To get even more mechanical advantage out of a rescue hauling setup, you can piggyback two systems. For example, establish a separate single-pulley setup to haul on the rope coming from a Z-pullcy system. This now gives you a 6-to-l theoretical mechanical advantage. Or set up a single pulley to haul on another single-pulley system for a 4-to-1 advantage.
To piggyback two systems, set up your initial hoist to the fallen climber, either a single pulley or a Z-pulley. Now establish a second anchor some distance behind the main one, to anchor the second system. Attach the second hoist, again either a single pulley or a Z-pulley, to the accident rope at the point where the rescuers would normally pull.
Continue reading here: The Bilgeri rescue
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