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Strength of tieline?

Discussion in 'Scenery, Props, and Rigging' started by gafftaper, May 21, 2008.

  1. gafftaper

    gafftaper Senior Team Senior Team Fight Leukemia

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    I just want to clarify that we are joking about the use of Tie Line in rigging. I got a PM from Photoadv and apparently he had two "professionals" tell him it is acceptable to use tie line for rigging because it has a test strength of 500lbs. So he was asking a serious question above. Let's be really clear here... It IS NOT acceptable to use tie line for any form of rigging. These "professionals" who told photoatdv it's safe ARE WRONG and I would be concerned for my own safety working in their theater.

    While I must admit that my love of tie line is nearly as strong as my love of Gafftape let's be very clear...
    It doesn't matter how strong the test strength of tie line, rope, chain, or any other material is. The question is, is it rated for overhead lifting? The answer to most of those things is No. Even in super high strength chain there are many types that are not approved for overhead lifting. We are in that gray area where the answer to many questions is, "If you have to ask the question, don't do it find a qualified rigger." Unfortunatley many people just go to home depot and find some cheap Chinese chain and quicklinks rated at 500lbs and figure it will be safe to hang a batten. It IS NOT safe and you need to educate yourself more before doing any rigging.

    The only acceptable ways I can think of to use tie line over head is to secure a cable to a batten or to secure a drop/curtain to a batten (and there better be a proper tie grommet at least every 12 inches on that drop or it's no good).

    Now standby for a fabulous rant from WhatRigger? on the stupidity of using tie line for real rigging...
     
    Last edited: May 21, 2008
  2. JD

    JD Well-Known Member

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    Re: Truss on crank lifts

    Umm.. It is worth mentioning that there is a big difference between the term "Tensile Strength", the point at which something breaks, and "working load" which indicates the normal stress area that is acceptable. What was said above is correct, much like scaffold planks, the object in question needs to be rated for its usage, which includes the ramifications of failure.

    Rigging and Electrical are two fields we do not discuss here. It has been said before:
    "If at first you don't succeed, don't become a rigger!" There is no room for error in either field.
     
    Last edited: May 22, 2008
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  3. derekleffew

    derekleffew Resident Curmudgeon Senior Team Premium Member

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    Re: Truss on crank lifts

    Yes, JD. "Tinsel Strength" is how strong the silver ribbons are that one puts on Xmas trees. "Tensile Strength" is the breaking point. SWL, (Safe Working Load) is Tensile Strength divided by the safety factor, usually 5:1 or 10:1, depending on the application.

    It is possible to buy #4 (0.125") Black [FONT=Helvetica,Arial][FONT=Helvetica,Arial]BRAIDED POLYESTER CORD, [/FONT][/FONT]with a stated SWL, but the stuff should not be called tieline. It's almost as expensive, but not nearly as strong, as 1/8" aircraft cable. By the time the efficiency of the knots used are factored, load limit is severely minimized. Due to it's vulnerability to heat (fire) should not be used for overhead suspension.

    The only time I've used it was when working with a company called Transformit (cool website--nice pictures). [Rose Brand offers a similar product. Buying the raw fabric makes for an inexpensive set.] It was supporting ten pounds of spandex, maximum. Hey, where'd that "wedding guy" go? This would be good for him.
     
  4. derekleffew

    derekleffew Resident Curmudgeon Senior Team Premium Member

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    Strenth of tieline?

    Posts above "pruned" from "Truss on Crank Lifts" thread.
     
  5. gafftapegreenia

    gafftapegreenia CBMod CB Mods

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    The following is a true story, shared from my experiences. Do not lecture me, it was not my fault.

    Junior year in high school we had, as usual, dozens of muslin coverd flats to hang. Hey, highschool was old skool like that. Anyway, the rigger/local tech we had hired to help us with load-in/lighting focus assured me and my TD that it was fine to hang a row of 8 flats with tie line.

    Despite me voicing my conerns, we did it anyway. WE GOT LUCKY. The next day we came in, and nothing had fallen, but half of the line has had their outer braided jacket snap, and the flats were hanging from at precarious angle from the inner core of the tie line. Let that be a lesson.

    In addition, the next year I made the school buy D-ring plats and hanging irons so they would stop using eye hooks screwed into the top 1x4 pieces of the flats.
     
    Last edited: May 23, 2008
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  6. gafftaper

    gafftaper Senior Team Senior Team Fight Leukemia

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    Oh you bring up another VERY dangerous bit of "rigging" that is VERY common in high schools. Kids, eye hooks screwed into the top of a flat are NOT a safe way to hang them. What happens if the wood splits? Think about all that weight you have depending on the tiny little threads of those screws. Tell your teacher they are wrong and it's not safe. If they don't believe you, send an e-mail to myself( or any of the usual suspects around CB) for a stern lecture as to why it isn't safe.

