Alpine Tips
Crevasse rescue: the drop loop 6:1
Want to learn a simple, minimal gear, high mechanical advantage rigging that's great for crevasse rescue? Look no further than the drop loop 6:1. Here’s how to set it up.
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Do you want an efficient, simple and minimal gear mechanical advantage rigging system to pull your buddy out of a crevasse (or maybe your car out of the ditch?
Look no further than the drop loop 6:1.
Let's learn how to rig it.
Gear you need for the drop loop 6:1:
A fair bit of extra rope you can use for the rescue. This could be the rope that you were tied in with when walking on the glacier, or an extra rescue rope that’s in your pack
Some sort of friction hitch, or rope grabber like a Petzl Tibloc
Some sort of progress capture system at the anchor, ideally a progress capture pulley like the Petzl Traxion
A few spare carabiners, two of them locking
A pulley if you have it (optional)
Notes . .
To keep the rigging easier to see, I’m not showing the original rope that might be attached to the unfortunate person in the crevasse. In this example, let's assume a team of two people skiing on a glacier unroped, and one of them falls in. Each skier is carrying a 30 meter rescue rope, so the person on top has all the gear to do the rescue.
One other benefit of this system: you’re dropping a new rescue loop to your victim. So, if the original rope they fell in on has brake knots in it, or is deeply entrenched in the lip of the crevasse, it doesn't matter.
Step 1: Build a solid anchor, and attach the rope to the master point. This could be the end of the rope, as I'm showing in this example, or a bight knot that the person on top was clipped to.
Step 2: Clip a locking carabiner to the rope, and lower it down to the person in the crevasse. Instruct them to clip the locker to their belay loop.
This is the “drop loop” portion of the anchor. If you have an extra pulley, you could put one here to reduce friction a bit.
For this to work as shown, you need to have a bit more than twice the amount of rope available to drop this loop to your partner. If you don't have that, you need to get resourceful with some other methods, such as the drop end 3:1 or the simplified drop loop 2:1.
Step 3 - Pass the other side of the loop that you dropped through some sort of progress capture on your anchor. A progress capture pulley (here, I’m using a Petzl Nano Traxion) is the easiest. You can also use some other options like a friction hitch on a carabiner; here's an article about different ways to do progress capture.
You now have a 2:1 mechanical advantage system, with the progress capture on the anchor.
If you have more than one rescuer, you might start pulling on this to see if you can move the load. (With hauling systems, it's usually best to use the lowest mechanical advantage that gets the job done, so try this first.)
In our case, let's assume that the you can’t pull up your buddy, so we need to add more boost to our system.
Step 4 - Tie a friction hitch to the side of the drop loop that’s coming up from your partner to the progress capture. Clip a pulley (if you have one) to the friction hitch. Clip the tail end of the rope to the carabiner / pulley on the friction hitch.
Give yourself a high five! You just built a 3:1 system on top of a 2:1 system, giving you a 6:1.
If you pull 6 meters of rope through your hauling system, your load will move 1 meter.
This is a compound pulley system.
What's the real world mechanical advantage of this rigging?
Wanna see a video of me going through the “T method” with this exact anchor to show the mechanical advantage?
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Two ways to rig a 2:1 “C” haul
The 2:1 haul is a fundamental system in rope rescue. If you use a progress capture pulley, there are two places you can put it: on the load, and on the anchor. There are pros and cons to each; learn ‘em here.
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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.
With a 2:1 haul: the progress capture can go in one of two places:
On the load
On the anchor
Here are the two different setups.
1 - Progress capture on the LOAD
2 - Progress capture on the ANCHOR
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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Hauling systems: boost your 3:1 to a 5:1
Do you have a 3:1 hauling system set up, and need a little extra pulling power? Here's a simple way to turn it into a 5:1 with minimal extra gear.
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If you have a basic 3:1 mechanical advantage “Z drag” set up, and need some extra pulling power, here’s a slick way to convert it into a 5:1 system.
Advantages:
Easy to convert from an existing 3:1 system
May allow a small person to haul up a relatively large / heavy person
Requires minimal extra equipment (only 2 spare carabiners and a cordelette)
There's no change of direction at the anchor, so your pulling efficiency is increased
Easy reset
Because there are two different lines in the system, you could distribute this load across two different anchors.
Don’t have a long sling or a cordelette? You could also use the other end of the climbing rope.
Here’s how to convert a 3:1 to a 5:1.
Start with a standard 3:1 “Z” haul.
Clip a sling to the anchor. Clip a carabiner into the other end of the sling.
(If you're doing a crevasse rescue, using an untied (aka “open”) cordelette works better. Photo of that rigging is below.)
Unclip the rope from the carabiner on the friction hitch.
Clip your sling to the friction hitch.
Clip the rope to the carabiner on the end of the sling.
Start hauling!
You made a 5:1 system. Schweeeet, give yourself a high five!
For every 5 meters of rope you pull through the system, your load moves 1 meter.
In a theoretical frictionless world, you could move a 100 kg load with about 20 kg of pulling power. In the real world, your actual efficiency is probably about 3.5 to 1, but that should be enough to pull your buddy out of the crevasse.
You can increase your efficiency a bunch by having a pulley at each change of direction rather than a carabiner.
Both carabiners/pulleys are moving the same direction (toward the anchor) when you're pulling, so you don't need to reset the tractor as often.
Definitely practice with this a few times in a controlled environment. It may look simple when you're reading it here, but it can cause some brain lock when you're trying to do it under some real world pressure.
Want to see an photo and video of how to set this up with a cordelette for crevasse rescue?
How can you apply the “T method” to show that this actually is a 5:1?
How about another way to set up a 5:1: with a distinct disadvantage to the method shown here?
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Using the “T method” to calculate mechanical advantage
It's easy to get crosseyed looking at a pulley system and trying to figure out the mechanical advantage. Fortunately, there's an easy way to calculate it, requiring the math skills of a third grader. (Yes, you can do this.) Let’s learn the “T method.”
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For climbers, mechanical advantage (MA) systems are used in self rescue, and in big wall climbing to lift heavy haul bags. They're also helpful for getting your truck out of the ditch, pullings stumps in your garden, hoisting sails on a boat, building pyramids, and other useful life applications.
Even if you have a basic understanding of how they work, some of the more esoteric ones make most folks (like me) get cross-eyed counting all the strands and trying to figure out the MA!
Fortunately, there is a pretty straightforward way to figure out the theoretical MA of any system, using math that you learned in the third grade: The T method.
The method assigns a T (Tension) value to each rope segment. You add up the tensions at various points in the system to determine the overall mechanical advantage.
