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USnavy
Sep 20, 2008, 3:04 AM
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vegastradguy
Sep 20, 2008, 3:25 AM
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USnavy wrote: Well I have also seen many reports of people who have been exposed to forces well over 20 kN without sustaining injuries. For example, not that long ago I read an article where a climber was clipped into a bolt with a long quickdraw. He climbed up past the bolt, slipped off the rock and took a factor two fall onto the bolt with the quickdraw. The quickdraw failed in the closed gate position and he fell to the ground but sustained no injuries. After examination it was shown that the quickdraw simply failed due to excessive force despite the 24 kN. closed gate rating. I also recently read an article where a climber took a factor two fall on a 24" sling causing the sling to break. Analysis’s found that the sling broke because the force of the fall exceeded the breaking strength of the sling (24 kN).
care to tell us where you got this info?
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alleyehave
Sep 20, 2008, 3:26 AM
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USnavy wrote: I have read multiple articles that say the human back is only capable of absorbing 12 - 14 kN for a fraction of a second. The articles state that if your back is exposed to forces beyond this level it will simply break. UIAA themselves state that they choose the 12 kN maximum impact force rating for ropes because 12 kN is the maximum amount of force a human can safely sustain. Well I have also seen many reports of people who have been exposed to forces well over 20 kN without sustaining injuries. For example, not that long ago I read an article where a climber was clipped into a bolt with a long quickdraw. He climbed up past the bolt, slipped off the rock and took a factor two fall onto the bolt with the quickdraw. The quickdraw failed in the closed gate position and he fell to the ground but sustained no injuries. After examination it was shown that the quickdraw simply failed due to excessive force despite the 24 kN. closed gate rating. I also recently read an article where a climber took a factor two fall on a 24" sling causing the sling to break. Analysis’s found that the sling broke because the force of the fall exceeded the breaking strength of the sling (24 kN). So my ultimate question is why are studies showing that humans cannot safely withstand more than 12 kN yet they have been reports of people breaking full strength gear rated for over 22 kN and not suffering any severe injuries from the impact?
22kn from the gear? how much of that force did the action of the carabiner and/or other gear absorb before it broke? Maybe 10kn?
Not to mention somebody falling ONE quickdrawk length(or 2 feet for that matter) directly onto a bolt be it a Fall factor of 2 or otherwise would produce NOWHERE near 24kn. Are you insane?
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shockabuku
Sep 20, 2008, 3:43 AM
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Because the connection (biner, sling, what have you) breaks before there is enough time for the body (which flexes quite a bit before it breaks) to suffer significant trauma.
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tradrenn
Sep 20, 2008, 4:00 AM
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I know that UIAA came up with 12kn, maybe you could email them and report back.
Thanks.
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USnavy
Sep 20, 2008, 4:14 AM
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shockabuku
Sep 20, 2008, 4:26 AM
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USnavy wrote: alleyehave wrote: USnavy wrote: I have read multiple articles that say the human back is only capable of absorbing 12 - 14 kN for a fraction of a second. The articles state that if your back is exposed to forces beyond this level it will simply break. UIAA themselves state that they choose the 12 kN maximum impact force rating for ropes because 12 kN is the maximum amount of force a human can safely sustain. Well I have also seen many reports of people who have been exposed to forces well over 20 kN without sustaining injuries. For example, not that long ago I read an article where a climber was clipped into a bolt with a long quickdraw. He climbed up past the bolt, slipped off the rock and took a factor two fall onto the bolt with the quickdraw. The quickdraw failed in the closed gate position and he fell to the ground but sustained no injuries. After examination it was shown that the quickdraw simply failed due to excessive force despite the 24 kN. closed gate rating. I also recently read an article where a climber took a factor two fall on a 24" sling causing the sling to break. Analysis’s found that the sling broke because the force of the fall exceeded the breaking strength of the sling (24 kN). So my ultimate question is why are studies showing that humans cannot safely withstand more than 12 kN yet they have been reports of people breaking full strength gear rated for over 22 kN and not suffering any severe injuries from the impact? 22kn from the gear? how much of that force did the action of the carabiner and/or other gear absorb before it broke? Maybe 10kn? Not to mention somebody falling ONE quickdrawk length(or 2 feet for that matter) directly onto a bolt be it a Fall factor of 2 or otherwise would produce NOWHERE near 24kn. Are you insane? In the case of the quickdraw he did not fall on a 1 foot long quickdraw. It was quite a bit longer than that. Anyway in both cases the manufacturers stated the equipment broke from tensile overload which meant the force of the fall exceeded the breaking strength of the equipment and thus it failed. And yes a 4 foot factor two fall on a static sling could easily exceed 24 kN. Slings do not stretch much and carabineers do not stretch at all much either. Go play around on the Petzl fall simulator and you will see that taking factor two falls on static equipment can easily produce forces beyond 20 kN.
