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Has a rope ever broke with no extenuating circumstances?
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ptlong2


Apr 2, 2012, 6:23 PM
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Re: [petsfed] Has a rope ever broke with no extenuating circumstances? [In reply to]
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petsfed wrote:
...the claim that 12g is equal to 12kN for the average climber is clearly false.

Nobody has made a claim about the average climber except for you.

I believe the 12g number originally came from military parachute jump injury statistics. Granted, for a given fall and rope a lighter person will experience a higher peak deceleration. But how deceleration and body mass scale with respect to injury rate is not obvious, at least not to me.


petsfed wrote:
If they wanted to minimize the possibility of injury to the average climber (not some worst case scenario), they'd set it at around 9kn, if not lower.

But there are tradeoffs to consider. In the case of the military jumper a lower force means waiting longer for the parachute to open. For a climber it means the rope stretches further.

Nonetheless, many ropes already meet your criteria.


petsfed wrote:
...the human body can actually handle 12 kn for very brief periods of time...

I just finished reading Mary Roach's recent book and she wrote about this. Back in the day a guy named Stapp and his associates rode rocket carts that decelerated very abruptly. Mr. Stapp himself reached a peak of over 40g for a short period of time. It's funny, there's a guy who is planning to beat Kittinger's 100,000+ foot parachute jump but I haven't heard of anyone who wants to take on the G-force record.


dead_horse_flats


Apr 2, 2012, 7:20 PM
Post #27 of 33 (1306 views)
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Re: [USnavy] Has a rope ever broke with no extenuating circumstances? [In reply to]
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USnavy wrote:
dead_horse_flats wrote:
......
First, we need to define what "rope failure" actually is. No, I dont think anyone has ever completely severed a rope in half from "too big" of a lead fall (aside from failure due to sharp edges or chemical alteration). However complete sheath failure, resulting in serious injury, has occurred. When rappelling a 11mm static rope in Yosemite this happened to me:

[img]http://img853.imageshack.us/img853/7739/img0203tp.jpg[/img]

The rope deshethed as my belay device hit a worn section of the rope. I slid down the rope until the sheath jammed in my belay device, stopping me. A few of the core strands failed as my Trango Cinch attempted to jam the core strands, but failed to. The rope could have failed and if it had, my death/ injury would have been a result from rappelling on an excessively worn rope, which seems to meet your qualifications. Someone in Hawaii had the same thing happen to her a few years back. She was rappelling on a rope and the sheath failed sending her 60 feet to the deck. The rope did not completely fail, however, because belay devices grab onto the sheath of the rope, she just slid down the core strands to the ground. I did not have that problem because in my case, the sheath failed in the belay device, not after the belay device. Had the sheath severed after it passed through my belay device, it would have been pinching the detatched sheath instead of the core strands and I would have likely decked (think of trying to rappel by holding onto the rope through a banana peel)

Dang. Damned. Crap. That is basically the repetitive nightmare that I keep having, and why I asked this question. Would the moderator please delete USNavy's post and I'll pretend I never read this.

Isnt there something on this website that lets me block USNavy's posts?

Seriously tho, how old was the rope and how bad was the wear?


(This post was edited by dead_horse_flats on Apr 2, 2012, 10:03 PM)


dagibbs


Apr 3, 2012, 12:25 PM
Post #28 of 33 (1265 views)
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Re: [dead_horse_flats] Has a rope ever broke with no extenuating circumstances? [In reply to]
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dead_horse_flats wrote:
USnavy wrote:
dead_horse_flats wrote:
......
First, we need to define what "rope failure" actually is. No, I dont think anyone has ever completely severed a rope in half from "too big" of a lead fall (aside from failure due to sharp edges or chemical alteration). However complete sheath failure, resulting in serious injury, has occurred. When rappelling a 11mm static rope in Yosemite this happened to me:

[img]http://img853.imageshack.us/img853/7739/img0203tp.jpg[/img]

The rope deshethed as my belay device hit a worn section of the rope. I slid down the rope until the sheath jammed in my belay device, stopping me. A few of the core strands failed as my Trango Cinch attempted to jam the core strands, but failed to. The rope could have failed and if it had, my death/ injury would have been a result from rappelling on an excessively worn rope, which seems to meet your qualifications. Someone in Hawaii had the same thing happen to her a few years back. She was rappelling on a rope and the sheath failed sending her 60 feet to the deck. The rope did not completely fail, however, because belay devices grab onto the sheath of the rope, she just slid down the core strands to the ground. I did not have that problem because in my case, the sheath failed in the belay device, not after the belay device. Had the sheath severed after it passed through my belay device, it would have been pinching the detatched sheath instead of the core strands and I would have likely decked (think of trying to rappel by holding onto the rope through a banana peel)

Dang. Damned. Crap. That is basically the repetitive nightmare that I keep having, and why I asked this question. Would the moderator please delete USNavy's post and I'll pretend I never read this.