It's particularly useful for more complicated systems beyond a basic 2:1 and 3:1.
Here’s how the T method works.
1 - Start with “1”. Begin with a value of 1 “tension” at the point where you pull on the rope. Think of tension as how much force you (and maybe your pals) are pulling on the haul strand.
2 - Follow the tension. Trace the tension through each pulley and other components of the system.
3 - Adding the tensions.\
At each pulley (aka change of direction), the tension on the rope entering and exiting the pulley is EQUAL.
At the pulley “eye” (aka, the thing the pulley is clipped to) the tension is the SUM of the tension on the rope entering and exiting the pulley. For example, if 1 tension enters the pulley, then 2 tensions are applied to whatever the pulley is clipped to. If 2 tensions enter the pulley, then 4 tensions get applied to the pulley clipping point. (See pulley photo below.)
When tensions join (e.g., at a prusik hitch), you ADD the values.
4 - Mechanical advantage:
The final tension value at the load is the theoretical mechanical advantage of the system.
Check out those numbers printed on the pulley.
If you have a force of “X” (or 10 kn) on one side of the pulley, you have that same force of “X” (10 kN) coming out of the other side.
In the “eye” of the pulley, where it's clipped to something, you have “2X” the force that's being applied. In this case, if you have an input force of 10 kN, then 20 KN gets supplied to whatever the pulley is clipped to.
Does this sound a bit dry and complicated? That's how I felt when I first heard of it.
But, after you try it a few times, it's quite simple. If you're even slightly a mechanical advantage nerd like I am, it's actually kind of fun!
Let's look at some examples of a 2:1, 3:1, and a 6:1.
Let's start with the easiest system, a 2:1 (aka the “C pull”)
To move the load 1 meter, you need to pull 2 meters of rope through the system.
In a theoretical frictionless world, you could lift a 100 kg load by pulling with about 50 kg of force.
(Note: in this example, the progress capture pulley is attached to the load, not the anchor.)
Begin with an input of 1, you pulling on the rope.
That input force of 1 is doubled to 2 when it changes direction at the red progress capture pulley. That gets applied to the load.
The input force of 1 comes out the other side of the red pulley, remaining at 1, and then goes onto the anchor.
Summary of a 2:1 MA system:
2 units of tension go to the load.
When you’re pulling, 1 unit of tension goes to the anchor.
Got that? Good, let’s look at a 3:1 system (aka the “Z pull”)
To move the load 1 meter, you need to pull 3 meters of rope through the system.
In a theoretical frictionless world, you could lift a 100 kg load by pulling with about 33 kg of force.
Begin with an input of 1, you pulling on the rope.
That input force of 1 is doubled to 2 when it changes direction at the blue pulley. That gets applied to the prusik that the pulley is clipped to.
The input force of 1 comes out the other side of the blue pulley remaining at 1. That travels to the red progress capture pulley on the anchor, where it's doubled to 2.
The input force of 1 continues at the left side of the red pulley down toward the load. Here it says “hello!” to the yellow prusik, which has a force of 2.
We add these together to get 3, the force applied to the load.
Summary of a 3:1:
3 units of tension go to the load.
When you’re pulling, 2 units of tension go to the anchor.
OK, you got all that? Sweet! Let's step it up to a 6:1.
In this example, we’ll start with a 3:1 Z drag, and then make a 2:1 C pull (with a separate cord) on top of it. This rigging is also known as a “C on a Z”.
To move the load 1 meter, you need to pull 6 meters of rope through the system.
In a theoretical frictionless world, you could lift a 100 kg load by pulling with about 17 kg of force.
How want to learn how to apply the T method to figure out a 6:1?
What's the difference between theoretical and real world MA?
How can real world MA improve by using pulleys in different places?
How about a link to a great YouTube video that describes the T method in even more detail than this?
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Hauling systems - Clove hitch can replace a prusik
Some mechanical advantage hauling systems, such as a 5:1 or 6:1, can require two rope grabs. If you only have one prusik loop, you may be able to rig it by using a clove hitch.
When you're setting up a more involved mechanical advantage hauling system, such as a 5:1 or 6:1, those often require two rope grabs / friction hitches.
What if you only have one?
Depending on the rigging, you might be able to substitute an actual knot, like a clove hitch, instead of a friction hitch.
Yes, you will have to re-tie the knot every time you reset your system, but if that's what it takes to get your partner out of the crevasse, then that's what you do.
Bigger picture: if you think you might need to set up a 6:1 for any reason, such as two person crevasse rescue, do yourself a favor and bring the right tools, such as a high-efficiency progress capture pulley like a Petzl Micro Traxion, and two short friction hitches.
Below is a 6:1 hauling system.
The system starts with a 3:1 “Z” drag, made with the white rope. then a 2:1 “C” is added on top, with the orange cord.
Typically that orange cord would be clipped to a second friction hitch . . . but it doesn't have to be.
Because this strand of the white rope isn’t under tension when you're not pulling, this connection can be a clove hitch.
When the carabiner on the orange cord arrives at the anchor, you need to reset the system. Untie the clove, slide the carabiner and prusik down the rope toward the load, re-tie the clove on the white rope, and continue pulling.
To learn more about 6:1 systems like this, check out this article.
Load transfer: The stirrup hoist
Do you have a big load that you need to move a short distance? Here's one crafty way to do it: the stirrup hoist. This may not be the most efficient method, but it's quick and simple.
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This is part of a series of articles that cover methods to move a large load a short distance, typically to unweight an anchor.
In some unusual climbing situations, you may need to lift a very large load a very small distance.
Maybe on a big wall, where you rigged your bags old school style (sheesh, use a docking cord, will ya!?) and you need to lift them a tiny bit to unclip the carabiner.
Maybe in a rescue scenario, when you have an unconscious person hanging off of a loaded anchor, and you need to lift them just enough to unclip them.
In either case, it's often better to use your bodyweight to try to do the lifting rather than your muscles. Work smart, not hard!
Don't make a habit out of this. It's almost always better to use some sort of releasable knot or hitch to anchor your load when you can. But for those cases when you didn't do that for some reason, the stirrup hoist might come in handy!
Here's a way to set that up, called the stirrup hoist.
This is not the most efficient method, but it's pretty fast and uses minimal gear, so it's a good one to have in the toolbox.
You might want to try this first and see if it solves your problem, before you try more elaborate systems, such as the alpine block and tackle, or the 2:1 redirected haul.
Clip a long sling onto the load. Slippery Dyneema would be a good choice, to minimize friction.