Fixed that for you. Matter of fact, I suspect that biners may stretch more due to deformity than dyneema runners do.
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alleyehave
Sep 20, 2008, 4:26 AM
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USnavy wrote: alleyehave wrote: USnavy wrote: I have read multiple articles that say the human back is only capable of absorbing 12 - 14 kN for a fraction of a second. The articles state that if your back is exposed to forces beyond this level it will simply break. UIAA themselves state that they choose the 12 kN maximum impact force rating for ropes because 12 kN is the maximum amount of force a human can safely sustain. Well I have also seen many reports of people who have been exposed to forces well over 20 kN without sustaining injuries. For example, not that long ago I read an article where a climber was clipped into a bolt with a long quickdraw. He climbed up past the bolt, slipped off the rock and took a factor two fall onto the bolt with the quickdraw. The quickdraw failed in the closed gate position and he fell to the ground but sustained no injuries. After examination it was shown that the quickdraw simply failed due to excessive force despite the 24 kN. closed gate rating. I also recently read an article where a climber took a factor two fall on a 24" sling causing the sling to break. Analysis’s found that the sling broke because the force of the fall exceeded the breaking strength of the sling (24 kN). So my ultimate question is why are studies showing that humans cannot safely withstand more than 12 kN yet they have been reports of people breaking full strength gear rated for over 22 kN and not suffering any severe injuries from the impact? 22kn from the gear? how much of that force did the action of the carabiner and/or other gear absorb before it broke? Maybe 10kn? Not to mention somebody falling ONE quickdrawk length(or 2 feet for that matter) directly onto a bolt be it a Fall factor of 2 or otherwise would produce NOWHERE near 24kn. Are you insane? In the case of the quickdraw he did not fall on a 1 foot long quickdraw. It was quite a bit longer than that. Anyway in both cases the manufacturers stated the equipment broke from tensile overload which meant the force of the fall exceeded the breaking strength of the equipment and thus it failed. And yes a 4 foot factor two fall on a static sling could easily exceed 24 kN. Slings do not stretch much and carabineers do not stretch at all. Go play around on the Petzl fall simulator and you will see that taking factor two falls on static equipment can easily produce forces beyond 20 kN.
Uhm, your lack of details is really making this discussion difficult. Exactly how long was this quickdraw. I've never seen a quickdraw longer than a foot. Is this some special quickdraw? And according to the petzl fall calculator, a FF of 2 on a static rope at 4ft which is 1.2meters only produced 200 dan...roughly 450lbs...so, where is the remaining 4,945lbs required to MEET(let alone exceed) 24kn?
The idea of this occuring is insane, I repeat insane. And two climbing accidents of this caliber where HIGH-strength climbing equipment was overcome during a fall would be pretty big damn news. So please post your sources or this discussion is useless and over as far as im concerned.
