Two ways to rig a 2:1 “C” haul

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A 2:1 haul is a fundamental mechanical advantage system for climbing self rescue.

• To move your load 1 meter, you must pull 2 meters of rope through the system.

• In a (theoretically frictionless) world, you could lift a 100 kg load by applying about 50 kg of pulling force.

• It's called a “C” because if you turn your head sideways, it kind of looks like the letter. =^)

It's common to rig this for crevasse rescue by using a progress capture pulley (PCP), such as the Petzl Micro Traxion.

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With a 2:1 haul: the progress capture can go in one of two places:

1. On the load

2. On the anchor

Here are the two different setups.

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1 - Progress capture on the LOAD

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2 - Progress capture on the ANCHOR

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• What are the forces on the anchor for each of these systems?

• If you do have a redirect like in the second photo, what’s something you can do to reduce the load on the anchor?

• For crevasse rescue, what are pros and cons of these two methods? (My opinion: I prefer to keep it on the anchor.)

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