Pass the sling through a carabiner on the anchor, and let the sling hang down below the anchor. If you happen to have a pulley, run the sling through that to minimize friction. (In the photo below, I’m not using a pulley.)
Step into this “stirrup”. Your body weight, along with lifting the load with your arms, should hopefully be enough to move it up a bit to solve your problem.
To give a little extra boost, you might try bouncing on the sling ,which will apply more force to the load than your static body weight.
Want to read more comments on this method and a photo of the set up?
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Load transfer - The 2:1 redirected haul
Do you have a big load that you need to move a short distance? Here's one crafty way to do it: the big waller's trick of the "far end haul". aka 2:1 redirected haul. (I learned this from big wall expert Mark Hudon, thanks Mark!)
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This is part of a series of articles that cover methods to move a large load a short distance, typically to unweight an anchor.
I learned this trick from big wall expert Mark Hudon, thanks Mark!
You may find yourself in a climbing situation where you need to transfer a BIG load from one anchor point to another.
Beginner big wall climbers, you know what I'm talking about; you clipped the haul bag in the wrong spot and it needs to get moved, whoops! (I’m an expert on this particular mistake; I probably did it five times on my first wall . . .)
Maybe a rescue situation (which you’re hopefully never in) where you need to lift the weight of your uncooperative partner off of the anchor to continue rappelling.
How can you do this the SMART way?
Brute force powerlifting is probably not going to cut it. It's much smarter to use a little mechanical advantage to make this happen. Work smart, not hard!
Here's one method: a redirected 2:1 haul with a progress capture pulley. In the big wall world this is known as the “far end haul”; here's an article on that.
The steps here might appear complicated when you see them the first time, but as soon as you give it a try you'll learn how easy it is.
Look through the step-by-step photos below and then watch a how-to video at the bottom.
You have a big load on the right anchor, and you need to move it to the left anchor. How do you do this the smart way?
Here’s a step-by-step sequence, with a tutorial video at the bottom.
Clip some cord or rope to the anchor.
Clip your progress capture pulley such as a Petzl Traxion, onto the rope is shown. (Remember to clip it “teeth to tail”, so the “teeth” on the device point to the “tail” side that you’re going to pull.)
Clip the Traxion onto the load.
Add a redirect to the anchor. A pulley is good here if you have it. In this example, I’m using the excellent Petzl Rollclip.
(In this example I clipped the redirect on to the anchor on the right. It also works fine if you clip it to the anchor on the left.)
Now you're ready to pull.
Put the rope or cord through a Grigri or a Munter hitch on your harness.
Pull DOWN with your body weight.
As you do this, you’re raising the load with a 2:1 mechanical advantage, and the Traxion pulley captures your progress. Nice!
With the high-efficiency Traxion on the load and the Rollclip/pulley on the redirect, your loss of pulling force due to friction is minimized.
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Load transfer: The alpine block and tackle
With nothing more than a cordelette and two carabiners, the “alpine block and tackle” creates a bit of mechanical advantage that can help you move a large load a short distance.
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This is part of a series of articles that cover methods to move a large load a short distance, typically to unweight an anchor.
If you tie your cordelette “bunny ears” style, as I recommend in this Tip, you can use it to make a low-tech block and tackle system. #CraftyRopeTrick for sure!
(History side note: The term “block” comes from the wooden blocks that were originally used on ships to raise heavy sails, and the “tackle” refers to the ropes/rigging running between the blocks.)
Climbers typically think that mechanical advantage systems only come into play in a rescue-type scenario. But there are some other situations where they can come in handy.
When might you want to use an alpine block and tackle?
In general, to move a large load a very short distance.
Maybe you're in some other kind of rescue scenario, and you need to momentarily lift a load off of a carabiner an inch or two to unclip something.
Maybe you're on a big wall climb, you screwed up your rigging somehow, and you need to lift your haul bag a few inches to get it unclipped. (Note, if you use a docking cord to attach your haul bag to the anchor, you should never have this problem.)
You have a strand of rope with a weighted knot, and you need to unweight the rope so you can untie the knot. To do this, put prusik loops above and below the knot, and rig the block and tackle between the two prusiks. See image below.
In the example shown in the video below, you can transfer or share the load in a crevasse rescue off a sketchy initial gear placement to a stronger second placement.
Want to see my test results for the real world mechanical advantage of this rigging?
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Show me the 9:1
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!
OK, I’m on a SAR team and need to know fancy systems, or I’m a river guide who might need to pull a wrapped raft off a midstream boulder, or I like to drive offroad and need to know how to pull my truck out of the ditch. I'm ready for the 9:1! How do I do it?
Well, if you’ve read this far, you're ready for the fancy stuff. A 9:1 is a compound system, with a 3:1 stacked on top of another 3:1. Remember, with a compound system, the forces of each section are multiplied together to get the final MA, so a 3:1 on a 3:1 gives you a 9:1.
Important: if you have a high mechanical advantage system, say 6:1 or 9:1, and you are REALLY pulling on it (several strong people) to move a serious load (stump, car in the ditch) you may be getting dangerously close to the safe working limit of some of your equipment, such as a pulley or carabiner.
If you’re in this situation and feel you need to apply more pulling force, it’s probably a good choice, provided you have the equipment, to set up a completely separate system, may be on a new anchor, and pull simultaneously on both systems.
Granted, recreational climbers should pretty much never find themselves in this situation, but if you’re pulling out a stump or your truck, keep this in mind.
Many people (like me!) find looking at a diagram of a 9:1 makes their head spin. But as we like to stay around here, it's a better show than a tell. When you see it demonstrated properly it's actually pretty simple. Here is a nice video that shows you how to do it.
And, if you're the diagram type, here’s a pretty slick example of a 9:1.
image: https://roperescuetraining.com/raising_5-to-1.php
What's the mechanical advantage? It's relative!
Think you have a good understanding of a simple 1:1 and 2:1 mechanical advantage systems? Well, it turns out there's one very interesting variable: who’s doing the pulling? If you, (i.e, the load) are lifting yourself, the mechanical advantage increases! No, this is not very intuitive, and yes it is helpful for climbers. (Thanks to ropelab.com.au for the diagrams.)
The illustrations in this article, used with permission, come from the excellent website RopeLab, run by Australian rigging expert Richard Delaney. RopeLab has a ton of great material for anyone who wants to dive into ropes, rigging, and mechanical advantage, check it out! There's a fair amount of quality free information, but getting an annual subscription unlocks the entire website. You can also connect with Richard on Instagram and his YouTube channel, where he has loads of concise, informative videos.
