we get entangled. The winch had three cables on the same drum, two "upgoing" for extending the lift, and one "downgoing" for retracting it. All were on the same drum at the same diameter.

The first stage of the lift had a pulley system that "slowed down" and extended the up going cable. This allowed the cable to move the same speed whether it was going up or down. I've attached a sketch of how we did it.