Do those pictures in the rock rescue book of a 5 :1 rescue system leave you scratching your head? Yeah, me too. These posts, written for the math-challenged, takes a deep dive into the theory and application of mechanical advantage systems for climbers.
Meet your new climbing partner, Sticky! Let’s start with the basics, a straight 1:1 pull. Then, we’ll add some components that make it into an MA system with progress capture.
Alpine climbers and big wall climbers have different requirements when it comes to MA systems. Here’s a summary.
Say you’re in a rescue situation with one pulley. You choice of where to put it can make a BIG difference in your ease of hauling.
We often have to improvise on gear for alpine rescue scenarios, but carabiners really do suck for hauling. This post may convince you to carry a pulley more often.
The progress capture / ratchet is a critical part of a hauling system. There are lots of devices you can use, and they vary greatly in terms of weight, cost, and most importantly, friction.
Here’s some test results from various combinations or pulleys and carabiners for 3:1 and 2:1 MA systems. Some things were as expected, but I got a few surprises.
You have lots of options for pulleys, carabiners and ratchet mechanisms. Some are wildly less efficient than others. There are two you should really avoid using.
No, it’s not a trick question. MA systems can be a definite benefit, but in the end, you’ve done the same amount of work.
Does an MA system always increase the load on the anchor? Usually yes, but sometimes no. Yes, it can be a bit confusing. This post will clarify.
Getting into slightly more advanced MA topics - the differences between simple, compound and complex pulley systems.
Pulley diameter and rope stretch do affect your hauling efficiency. It’s more relevant to mountain rescue teams and big wall climbers than to alpine climbers.
You can tie a Z drag in your sleep. You bring a pulley to the rock gym. You are a Mechanical Advantage ninja. You’re ready for the bug guns - bring on the 9:1!
This Crafty Rope trick (CRT) can give you up to about a 6 to 1 theoretical mechanical advantage, with nothing more than a cordelette and a few carabiners.