Forums: Climbing Information: Beginners: Re: [JimTitt] O-n-O lockers unsafe?: Edit Log




rescueman


Aug 25, 2011, 3:36 PM

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Registered: Mar 1, 2004
Posts: 439

Re: [JimTitt] O-n-O lockers unsafe?
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JimTitt wrote:
However an experienced rescuer, rigger, guide and whatever else you claim to be really should know that adding karabiners increases the friction at the top anchor.

Now comes Jim to take on the flaming role. Must be a tag team. If you would like to present an explanation, rather than merely vent, you might actually contribute to this discussion.

As your own published reports indicate, the smaller the sheave diameter the greater the internal friction (and potential exceeding of elastic fiber limit) and the lower the efficiency (more energy lost to internal friction).

As you well know from the capstan formula, friction around a pole varies exponentially with angle of wrap and friction coefficient and is independent of surface area of contact, other things being equal.

Given that the angle of contact (180 for a slingshot belay) is the same with one or two carabiners, and the friction coefficient is the same in either case, perhaps you'd care to explain how double carabiners at a top-rope change of direction increases friction?


(This post was edited by rescueman on Aug 25, 2011, 3:42 PM)



Edit Log:
Post edited by rescueman () on Aug 25, 2011, 3:42 PM


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