Forums: Climbing Information: The Lab: Re: [patto] Stupid Simple Elette: Edit Log




Neoshade


Aug 18, 2011, 1:28 AM

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Registered: May 11, 2009
Posts: 31

Re: [patto] Stupid Simple Elette
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patto wrote:
Neoshade wrote:
No one's telling you what anchor to use, this is The Lab, and we're discussing theory.

We if we are going to discuss theory could you please explain how the above device equalises dynamically? Furthermore lets discuss how no extension and dynamic equalisation are mutually exclusive. Finally how about we discuss how extension in a typical scenario results in shock loading the anchor and can result significantly higher forces.

I don't want to get to far into it, Really, much of all that has been discussed over and over elsewhere in these forums.
But basically, the Doudle Figure 8 will allow rope to slide from one loop to another a bit until the knot is loaded. That's what I mean by dynamic equalization - it equalizes on the fly as the rope moves. I'll look more into other discussions of the knot, most importantly how much slippage and equalization takes place under a fall load. Sorry, can't say yet. Good point. There are other tricks to make it slide continuously without ever tightening the knot though, should one wish. (I'll post later).

Also, extension causing "shock loading" and "significantly" higher forces has been debunked a long time ago. Jim Ewing at Sterling Ropes conducted load cell testing completely disproving the idea, showing there is almost no concern over small amounts of extension (a foot or less), that overall force was not increased during tests where a piece blew, and that "shock loading" is a vague term that doesn't apply to a system involving an elastic climbing rope.
Read Climbing Anchors by John Long. All that testing is in the book, the book which starting all this new anchor discussion.
Finally, This thing is suposed to extend if a piece blows. Not very much, that's the whole point of limiter knots and using this double Figure 8 as only a small part of the rig.
But nonetheless, I'm proposing the use of the double 8 based on the premise that you're up to date on the subject of small extension being OK, and moved on.
We're talking about starting with an equalette here, so if you don't like anything sliding with the understanding that some extension is inherent, then there's not much more to discuss (without repeating other, older threads).

See this thread for discussion on sliding X's, limiter knots and shock loading:
http://www.rockclimbing.com/...um.cgi?post=1306133;

And further details on the testing done:
http://www.supertopo.com/...id=307091&tn=108


(This post was edited by Neoshade on Aug 18, 2011, 1:30 AM)



Edit Log:
Post edited by Neoshade () on Aug 18, 2011, 1:30 AM


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