These diagrams come from a Ropelab online mechanical advantage quiz, which you can find here.
Okay, clever rope wizards and mechanical advantage fans. Here are some questions and diagrams that might leave you scratching your noggin.
A standard principle in mechanical advantage systems is that any change of direction that's on the anchor only serves as a redirect, and does not add mechanical advantage. Well . . . that's true most of the time, but not when the “load is also doing the lifting.”
The mechanical advantage of the system depends not just on the rigging. It depends on who is doing the pulling - a person who’s “in the system” or a person who’s out of it. Let's look at a few examples.
1 - This image shows someone standing on the ground attempting to raise their partner. What’s the Ideal Mechanical Advantage of this system (ignoring friction)?
image: https://www.ropelab.com.au/ropelab-quiz-1-mechanical-advantage/
Answer: It's a 1:1 mechanical advantage. The person on the ground is pulling the weight of the person hanging from the rope 1:1 through a redirect. No mechanical advantage is gained. The person on the ground needs to pull 1 meter of rope to lift their partner 1 meter, so it's a 1:1.
2 - This image shows a person attempting to raise themself by pulling down on the rope. What’s the Ideal Mechanical Advantage of this system (ignoring friction)?
image: https://www.ropelab.com.au/ropelab-quiz-1-mechanical-advantage/
Answer: Exact same rigging as before, but this time the person hanging from the rope is doing the lifting. This time, the mechanical advantage is 2:1! For the climber to go up 1 meter, they need to pull 2 meters of rope through their hand, so the mechanical advantage is 2:1.
Richard Delaney, from the YouTube video link at the bottom of this page: “Mechanical advantage is technically the ratio of the applied force to the input force.” There are two strands of rope holding the climber’s weight. If the climber weighs 100, that means each strand is holding 50. If the climber pulls down on the rope with a force slightly more than 50, they will start to move up. This means the applied force is 100, and the input force is 50, so therefore we have a 2:1.
Does this leave you scratching your head? It did for me when I first saw it! Next time you see a sport climber after a fall, pulling down on the belay rope to lift themselves back up to their high point, this is how they’re doing it, with a 2:1.
3 - Let's take this idea a step further. This image shows someone attempting to raise their partner by pulling down on the rope. What’s the Ideal Mechanical Advantage (ignoring friction) of this system?
image: https://www.ropelab.com.au/ropelab-quiz-1-mechanical-advantage/
Answer: 2:1, with a redirect through a second anchor point. There are two rope strands supporting the climber’s weight, so it's a 2:1.
4 - This image shows a person attempting to raise themself by pulling down on the yellow rope. What’s the Ideal Mechanical Advantage (ignoring friction) of this system?
image: https://www.ropelab.com.au/ropelab-quiz-1-mechanical-advantage/
Answer: 3:1. Just as in example #2, if the person pulling on the rope is the same as the load, the mechanical advantage increases, even though the rigging is exactly the same. In this case, there are three rope strands supporting the climber’s weight. For the climber to move up 1 meter, 3 meters of rope needs to be pulled, so the mechanical advantage is 3:1.
Back to Richard’s explanation of the ratio of input force to applied force: We have THREE strands of rope holding the climber’s weight. If the climber weighs 100, that means each strand is holding 33. If the climber pulls down on the rope with a force slightly more than 33, they will start to move up. This means the applied force is 100, and the input force is 34, so therefore we have a 3:1.
Isn't that interesting? The mechanical advantage of the system depends not just on the rigging, but on where the pulling force is coming from.
Here’s a climbing application of this principle.
Below is a screen grab from a video featuring IFMGA Guide Jeff Ward ascending out of a crevasse. He's using this 3:1 mechanical advantage system to help him climb the rope. I have an entire article on this clever ascending system, read it here.
Here's the set up. This works way better than the traditional “go up the rope with two prusiks” method.
Here's another way to think about it, in a horizontal plane.
You're out 4x4 wheeling in your truck, and you get stuck. You take the winch cable from the front of your truck, put it around a tree anchor, and then bring it back and connect it to your truck. You turn on the winch and slowly pull yourself out. What is the mechanical advantage?
If you clip the end of the winch cable to the tree, you would have a 1:1. But if you attach it back to the truck, you create a 2:1, because the load (truck) is also doing the pulling.
image: https://www.ropelab.com.au/ropelab-quiz-1-mechanical-advantage/
Convert a 1:1 to a 3:1
When hauling on a big wall a 1:1 mechanical advantage system might need a boost, if your bag gets hung up or is dragging on a slab. Here's a quick way to increase your pulling power to a 3:1.
I learned this tip from big wall ace Andy Kirkpatrick’s excellent aid climbing and big wall book, “Higher Education”. Definitely recommended for all big wallers! Connect with Andy on his website and his Substack.
A few words on hauling, from Andy Kirkpatrick:
“Hauling is potentially one of the most dangerous aspects of big wall climbing. This translates to ultra-caution in all parts of your hauling system and interaction with bags, haul lines, docking cords, and pulleys. If you rush and make a mistake, drop a load or have it shift where it's not wanted, you could easily kill someone or yourself. I try and teach climbers to view their bags as dangerous creatures, like a great white shark, rhino, or raptor that is in their charge. The ability to keep them calm and under your control comes down to paranoia, foresight, and heavy respect for the damage they can do.”
When hauling light to moderate loads on a big wall, you can hopefully use a 1:1 mechanical advantage system most of the time. Yeah, it’s gonna hurt, but it’s usually going to be the fastest. (For bigger loads, you might prefer a 2:1 haul, which we cover extensively at this article.)
However, there may be times when you want to ramp up your pulling power from a 1:1 to 3:1. Typically, this happens when the bags are temporarily hung up, or are transitioning from being pulled from space onto a slab, or something else that introduces evil friction that you need to overcome. Or, maybe you're just feeling beat from a long day and want to make your haul easier, even if it takes a little longer.
Here's one way to set this up fairly quickly. You’ll need a bit of extra gear to do this, but hey you're big wall climbing so you have this with you, right? I’m showing this with pulleys for maximum efficiency. If you don't have those, you could also do it with carabiners at each change of direction, but you're going to be losing about 50% of your pulling efficiency, so pulleys are a better choice if you have them.
The basic idea is to make a 3:1 Z drag, with the pull strand redirected to the anchor point so you're pulling down instead of up. If that didn't make any sense, look through the photos below, and think it through. Once you understand the basic concepts, it takes just a minute or two to set up.
The photos are meant to illustrate the general procedure, and not to specify the exact gear that you should use. Everyone carries different equipment; use what you have.
