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Topic Date User

Slack line anchors !?! 8-May-2012 At 9:57:30 PM Cool Hand Lock

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On 14/03/2012 sliamese wrote:
>Do people get that an american death triangle will put about 140% of the
>load onto EACH anchor?

It dosn't put 140% on each anchor. Only 50%. And 50% of body weight on a dynamic rope = fudge all.

Heres some maths on a slack line anchor. Using a tight line with a 10degree deflection. An 80kg climber falls from it 2m untill his back up catches him. Gravity(10ms/s) Aparent weight of someone falling would be 400kg roughly. 400kg relative weight because you'll be falling at about 5m/s when the line catches you.

Load angle calculation. Sin(10) = .17 then 1/.17= 6ish multiplier.

Multiply your relative falling load (400) by 6 = 2400kg Is the load on the anchors.

Load ratings of anchors.

1. Rigging equipment such a crane slings, chains, strops and shackles has a SWL (safe workign load) with a safety factor. X5 for steel, X7 for fabric.2ton working = 10/14ton breaking.

2. Climbing anchors have a MBS (minimum breaking strain). ie what they have written on them is what they will break at.

So when you put your 2 ton shackle into a climbing 2 ton anchor. Your really putting a 10 ton link in a 2 ton anchor.

If you have questions on rigging loads, feel free to ask, or read John Longs, Climbing anchors or More climbing anchors. Or go do a rigging course. Personally I've all of those things, out of greed, because it pays well.