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USnavy
Sep 20, 2008, 4:39 AM
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majid_sabet
Sep 20, 2008, 5:07 AM
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USnavy wrote: alleyehave wrote: USnavy wrote: alleyehave wrote: USnavy wrote: I have read multiple articles that say the human back is only capable of absorbing 12 - 14 kN for a fraction of a second. The articles state that if your back is exposed to forces beyond this level it will simply break. UIAA themselves state that they choose the 12 kN maximum impact force rating for ropes because 12 kN is the maximum amount of force a human can safely sustain. Well I have also seen many reports of people who have been exposed to forces well over 20 kN without sustaining injuries. For example, not that long ago I read an article where a climber was clipped into a bolt with a long quickdraw. He climbed up past the bolt, slipped off the rock and took a factor two fall onto the bolt with the quickdraw. The quickdraw failed in the closed gate position and he fell to the ground but sustained no injuries. After examination it was shown that the quickdraw simply failed due to excessive force despite the 24 kN. closed gate rating. I also recently read an article where a climber took a factor two fall on a 24" sling causing the sling to break. Analysis’s found that the sling broke because the force of the fall exceeded the breaking strength of the sling (24 kN). So my ultimate question is why are studies showing that humans cannot safely withstand more than 12 kN yet they have been reports of people breaking full strength gear rated for over 22 kN and not suffering any severe injuries from the impact? 22kn from the gear? how much of that force did the action of the carabiner and/or other gear absorb before it broke? Maybe 10kn? Not to mention somebody falling ONE quickdrawk length(or 2 feet for that matter) directly onto a bolt be it a Fall factor of 2 or otherwise would produce NOWHERE near 24kn. Are you insane? In the case of the quickdraw he did not fall on a 1 foot long quickdraw. It was quite a bit longer than that. Anyway in both cases the manufacturers stated the equipment broke from tensile overload which meant the force of the fall exceeded the breaking strength of the equipment and thus it failed. And yes a 4 foot factor two fall on a static sling could easily exceed 24 kN. Slings do not stretch much and carabineers do not stretch at all. Go play around on the Petzl fall simulator and you will see that taking factor two falls on static equipment can easily produce forces beyond 20 kN. And according to the petzl fall calculator, a FF of 2 on a static rope at 4ft which is 1.2meters only produced 200 dan...roughly 450lbs...so, where is the remaining 4,945lbs required to MEET(let alone exceed) 24kn? . Really? [img]http://img87.imageshack.us/img87/2707/88397171wx6.jpg[/img] Note that that’s only a factor ONE fall. Its not even a factor two fall and the anchor already sees over 21 kN and the climber sees over 13 kN. They do make quickdraws longer then a foot. I have two myself. Petzl makes some that are like 15" long plus the length of the carabineers equates to around 20" or so. The article regarding the climber falling onto the quickdraw was in some climbing magazine that I read about six months ago. The article of the climber falling on the sling was on rc.com a while back. I will go look for them and try to post them. After the incident where the climber fell on the draw Petzl did an investigation and came to the conclusion that the fall produced over 30 kN. They posted their findings somewhere on the net. I will look around and see if I can find them. |
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shockabuku
Sep 20, 2008, 5:15 AM
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majid_sabet wrote: USnavy wrote: alleyehave wrote: USnavy wrote: alleyehave wrote: USnavy wrote: I have read multiple articles that say the human back is only capable of absorbing 12 - 14 kN for a fraction of a second. The articles state that if your back is exposed to forces beyond this level it will simply break. UIAA themselves state that they choose the 12 kN maximum impact force rating for ropes because 12 kN is the maximum amount of force a human can safely sustain. Well I have also seen many reports of people who have been exposed to forces well over 20 kN without sustaining injuries. For example, not that long ago I read an article where a climber was clipped into a bolt with a long quickdraw. He climbed up past the bolt, slipped off the rock and took a factor two fall onto the bolt with the quickdraw. The quickdraw failed in the closed gate position and he fell to the ground but sustained no injuries. After examination it was shown that the quickdraw simply failed due to excessive force despite the 24 kN. closed gate rating. I also recently read an article where a climber took a factor two fall on a 24" sling causing the sling to break. Analysis’s found that the sling broke because the force of the fall exceeded the breaking strength of the sling (24 kN). So my ultimate question is why are studies showing that humans cannot safely withstand more than 12 kN yet they have been reports of people breaking full strength gear rated for over 22 kN and not suffering any severe injuries from the impact? 