Like with all big wall hauling systems, you practice this thoroughly until you have it dialed, with a realistic load, in a controlled environment, with the gear you’ll actually have with you.
Safety note: If you think your bag is slightly hung up, you can try this to get it free. However, if it's really stuck, it might be a better choice to rappel down (or have your second pendulum over, if possible) and actually remove the bag from the obstacle instead of putting a really large load on your hauling system.
Here's your basic 1:1 hauling system. The rope goes through Petzl Micro Traxion progress capture pulley at the anchor. There's a toothed cam on the pulley that captures the progress of your pull; if you let go of the rope, the pig does not slip down.
The Traxion is on a locking quickdraw. The quickdraw lets the pulley twist a bit and better align itself with the direction you're pulling, which slightly increases efficiency.
The rope going through the pulley on the anchor does not create any mechanical advantage. It merely changes the direction of the pulling force, in this case downward, so you can pull the rope down with your body weight rather than lifting up with your muscles. For every 1 meter of rope pulled down on the right strand, the pig goes up by 1 meter.
Step 1: Add a sling, carabiner, and pulley to the anchor. This will become the redirect for your pulling strand. Here, I girth hitched a 30 cm sling onto the top carabiner of the quick draw. This extends the redirect pulley a bit below the progress capture pulley so they don't clank around on each other. (If you have a schweet progress capture pulley with a hole at the bottom, like the Petzl Pro Traxion, skip the sling and clip the carabiner/pulley through that hole.)
Step 2: Clip an ascender upside down onto the load strand, add a carabiner and pulley, and clip the pull strand to the pulley. Here I'm using a Petzl Rollclip, an nifty integrated locking carabiner and high efficiency pulley wheel that works great in this application. But any combination of carabiner and pulley will work.
I'm using a handled ascender because that's pretty common gear you would have with you on a big wall. You can also clip a water bottle or two onto the top of the ascender, which can help it reset itself when you give it slack between pulls. However, any kind of a rope grabber would work here.
This is now your “tractor” pulley, meaning the one that's doing the work. If you pull upwards (toward the anchor) at this point, you have a 3:1.
Step 3: Clip the pull strand through the redirect carabiner that's on the anchor. Pulling upwards is a lot of work! We want to use our body weight and pull down. The redirect lets us do that.
Schweeeet! Now we have a 3:1, redirected for a downward pull. Pulling 3 meters of rope through the system will move the pig 1 meter. We have pulleys at every change of direction, which maximizes our efficiency. Again, you could use carabiners at every change of direction, but it's going to make the pulling significantly harder because of the extra friction. (Carabiners are about 50% efficient, a good quality pulley is about 90% efficient.)
Slide the ascender as far down toward the load as you can, and then pull downward, where the glove is. If raising a large load, you probably don't want to actually be yanking on the rope with your hand. Clip the pull strand through a Grigri or ascender, clip it to your harness, and start doing squats, using your bodyweight to lift. Or, you can clip another ascender to the rope where the glove is, clip an aider onto that, and then step down on the aider with your foot to lift the load. Use body weight, not arm strength.
When the ascender and redirect pulley come together, reset the system by sliding the ascender down toward the pig, and continue lifting. To help the blue ascender slide down on its own, you can clip a few cams onto it. The extra weight should help it reset itself.
Here's a diagram of this anchor, using the “T method” for counting tensions, to show the theoretical mechanical advantage.
If you want to learn more about the T method, check out my article here.
Notice that by adding the redirect, we increase the force on the anchor to about 4x your pulling force, as opposed to two times of the pulling force with a normal Z drag.
The previous photos were done horizontally to spread out the gear and more easily see how it works. Here’s the same set up done vertically, so you can see how the ropes hang in (semi) real life.
You can easily convert back to the standard 1:1 at any time, by removing the tractor and the redirect.
The 2 to 1 “Z pull” haul, explained
On a longer big wall, with bigger loads, using mechanical advantage to lift your haul bags can be extremely helpful. Here's a deep dive into the 2 to 1 hauling system.
Credits for this idea, as best I can. The 2:1 Z pull haul is generally attributed to Chongo, a legendary Yosemite dirtbag who was famous for extended vertical camping trips on El Capitan with ridiculously large loads. Pete Zabrok, also no stranger to multiple week outings on the captain with huge loads, popularized it via a 2004 Tech Tip in Climbing magazine, and now climbers such as Mark Hudon have refined it further.
This technique is explained nicely in the comprehensive aid climbing manual “Hooking Up, by Pete Zabrok and Fabio Elli, highly recommended for all big wall climbers!
A few words on hauling, from the excellent book “Higher Education” by Andy Kirkpatrick.
“Hauling is potentially one of the most dangerous aspects of big wall climbing. This translates to ultra-caution in all parts of your hauling system and interaction with bags, haul lines, docking cords, and pulleys. If you rush and make a mistake, drop a load or have it shift where it's not wanted, you could easily kill someone or yourself. I try and teach climbers to view their bags as dangerous creatures, like a great white shark, rhino, or raptor that is in their charge. The ability to keep them calm and under your control comes down to paranoia, foresight, and heavy respect for the damage they can do.”
Think before you act. Before you connect or disconnect anything, always think a step or two ahead and anticipate what will happen and potential problems. “If I untie this docking cord, then the load is going to go there, and after that happens, I’m going to do this . . . ”
On big wall climbs taking two or three days with a team of two, you can probably use a traditional 1:1 hauling system. However, for climbs much longer than this, or a team of three, or when you or your teammate are significantly lighter than the bags, or if the hauling is on terrain less then vertical, or maybe when you simply want to suffer a lot less, you may well want to add some mechanical advantage. As the saying goes, you can work hard, or you can work smart. For a big load, a 2:1 haul is working smart. (If you’re taking a truly ridiculous amount of stuff and need a 3:1 or 4:1, you're probably an expert enough climber to figure that out on your own, so I'm not going to cover that here.)
Say you have a pair of haul bags that together weigh 200 pounds. If you rig a 2:1 haul, you (theoretically) can lift this load with only 100 pounds of force. The catch is, you have to pull twice as much rope in order to get the load to the anchor, but for many people that’s a fine trade off to make. Think of it this way: do you want to lift 200 pounds once, or 100 pounds twice?
Now, there is Google-load of information out there about 2:1 haul systems. But like most things on the interweb, especially discussion forums, the signal to noise ratio is not so great; you’ll have to wade through pages of the usual randomness to get anything worthwhile.
