May 13, 2009, 10:48 PM
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Re: [majid_sabet] Two piece anchors are plenty strong! Poll!
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majid_sabet wrote:
and not by some imaginary numbers out of your as* like how some of the climbers are using these days.
TIME FOR PULLING NUMBERS OUT OF MY ASS........
So everything is climbing is based upon matching the ultimate strength of your rope. Ropes are assumed to have a breaking strength of 30kN. Tie a knot in it and you are down to 20 kN.
So assuming you have only two pieces, sharing an equal load of 10 kN each then you are matching the strength of the rope.
Of course there is a hitch..... Sure SOME pieces of trad gear are rated at 10 kN (or higher) but the majority are around 7 - 8 kN, and of course rock quality varies greatly from area to area.
I have done everything from 0 pieces (firm stance w. hip belay) to 11 pieces (2 person rescue belay on terrible rock w. 8 more pieces for the haul system)
As previsly stated, it really depends. Rock quality, risk of loading the anchor, consequences of loading the anchor, available equipment... I could go on.
I have rappelled off of mushroom in squamish before the anchor was replaced, and was terrified (5 old bolts and a piton in a drillhole, equalized) and have been completely fine rapping off a single bomber nut.
May 14, 2009, 12:01 PM
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Re: [summerprophet] Two piece anchors are plenty strong! Poll!
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summerprophet wrote:
majid_sabet wrote:
and not by some imaginary numbers out of your as* like how some of the climbers are using these days.
TIME FOR PULLING NUMBERS OUT OF MY ASS........
So everything is climbing is based upon matching the ultimate strength of your rope. Ropes are assumed to have a breaking strength of 30kN. Tie a knot in it and you are down to 20 kN.
Try more like 9.3 kN for a "typical" climbing rope. And while I'm making up numbers, a "typical" belayer can only hold 3-4 kN with an ATC, so the reality is that is max force on both belayer and climber, double that for the highest anchor. If the "Jesus Nut" holds there should be little or no force on the belay anchor.
May 14, 2009, 12:46 PM
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Re: [swoopee] Two piece anchors are plenty strong! Poll!
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Seemingly overlooked in this discussion is actually getting the climb done.I lead 95% of the pitches I climb.What use is a terrific three piece cam anchor that sucks up your red,yellow and blue C4 if there is a hand crack looming above?Belay anchors can't always,or even frequently look like Majid's truckstops,because some of us want to climb above that point,and get some gear in.
So,in reality,you may belay from four iffy stoppers equalised however you prefer,despite the existance of a great cam crack,because the person leading the next pitch is going to need the goods.
I'll take a solid Jesus piece over a nine piece POS like Majid posted every time.
May 14, 2009, 1:57 PM
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Re: [swoopee] Two piece anchors are plenty strong! Poll!
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swoopee wrote:
Try more like 9.3 kN for a "typical" climbing rope....
I think you should check your sources on that, the olny numbers I have encountered that low were BD's testing on 9.1mm ropes WELL past retirement age.
In addition, grip strength alone is well under 1kN for most individuals, but given the efficiency of an ATC, working loads are a little higher than what you stated at 4-5 kN.
I am willing to accept your belay stats as diferent studies can pull different results (gloves on vs gloves off), but I am curious as to where you read about the breaking strengths of ropes?
Admittedly, there could be a high amount of variability in a dynamic rope. The very qualities of a rope designed to stretch make it difficult to determine exact breaking point, and require repeated pulls, to weaken the cord. Unlike steel cable which has a fairly predictable failure point.
(edited to fix quote)
(This post was edited by summerprophet on May 14, 2009, 4:57 PM)
May 14, 2009, 4:55 PM
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Re: [summerprophet] Two piece anchors are plenty strong! Poll!
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Well how about 22 kN? That's a nice round imaginary number that often gets batted around. Where does that come from? At least I did qualify my post by commenting that I was making up numbers, which is pretty much what everyone else does when it comes to discussing anchors. I am fairly certain that when hanging from a rope I put a force of ~0.91 kN on it, anything beyond that is purely speculation when it comes to dynamic systems.
May 14, 2009, 6:10 PM
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Re: [pendereki] Two piece anchors are plenty strong! Poll!
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I chose sometimes 2 pieces, not because as majidiot wants everyone to believe, 2 piece anchors are the norm (they most certainly are NOT the norm), but because that was all that was available to me. I have also rapped off of a single nut on occasion, but my typical anchor consists of either 3 or 4 pieces (more if necessary).
May 17, 2009, 6:13 AM
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Re: [summerprophet] Two piece anchors are plenty strong! Poll!