22kn from the gear? how much of that force did the action of the carabiner and/or other gear absorb before it broke? Maybe 10kn? Not to mention somebody falling ONE quickdrawk length(or 2 feet for that matter) directly onto a bolt be it a Fall factor of 2 or otherwise would produce NOWHERE near 24kn. Are you insane? In the case of the quickdraw he did not fall on a 1 foot long quickdraw. It was quite a bit longer than that. Anyway in both cases the manufacturers stated the equipment broke from tensile overload which meant the force of the fall exceeded the breaking strength of the equipment and thus it failed. And yes a 4 foot factor two fall on a static sling could easily exceed 24 kN. Slings do not stretch much and carabineers do not stretch at all. Go play around on the Petzl fall simulator and you will see that taking factor two falls on static equipment can easily produce forces beyond 20 kN. And according to the petzl fall calculator, a FF of 2 on a static rope at 4ft which is 1.2meters only produced 200 dan...roughly 450lbs...so, where is the remaining 4,945lbs required to MEET(let alone exceed) 24kn? . Really? [img]http://img87.imageshack.us/img87/2707/88397171wx6.jpg[/img] Note that that’s only a factor ONE fall. Its not even a factor two fall and the anchor already sees over 21 kN and the climber sees over 13 kN. They do make quickdraws longer then a foot. I have two myself. Petzl makes some that are like 15" long plus the length of the carabineers equates to around 20" or so. The article regarding the climber falling onto the quickdraw was in some climbing magazine that I read about six months ago. The article of the climber falling on the sling was on rc.com a while back. I will go look for them and try to post them. After the incident where the climber fell on the draw Petzl did an investigation and came to the conclusion that the fall produced over 30 kN. They posted their findings somewhere on the net. I will look around and see if I can find them. |
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tradrenn
Sep 20, 2008, 6:39 AM
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shockabuku wrote: majid_sabet wrote: USnavy wrote: alleyehave wrote: USnavy wrote: alleyehave wrote: USnavy wrote: I have read multiple articles that say the human back is only capable of absorbing 12 - 14 kN for a fraction of a second. The articles state that if your back is exposed to forces beyond this level it will simply break. UIAA themselves state that they choose the 12 kN maximum impact force rating for ropes because 12 kN is the maximum amount of force a human can safely sustain. Well I have also seen many reports of people who have been exposed to forces well over 20 kN without sustaining injuries. For example, not that long ago I read an article where a climber was clipped into a bolt with a long quickdraw. He climbed up past the bolt, slipped off the rock and took a factor two fall onto the bolt with the quickdraw. The quickdraw failed in the closed gate position and he fell to the ground but sustained no injuries. After examination it was shown that the quickdraw simply failed due to excessive force despite the 24 kN. closed gate rating. I also recently read an article where a climber took a factor two fall on a 24" sling causing the sling to break. Analysis’s found that the sling broke because the force of the fall exceeded the breaking strength of the sling (24 kN). So my ultimate question is why are studies showing that humans cannot safely withstand more than 12 kN yet they have been reports of people breaking full strength gear rated for over 22 kN and not suffering any severe injuries from the impact? 22kn from the gear? how much of that force did the action of the carabiner and/or other gear absorb before it broke? Maybe 10kn? Not to mention somebody falling ONE quickdrawk length(or 2 feet for that matter) directly onto a bolt be it a Fall factor of 2 or otherwise would produce NOWHERE near 24kn. Are you insane? In the case of the quickdraw he did not fall on a 1 foot long quickdraw. It was quite a bit longer than that. Anyway in both cases the manufacturers stated the equipment broke from tensile overload which meant the force of the fall exceeded the breaking strength of the equipment and thus it failed. And yes a 4 foot factor two fall on a static sling could easily exceed 24 kN. Slings do not stretch much and carabineers do not stretch at all. Go play around on the Petzl fall simulator and you will see that taking factor two falls on static equipment can easily produce forces beyond 20 kN. And according to the petzl fall calculator, a FF of 2 on a static rope at 4ft which is 1.2meters only produced 200 dan...roughly 450lbs...so, where is the remaining 4,945lbs required to MEET(let alone exceed) 24kn? . Really? [img]http://img87.imageshack.us/img87/2707/88397171wx6.jpg[/img] Note that that’s only a factor ONE fall. Its not even a factor two fall and the anchor already sees over 21 kN and the climber sees over 13 kN. They do make quickdraws longer then a foot. I have two myself. Petzl makes some that are like 15" long plus the length of the carabineers equates to around 20" or so. The article regarding the climber falling onto the quickdraw was in some climbing magazine that I read about six months ago. The article of the climber falling on the sling was on rc.com a while back. I will go look for them and try to post them. After the incident where the climber fell on the draw Petzl did an investigation and came to the conclusion that the fall produced over 30 kN. They posted their findings somewhere on the net. I will look around and see if I can find them.
