Forums: Climbing Information: The Lab: Re: [loyota] Common KNs in real world falls: Edit Log




colatownkid


May 12, 2009, 6:28 PM

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Registered: Nov 27, 2007
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Re: [loyota] Common KNs in real world falls
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loyota wrote:
Since we know that most, if any falls don't produce the kind of KN force generated by the x2 lab drop test, and 10KN+ gear isn't exaclty breaking left and right... etc etc

Are there any studies or data out there regarding what range of KNs are typically generated in more real world falls (not necessarily factor 2).

John Long cites scientist Craig Connally in his book who throws out a 5.5-8.5 KN max figure. JL also mentions that in an eight year period QA at Black Diamond hadn't seen any stopper over 10KN fail and only a few 10KN carabiners fail in closed gate mode.

I guess if some yates screamers kick in at 2KN, we know we can get into that range probably without trying too hard :-D

I can't recall of hearing of any 5KN type gear breaking, I hear of Micros breaking but I don't know how low they were rated.

Anyway, just curious, be nice to know what's a little more based in the real world when you're forced / choose to start placing pro that's dropping into the lower KNs

Real world the greatest force is not necessarily a factor-2 fall. this situation actually produces a greater force:

hanging belay on a multipitch climb, the leader clips the top piece of the anchor or places a piece shortly after the anchor. the leader then continues for some distance without placing any gear and then falls. this results in a high-factor fall (though not factor 2). however, the pulley effect on the top piece results in a greater total force than a simple factor-2 fall. depending on how far the leader climbed, this force could be theoretically massive.

the max force from a factor-2 is somewhere around 9kN by my calculations. this assumes the belay is static, the belayer is about 1 meter from the anchor, and the leader is the standard 80kg climber. i don't remember the rope impact force i used in the calculations, but it was a decent median of single ropes currently on the market. these calculations were largely based on a paper rgold put together a while ago that i can't find the link to right now.

of course, assuming a static belay is not entirely realistic as the belayer will move and rope may slip, so forces could conceivably be even lower.

hope that helps.

edited to add: as fishclimb pointed out, this calculation also assumes the rope is an ideal spring and is not critically dampened (as it is in real life).


(This post was edited by colatownkid on May 12, 2009, 7:19 PM)



Edit Log:
Post edited by colatownkid () on May 12, 2009, 7:19 PM


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