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Thread: Deep groove in carabiner?

  1. #21
    X2!
    1/3 rule, fat biners are best.
    Also we have found that rappel devices with more surface area seem to help the 'biner by taking some of the heat (so to speak) from a sandy rope.
    We have found, in sandy conditions that the devices that last longest with the 'biner, from worst to best are:
    ATC
    ATS
    Pirana
    CRITR
    (A TOTEM user will have to tell us how they wear!)
    We also presume, because of it's surface area, that the SQWURL will perform well in this regard.

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  3. #22
    Quote Originally Posted by harness man View Post
    X2!
    1/3 rule, fat biners are best.
    Also we have found that rappel devices with more surface area seem to help the 'biner by taking some of the heat (so to speak) from a sandy rope.
    We have found, in sandy conditions that the devices that last longest with the 'biner, from worst to best are:
    ATC
    ATS
    Pirana
    CRITR
    (A TOTEM user will have to tell us how they wear!)

    We also presume, because of it's surface area, that the SQWURL will perform well in this regard.
    Hmm, I was a Totem user until I got the CRITR. I think the CRITR might wear just a tad faster than the Totem?? but probably because the Totem has various rigging options that spread out the wear a bit more (but after time, I decided I would rather just rig the "easy way" instead of having several inferior options for rigging that the Totem provides). However, I have a hypothesis about the CRITR vs Totem in that . It is basically that the CRITR spreads some of the wear to the carabiner, where the Totem takes all of the wear itself (the way I rigged the Totem). Time will tell...

  4. #23
    Quote Originally Posted by Skeeter View Post
    Why do you shuffle carabiners around on your rappel device?
    I have the same question. My rap device biner stays put, attached to the rap device. Also I generally use an auto-locker on my rap device (screwgates for all else) so don't want to share that around.

  5. #24
    Quote Originally Posted by hank moon View Post
    I have the same question. My rap device biner stays put, attached to the rap device. Also I generally use an auto-locker on my rap device (screwgates for all else) so don't want to share that around.
    X2 Except: I sure as hell don't want to share my rap device. (emergencies excepted)

    Ken

  6. #25
    Quote Originally Posted by Skeeter View Post
    Why do you shuffle carabiners around on your rappel device?
    Rap 2 biners with an atc one rappel, then one biner with an atc on the next rappel, then two...

    Then remove the ATC while I meat anchor, place it on a side biner.

    No sense in trying to keep it all straight. A waste of energy.

    They all get very mixed up in the group, then mostly sorted out at the end of the day.
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  8. #26
    I have dug up some biners and rap devices that I have retired. Notice that I have not melted them down and they are still in my gear box but no longer on my harness.

    When I look at these now, these notches do not look so deep.

    Here are my questions: Would you have retired these? Would you feel safe rapping on these? How compromised do you think these devices are as a percentage?

    If any one is interested in testing the breaking strength of these, please let me know, they are available for research.

    Ken

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  10. #27
    Quote Originally Posted by ratagonia View Post
    Are you an engineer?

    THIS engineer (mechanical engineering, B.S., 1982) thinks engineering is about UNDERSTANDING systems. I have the advantage of having seen 1000's of broken biners in my time at Black Diamond, and having seen the FEA of carabiners under development. There are critical locations on carabiners that you should have concern about compromising, but the basket, where the rope runs, is not one of them. I don't have too much concern about rope grooves from rappelling, and also use the "1/3 rule".

    However, I have also seen a carabiner cut half way through on a 100' rappel, when conditions were perfectly bad. Matter of fact, that was two carabiners under an ATC, and both carabiners were chewed pretty good. If I had only one biner, would it have cut all the way through?

    A good reason to use FAT carabiners like the Petzl Attache carabiner. And check it after every rappel.

    Tom
    Masters in structural engineering, and licensed structural engineer in California. Mostly practiced in steel design. I own only aluminum carabiners, and retire them with shallow grooves. If I ever get back into canyoneering, it will be with steel carabiners. I value my life a lot.

    Tom, real world experience always trumps theory, but 1/3 depth groove is something that I would never accept on a critical link in my life support system.

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  12. #28

    Black Diamond (where Tom worked) is famous for break testing every type of climbing gear under the sun: there is certainly some test results in their archives on carabiner wear....
    I think Tom's point is that 1/3 wear thru in this particular area of the carabiner does not compromise the strength much, as long as the carabiner gate is closed and locked. Also, 1/3 wear thru is when to RETIRE the biner (not keep using it).
    1/3 wear thru on a Petzl Attache is different than 1/3 thru on a micro-biner (which should not be used for rappelling in the first place).
    If you compare the mass of aluminum left on a FAT biner after 1/3 wear it will still be substantial compared to some micros.
    Spinesnaper, lets break some worn biners!
    Our ship to address is at http://canyonwerks.com if you want to send one.
    We have a couple worn biners of our own and will pull them out and pop 'em
    the test rig
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  14. #29
    Quote Originally Posted by spinesnaper View Post
    I have dug up some biners and rap devices that I have retired. Notice that I have not melted them down and they are still in my gear box but no longer on my harness.

    When I look at these now, these notches do not look so deep.

    Here are my questions: Would you have retired these? Would you feel safe rapping on these? How compromised do you think these devices are as a percentage?

    If any one is interested in testing the breaking strength of these, please let me know, they are available for research.

    Ken
    I wouldn't have a problem using those. Looks like some of the reflections in the pictures makes them look deeper than they actually are.

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  16. #30
    Quote Originally Posted by skunkteeth View Post
    I wouldn't have a problem using those. Looks like some of the reflections in the pictures makes them look deeper than they actually are.
    When I first discovered the grooving, I was freaked. However, I don't feel trouble in the slightest that they are off my harness. Probably reasonable to replace them but yeah, looking at them now, they do look meaty.