Well, good news you you, I’ve taken care of the sorting and sifting. This post is a summary of current (2020) best practices, clear photos, and some specific gear reccos for the 2:1 big wall haul.
I’ll be honest, the first time I saw this I found it pretty darn confusing, and wondered if it was really worth it. But once you get the components arranged correctly, and give a little thought to what is happening, and try some real world testing, you’ll get the hang of it. And, hopefully you will never have to use that all too common excuse for bailing, “The bags were too heavy . . .”
One of the best climbing diagrams ever made, IMHO. Drawing by Mike Clelland, first published in Climbing magazine (March 2004) article written by Pete Zabrok. Note, while the system has been refined in several areas since it was first published, this is still the core idea.
image credit: Mike Clelland
Big picture concepts:
Minimize stretch wherever possible
Use high quality/efficiency pulleys
Lift the load by doing squats using your body weight or pushing down with your legs, not by pulling with your arms
Practice a lot with real loads
Get it set up fast and haul the bags a few meters off the lower anchor ASAP so your follower can get to work
The basic set up is a 1:1 haul through a progress capturing pulley, such a Petzl Traxion. (This is a pulley that has a one-way rope grab on it like an ascender, that let you pull the rope through one direction but prevents it from sliding back.) Yes, these little suckers are expen$ive!
On the load strand of the haul line, you add on an entirely separate 2:1 lifting system. You raise the load with the 2:1 lifting system, and then pull the slack rope through the progress capture pulley.
In the rigging world, this is sometimes referred to as a “pig rig”, because you are “piggybacking” a 2-1 system on top of the main loaded rope. (And, that’s an entirely appropriate name for big wall climbing, because haul bags are affectionately known as “pigs”.)
One nice benefit to this system: you can add or remove the “pig rig” from either a slack or tensioned rope, which lets you switch as needed in the middle of a haul.
General diagram of a 2:1 “pig rig”. (The black rope is the main static haul line. The gray cord is the 2-1 “Z cord.” Tilt your head to the left; it looks like a letter Z, get it?)
In the diagram below, the system is spread out over two anchors. It also works fine on one.
(Note: if you've taken a crevasse rescue or rope rescue class, you might think of a “Z drag” as being a 3:1 mechanical advantage. That is correct. However, in this case, the “Z” is a 2:1 system, with a change of direction pulley, as you can see below. Trust me, it's 2:1, don't let the “Z” in the name confuse you.)
Here's how it works.
The hauler pulls down on the gray cord, maybe by squatting in the harness.
This lifts the black rope, creating slack.
Pull that slack through with your hand, capturing the progress with the pulley on the right anchor.
Repeat!
Image credit: Andy Kirkpatrick, from his excellent book “Higher Education”, used with permission
There are various ways to rig a 2-1 haul. Here's one.
Components
All parts live in a designated small stuff sack and stay clipped together between hauls, ready to deploy.
Large HMS locking “master point” carabiner
Short Dyneema dogbone quickdraw runner (hard to see in the photo, sorry.) Zero stretch, important! This could also be a large stopper or custom made metal quickdraw. This allows the carabiner and progress capture pulley below it (3 & 4) to rotate and align when pulling.
Locking carabiner
Progress capture pulley, here a Petzl Mini Traxion
The “tractor” pulley, so called because it’s doing the work
Quicklink, I think 8mm
Inverted ascender, here a Petzl Croll. Could be a Petzl Basic or similar small ascender without a handle.
The haulbag(s), aka “the pig”
Haul line, typically 70 meter, 10 mm, static rope
Handled ascender. Add this to the “pulldown” side of the haul line to make it easier on your tired wall hands. But remember, you want to be doing most of the hauling with your bodyweight and not your arms.
The Z cord - 7 mm cord, start with about 5 meters. If you find you have too much extra cord, trim some off. Could be a thinner 5.5 mm static spectra cord for a slightly more efficient pull. Be sure and tie a large stopper knot on the end to prevent your hardware from sliding off accidentally. (Pro tip, bring a second spare Z cord, in case the first one gets trashed.)
The “redirect” pulley, so called because redirects the Z cord downwards so you can use your body weight to lift. This pulley does not add any mechanical advantage. This should be a high quality pulley, see examples below.
Small loop of 11/16” webbing tied through the pulley. This webbing connection, rather than a carabiner, allows the redirect pulley to freely rotate and give a more efficient pull. It’s important to have this webbing loop small so the redirect carabiner is high, which gives you a longer, more efficient pulling stroke.
Not shown: Two carabiners with rounded cross sections on your belay loop. When you’re hauling, you can clove hitch the orange Z cord to both of these carabiners. Having two of them makes untying the loaded clove hitch easier. Old school oval carabiners work fine.
Another option is to clip an ascender with a stirrup of webbing or an aid ladder onto the Z cord, and pump down on the Z cord with your leg.
Here’s another way to rig this. Note the redirect pulley (orange) with an integrated swivel, smaller diameter static Z cord, a cable quick draw (zero stretch) and a Petzl Basic ascender. This looks a little simpler without the haul rope, but it's the same basic idea.
image: https://www.mountainproject.com/forum/topic/115790897/the-latest-greatest-21-hauling-kit
Side note: You might be tempted to use a rigging plate clipped to the master carabiner, because it has three things clipped to it and it's getting kind of busy. This would be a mistake. Reason being, that rigging plate is going to rock back-and-forth as it's loaded and unloaded on different sides, which will decrease your hauling efficiency.
Rigging plate - Do NOT use it in your 2-1 hauling system.
One of the beauties of the 2 to 1 haul kit is that you can set it up pretty much once, keep most of the components clipped together in the correct order, and leave it that way. It has its own small designated sturdy stuff sack (medium sized Fish “Beef Bag” works great). The haul kit is never taken apart, and is either being used or in the storage bag. Note that the hauling system hardware always stays clipped to the storage bag; can’t drop the bag if you do this.
Note that the leader does not have to take the haul kit up with them on lead. The leader can trail a tagline, and bring up the haul kit once they arrive at the anchor. Doing this saves weight and cluster on your harness. More on using taglines here.
At the belay, here’s what you do:
Build an equalized master point anchor from 2 bolts. (If the bolts look newish and extra stout, you can haul off just one, but I’ll leave that choice to you. Me, I like 2 bolts.) Use an “anchor kit” of several large locking carabiners, and maybe a pre-tied quad anchor or PAS that you and your partner can set up fast and the same way pretty much every time.
Clip the master point carabiner for the Z haul system to the anchor master point (or lone hauling bolt).