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summerprophet wrote:
majid_sabet wrote:
and not by some imaginary numbers out of your as* like how some of the climbers are using these days.
Ropes are assumed to have a breaking strength of 30kN. .
Not even close. Not even the most extreme duty 11 mm dynamic rope will hold that. A brand new 10.5 mm dynamic rope will hold about 9 - 10 kN with a figure eight. The used 10.5 mm rope I tested held about 6.1 kN with a munter hitch.
You will notice that the obviously new ropes tested on that page broke around 2200 lbs. Although I am not sure what diameter that rope is, it would be a safe to bet they are 10.5 mm or close.
(This post was edited by USnavy on May 17, 2009, 6:17 AM)
You will notice I said ASSUMED to have a breaking strength of 30 kN.
This assumption is accepted for all strength calculation of systems, anchors and general rigging. For simplicity, this "Magic Number" is the same for low stretch and high stretch ropes.
The very abilities we find desirable in climbing ropes make testing predictions incredibly complex. A new rope out of the bag will be virtually unbreakable as it will just continue to stretch more and more.
I have personally witnessed a VERY old rope, with multiple core shots lift a 10000 load (after stretching to about 140% of its length.
The only way in a testing environment is to subject the rope to continued cyclic loading, in which repeated stresses are applied to the point where the elastic properties of the rope are reduced, and the long fibers are fatigued.
This is the method in which I have discovered all the testing thus far, if you find others, I would like to read them.
Again, my background is rigging, not testing methods, so hopefully I haven't botched up too much, but you can certainly understand where I am coming from.
It is somewhat accepted that all ropes will have a ASSUMED strength of 30 kN. Simple physics would explain why bolts would approach this number, harnesses would be rated to half of that, and why I would have answered the OP in the fashion I did. In fact if you analyze most practiced methods, you will see that all systems we have been taught to use meet this 30kN(-30% for knots) strength.
May 17, 2009, 8:38 AM
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Re: [summerprophet] Two piece anchors are plenty strong! Poll!
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summerprophet wrote:
USNavy,
You will notice I said ASSUMED to have a breaking strength of 30 kN.
This assumption is accepted for all strength calculation of systems, anchors and general rigging. For simplicity, this "Magic Number" is the same for low stretch and high stretch ropes.
The very abilities we find desirable in climbing ropes make testing predictions incredibly complex. A new rope out of the bag will be virtually unbreakable as it will just continue to stretch more and more.
I have personally witnessed a VERY old rope, with multiple core shots lift a 10000 load (after stretching to about 140% of its length.
The only way in a testing environment is to subject the rope to continued cyclic loading, in which repeated stresses are applied to the point where the elastic properties of the rope are reduced, and the long fibers are fatigued.
This is the method in which I have discovered all the testing thus far, if you find others, I would like to read them.
Again, my background is rigging, not testing methods, so hopefully I haven't botched up too much, but you can certainly understand where I am coming from.
It is somewhat accepted that all ropes will have a ASSUMED strength of 30 kN. Simple physics would explain why bolts would approach this number, harnesses would be rated to half of that, and why I would have answered the OP in the fashion I did. In fact if you analyze most practiced methods, you will see that all systems we have been taught to use meet this 30kN(-30% for knots) strength.
Yes I know what you’re saying. You’re implying that the breaking strength of a rope under dynamic conditions is 30 kN. I am saying the static breaking strength is much less. That’s all. Was that old rope that held 10,000 lbs. an unmodified dynamic climbing rope 11 mm or less in diameter? Was the load being held by a single strand?
May 17, 2009, 5:01 PM
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Re: [summerprophet] Two piece anchors are plenty strong! Poll!
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summerprophet wrote:
USNavy,
You will notice I said ASSUMED to have a breaking strength of 30 kN.
This assumption is accepted for all strength calculation of systems, anchors and general rigging. For simplicity, this "Magic Number" is the same for low stretch and high stretch ropes.
The very abilities we find desirable in climbing ropes make testing predictions incredibly complex. A new rope out of the bag will be virtually unbreakable as it will just continue to stretch more and more.
I have personally witnessed a VERY old rope, with multiple core shots lift a 10000 load (after stretching to about 140% of its length.
The only way in a testing environment is to subject the rope to continued cyclic loading, in which repeated stresses are applied to the point where the elastic properties of the rope are reduced, and the long fibers are fatigued.
This is the method in which I have discovered all the testing thus far, if you find others, I would like to read them.
