Parallel Hauls, Doubled Mechanical Advantage or Not?

Written By: Craig McClure

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Today at Rigging Lab Academy, we’re going to bust this myth that parallel mechanical advantage systems somehow add together and double mechanical advantage. There are arguments out there that two 3:1s side by side pulled on the same load are a 6:1, or two 5:1s are a 10:1. It’s not true, and we’re going to break it down really simply.

 

To be totally clear on all of this, we can throw all the stuff out the window now, parallel 3:1s, ganged 3:1s, parallel hauls, no matter what you do, you’re not doubling your mechanical advantage. You’re just halving the force on each rope, halving the amount of pull you have to have on each rope. You still have to put in the same amount of work to get the job done. You’re just deciding on what rope you put it on.

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So on behalf of Craig,

Peace on your Days…

Lance

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  • Avatar Cliff Freer says:

    Thanks for doing this test. I don’t disagree with the findings but I think you guys focused a little tightly on the numbers and not the real world benefits of this setup. The load weighs what it weighs and the energy to move the load is a product of how gravity and the components are interacting with one another, those will always be the starting point. Halving the input force on each of the ropes requires much less coordination and effort on the haulers. I would never gang them together as this negates that benefit. The biggest advantage of the twin 3:1 system is the rate at which it collapses. Less resets, longer throw. Couple that with the haulers being able to hand over hand the ropes providing a smoother ride for the victim and maybe an attendant and this has been a tremendous improvement over a single Z rig or inline 5:1 used in most haul systems.

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