Run the haul rope through the progress capture pulley, engage the cam, and pull all the slack through the pulley. Then clip on the inverted ascender. Hopefully you have a rope bag; now would be a good time to start using it to stack the haul rope.
Extend your daisies or connection to the anchor so you are free to move. Find yourself a good stance and adjust the Z cord with the clove hitch on your harness. (Altenatively, clip an ascender to the Z cord, clip on an aid ladder, and press down with your leg.)
Start lifting your bags a few meters, so your partner below can get busy breaking down the anchor. (Once the bags have been lifted off the lower anchor, ONLY THEN you can take a break for a minute or two before you start the real hauling.)
A few notes . . .
As pointed out to me by wall ace Mark Hudon: Yes, you may be theoretically 2:1 efficient, but that can also mean 2:1 inefficient. Meaning, if you have 1 inch of slack in your lifting system, you’re actually losing 2 inches of lift with every stroke. When you push the lifting ascender down, be sure to Z cord comes tight to the clove hitch to your harness so there is no slack. Squat with your body weight. If you doing it right, there should be no pulling or lifting with your arms at all.
Practice, practice, practice with this system. Go find a retaining wall, a tree, a fire escape, an outside staircase, whatever, and load up a haul bag with water bottles or bricks or rocks, and really give it a work out. Which way should the master carabiner face (left or right off the bolt hanger) to be most efficient for you? Do you want to have the inverted ascender by your dominant hand or your weaker hand? How long exactly should the Z cord be? (This changes depending on your stance.) These are some subtle yet important adjustments that can only be found with practice. Taking the time to dial in your system will pay big dividends on the wall.
It's usually less energy to do more small squats than fewer big ones. Doing short little strokes might seem like it's gonna take forever, but you're probably going to expand less energy in the long run.
Ideally, you want your strong/dominant hand on the inverted ascender, and your weaker/non-dominant hand pulling the slack rope through the progress capture pulley. So, in the cartoon diagram at the top, and the labeled photo, this is set up for a left handed person. Experiment with this and see what work for you.
Ideally, both pulleys should be high efficiency, with sealed ball bearings with 1.5 to 2 inch aluminum sheaves/wheels. These will cost about $40 each, don’t skimp on these. If you have one pulley that’s better quality and/or has a larger diameter wheel, use this as as redirect pulley, and use the smaller or lower quality pulley on the tractor. The reasons for this get into some engi-nerd territory, but trust me, this is the best way to rig it. (But, don’t be a cheapskate, just spend an extra 10 bucks or so, get two high quality pulleys, and then it’s not an issue at all.)
When shopping for pulleys, go for quality from major manufacturers such as SMC, Petzl or CMI; they are used a lot by professional riggers and rescue teams. Look at the technical specifications. Stay away from cheaper pulleys that have plastic wheels (aka sheave) or bronze or nylon bushings. You want an aluminium sheave and sealed ball bearings. A small inefficiency in a pulley is magnified many thousands of hauling strokes over a single route, so the difference between say 70% and 80% efficient is significant. Fortunately you can have lightweight, high efficiency pulleys, you just need to buy the right ones.
Mark Hudon likes the 2" Single PMP and the Micro Single PMP, both made by SMC (Seattle Manufacturing Company). Some other good options would be the Petzl Rescue pulley or the CMI RP102.
Prusik minding pulleys (also known by the acronym of PMP) tend to be more expensive that regular pulleys. You don’t need a PMP in this system, because there are no prusiks.
When hauling, remove everything from your harness gear loops. You want to minimize extra weight when you’re repeatedly squatting and standing.
Bring a spare Z cord. If you're doing this over a ledge, the cord might get damaged. Bring a spare.
Practice will not only help you haul more efficiently, but it will help you get set up faster. This is important, because your partner can’t start to break down the anchor and begin cleaning until you haul the bags at least a meter or two and get them off the previous anchor.
If the leader wants to be extra courteous and helpful, they can break down the hauling kit when the bags are safely docked, package it back up in its stuff sack, and hang it on the first piece of gear for the next pitch, so the new leader can be sure and grab it. (If the second is using a tagline to pull up the kit when they need it, then no need to hang it on gear for the next pitch.)
Just like with any hauling system, you want to minimize friction in any way you can. If you have the option, build your hauling anchor as high up as possible, and try to eliminate or minimize the angle at which the rope may run over any rock edges. If the pitch is overhanging, lucky you. If you're pulling the bags up a slab, then you're theoretical 2:1 is going to act more like a 1:1. Prepare to suffer.
Wear gloves for big wall hauling. The Metolius 3/4 finger climbing gloves are great.
Here’s a video of Mark Hudon using this system to haul a big load on the first day on El Cap. Keep in mind Mark weighs about 130 pounds, but look at the great rhythm he has with the pull.
Mechanical advantage calculator from alpinerecreation.com
Here's a link to a very cool online mechanical advantage calculator! Choose your rigging method, choose your components, choose your load, click a button, and you instantly see all of the different forces in the different legs of your rigging system. Courtesy of the New Zealand-based guiding company, alpinerecreation.com.
I recently came across this clever online tool from alpinerecreation.com, a New Zealand based guiding company.
It’s a mechanical advantage calculator, very cool!
This is an excellent way to instantly see some of the forces involved with different rigging methods, and how using a carabiner rather than a pulley can change the efficiency of your system.
(Works fine on a mobile phone but it's easier to see the big picture on a wider computer screen.)
Choose your hauling system (2:1. 3:1, 5:1, 6:1, etc.)
Choose your components (Micro Traxion, rescue pulley, large carabiner, small carabiner, etc.)
Choose your load (default is 100 kg)
Choose your units (percentage of load, kg, or kN)
Press “Calculate” and it gives you values and forces all the way through the system!
Check it out here.
Here’s a screen grab showing values for a 3:1 Z drag, using a Micro Traxion as the progress capture and a good quality pulley on the “tractor”.
You can see that if you pull with about 38 kg of “force”, that should be enough to move your 100 kg load.
image: https://www.alpinerecreation.com/mechanicaladvantagecalculator.html
Can you have "too much" mechanical advantage?
A good general rule: use the least amount of mechanical advantage (MA) that you can to get the job done. Adding additional pulleys and ropes grabs also introduces more friction. In some cases, what you think is giving you extra MA may actually be worse than what you had before.
A good general principle in setting up mechanical advantage (MA) systems: use as little as you need to get the job done. Are you able to move your load with a 3:1? Great, use that, and don't make it a 6:1!
Or, to put it another way, just because you CAN add more MA doesn't mean you SHOULD add more MA.