He just did. Did you follow the link? BD tested 4 rope samples with in a static pull test, and they found that they all failed at around 2200–2300 lbf, about 10 kN. How do you reconcile that test with your claim that ropes have an "assumed" strength of 3 times that figure.
Yes I know what you’re saying. You’re implying that the breaking strength of a rope under dynamic conditions is 30 kN. I am saying the static breaking strength is much less. That’s all. Was that old rope that held 10,000 lbs. an unmodified dynamic climbing rope 11 mm or less in diameter? Was the load being held by a single strand?
What I am trying to say, is static breaking strengths are an inaccurate method for measuring high stretch ropes. For example this is what I would expect to see in a test of breaking strength (although as mentioned, I am a rigger, not a tester)
Phase 1 - rope stretches and machine maxes at 5000 lbs. Phase 2, machinery reset for further pull, DURING WHICH the load is reduced to 1500 lbs as the rope stretches Phase 3 - rope stretches to machine maximum at 5000 lbs Phasse 4 - Machine reset and load again reduces to 2600 lbs as rope stretches Phase 5 - machine stretches, rope fails at 2700 lbs.
(Again these numbers are totally made up, but this is my understanding of how ropes are broken, and explains why static testing does not represent rope strength during use. Ropes are designed to reduce forces, and by that nature, testing ropes eliminates any represeantation of actual use.
The rope we used (EXTREMELY NON SCIENTIFIC TEST) was a beat up 11mm gym rope. Single strand, 1 m long, bowline on each end. lifted ballast using a forklift, maved and placed at another location, total load time around 45 seconds, rope sheath cut at three locations, two where it ran over the 90 degree bends on the forklift forks and one where it ran through the steel cable on the ballast.
He just did. Did you follow the link? BD tested 4 rope samples with in a static pull test, and they found that they all failed at around 2200–2300 lbf, about 10 kN. How do you reconcile that test with your claim that ropes have an "assumed" strength of 3 times that figure.
Jay
As stated below, static pull testing is not a representaion of real world scenarios. Jay, you have a fair amount of miles on hard routes and I assume you have taken your fair number of whippers.
You can agree that whipping repeatedly at the same spot, the rope begins to lose some of its elasticity and the catches start to feel a bit harder.
Between these falls the rope contracts, resoring its elasticity and therin is where the strength of the rope lies. In its elasticity.
Static testing subjests the rope to unrealistic situations as far as the method you and I use ropes.
I didn't make up this 30kN number, look into any of the high angle rigging, rigging for rescue, or ropes that rescue and you will see this number repeated.
May 17, 2009, 8:19 PM
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Re: [summerprophet] Two piece anchors are plenty strong! Poll!
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summerprophet wrote:
USnavy wrote:
Yes I know what you’re saying. You’re implying that the breaking strength of a rope under dynamic conditions is 30 kN. I am saying the static breaking strength is much less. That’s all. Was that old rope that held 10,000 lbs. an unmodified dynamic climbing rope 11 mm or less in diameter? Was the load being held by a single strand?
What I am trying to say, is static breaking strengths are an inaccurate method for measuring high stretch ropes. For example this is what I would expect to see in a test of breaking strength (although as mentioned, I am a rigger, not a tester)
Phase 1 - rope stretches and machine maxes at 5000 lbs. Phase 2, machinery reset for further pull, DURING WHICH the load is reduced to 1500 lbs as the rope stretches Phase 3 - rope stretches to machine maximum at 5000 lbs Phasse 4 - Machine reset and load again reduces to 2600 lbs as rope stretches Phase 5 - machine stretches, rope fails at 2700 lbs.
(Again these numbers are totally made up, but this is my understanding of how ropes are broken, and explains why static testing does not represent rope strength during use. Ropes are designed to reduce forces, and by that nature, testing ropes eliminates any represeantation of actual use.
Well, there is nothing in that link to black diamond suggesting that there were any such phases and machine resets in the tests, but I hope you're right, because otherwise those BD numbers look pretty low.
May 17, 2009, 8:29 PM
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Re: [king_rat] Two piece anchors are plenty strong! Poll!
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king_rat wrote:
...For trad gear I would pretty much always use at least 3 peaces. There are however occasions, ie where there are large tree’s, boulders or bolts to use, where the anchors are clearly so good that two or even one is OK, on the other hand there have been times when I have used 6 or seven peaces of gear to build an anchor.
I whole heartedly agree. I've belayed off of a solid stance with no pieces (4th class), a single nut (large and really solid, and all I had left at the end of the pitch), 2 and 3 piece anchors are the norm, but Ive used up to 7 or 8 pieces in an anchor. Its all dependant on what you have and what will suffice.