    Perhaps we need a wiki/colaborative article on Unsafe rigging practices. As long as we are only telling people what not to do would that be ok with the TOS?
     
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  7. gafftapegreenia

    gafftapegreenia CBMod CB Mods

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    I think that was the most unsafe thing we ever did regularly in highschool. I know our sets were usually overbuilt/securely braced.
     
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  8. derekleffew

    derekleffew Resident Curmudgeon Senior Team Premium Member

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    And I suppose you hung the blacks, too?
     
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  9. gafftapegreenia

    gafftapegreenia CBMod CB Mods

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    Can I blame Freud on that one?
     
  10. gafftaper

    gafftaper Senior Team Senior Team Fight Leukemia

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    Hey Gaffbrother, Do you Dutch your Muslims?
     
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  11. gafftapegreenia

    gafftapegreenia CBMod CB Mods

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    Why, indeed we do!
     
  12. What Rigger?

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

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    I second everything Gaff said in the original post here.

    Tie line for rigging rates right up there with the so-called, and NON EXISTENT, 'rated zip-ties'. Or, as a better rigger than I once said: rig right or die!
     
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  13. photoatdv

    photoatdv Active Member

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    To be real honest, though obviously tie line should not be used for rigging, the way they did it nothing was going to fall. The thing that suprises me is that they told me that it is okay to use-- they usually both take rigging quite seriously. I'm wondering if I just misunderstood them or something. You don't want to see how mad they get when someone screws around while we are reweighting.
     
  14. gafftaper

    gafftaper Senior Team Senior Team Fight Leukemia

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    You never said exactly how they were using it.
     
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  15. Charc

    Charc Well-Known Member

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    So, this is really OT, sorry:

    A local H.S., whose name I'll withhold, had a spectacularly huge show last season. They really pulled out all the stops, the have 2-4 movers in the air, and had hired a great LD. The scenic design was a senior project by a student, and some really good work. All in all it was a really well put together musical, and they got away with charging $15 per ticket, and had two weekends of shows.

    Only one problem: their theater doesn't have an orchestra pit... so guess what they did? Created a large platform structure, suspended from the grid. Must have had at least a dozen people on it. Ya know, Sapsis is in town, but somehow I doubt the school called them in.
     
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  16. gafftaper

    gafftaper Senior Team Senior Team Fight Leukemia

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    Wow that is SO dangerous. I've got to admit I've done a few stupid things in my past but they always had some logic behind them. That however is so far off the chart. Wow.
     
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  17. photoatdv

    photoatdv Active Member

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    What teacher okayed that one? Were they on something? Most HS crews can hadly build safe 2 story sets. (No offense to anyone, some HS crews a excellent, many aren't)
     
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  18. gafftaper

    gafftaper Senior Team Senior Team Fight Leukemia

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    How many HS crews have the welding skills to safely build a hanging platform? None... the odds are pretty good it was made with a bunch of 16' long 2x12's and hung with Chinese chain from Home Depot.

    The horror. They are so lucky no one was killed.
     
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  19. photoatdv

    photoatdv Active Member

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    Wow... I just saw this thread in one of the similar threads...

    Boy was I wrong then. The 500lb tieline was a joke... I just misunderstood them. The things they hung with it weighed about 5 lbs... and had a safety on it (I just didn't see it at the time... it was intentionally masked).

    The best part is both of them are very safe when it comes to rigging... I once got in trouble for not rigging posters properly!
     
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  20. Smatticus

    Smatticus Active Member

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    Having a conversation with someone about the acceptability of using tie line or single-strand solid steel wire to rig Luan tree cut-outs with 1x3 spines (about 6' tall, 4' wide). My advice: don't do it, plain and simple. That I see shopping online, tie line does not have a clearly published safe working load or breaking strength. As discussed here, it's not approved or acceptable for overhead rigging. Single-strand solid steel wire, just like any kind of mono-filament, should not be used for overhead rigging either due to it's potential single point of failure and higher susceptibility to fatigue failure.

    My question though, then, is how do we justify the use of tie line to rig curtains overhead? Or to secure cabling overhead? Obviously, part of the answer has to do with the distribution of a load. If a 200 pound curtain is hung from 50 tie lines all girth-hitched to the grommets, then each individual leg of tie line is only seeing a couple pounds of load. The same generally applies to securing cabling. Unless you are doing a single-pick to relieve stress on a big bundle of cable (which I wouldn't want to do with tie line), the loads involved are usually very distributed and therefore very small at any individual tie line. Someone could therefore make the argument that it is acceptable to use a piece of tie line to rig an object overhead that only weighs a few pounds (provided the knots/connections are appropriately made). I'm not saying that it's okay, I'm just saying someone could make the argument or assumption that it would be okay. At what load or under what conditions do we therefore consider it unacceptable to rely on tie line?
     
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