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p8ntballsk8r
Sep 4, 2010, 11:06 PM
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I noticed that on all the nuts i've ever used to looked at, the wire (or entire unit) is only rated to 10kn. Is this truly strong enough to take a lead fall above the nut?
If 10kn is strong enough, why are the carabiners we use so much stronger? Even the cheapest nonlocking oval biners are rated to 18kn. what gives?
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dugl33
Sep 4, 2010, 11:32 PM
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p8ntballsk8r wrote: I noticed that on all the nuts i've ever used to looked at, the wire (or entire unit) is only rated to 10kn. Is this truly strong enough to take a lead fall above the nut? If 10kn is strong enough, why are the carabiners we use so much stronger? Even the cheapest nonlocking oval biners are rated to 18kn. what gives?
You might try plugging numbers into JTs force calculator. http://jt512.dyndns.org/impactcalc.html
Use your own weight, your ropes impact force, and play around with different fall factors. Yes, a hard enough fall could break a 10kn cable, but in reality this rarely happens. It would have to be a really harsh fall.
Biners are strong enough that even the harshest fall should not break them unless the gate comes open or they are loaded funny.
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climboard
Sep 5, 2010, 12:22 AM
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The former QA manager at Black Diamond once stated that he'd never seen a nut rated 10kn or greater fail in the field, leading to speculation that forces that great are rarely encountered.
Along the same lines, the only biner failures you hear about involve open gates or biner weighted over an edge. I pay more attention to open gate strength than closed.
The bottom line is you shouldn't worry that much about the strength of non-micro gear. Gear is far more likely to fail due to bad placements, bad rock, or a combination of both. Focus on how to use the gear, not the gear itself.
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USnavy
Sep 5, 2010, 11:04 AM
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Yes a nut rated to 10 kN could fail if you take a factor one or larger fall on it. But that does not normally happen. More often then not gear pulls before it fails. Most commonly the placement fails, in the middle, the rock fails, and least commonly the gear fails.
(This post was edited by USnavy on Sep 5, 2010, 11:05 AM)
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chrisJoosse
Sep 5, 2010, 10:22 PM
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p8ntballsk8r wrote: I noticed that on all the nuts i've ever used to looked at, the wire (or entire unit) is only rated to 10kn. Is this truly strong enough to take a lead fall above the nut? If 10kn is strong enough, why are the carabiners we use so much stronger? Even the cheapest nonlocking oval biners are rated to 18kn. what gives?
this is just a guess, but:
10kn is about the failure strength of a very good biner's open-gate/crossload rating. When planning for safety, plan against the weakest possible failure mode of your system, not against the strongest dimension. If it happens to be stronger in the strongest direction, sweet.
Most biners are designed around keeping their weakest dimension within an acceptable range of open gate/crossloaded failure ratings, and the resulting long axis strength is always that much greater.
How strong is strong enough?
I'm sure it would be possible to make these pieces stronger, but at what cost, and for what benefit? At what point does your pro become too heavy, and would you really be better off if your nut was rated to, say, 25kn? Would you survive a catch under those kinds of forces without serious injury- or would you be better off if a piece were to fail before your spleen ruptured?
Edit: removed examples because they were based on the outputs of a suspect force calculator and my math is teh sux
(This post was edited by chrisJoosse on Sep 6, 2010, 11:05 PM)
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jt512
Sep 5, 2010, 10:41 PM
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chrisJoosse wrote: this is just a guess, but: [ . . . ] [T]o generate 10kn on your top piece with 45' of rope out, a 190lb climber would have to bomb over 40' onto that piece. Of course, without a dynamic rope in the system, it's possible to generate enormous loads with relatively modest falls- a fall from 2' above your piece on 2' of static runner will generate 19kn for that same 190lb climber....
Is that all part of the guess? If not, how did you come up with these forces?
