Forums: Climbing Information: The Lab: Re: [dead_horse_flats] $40 bet - two non-locking biner anchor failure.: Edit Log




Partner cracklover


Apr 7, 2012, 7:46 AM

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Registered: Nov 14, 2002
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Re: [dead_horse_flats] $40 bet - two non-locking biner anchor failure.
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dead_horse_flats wrote:
This is a $40 offer to anyone who can demonstrate a scenario of the failure of a top rope anchor using two non-locking opposed biners at the power point.

Disclaimers.
1. Opposed means opposed.
2. No manually holding the biners to force the rope thru them.
3. No wrapping the rope around the biners unless you can create a situation where this could happen un-intentionally.
4. Failure means the rope escaped from BOTH biners. Both means both.
5. No theories, microfractures, CE marks, or alien abductions.

Prove it and I will mail you $40.

Okay, here ya go.

Note - this post is getting quite long, so I'm going to split it up into sections. Here's the first part....

Setup - anchor configuration:
------------------------------------
- Two non-locking wiregate oval biners, opposite and opposed, with gates facing down and out
- Static rope anchor, tied in a fig-8 knot on a bight.



Step one - biner location:
-----------------------------------
Two things have to happen, in no particular order:
- The gates wind up inside the spine of the other biner. When you jostle the biners around, the gates will always settle either inside or outside the spine of the other biner.
- The biners wind up sitting on the edge. A few things that could cause this are that one of the anchor points snags on something, shortening that arm, or that the anchor was set up poorly, such that when weighted, the biners are over the edge, but when some of the weight is released, the biners get pulled up onto it.



Step 2 - gate opens:
--------------------------------
If the edge is rough, the gate on the inner biner can get caught on even a small jut. Then a downward pull on the anchor can cause that gate to open. This can happen even without any sideways pull in the direction of the jut. Once the gate gets caught, the biners can rotate onto the bump on the rock, making it so that any force will cause the gate to open.


link to video 1

Let's step back for a second - Why should it matter all that much if, when the climber's weight comes off the anchor, it can wind up sitting on the edge, and then if the weight goes back on it, it causes the gate to open momentarily? After all, I'm sure plenty of you are thinking, the biners are plenty strong enough to hold a small toprope fall, even with one gate open. And if a fall on the anchor causes it to get pulled all the way back over the edge, the gate will close on its own.

All true!

But... what if there were something that could cause the rope to escape the biner while it's open? Well it turns out that, given the following scenario, that's exactly what can happen.

Read on...


(This post was edited by cracklover on Apr 7, 2012, 10:44 AM)



Edit Log:
Post edited by cracklover () on Apr 7, 2012, 7:47 AM
Post edited by cracklover () on Apr 7, 2012, 7:51 AM
Post edited by cracklover () on Apr 7, 2012, 9:08 AM
Post edited by cracklover () on Apr 7, 2012, 10:41 AM
Post edited by cracklover () on Apr 7, 2012, 10:44 AM


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