Are you guys feeling Okee Dokee ?
Quoting without replying that is.
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alleyehave
Sep 20, 2008, 6:42 AM
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USnavy wrote: alleyehave wrote: USnavy wrote: alleyehave wrote: USnavy wrote: I have read multiple articles that say the human back is only capable of absorbing 12 - 14 kN for a fraction of a second. The articles state that if your back is exposed to forces beyond this level it will simply break. UIAA themselves state that they choose the 12 kN maximum impact force rating for ropes because 12 kN is the maximum amount of force a human can safely sustain. Well I have also seen many reports of people who have been exposed to forces well over 20 kN without sustaining injuries. For example, not that long ago I read an article where a climber was clipped into a bolt with a long quickdraw. He climbed up past the bolt, slipped off the rock and took a factor two fall onto the bolt with the quickdraw. The quickdraw failed in the closed gate position and he fell to the ground but sustained no injuries. After examination it was shown that the quickdraw simply failed due to excessive force despite the 24 kN. closed gate rating. I also recently read an article where a climber took a factor two fall on a 24" sling causing the sling to break. Analysis’s found that the sling broke because the force of the fall exceeded the breaking strength of the sling (24 kN). So my ultimate question is why are studies showing that humans cannot safely withstand more than 12 kN yet they have been reports of people breaking full strength gear rated for over 22 kN and not suffering any severe injuries from the impact? 22kn from the gear? how much of that force did the action of the carabiner and/or other gear absorb before it broke? Maybe 10kn? Not to mention somebody falling ONE quickdrawk length(or 2 feet for that matter) directly onto a bolt be it a Fall factor of 2 or otherwise would produce NOWHERE near 24kn. Are you insane? In the case of the quickdraw he did not fall on a 1 foot long quickdraw. It was quite a bit longer than that. Anyway in both cases the manufacturers stated the equipment broke from tensile overload which meant the force of the fall exceeded the breaking strength of the equipment and thus it failed. And yes a 4 foot factor two fall on a static sling could easily exceed 24 kN. Slings do not stretch much and carabineers do not stretch at all. Go play around on the Petzl fall simulator and you will see that taking factor two falls on static equipment can easily produce forces beyond 20 kN. And according to the petzl fall calculator, a FF of 2 on a static rope at 4ft which is 1.2meters only produced 200 dan...roughly 450lbs...so, where is the remaining 4,945lbs required to MEET(let alone exceed) 24kn? . Really? [img]http://img87.imageshack.us/img87/2707/88397171wx6.jpg[/img] Note that that’s only a factor ONE fall. Its not even a factor two fall and the anchor already sees over 21 kN and the climber sees over 13 kN. They do make quickdraws longer then a foot. I have two myself. Petzl makes some that are like 15" long plus the length of the carabineers equates to around 20" or so. The article regarding the climber falling onto the quickdraw was in some climbing magazine that I read about six months ago. The article of the climber falling on the sling was on rc.com a while back. I will go look for them and try to post them. After the incident where the climber fell on the draw Petzl did an investigation and came to the conclusion that the fall produced over 30 kN. They posted their findings somewhere on the net. I will look around and see if I can find them.
Yes, really:
You are fubaring its math by putting in fractions of a meter as a running belay. Certainly, if your theory is true, a fall factor of 2 would produce a greater force than 1, obviously. Yet, my example illustrates a perfect factor 2 fall that doesn't even reach 500lbs of force. Make your example a little more realistic... .1m .2m 1m....then with a 2m fall? wtf is that.
Yes, PLEASE find these articles, im already amazed that someone was able to put down 5000+ pounds of force onto an anchor from a 20" quickdraw, this dude must of been atleast 2500 pounds to begin with. Amazing.
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curt
Sep 20, 2008, 7:07 AM
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alleyehave wrote: ...Yes, PLEASE find these articles, im already amazed that someone was able to put down 5000+ pounds of force onto an anchor from a 20" quickdraw, this dude must of been atleast 2500 pounds to begin with. Amazing.
Those screen captures from the Petzl website are too small for me to read, so I can't really see what's going on there. However, it is quite easy for a climber of average weight (UIAA says 80 kg--although that sounds a bit high to me) to generate peak forces in excess of 12kN in a FF=2 fall employing a 20 inch long runner in place of a rope.