Jay
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chrisJoosse
Sep 6, 2010, 1:52 AM
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jt512 wrote: chrisJoosse wrote: this is just a guess, but: [ . . . ] [T]o generate 10kn on your top piece with 45' of rope out, a 190lb climber would have to bomb over 40' onto that piece. Of course, without a dynamic rope in the system, it's possible to generate enormous loads with relatively modest falls- a fall from 2' above your piece on 2' of static runner will generate 19kn for that same 190lb climber.... Is that all part of the guess? If not, how did you come up with these forces? Jay
sorry, I used this for force numbers, and should have said so.
http://www.myoan.net/...t/climbforcecal.html
The 'guess' part was about why 'biners and pro are designed to the tolerances they are.
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jt512
Sep 6, 2010, 2:33 AM
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chrisJoosse wrote: jt512 wrote: chrisJoosse wrote: this is just a guess, but: [ . . . ] [T]o generate 10kn on your top piece with 45' of rope out, a 190lb climber would have to bomb over 40' onto that piece. Of course, without a dynamic rope in the system, it's possible to generate enormous loads with relatively modest falls- a fall from 2' above your piece on 2' of static runner will generate 19kn for that same 190lb climber.... Is that all part of the guess? If not, how did you come up with these forces? Jay sorry, I used this for force numbers, and should have said so. http://www.myoan.net/...t/climbforcecal.html
That explains it. That "calculator" is completely bogus. It doesn't even calculate fall factor correctly, never mind impact force.
Use my calculator if you at least want numbers that conform to theoretical models.
Jay
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rightarmbad
Sep 6, 2010, 4:25 AM
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I broke a 6KN rated nut, snapped the cable in the middle of it's length a bit below the swage.
It didn't feel that hard of a fall, but I am over 90KG at the moment.
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killingmorethancancer
Sep 6, 2010, 1:26 PM
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Correct me If I am wrong but most ropes are right around 8KN max impact force. I have one that is 8.5 but I dont even know if I have seen one that is 10. So with a rope that has a max impact force lower than a nuts breaking force I would not be worried about it. Anytime I would be running out even close to far enough to build that type of force I would stick a few pieces in and equalize them.
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Rudmin
Sep 6, 2010, 2:15 PM
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Impact force is just the peak measured force in a UIAA controlled test. I believe it is for an 80 kg weight dropped from 2.3 metres above an anchor with 2.5 metres of rope available. If you weigh more than 80 kg be warned. Also if you climb on old ropes or wet ropes or cold ropes or have other shenanigans going on.
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killingmorethancancer
Sep 6, 2010, 2:18 PM
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Thanks for the heads up I did not know that was just for the test.
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jt512
Sep 6, 2010, 6:55 PM
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killingmorethancancer wrote: Thanks for the heads up I did not know that was just for the test.
"Just" the test? The test is pretty harsh: 80 kg "climber," 1.78 fall factor, and a completely static "belay." However, the result of the test, reflected in the UIAA rating of the rope, is the impact force on the "climber." The force on the anchor would be on the order of 13 kN (2 time the force on the climber minus friction between the rope and the anchor). See my calculator (linked up-thread).
Jay
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petsfed
Sep 6, 2010, 8:58 PM
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Per JT above, most fall calculators will overestimate the force felt by the climber and belayer, since friction in the system will dissipate energy from a fall in ways that aren't easily measured by climber or belayer. Jay's uses an assumed value, which obviously is not knowable in the field.
I read a while back that Wild Country Rocks used to feature much heavier cable until one of their engineers noted that in every case of Rock failure, the metal of the nut failed before the cable, including in the lab. I don't recall where I read that, or if it was true, but the gist of it was to give the impression that the manufacturers are not trying to give you equipment designed to fail under regular usage.
Speaking from experience, your placement will fail well before parts start breaking on your average nut.
Edited for glaring errors, omissions, idiocy, etc.
(This post was edited by petsfed on Sep 6, 2010, 9:06 PM)
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chrisJoosse
Sep 6, 2010, 11:11 PM
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"jt512 wrote: chrisJoosse wrote: ... I used this for force numbers, and should have said so. http://www.myoan.net/...t/climbforcecal.html That explains it. That "calculator" is completely bogus. It doesn't even calculate fall factor correctly, never mind impact force. Use my calculator if you at least want numbers that conform to theoretical models. Jay
Thanks for the review, the correction, and the link to your calculator.