    Harnessman

    I am packing up the gear and shipping it to you. Please let us know what you learn.

    Ken

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  18. #31
    Just wanted to comment that the groove in the picture I uploaded when posted this thread was from a single 150' rappel on a fairly new carabiner.

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  20. #32
    Thanks Spinesnaper!
    we are in breaking mode (check out the SLING thread) and will post
    Best
    Todd and Desi

  21. #33
    Thank you Spinesnaper for sending your gooved biner samples
    Now we have a nice little collection to try to get a handle on the burning question: how strong are grooved/worn biners?

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    We have utilized our very best grade-school math and a set of calipers to estimate the amount of missing material on each biner.
    Close up of the last two 30% biners:

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    Next step- the set up on the test rig.....

  22. #34
    Content Provider Emeritus ratagonia's Avatar
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    Quote Originally Posted by harness man View Post
    Thank you Spinesnaper for sending your gooved biner samples
    Now we have a nice little collection to try to get a handle on the burning question: how strong are grooved/worn biners?

    We have utilized our very best grade-school math and a set of calipers to estimate the amount of missing material on each biner.
    Close up of the last two 30% biners:

    Next step- the set up on the test rig.....
    Could you be more specific on what your number means? Did you make several measurements and do some geometry to estimate the total amount of (cross sectional) material missing? or does " -30%" mean that the narrowest measurement was down 30% from the original.

    From a mechanical engineering perspective, the part that is grooved out is primarily stressed in bending, and therefore the stiffness is not proportional to the amount of material, but to it's "beam stiffness" ~ w * h^^2. Therefore removing the material as shown would make it a LOT weaker. A more recent ME grad could probably spin those calculations off pretty quick (but not me).

    My hypothesis, however, is that even with a 30% cutting, this is still not the critical point on the carabiner, so they should still go to full strength. I hope you are using the appropriate 9mm steel pins when you pull these, or something similar, such as a shackle. On these carabiners, the pin used probably does not make much difference. On D-shaped carabiners where the pin sits against the spine, it can.

    Tom

  23. #35
    Note: the majority of our biners are Petzl Attaches rated at 23 kN.
    Also in the mix: a Petzl William (marked B2) at 25 kN.
    And a Rock Exotica Pirate (marked B6) at 26 kN.
    I our test set up we connected all biners with the basket (wide part) on the bottom and placed the shackle IN the biggest groove in the biner.

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    then we pulled until failure (BOOM!)
    Here are results in lbs:

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    Notice something STRANGE about the breaking strengths?
    The biners are arranged by how much wear (grooving) from least to worst.......but the breaking strengths DO NOT match up!
    In fact, the BRAND NEW biner broke at the lowest value, 3,700 lbs.
    Can you figure out (from the photos) why?
    Hint: I marked the position of the lower shackle on the basket in blue pen...

  24. #36
    Presumably this means that the grooved spot closer to the spine of the biners is stonger than the more lateral spot that the shackle sat it for the unused biner. This makes sense since the shackle sitting away from the spine of the unused biner will have some addition torsional forces applied into the spine of the biner.

    I am not an engineer but I did stay at a Holiday Inn Express last night.

    Ken

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  26. #37
    It turns out, at least in this group of test samples, that the amount of 'grooving' (up to 30%) does NOT significantly affect the breaking strength.
    What DOES effect the breaking strength is how far the rope or connection point at the bottom is from the spine of the biner.
    HMS biners have a big "basket" at the bottom to allow for smooth flow of double ropes for rappelling.
    If the groove we were pulling from at the bottom was close to the spine (less leverage on the spine) then the carabiner was STRONGER.
    If the groove was further from the spine (more leverage on the spine) then it was weaker.
    The amount of grooving seemed to have no effect!
    Here are the same carabiners arranged by how close the groove (or shackle placement) was to the spine, from closest to farthest:

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    In order to prove the point we set the shackle on the New biner furthest from the spine, and it broke the lowest at 3,700lbs.
    Conclusion: Ratagonia is Right!!!!

    (up to 30% grooving does not lower the breaking strength in this test)

  27. #38
    Content Provider Emeritus ratagonia's Avatar
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    Quote Originally Posted by harness man View Post

    In order to prove the point we set the shackle on the New biner furthest from the spine, and it broke the lowest at 3,700lbs.
    Good to clarify this point - that the new carabiner did not "break below its rating"... it broke below its rating because the loading point was constrained to an un-natural position.

    Thanks for your work on this Todd. Let me go take pics of these slings I have for you and get them shipped off.

    Tom

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  29. #39
    So the logical question would be at what point should these biners be retired? Obviously one can tolerate more and 20% grooving and more than 30% grooving.

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  31. #40
    Thanks for the clarification, Tom.
    Sample B3 is a lightly used Petzl Attache and the groove in this sample was in a position close to the spine similar to how the carabiner would normally be tested. B3 broke at 5,820 lbs, well above it's rated strength of 5,170 lbs(23 kN). This, in spite of the 20% groove. So the petzl Attache seems to perform well (it is my favorite CRITR/rap biner combo).

    By contrast, here is the position that we broke the new Attache in (sample B1), with the bottom shackle the furthest from the spine, in the LEAST favorable position, yielding a lower breaking strength of 3,700 lbs.

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    Spinesnapper: when to retire a worn biner?
    The testing we have done is "theoretical" in the sense that it is a simple tensile test in the main axis pulling end to end,, but there could be other weird, unanticipated forces in real world use.
    So we are retiring our biners at 30%!
    Best
    Todd and Desi

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