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Unread 06-12-2014, 12:35 PM   #16
wilson1010
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Quote:
Originally Posted by BYuen View Post
That's not a good way to hook things up. You are putting a ton of side load on the recovery points, even more so than if you did it the other way.

http://en.wikipedia.org/wiki/American_death_triangle
Not if your recovery points are hanging D Shackles, which they should be.

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Unread 06-12-2014, 12:59 PM   #17
biffgnar
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Originally Posted by wilson1010 View Post

I think you are right about that. But, it is a good idea to scare the newbs.

Here is the diagram.
Yes, that was how I envisioned your description. Still seems like it creates competing inward forces on those recovery points that you don't want. Honestly the forces created seem to me not that much different than a bad bridle rigging. Maybe I just don't get it.
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Unread 06-12-2014, 01:04 PM   #18
BYuen
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Originally Posted by wilson1010 View Post
Not if your recovery points are hanging D Shackles, which they should be.
The OP doesn't have D-shackles.

Regardless, D shackles especially should not be side loaded. It will easily bend or tweak them or cause complete failure. Not only is the triangle creating side load, it is also a huge force multiplier. As the bottom angle increases, the forces significantly increase on both anchor points. This is why at minimum, the bridal length needs to be at least twice that of the distance between the two recovery points. This will keep that bottom angle down and reduce the lateral forces.

http://www.onrope1.com/ADT.htm
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Unread 06-12-2014, 01:17 PM   #19
BYuen
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Originally Posted by biffgnar View Post
... Honestly the forces created seem to me not that much different than a bad bridle rigging. Maybe I just don't get it.
The forces are similar as the bridle rigging, but worse since the bottom angle of the triangle is larger than it would be with the bridle. This creates more side load as well as multiplying the force each recovery point sees.
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Unread 06-12-2014, 01:42 PM   #20
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Actually, what they did was to side load the one shackle. I'd never suggest a bridle anyway unles we were hanging the jeep from a crane.
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Unread 06-12-2014, 03:53 PM   #21
BYuen
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Originally Posted by wilson1010 View Post
Actually, what they did was to side load the one shackle. I'd never suggest a bridle anyway unles we were hanging the jeep from a crane.
Side loads when lifting are static and should be ok to a certain extent. You have to take in account the decreased shackle load capacity with the side load. They have rigging charts that calculate all that for you.

But for recovery when the loads are not static, it is best to avoid bridles or triangles. Much better to hook to one point and pull in as straight of a line as possible.
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Unread 06-12-2014, 05:00 PM   #22
wilson1010
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Originally Posted by BYuen View Post
Side loads when lifting are static and should be ok to a certain extent. You have to take in account the decreased shackle load capacity with the side load. They have rigging charts that calculate all that for you.

But for recovery when the loads are not static, it is best to avoid bridles or triangles. Much better to hook to one point and pull in as straight of a line as possible.
There are real concerns of recovery and theoretical concerns. I have never even bent a shackle mount yanking on them with my 10,000 pound Unimog, much less pulling a little Wrangler up a little dirt hill with a little truck.

If I was going to lower a Jeep from an Interstate overpass with my hydraulic winch, I'd be all over those tables.
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Unread 06-13-2014, 12:09 PM   #23
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Back in my rock climbing days, that is dangling by finger tips to avoid death, self equalizing slings setups were important to know. Redundancy isn't always a bad thing. And it can be applied in other facets of life. So here's an easy one.



You can do away with the double overhands, the twist allows the loaded point to slide and still keep stress pretty equal between both anchors. The greatest risk is the sling itself failing, but it's a small risk.
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