What you need to keep in mind is that F = ma and the "a" here can become very large--because the distance over which the energy of the fall is absorbed becomes very, very short. This is due to the fact (as others have pointed out) that neither runners nor carabiners stretch much.
Curt
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boombewm
Sep 20, 2008, 7:11 AM
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my post got posted before i posted it. conniving bastards...
(This post was edited by boombewm on Sep 20, 2008, 7:15 AM)
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boombewm
Sep 20, 2008, 8:28 AM
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http://www.myoan.net/climbart/climbforcecal.html
this one is my favorite:
http://hyperphysics.phy-astr.gsu.edu/hbase/flobi.html#c1
I think the folks at petzl make good ice tools, reversos, helmets, harnesses (harn-i?), and good tacos. However, I hear the rope sucks and I know from the test I took this morning in PDE, its always nice to have simple things and know formulas.
This thread has no value (or context) except I like typing shit in rc.com when I'm drunk. There are still no sources to prove this claim (not that you actually need anything tangible on the internet). And because we know that if the real world and petzl's armageddon calculator had a conversation it would go like this:
-reality: "this sucks, why am I made of atoms and apparently chill in 12 dimensions? what is the probability that I'm actually here?"
-the french: "waaa waaa spend $80 on gri gri so I can get a crapper that cools my colon off after my jurassic crap"
-reality:"wtf?, why is that calculator covered in shit?"
-communication major: "actually, the shit is covered in calculator. Yeah, turns out if you don't know what your doing--the fecal matter will explosively eject a calculator. I saw a picture in a few articles...
aight I'm tired
(This post was edited by boombewm on Sep 20, 2008, 8:31 AM)
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sbaclimber
Sep 20, 2008, 8:44 AM
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boombewm wrote: http://www.myoan.net/climbart/climbforcecal.html this one is my favorite: http://hyperphysics.phy-astr.gsu.edu/hbase/flobi.html#c1 I think the folks at petzl make good ice tools, reversos, helmets, harnesses (harn-i?), and good tacos. However, I hear the rope sucks and I know from the test I took this morning in PDE, its always nice to have simple things and know formulas. This thread has no value (or context) except I like typing shit in rc.com when I'm drunk. There are still no sources to prove this claim (not that you actually need anything tangible on the internet). And because we know that if the real world and petzl's armageddon calculator had a conversation it would go like this: -reality: "this sucks, why am I made of atoms and apparently chill in 12 dimensions? what is the probability that I'm actually here?" -the french: "waaa waaa spend $80 on gri gri so I can get a crapper that cools my colon off after my jurassic crap" -reality:"wtf?, why is that calculator covered in shit?" -communication major: "actually, the shit is covered in calculator. Yeah, turns out if you don't know what your doing--the fecal matter will explosively eject a calculator. I saw a picture in a few articles... aight I'm tired  
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glytch
Sep 20, 2008, 1:34 PM
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alleyehave wrote: 22kn from the gear? how much of that force did the action of the carabiner and/or other gear absorb before it broke? Maybe 10kn?
Force is not "absorbed" by the gear. If the biner on the bolt is pulling at 24kN, the biner on the person is also pulling at 24kN... and that's the force his body is experiencing. The QD doesn't "absorb" any force... which doesn't make any sense physics-wise, anway.
In reply to: Not to mention somebody falling ONE quickdrawk length(or 2 feet for that matter) directly onto a bolt be it a Fall factor of 2 or otherwise would produce NOWHERE near 24kn. Are you insane?
Without knowing the material the QD was made of and finding some test data, it's hard to say exactly the forces that will come into play. That said, 24kN is certainly in the realm of possibility for a ff2 onto a static sling. Hell, a clean FF2 fall of a few feet on a dynamic rope would generate ~10kN of force.
Falls onto static slings are really dangerous. If that's a danger you don't recognize or understand, you should do some reading before you tie in again.
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shockabuku
Sep 20, 2008, 2:52 PM
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Feeling okay? Yeah. I thought Majid was setting a trend and I wanted to get in on it early.
