Crevasse rescue tips - Pulleys and mechanical advantage 101

Crevasse rescue (along with crevasse avoidance!) is an essential skill for climbing many of the glaciated peaks of the NW.  While cautious climbers may never have to use these techniques, knowing how to quickly extricate a teammate from a crevasse fall is taught in many Mazamas classes.  While a simple 1:1 direct haul can work with enough pullers on the surface, with a smaller team you might need to build a hauling system that creates mechanical advantage.

The simplest of these are a 2:1 and 3:1 system, meaning (in theory) that for you can raise a 100 lb load with 50 pounds and 33 pounds of pull, respectively.
If you want to get really fancy, (or help pull a car out of a ditch) you can make more elaborate systems that can generate 4:1, 5:1, and 6:1 and more mechanical advantage.  The prussiks, pulleys and lines needed for these can create a real tangle, and it’s easy to get confused - are you really adding more mechanical advantage, or just redirecting the pull?

Here’s a simple tip to know for sure - If the pulling point you add is fixed, you are merely redirecting the pull and not adding more mechanical advantage.  If you add a pulling point to a traveling part of the rope, then you are adding mechanical advantage.

Want to learn more?  Check out the Mazamas skill builder crevasse rescue class.