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tomtom
Sep 7, 2010, 12:14 AM
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petsfed wrote: Jay's uses an assumed value, which obviously is not knowable in the field.
So Jay's calculator uses 'assumed' values.
Sounds like garbage in, garbage out.
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jeepnphreak
Sep 7, 2010, 1:08 AM
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p8ntballsk8r wrote: I noticed that on all the nuts i've ever used to looked at, the wire (or entire unit) is only rated to 10kn. Is this truly strong enough to take a lead fall above the nut? If 10kn is strong enough, why are the carabiners we use so much stronger? Even the cheapest nonlocking oval biners are rated to 18kn. what gives?
I have fallen a few feet on a number 3 bd nut rated at 5kn (i think). It held no problem. to bust a 10kn would take a big hard nasty fall. I suppose breaking one could happen but I have never seen it
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jt512
Sep 7, 2010, 1:13 AM
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tomtom wrote: petsfed wrote: Jay's uses an assumed value, which obviously is not knowable in the field. So Jay's calculator uses 'assumed' values. Sounds like garbage in, garbage out.
Sounds like you have no understanding of the model and thus have a completely uninformed opinion.
Edit: I just checked your post history. *plonk*
Jay
(This post was edited by jt512 on Sep 7, 2010, 1:17 AM)
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petsfed
Sep 7, 2010, 2:30 AM
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tomtom wrote: petsfed wrote: Jay's uses an assumed value, which obviously is not knowable in the field. So Jay's calculator uses 'assumed' values. Sounds like garbage in, garbage out.
Absolutely. If the frictional coefficient you input is incorrect, then the calculations won't mean much. Just like if you make a typo entering your mass, fall factor, and rope modulus, the model will output a bunk prediction. GIGO is not a way to criticize a model, its a way to criticize the use of a model.
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wolfpackman409ataoldotcom
Sep 7, 2010, 4:44 AM
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its all about your fall force. 10k is plenty for a lead fall, but only if your placement is correct.
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chotoken
Sep 9, 2010, 12:40 AM
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I have been doing rope rescue work for several years. Many of the concepts apply in rock climbing. One thing that is standard for rescue purposes is a 15:1 safety ratio. Meaning that for every one pound you intend to put on the rope, the system should be able to hold 15 times that. The general rule of thumb is that the rope should be the weakest link in the system. There is actually a national standard based on this rule. This is not always practical for rock climbing, however I thought it would be worth mentioning.
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bearbreeder
Sep 9, 2010, 12:51 AM
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biners are full strength as you need to depend on a single locker for the worst case ... ie belay biner, focal point biner ... etc ...
you never depend on a single nut by itself except for possibly rapel if its totally bomber .... and even then an extra biner and nut are worth wasting for your life
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acorneau
Sep 9, 2010, 12:55 AM
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chotoken wrote: I have been doing rope rescue work for several years. Many of the concepts apply in rock climbing. One thing that is standard for rescue purposes is a 15:1 safety ratio. Meaning that for every one pound you intend to put on the rope, the system should be able to hold 15 times that. The general rule of thumb is that the rope should be the weakest link in the system. There is actually a national standard based on this rule. This is not always practical for rock climbing, however I thought it would be worth mentioning.
Perhaps you should read the myth-busting article I linked in another thread which states,
In reply to: Misconception No. 4: We are required to use a safety factor of 15:1
Thread is here:
http://www.rockclimbing.com/...post=2387997#2387997
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redlude97
Sep 9, 2010, 1:32 AM
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bearbreeder wrote: biners are full strength as you need to depend on a single locker for the worst case ... ie belay biner, focal point biner ... etc ... you never depend on a single nut by itself except for possibly rapel if its totally bomber .... and even then an extra biner and nut are worth wasting for your life
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