Isnt there something on this website that lets me block USNavy's posts?

Seriously tho, how old was the rope and how bad was the wear?

Just looking at the rope, it looks quite old. Gone grey from UV exposure, among other things.

What that post tells me is not that ropes break, but that you should take extra care with fixed ropes, because you don't know how long they've been installed.


Kinobi


Apr 4, 2012, 1:04 PM
Post #29 of 33 (1202 views)
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Re: [dagibbs] Has a rope ever broke with no extenuating circumstances? [In reply to]
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A deshethled rope should not break.
Sorry, in Italian...
http://www.caipadova.it/articoli/singola-news/list/2011/10/18/usura-delle-corde-in-arrampicata.html
E


tower_climber


Apr 4, 2012, 9:00 PM
Post #30 of 33 (1157 views)
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Re: [ptlong2] Has a rope ever broke with no extenuating circumstances? [In reply to]
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ptlong2 wrote:
I believe the 12g number originally came from military parachute jump injury statistics. Granted, for a given fall and rope a lighter person will experience a higher peak deceleration. But how deceleration and body mass scale with respect to injury rate is not obvious, at least not to me.

The figure I have heard and seen referenced in regards to falling is 12kN. The military parachuting experiments showed that organ displacement occurred at 12kN. I have not heard g-forces referenced in relation to these experiments.

In the following article, the researchers found that lumbar vertebrae suffered fracturing at an average of 6.5kN, though they state that spinal muscle and connective tissue would likely cushion and reduce peak impact forces in a real-world situation. In the study the majority of the specimens fractured at less than 9kN of peak load, though one set (21yo male subject) exceeded 15kN before breaking.

http://www.ncbi.nlm.nih.gov/.../janat00240-0080.pdf

Regardless: if you take a fall that registers more than 6kN of impact force it is going to hurt like a BITCH.


JAB


Apr 5, 2012, 5:03 AM
Post #31 of 33 (1132 views)
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Re: [tower_climber] Has a rope ever broke with no extenuating circumstances? [In reply to]
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I remember a Mythbusters episode, where they tested the brace position in airplane crashes. In this test, they put the minimum injury level at 50 G (i.e. less than that can lead to some injury but is not fatal).

Link here: http://kwc.org/...ler_brace_posit.html


ptlong2


Apr 5, 2012, 3:50 PM
Post #32 of 33 (1086 views)
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Re: [tower_climber] Has a rope ever broke with no extenuating circumstances? [In reply to]
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tower_climber wrote:
The figure I have heard and seen referenced in regards to falling is 12kN. The military parachuting experiments showed that organ displacement occurred at 12kN. I have not heard g-forces referenced in relation to these experiments.

The US military specification 9479A considers 12.1G to be the 5% "probability of injury level". This is according to Survivable Impact Forces on Human Body Constrained by Full Body Harness (which you can find at http://www.hse.gov.uk/...df/2003/hsl03-09.pdf).


tower_climber wrote:
In the following article, the researchers found that lumbar vertebrae suffered fracturing at an average of 6.5kN, though they state that spinal muscle and connective tissue would likely cushion and reduce peak impact forces in a real-world situation. In the study the majority of the specimens fractured at less than 9kN of peak load, though one set (21yo male subject) exceeded 15kN before breaking.

http://www.ncbi.nlm.nih.gov/.../janat00240-0080.pdf

There was a very wide spread of values. The female vertebrae fractured on average at around half that of the male vertebrae. It seems likely that there is a dependence on body mass which the study ignored.

It's also not clear to me how the force on the vertebrae they were measuring relates to the force on the climber as a whole (i.e. the rope tension).


billcoe_


Apr 25, 2012, 9:41 AM
Post #33 of 33 (925 views)
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Re: [dead_horse_flats] Has a rope ever broke with no extenuating circumstances? [In reply to]
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dead_horse_flats wrote:
Has a rope ever broke with no extenuating circumstances? More specifically, has a climber ever taken a fall and had the rope break because the force of the fall exceeded the breaking strength of the rope.

Typical extenuating circumstances that dont apply to this question:
--Rope cut by sharp edges in gear or rocks.
--Rope exposed to chemicals.
--Manufacturer defects like the disintegrating petzl ropes.
--dan osman.

And by rope, I mean a modern dynamic kernmantle rope.

No

End of story. There's only extenuating circumstances when ropes fail and people get hurt or die. I was swinging on that very rope US Navy posts above about a month before he was. Extenuating circumstance there too.

There is always extenuating circumstances.

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