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rocknice2


Sep 6, 2012, 4:54 PM
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Re: [JimTitt] Ultimate Strength of a Multiple Point Anchor [In reply to]
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JimTitt wrote:
EEk, back to step one!
The rope applies a force onto the cam, the cam applies a force onto the flake, if there is enough force the stress (force per unit area of the material) exceeds the strength of the material and it breaks. The energy required to do this breaking depends on the material, a good steel takes several hundred times more energy to break as concrete for example. A steel karabiner with the same breaking strength as an aluminium one would take roughly twice as much energy to break, this is why some materials are known as tough and others as brittle. How much force is taken out of the fall depends on how much energy was removed by the flake breaking, not the force required to do so.

The energy from our tracking cam would either be friction or the work done to gouge the rock out or rip the aluminium off the lobes, probably a bit of each at a guess!

Let's see if I understand. 2 carabiners both rated @ 10kn. One very brittle the other very tough.
I drop a heavy weight attached to the carabiner via a stretch-proof cable.
The weight breaks both biners. The difference is the brittle biner absorbs nothing because it just snaps like a potato chip. The tough biner will elongate and therefore absorb energy. The weight still hits the floor but with less force, energy or speed just fill in the blank.

Now if I replace the cable with a bungee cord. Won't it absorb energy as the brittle biner is breaking.


patto


Sep 6, 2012, 4:57 PM
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Re: [cracklover] Ultimate Strength of a Multiple Point Anchor [In reply to]
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cracklover wrote:
This type of cascade failure is, among other reasons, why many of us have objected for years to the standard cordelette as a universal method of anchoring.
Oh, dear not this again! Crazy

cracklover wrote:
Now let's say the leader falls on the anchor with a fall sufficient to generate 12 kN of force. What happens?
Has this EVER occurred? Do you know what the impact force ratings for ropes?

Now, if you were quite ingenious you might just be able to contrive a situation where a fall would approach 12kN. However has this ever occurred? What are the chances?


You have much more chance of being struck by lightning on a cliff than of this occurring. Lets not discuss absurdities. Wink


rocknice2


Sep 6, 2012, 5:09 PM
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Re: [patto] Ultimate Strength of a Multiple Point Anchor [In reply to]
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Patto, the number are arbitrary and are only used as a base line for discussion. This is my fault for not formulating a more realistic scenario but changing the numbers would just add even more confusion to the mix.
I think cracklover and is doing a great job in understanding what it is I was trying to get at and explaining it to me.

It's obvious that any dynamic rope couldn't break the first pro let alone 3. Although scenario #3 is looking really scary.


(This post was edited by rocknice2 on Sep 6, 2012, 5:12 PM)


majid_sabet


Sep 6, 2012, 10:30 PM
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Re: [cracklover] Ultimate Strength of a Multiple Point Anchor [In reply to]
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cracklover wrote:
And because a picture is worth a thousand words:

[image]http://i47.tinypic.com/34q08kl.jpg[/image]

GO


something like this




JimTitt


Sep 7, 2012, 12:17 AM
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Re: [rocknice2] Ultimate Strength of a Multiple Point Anchor [In reply to]
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rocknice2 wrote:
JimTitt wrote:
EEk, back to step one!
The rope applies a force onto the cam, the cam applies a force onto the flake, if there is enough force the stress (force per unit area of the material) exceeds the strength of the material and it breaks. The energy required to do this breaking depends on the material, a good steel takes several hundred times more energy to break as concrete for example. A steel karabiner with the same breaking strength as an aluminium one would take roughly twice as much energy to break, this is why some materials are known as tough and others as brittle. How much force is taken out of the fall depends on how much energy was removed by the flake breaking, not the force required to do so.

The energy from our tracking cam would either be friction or the work done to gouge the rock out or rip the aluminium off the lobes, probably a bit of each at a guess!

