Gravity does do the work. Each ramp is pushed over center by a Banebot 64:1 gearmotor hooked to a lead screw. It then detaches and the ramps fall to the ground. The key is control. The big ramp has lots of air resistance and the smaller one is not let drop very far. Both ramps have energy absorbing material that dampen their impact with the ground. We've even thought of using "whoopy cushions" for that function.
