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.

(No, I have absolutely no idea why it’s called the “Spanish Burton”. Guessing it had to do with a guy named Burton who found himself on a Spanish sailboat about 400 years ago . . . )

Why might the Spanish Burton be applicable in rope rescue?

1. 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.

2. 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.