Let's see if I understand. 2 carabiners both rated @ 10kn. One very brittle the other very tough.
I drop a heavy weight attached to the carabiner via a stretch-proof cable.
The weight breaks both biners. The difference is the brittle biner absorbs nothing because it just snaps like a potato chip. The tough biner will elongate and therefore absorb energy. The weight still hits the floor but with less force, energy or speed just fill in the blank.

Now if I replace the cable with a bungee cord. Won't it absorb energy as the brittle biner is breaking.

Yup, the tougher karabiner breaking absorbs more of the fall energy and so the weight is slowed more so hits the floor slower.

The bungee cord will absorb energy BUT doesn´t dissipate it, it stores the energy and when the karabiner breaks fires the remains at you at a million miles an hour! The total energy in the falling weight, bungee and broken part of the karabiner has stayed the same. Admittedly as a falling climber we would probably prefer to be slowed down a bit and accept the fling scrap as the lesser of two evils!
Climbing ropes do dissipate a certain amount of energy in real life but their main function is to act as an impact attenuator, turning a brief but very high impact into a longer, milder one.


sittingduck


Sep 7, 2012, 8:56 AM
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Re: [cracklover] Ultimate Strength of a Multiple Point Anchor [In reply to]
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cracklover wrote:
And because a picture is worth a thousand words:

[image]http://i47.tinypic.com/34q08kl.jpg[/image]

GO


Cascade failure Cool


surfstar


Oct 30, 2012, 11:22 AM
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ski.ninja


Nov 12, 2012, 2:49 AM
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Do I read correctly in that AMGA paper that they were using static (<5% stretch) ropes for these drop tests?


JimTitt


Nov 12, 2012, 11:32 AM
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Re: [ski.ninja] Ultimate Strength of a Multiple Point Anchor [In reply to]
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ski.ninja wrote:
Do I read correctly in that AMGA paper that they were using static (<5% stretch) ropes for these drop tests?

The title:- Measurement of Dynamic Rope System Stiffness in a Sequential Failure for Lead climbing Falls should give you a clue, from page 17 on they describe the difference when using a static rope.


Colinhoglund


Nov 13, 2012, 11:15 AM
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Re: [surfstar] Ultimate Strength of a Multiple Point Anchor [In reply to]
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surfstar wrote:
[image]http://www.mountainproject.com/images/85/55/106368555_large_c48104.jpg[/image]

If i got to an anchor and saw this and survived, said partner would never leave the ground with me again. Theres do the best you can with what you got, been there many times. And then theres sketch . . .


theextremist04


Dec 9, 2012, 12:43 PM
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Re: [Colinhoglund] Ultimate Strength of a Multiple Point Anchor [In reply to]
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Colinhoglund wrote:
surfstar wrote:
[image]http://www.mountainproject.com/images/85/55/106368555_large_c48104.jpg[/image]

If i got to an anchor and saw this and survived, said partner would never leave the ground with me again. Theres do the best you can with what you got, been there many times. And then theres sketch . . .
There are exponentially worse anchors out there when it comes to hard aid climbing.


(This post was edited by theextremist04 on Dec 9, 2012, 12:46 PM)


Colinhoglund


Dec 9, 2012, 4:30 PM
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Re: [theextremist04] Ultimate Strength of a Multiple Point Anchor [In reply to]
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theextremist04 wrote:
Colinhoglund wrote:
surfstar wrote:
[image]http://www.mountainproject.com/images/85/55/106368555_large_c48104.jpg[/image]

If i got to an anchor and saw this and survived, said partner would never leave the ground with me again. Theres do the best you can with what you got, been there many times. And then theres sketch . . .
There are exponentially worse anchors out there when it comes to hard aid climbing.

Two points on that.

