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Rescue Type Stuff

Try some of these links for info on rope rescue stuff including rope data and tests.





Mechanical Advantage

Mechanical advantage, or hauling more weight with less work by means of some system, is one of the best things you can learn. With this you can haul your pig on El Cap, retrieve a partner who can no longer move under their own power, or do some nifty yardwork tricks. My bad drawings below will get you going on the basic idea. There are numerous ways to set up these systems, yet all give the same effect. For some fine reading on these systems and way more, see Wilderness Search and Rescue, by Tim Setnicka.

Paraphrased from the book, Wilderness Search and Rescue:
For the below drawings we will consider the pulley systems in a state of equilibrium. Equilibrium is when a pulley system under load is not moving; the forces trying to raise the load are equal to the load. These theoretical pulley arrangements have no friction in the pulleys or elsewhere. In reality however, there is a tremendous difference between trying to raise a load with a 3:1 system using efficient pulleys and one using only carabiners.

 Pulley  Pulley Factor  Actual Mech. Advantage  Theoretical Advantage
 carabiner  .66  1:.98  3:1
cheapo pulley .75 2:.42 3:1
 rescue pulley .93 2:.79 3:1
 frictionless  1.00  3:1  3:1

(note: these are numbers from 1977. YMMV)

If any load (use 100lbs as an example) is fully supported by a rope, it represents a 1:1 system. It will take 100 lbs of pull to keep the load in equilibrium.


Each portion of the rope on either side of the pulley is supporting half the weight of the load. It is the continuity of the rope around the pulley that equalizes forces T1 and T2. the reason each side of the rope takes half the load is because they coordinate movement. In any mechanical advantage system, it is the continuity of one rope going around the all the pulleys that automatically coordinates the distribution of the load. This is the fundamental concept behind pulley use. Since the system is in equilibrium, it is easy to see that if one more pound of force were added to T2, the system would be out of equilibrium and the load would slowly begin to rise. At equilibrium the rope tension always equals the load.

Of note is when you are using a mechanical advantage system, there is a lot more force being applied to some part of that system than it would seem. It is very important to know what that force is doing on the other end of the rope... for example: You are raising your unconscious partner with a 3:1 or higher pulley system. You are yarding away and barely notice the the hauling got a bit harder for a second.... no problem you pull a bit harder and then the hauling is normal again...guess what, his head got wedged in fissure and has now popped off...yep, you pulled his head clean off. Could happen. I once set up a free air haul with a mechanical advantage to help raise some really heavy bags on El Cap. The bags got hung up under a small roof. I pulled and pulled....finally something gave...it was the sheath on the haul rope, below the system I had set up. Not a pretty sight on day one..... No way I could have done this without the mechanical advantage.... but, with the set-up, it was not very hard to do.

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