Triaxial Loading

Discussion in 'Question of the Day' started by dvsDave, Aug 22, 2019.

  1. dvsDave

    dvsDave Benevolent Dictator Administrator Senior Team CB Mods Fight Leukemia

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    What is triaxial loading: What does the term mean, where is it encountered and why is it often a concern? For bonus points: Explain how you'd circumvent the issue.

    Students ONLY for 10 days.

    Questions will be judged/commented on by @egilson1 and @What Rigger?

    Thanks to @RonHebbard for suggesting the question.
     
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  2. Lynnchesque

    Lynnchesque Member

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    My first guess was that this is some kind of exotic concept of electricity..
    But now I am envisioning dangerous situations where truss buckles and boom lifts tip over.
     
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  3. josh88

    josh88 Remarkably Tired. Fight Leukemia

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    Don't ask Ringling Brothers.
     
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  4. What Rigger?

    What Rigger? I'm so fly....I Neverland.

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    :shock:
     
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  5. eadler

    eadler Active Member

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    Clearly this is what happens when someone hangs a drop from a piece of triax camera cable.
     
  6. RonHebbard

    RonHebbard Well-Known Member Premium Member

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    @eadler Oh you innovators inside your walls; What's the safe working load of your triax and what kind of knots do you use?? ( Inquiring minds yada, yada. . . )
    Toodleoo!
    Ron Hebbard
     
  7. eadler

    eadler Active Member

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    I mean, Belden does spec a max recommended pulling tension of 124 lbs. I imagine the stranded version is higher... This is what we really have so 264 lbs of pull tension, give it a 10:1 safety factor and you can hang about 25 lbs from it without damage!
    Oh, and always a bowline.

    (For anyone thinking this is serious - No. Don't. Please.)
     
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  8. JChenault

    JChenault Well-Known Member

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    Somehow this discussion reminds me when our tour u haul truck brok down and we towed it with a length of 12/3 SJ cable
     
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  9. RonHebbard

    RonHebbard Well-Known Member Premium Member

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    Where's that Double LIKE button?
    @eadler
    Thanks for your tongue in cheek reply, clearly better than coax with BNC's and FAR superior to solid coax with F connectors.
    @What Rigger? @egilson1 @FMEng and @Ancient Engineer Would you care to play along?? PLEASE!!
    Toodleoo!
    Ron Hebbard
     
  10. RonHebbard

    RonHebbard Well-Known Member Premium Member

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    Understood and appreciated. Did you by any stretch employ two lengths of SJ and anchor them with ONE ( Singular ) carabiner??
    Toodleoo!
    Ron ( with my tongue so firmly in my cheek as to likely require surgical extraction. ) Hebbard
     
  11. sk8rsdad

    sk8rsdad Well-Known Member Premium Member Fight Leukemia

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    Your math is wrong. A bowline reduces the strength (of rope) by about 1/3 so the maximum load would be about 16 lb or about 7 kg for every country other than the United States, Myanmar, and Liberia.
     
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  12. josh88

    josh88 Remarkably Tired. Fight Leukemia

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    Since it's been enough time and nobody has answered, its 3 points of loading under tension, most problematic with a carabiner, (see the providence Ringling Brothers accident where a carabiner that was triaxially loaded broke, and dropped a bunch of people) though you can do it with shackles as well. In the case of the Ringling incident, they had 2 pear rings on a carabiner which caused it to break. The osha findings cited that a shackle would have abated that. With a carabiner, the strength is inline with the spine, so a triaxial load spread that out at an angle and therefore distribute the load in a way that lowers the overall strength of the carabiner and puts stress on it.

    As far as I know, nobody recommends or says doing this with a carabiner is safe.
     
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  13. BillConnerFASTC

    BillConnerFASTC Well-Known Member

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    It's a complicated issue so safe to say no, but I believe some common climbing situations require tri- and quad-axial loading.

    shorturl.at/ehlzW

    As this report shows, the ultimate strength of the triaxially loaded biner is less than when properly loaded in line with the spine, but not substantially.

    Generally, I try not to rely on biners. Don't load a biner other than (bi)axially unless you really have done the work. And I think most of the time that work is finding the worst case impact. When it all goes fubar, what is that impact? Requires a lot of education and mentored experience to calculate that.
     
    Last edited: Sep 6, 2019
  14. RonHebbard

    RonHebbard Well-Known Member Premium Member

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    Uh, Bill? Your link's not working for me.
    Toodleoo!
    Ron Hebbard
     
  15. RonHebbard

    RonHebbard Well-Known Member Premium Member

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    Prior to posting the current QOTD, @dvsDave included an excellent video in a PM.
    I'll try to cut 'n paste it but I may not be successful. @dvsDave could post it if my cut 'n paste is unsuccessful.
    I found a great video on triaxial loading done by Chicago Flyhouse, Inc!


    ""Literature and fiction are two entirely different things. Literature is a luxury; fiction is a necessity. A work of art can hardly be too short, for its climax is its merit. A story can never be too long, for its conclusion is merely to be deplored."
    -G.K. Chesterton


    Toodleoo!
    Ron Hebbard
     
  16. BillConnerFASTC

    BillConnerFASTC Well-Known Member

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    That should work.
     
  17. RonHebbard

    RonHebbard Well-Known Member Premium Member

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    On my screen (MS10 / Chrome), a message appears stating: "Control Booth error. Invalid Advertiser Id, Publisher Code, Offer, or Publisher - Advertiser Partnership Status"
    @dvsDave Help!?
    Toodleoo!
    Ron Hebbard
     
  18. eadler

    eadler Active Member

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    To be fair, if I were to actually want to do this and have the cable come out usable, it'd probably be less than a pound of force before it pulled the cable tighter than the minimum bend radius with any knot or hitch (short of putting hitches around a 279.4mm or larger O.D. pipe). If I actually wanted to do this for loading and not care about the ~$10/m cable, I would go through the spec sheet and account for the breaking strength of the various insulation and jacket materials and likely find a much higher rating -- the maximum pull tension (1174.320 N) is a spec for maintaining the cable's ability to meet the specified electrical characteristics - essentially at this pull strength the cable will not deform (or will deform 'evenly' across all layers/insulations/dielectrics).

    Step one of course for this exercise is to place ones tongue firmly against a cheek.
    Here's the metric spec sheet in case you want to do some real math :)
     
    Last edited: Sep 6, 2019
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  19. dvsDave

    dvsDave Benevolent Dictator Administrator Senior Team CB Mods Fight Leukemia

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    Shoot me a Private Message if you are still showing this error.
     
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  20. What Rigger?

    What Rigger? I'm so fly....I Neverland.

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    Like I even know what triax cable is. I mean, I have the Google, but you can't expect me to look things up.
     
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