1 that's what bolts are for. (FYI I'm no sport wanker, bolts have their place)

2 hard aid scares the shit out of me and doesn't l look like fun. (And I firmly embrace type 2 fun) if the rock is too soft for bolts, it's too soft to climb. (And yes I have been to Moab, used a scary five bolt anchor and had a great time)


theextremist04


Dec 10, 2012, 9:05 AM
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Re: [Colinhoglund] Ultimate Strength of a Multiple Point Anchor [In reply to]
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Colinhoglund wrote:
theextremist04 wrote:
Colinhoglund wrote:
surfstar wrote:
[image]http://www.mountainproject.com/images/85/55/106368555_large_c48104.jpg[/image]

If i got to an anchor and saw this and survived, said partner would never leave the ground with me again. Theres do the best you can with what you got, been there many times. And then theres sketch . . .
There are exponentially worse anchors out there when it comes to hard aid climbing.

Two points on that.

1 that's what bolts are for. (FYI I'm no sport wanker, bolts have their place)

2 hard aid scares the shit out of me and doesn't l look like fun. (And I firmly embrace type 2 fun) if the rock is too soft for bolts, it's too soft to climb. (And yes I have been to Moab, used a scary five bolt anchor and had a great time)
As anther primarily trad climber, I agree with your first point. And your second. But there are guys out there who have their fun hanging off of nothings, and some of the things they do are insane.


Colinhoglund


Dec 10, 2012, 11:21 AM
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theextremist04 wrote:
Colinhoglund wrote:
theextremist04 wrote:
Colinhoglund wrote:
surfstar wrote:
[image]http://www.mountainproject.com/images/85/55/106368555_large_c48104.jpg[/image]

If i got to an anchor and saw this and survived, said partner would never leave the ground with me again. Theres do the best you can with what you got, been there many times. And then theres sketch . . .
There are exponentially worse anchors out there when it comes to hard aid climbing.

Two points on that.

1 that's what bolts are for. (FYI I'm no sport wanker, bolts have their place)

2 hard aid scares the shit out of me and doesn't l look like fun. (And I firmly embrace type 2 fun) if the rock is too soft for bolts, it's too soft to climb. (And yes I have been to Moab, used a scary five bolt anchor and had a great time)
As anther primarily trad climber, I agree with your first point. And your second. But there are guys out there who have their fun hanging off of nothings, and some of the things they do are insane.

Exactly, key word insane.


marc801


Dec 10, 2012, 1:11 PM
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Re: [Colinhoglund] Ultimate Strength of a Multiple Point Anchor [In reply to]
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Colinhoglund wrote:
surfstar wrote:
[image]http://www.mountainproject.com/images/85/55/106368555_large_c48104.jpg[/image]

If i got to an anchor and saw this and survived, said partner would never leave the ground with me again. Theres do the best you can with what you got, been there many times. And then theres sketch . . .
,,,and there's maybe investigating the story behind that photo before passing judgement about it and the person who put it in.

Its part of a belay on the FA of Sea of Dreams on El Cap (Jim Bridwell, Dave Diegelman, Dale Bard [the climber in the photo]).

Here's what Dave Diegelman says about it on his web site [ http://davediegelman.blogspot.com/...eams-el-capitan.html ]:

Dave Diegelman wrote:
Upon reaching the logical belay point, I whipped out my drill and started drilling a ¼” hole to place a 1.5" belay bolt. We were running very low on good drill bits as lack of financial stability was unanimous and expending money into drill bits didn’t take precedent over visits to the mountain room bar prior to leaving on our granite voyage. As a result were in the habit of starting the hole with a dull bit and then breaking off the tip for a fresh, sharp edge to drill with. After 25 minutes of non-stop drilling my sad little hole was only ¾” deep.

I was loosing patience and tired of drilling so I yelled down to my partners, Jim Bridwell and Dale Bard, “let’s not haul from here, let’s just climb through and fix ropes. It’s taking too long to get the bolts in and I’m out of bits. Is it ok to belay off off 5 equalized rurps and a rivet?” Although this may seem ridicules [sic] the seam that the rurps were in was harder than a W*****’s heart and quite solid. Besides nothing like that had ever been done before to my knowledge and the pure novelty of it … I thought. Thankfully Dale strongly protested, as he would be the one cleaning the pitch so I slogged on and put in a 1” bolt, still very substandard for a belay, and backed it up with a rivet. The drilling must have taken an additional half-hour.