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roy_hinkley_jr
Sep 20, 2008, 5:31 PM
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USnavy wrote: So my ultimate question is why are studies showing that humans cannot safely withstand more than 12 kN yet they have been reports of people breaking full strength gear rated for over 22 kN and not suffering any severe injuries from the impact?
The 12 kN figure dates back to studies of paratroopers in WWII. They needed to determine a maximum force that the vast majority of soldiers could withstand and still be able to fight. Sure, you can survive higher forces, sometimes, when everything goes just right, but it becomes a matter of luck. So a 22kN might be survivable if you land just right, though you may be visiting the chiro for a few months. Or that same load could cripple you if you hit sideways. "No injuries" is a vague term too since somethings may not show up for a few days and what a 20-year-old kid can take would sideline a 50-year old.
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sungam
Sep 20, 2008, 5:58 PM
Post #21 of 54
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Roy seems to have clicked it. (whatever that means).
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shockabuku
Sep 20, 2008, 5:58 PM
Post #22 of 54
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You have to consider more than just the force. Force is a consideration best applied to static situations. In a dynamic environment you need also to consider over what distance and/or time that force is applied, and how much energy transfer takes place.
With predominantly static materials the distance and time over which those large forces are applied is relatively small/short. The low stretch of static materials vs. high stretch is what causes large force factors. Force can be thought of as a measure of how fast the combination of speed and mass of an object changes. When a moving object gets to the end of a static material it tries to slow down very quickly, causing large forces. However, because the large force only acts for a short time before the static material reaches its strength limit and breaks, there is not much energy transfer. Energy (a different measure of speed and mass) transfer takes time; i.e. you don't start falling at 50 m/s, it takes gravity a bit of time to get you going that fast. So, a falling human will quickly place a very large force on a static piece of material and break it, but that human won't slow down much because not much energy transfer has occurred. Since not much energy transfer occurs, the human body doesn't notice much effect of the breakage. It's when the piece doesn't break, and all of the energy transfer occurs, that you notice it.
It's like the difference of punching a wall vs. punching through a wall; one hurts a lot more than the other.
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sungam
Sep 20, 2008, 6:21 PM
Post #23 of 54
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IThat would depend greatly on the wall...
http://www.youtube.com/watch?v=B9Sp4fEzl-M
(VERY funny, btw.)
[downclimbzed to save n00bs from confooshon]
(This post was edited by sungam on Sep 20, 2008, 8:11 PM)
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milesenoell
Sep 20, 2008, 8:07 PM
Post #24 of 54
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Registered: Sep 19, 2006
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Oh my god that is so fu(kin' funny! I can't even stop laughing at that video.
But seriously, Screamers are based on this concept of absorbing part of the load and failing, in that case to protect the pro rather than the climber.
God damn that video is still cracking me up!
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veganclimber
Sep 20, 2008, 9:29 PM
Post #25 of 54
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alleyehave wrote: Yes, PLEASE find these articles, im already amazed that someone was able to put down 5000+ pounds of force onto an anchor from a 20" quickdraw, this dude must of been atleast 2500 pounds to begin with. Amazing.
Lets do a simplified calculation here. Say you fall through a distance d before the sling catches you. Your velocity at the end of the fall is given by:
v^2 = 2gd (g is the acceleration due to gravity)
When the sling catches you, you accelerate through a distance x (assume constant acceleration). The acceleration you go through during that period is given by:
a = v^2/2x = 2gd/2x = gd/x
You can write it as:
a/g = d/x
So you acceleration in terms of g is simply the distance fallen divided by the distance at which you come to a stop. If you fall 1 meter (about 18 inches above the anchor to 18 inches below the anchor), and come to a rest in one centimeter, your acceleration would be about 10g during that period.
The force you experience is given by
F = ma = mgd/x
In the above example an 80 kg climber would experience a force of
F = 80 kg * 10 m/s^2 * 1 m / .1 m = 8000 N or 8 kN
Thats about 2000 pounds of force.
The biggest uncertainty here is the stretch of the sling, carabiner, belay loop. ect. I have no idea how much they would stretch in a fall. If it was only 1/3 of a centimeter we would already be at 24 kN.
Also keep in mind that this is a bit simplified. I assumed constant acceleration, which may not be too realistic. I would imagine that the peak force could be significantly higher than the average.
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