Every time you increase mechanical advantage:
You add extra gear, changes of direction, introduce more friction, and create more chances for ropes to twist, rub, cross etc. that reduces the overall efficiency
You increase the force on the anchor
A fundamental principle of economics (and many other aspects of life, including climbing) is the law of diminishing returns. In econ-speak, means that adding additional factors of production eventually results in smaller increases in output. Say that it takes one builder one year to build a house. So, if you have 365 builders, can you build a house in one day? Of course not, because after a certain point, the extra production (builders) result in lower output (less work getting done because they are tripping over each other).
MA systems work in somewhat the same way. Past a certain point, it doesn’t make sense to keep adding components to the system, because you're actually decreasing efficiency.
Here's an example, with a common self rescue techniques taught in many books and classes.
You’re belaying your second with a Grigri off the anchor. They get to the hard part, and need a short lift / assistance to get past a hard move or two.
No prob! You set up a theoretical 3:1 as shown on the left. Simply add a rope grab on the loaded rope going down to them, clip a carabiner onto the rope grab, and pull up. Voilà, a nifty 3:1! Start pulling and up they go, right?
Well, not quite! Let's have a closer look at the top photo.
Because you’re using a fairly inefficient carabiner (about 45% efficient) and a really inefficient Grigri (about 28% efficient) as your progress capture, at every change of direction where the rope goes through these devices, they are going to rob you of some of your pulling force. This means your real world efficiency is somewhere around 1.6 to 1, not 3 to 1.
Depending on your strength and the rope running over any edges or gear and adding additional friction, etc. might mean it's still impossible to move your partner!
No problem, let's make it a 5:1!
“Wait”, you say, “I know what to do! I have another rope grab. I’ll put that on the backside of the rope coming from the Grigri, and clip my pull strand to that. Now I have a 5:1 pulley system! With that I should surely be able to lift my lard-ass partner. Besides, now I get to lift DOWN with my body weight instead of UP with my arms. That must be easier, right?”
Well . . . Let's have a look at the photo on the right.
Turns out, rigging a theoretical 5:1 like this gives you something pretty much close to a 1:1 in real life! That red carabiner on the rope grab introduces so much additional friction at the start of the system, that the rest can't really overcome it. You probably be better off staying with that 3:1.
You have also created what's called a “complex” pulley system. In a complex system, you have two pulleys moving toward each other when you pull. This can be a bother when you’re at a small stance, and requires that you reset the system more often.
There are some good ways to set up a 5:1 or a 6:1 at a small stance that require minimal gear and offer reasonable efficiency. Unfortunately this is not one of them.
So, if you build a lame hauling system like this and it's not working . . . you need to yell down to your partner to get out a couple of their own friction hitches and start prusiking up. =^)
Takeaways:
There can be a giant difference between theoretical MA and a real world MA.
Adding more MA is not always better.
Use pulleys when possible to increase your efficiency.
If you have a limited pulleys, use them closest to your hand that’s doing the pulling.
The 3:1 Spanish Burton haul system
After you have the basics of a 2:1, 3:1 and 6:1 hauling system dialed, rope geeks and mechanical advantage fans might want to learn some more esoteric rigging. Here's one of them, the 3:1 Spanish Burton. It lets you pull down, instead of up, which could be helpful in a vertical haul. Practice with it, it's fun!
When learning mechanical advantage for rope rescue, I think it’s important to start with the basics: a 2:1 “C” and a 3:1 “Z”.
Once you have those dialed, one can be added on top of another one to create what’s called a compound 6:1 if you need extra pulling power. In just about every rope rescue scenario, some combination of a 2:1, 3:1 or 6:1 should cover all of your needs.
However, if you like playing around with ropes (and I know you do, otherwise you wouldn't be reading this) here’s an interesting one to learn: the 3:1 Spanish Burton.
It's traditionally used for rigging on ships.
What’s up with the name?
For long time, I had no idea. Then some helpful Instagram fans offered the following;
Burton is “small tackle” British or old English term. Spanish Burton in old British navy manuals was the use of a MA system to pull another MA system.
and:
“On traditionally rigged ships, the advantage of the Spanish Burton is to keep the MA system from twisting. Three strands of line wants to twist, and if the blocks aren't fixed on both ends, a pulling force will cause the strands to wrap up and massively increase friction. By having a MA pull on an MA, it ensures no twists by creating a force vector offset from the main line to pull on the MMA system attached to the load.”
There you go! Thank you, Instagram friends, for unconfusing me on this!
Why might the Spanish Burton be useful?
In a vertical lift, you can pull DOWN with your body weight to lift the load. (In a more typical 3:1 Z drag, you need to pull UP.) For a vertical lift, it's helpful to have the anchor point as high up as possible so you can use your body weight most effectively.
It lets you set up a 3:1 with basically zero extra rope. Such as, you're only carrying a meter or two of extra rope, your partner falls in a crevasse, and you need to set up a 3:1. (Yes I know, not super-practical, but could be helpful.)
Spanish Burton rigging notes . . .
The purple sling is tied to the green rope with a Klemheist hitch. You could also use another rope grab here, like a Tibloc. (I used a sling here; any bit of cord or sling will work.)
The 120 cm purple sling means you need to reset the system often. If you have more room to work, you could replace this with an untied cordelette, which would give you a much longer pull.
The always handy Petzl Micro Traxion is the progress capture pulley on the anchor.
We have two “traveling” rope grabs moving toward each other. This means you need to reset your system more often, which can be a hassle if you have a small workspace, or no big deal if you have a large area to work in, like on a snowfield.
Note that the Spanish Burton increases the load on the anchor. For example, if you pull with 1 “unit” of force, this puts a load of about 4 “units” on the anchor. Compare this with a traditional 3:1 Z drag. With a Z drag, if you pull with 1 unit of force, you have 2 units of force on the anchor. If your anchor is unquestionably strong, no worries. If it's not, this may be something to consider.
Using the “T method” to determine the mechanical advantage
There's a technique called the “T method”, or the tension method, which can determine the mechanical advantage of many rigging systems.
We start with an input force of 1, that's your hand pulling on the purple sling.
At the blue pulley, the input force is doubled to 2. That gets transmitted to the prusik hitch, and to the green rope.
The 2 on the green rope goes into the Traxion. That is doubled for a total force of 4 on the anchor.
The input force of 2 comes out of the Traxion on the other side as 2.
This force of 2 travels down the green rope on the load side. There, it meets the force of 1 on the left side of the purple sling.
You add those together for total mechanical advantage of 3:1.
If you want to learn more about this, here’s an excellent tutorial video on how to count tensions using the T method.