Yes I know what you’re saying. You’re implying that the breaking strength of a rope under dynamic conditions is 30 kN. I am saying the static breaking strength is much less. That’s all. Was that old rope that held 10,000 lbs. an unmodified dynamic climbing rope 11 mm or less in diameter? Was the load being held by a single strand?
What I am trying to say, is static breaking strengths are an inaccurate method for measuring high stretch ropes. For example this is what I would expect to see in a test of breaking strength (although as mentioned, I am a rigger, not a tester)
Phase 1 - rope stretches and machine maxes at 5000 lbs. Phase 2, machinery reset for further pull, DURING WHICH the load is reduced to 1500 lbs as the rope stretches Phase 3 - rope stretches to machine maximum at 5000 lbs Phasse 4 - Machine reset and load again reduces to 2600 lbs as rope stretches Phase 5 - machine stretches, rope fails at 2700 lbs.
(Again these numbers are totally made up, but this is my understanding of how ropes are broken, and explains why static testing does not represent rope strength during use. Ropes are designed to reduce forces, and by that nature, testing ropes eliminates any represeantation of actual use.
It appears the devices they used to test those ropes had enough clearance to test the ropes in a single phase. If the machine did not have the clearance to break the rope, they would have to have untied the knot and retied it to make the rope shorter after the first pull. Well there is no way in hell your untying a figure eight after its been loaded to thousands of pounds.
If you look at the entire BD article, there are some 20 tests they did in which the breaking strength of the rope was determined. In all cases it appears they tested the rope until it broke in one pull. In all cases the rope broke well below 30 kN. In fact many broke below 10 kN. Just read through the whole page and you will see.
Although it is interesting to note the breaking strength of the ropes they tested seem to very quite sporadically, and many smaller ropes were stronger then larger ropes, none of them broke anywhere close to 20 kN. let alone 30.
(This post was edited by USnavy on May 18, 2009, 6:23 AM)
Dynamic ropes are tested for a maximum impact force which is far below 30kN. As long as they can stretch far enough to dissipate the energy of the fall they will have a tension that is not much above that impact force.
A static pull test will show you how far they can stretch. My understanding is that the drop tests are pretty damn severe and have high energies compared to even the most severe of climbing falls.
It seems reasonable that holding a 30kN static force is not needed for safety.
May 25, 2009, 10:31 PM
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Re: [hafilax] Two piece anchors are plenty strong! Poll!
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hafilax wrote:
Dynamic ropes are tested for a maximum impact force which is far below 30kN. As long as they can stretch far enough to dissipate the energy of the fall they will have a tension that is not much above that impact force.
That is false. The tension is proportional to the relative elongation of the rope. Hooke's Law.
Oh yeah. I wasn't thinking about it clearly. The maximum impact force is for the test which is what, 80kg and a 1.78 FF?
Let me restate that as long as you don't exceed the energy of the test by much you won't get a tension in the rope much higher than the rated impact force.
Maximum impact forces are usually around what 8 or 9 kN? The ropes in the BD test were breaking pretty close to that. The new rope broke at around 15kN. A factor of 2 seems pretty slim and yet the ropes all pass the UIAA certification.
Many of those old ropes should snap on the first 1.78 FF, 80kg drop. It would be interesting to see if that happens and if the dynamic breaking strength is different from the static.
May 25, 2009, 10:59 PM
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Re: [pendereki] Two piece anchors are plenty strong! Poll!
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Now that we're not really addressing the question could somebody who always uses three pieces make a justification why two is not adequate if they're bomber?
May 25, 2009, 11:13 PM
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Re: [jmeizis] Two piece anchors are plenty strong! Poll!
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jmeizis wrote:
Now that we're not really addressing the question could somebody who always uses three pieces make a justification why two is not adequate if they're bomber?
One bomber piece is strong enough. If there is zero chance of that one piece failing, it would not be necessary to back it up. I do not feel 'zero chance' is realistic; there is at least a small chance that a placement may fail. Therefore I back it up, I do not ever want to be hanging from just one piece. If one of two pieces fails, you are then hanging on a single piece of protection, and I have admitted that there is a chance a piece could fail. Three pieces of protection allows for one piece to fail, and a person to still have back up.
May 25, 2009, 11:28 PM
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Re: [pendereki] Two piece anchors are plenty strong! Poll!
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There's still a small chance that all the pieces will fail so why not place 4 or 27. If you have a 12 piece anchor and 11 of the pieces fail then you'll be on one. So by that trend of thinking we can't possibly be safe...ever. We're all gonna die!