Progress capture options
The progress capture (aka ratchet), is a critical part of a hauling system. It allows you to take your pulling tension off the rope to rest or reset, without the load sliding backward.
There are a few possibilities for the ratchet. Here are some common ones, listed in increasing order of cost and/or weight:
Garda hitch
prusik
plaquette style belay device (like a Black Diamond ATC Guide or Petzl Reverso)
Grigri
Petzl Traxion
Let’s have a look at the pros and cons of these.
Note: especially for crevasse rescue, it’s really important to practice these different ratchet systems in the real world. It’s one thing to have them work in your living room floor, it can be completely different to see how they work under a lot of tension with snow being jammed up inside them.
I measured the efficiencies of these systems and wrote about them here.
Garda hitch
Pros: free and weightless. (So far, so good!) Cons: even when it’s set up correctly the carabiners can get a little wonky and fail to lock up, so it’s not the most reliable system, in my opinion. Plus, it adds a HUGE amount of friction, making your haul a lot harder! Personally, I would maybe use the Garda hitch for some non-critical tasks like hauling up a backpack, but not in a rescue scenario unless it was really the only option. Read more on the Garda hitch here. (And yes, I know it’s best not to use screwgate lockers for a garda hitch, sorry about that in the photo . . .)
Prusik loop
The classic method, and one still often used by guides, rescue teams, fire departments, etc. Pros: inexpensive, lightweight, can be improvised out of almost any kind of sling material. Cons: If it’s cinched down hard on the rope, it can add friction to your pull. You always want the prusik to be loose when you’re pulling, but in the confusion and stress of a rescue this can be an easy step to overlook. Unless you have a prusik minding pulley, (also known with the great acronym of “PMP”), or an extra person sitting next to it with the unenviable title as “prusik minder”, or someone who’s coordinated enough to do both the hauling AND the prusik minding at once, the prusik can get sucked into the pulley and cause all kinds of problems. Plus, every time you slack off from pulling, unless someone slides the prusik back toward the load, the load is going to slide backwards the length and stretch of the prusik loop, which can mean when you reset your pulley you’re losing a foot or so of hard-earned lift. (Your partner stuck in the crevasse will NOT appreciate being a lowered a foot or two when this happens.)
An old-school Crafty Rope Trick (CRT): if you don’t have a prusik minding pulley or just a carabiner at the anchor: run the rope through a tube style belay device like an ATC before you clip it through the carabiner. The belay device keeps the prusik loop from getting pulled through the carabiner. It actually works surprisingly well, give it a try. See photo below.
Black Diamond ATC Guide
(or similar plaquette-style device). If you set these up in autolocking belay mode, the rope will slide through as you pull, but when you let go, will lock down immediately. Pros: no loss of progress when you stop pulling. If you’re already belaying your second from the ATC, it's very simple to set up a 3:1 left. Cons: An extra piece of gear you may not have with you, especially on a glacier climb.
I did some informal testing on this, and believe it or not, found it does not add any significant friction. This surprised me a lot, because when I tested the ATC simply as a redirect for 1:1 progress capture, it had a terrible efficiency of only about 15%, and I assumed this would also transfer over to doing at 3:1. Happily, it does not!
I tested this with both a 10 pound load and a 100 pound load. Real world mechanical advantage was the same in both cases: about 1.5 to 1. This is pretty much the same as using only carabiners and no progress capture at all.
I'm not entirely sure, but I think I know why this is happening. When you start to pull, you generate a little bit of slack at the ATC, and this slack means the rope passes through the ATC with minimal tension, so no extra friction. I am no engineer, and this is just one observational study, but it seems to me that’s why it works reasonably well.
Grigri
The Grigri functions much the same as the plaquette style belay device, with pretty much the same pros and cons. You may well have one with you when rock climbing, but not for a crevasse rescue situation. A Grigri also has the benefit of being able to release under load, which can be a great help if you need to release tension for some reason.
As mentioned just above with the ATC Guide, I did some testing on the Grigri to check the real world efficiency. It turns out to be the same as the ATC guide, which is pretty much the same as just running the rope to the carabiner. In other words, it does not introduce any significant extra friction. I tested agree with a 10 pound weight and a 100 pound weight; the results were the same in both cases.
The real world mechanical advantage with the Grigri as a progress capture is about 1.5 to 1. This is a good thing! It means you can use commonly carried devices as a progress capture with no friction penalty of decreased efficiency.
Petzl Traxion
These little suckers have a high efficiency pulley combined with an ascender type spring loaded rope grab. They give you a great easy pull combine with zero loss of progress . Pros: work perfect. Cons: cost about $100, ouch! (Kind of a lot for seldom-used rescue gear, IMHO . . .) Traxions come in various flavors: the Micro, the Mini (the one I have, in the photo below, now discontinued) and the Pro. For alpine climbing, you want the Micro.
If you’re doing a 1:1 haul of fairly heavy bags on a big wall climb, you probably want a slightly larger diameter pulley wheel to get a small increase in efficiency. One popular ratchet pulley for big wall climbers is called the Kong Block Roll. (I don’t have one, but word is they work great.)