I knew that when Dale reached the anchors it would be an amazing photo op so I brought up the camera on the tag line and got positioned. Unfortunately it was so windy that when the time came one of my aiders blew up into the image and there was no way to stage his reaction so that’s why there’s this big blur in the photo behind his head.


Colinhoglund


Dec 10, 2012, 4:40 PM
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Re: [marc801] Ultimate Strength of a Multiple Point Anchor [In reply to]
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I'm not questioning the pro. In a picture like this I can't tell if those are rurps or knifeblades. What I'm questioning is how the pro is strung together. The series clove hitch method seen in this photo has been superseded by multiple other anchors that equalize and allow no extension if a piece fails. Climbing trad on limestone choss has taught me that overall, you want to spread the load between multiple pieces and also most importantly as mentioned above, allows minimal extension. For example, if each of those pieces would hold 5kn, and were subjected to 7kn load, each would fail in series. However if equalized, 5 pieces at 5kn could hold 25kn in a perfect environment. In the real world because perfect equalization is impossible, the sharing would be less than ideal. However if each holds 2kn and one gets 1kn, our 7kn is absorbed.
Disclaimer
If poor equalization occures and the weakest/highest loaded piece fails, the remaining pieces can share the load and the anchor holds. Not to mention the fact that inan anchor with low extension the piece that fails will probably just slip a bit until the others become loaded more.
2nd disclaimer
I'm sure one can find a way to make any ideal (or lest than ideal) anchor setup fail. My point still stands, if you don't know how to build a better anchor of good or bad gear better then cloving them in series, I'm not climbing with you anymore unless you learn how do do it better.


marc801


Dec 11, 2012, 6:22 AM
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Colinhoglund wrote:
I'm not questioning the pro. In a picture like this I can't tell if those are rurps or knifeblades. What I'm questioning is how the pro is strung together. The series clove hitch method seen in this photo has been superseded by multiple other anchors that equalize and allow no extension if a piece fails. Climbing trad on limestone choss has taught me that overall, you want to spread the load between multiple pieces and also most importantly as mentioned above, allows minimal extension. For example, if each of those pieces would hold 5kn, and were subjected to 7kn load, each would fail in series. However if equalized, 5 pieces at 5kn could hold 25kn in a perfect environment. In the real world because perfect equalization is impossible, the sharing would be less than ideal. However if each holds 2kn and one gets 1kn, our 7kn is absorbed.
Disclaimer
If poor equalization occures and the weakest/highest loaded piece fails, the remaining pieces can share the load and the anchor holds. Not to mention the fact that inan anchor with low extension the piece that fails will probably just slip a bit until the others become loaded more.
2nd disclaimer
I'm sure one can find a way to make any ideal (or lest than ideal) anchor setup fail. My point still stands, if you don't know how to build a better anchor of good or bad gear better then cloving them in series, I'm not climbing with you anymore unless you learn how do do it better.
Those are indeed RURPs. Recall the year when that route was done. Many of the concepts that you just described weren't known yet as they applied to climbing. (Meaning that the majority of climbers didn't know/understand then nor were they widely written about.)

Yes, I'd freak quite a bit if I came up to that anchor, as did Dale Bard in that photo, but times and knowledge were different then.


Colinhoglund


Dec 11, 2012, 7:48 AM
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Agreed, today or in the golden age of Yosemite that anchor is still scary. I climb with some older gentlmen who have told me how they used to do things, and the learning process of constantly rethinking their methods through the decades. Im sure glad that some guys way smarter then me figured out the modern methods we have, and shared them with the community. Cool to hear the back story from this photo and thanks for the good discussion. Wink

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