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Adding Hang position between catwalks - Cheeseboroughs enough?

Discussion in 'Scenery, Props, and Rigging' started by stolympiakos, Aug 11, 2018.

  1. stolympiakos

    stolympiakos Member

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    I have three catwalks in my black box that run parallel to one another. They are fantastic to hang from, but there are no hang positions (grid or otherwise) between the catwalks, which leads to inadequate focus positions. What I'm hoping to do is to run a standard batten pipe across those spans (about 12 feet) and attach them with cheeseboroughs (burgers? idk). The span doesn't SEEM long enough to cause any sag (and we're not going to exceed 50-75 lbs per pipe), but I want to check with the hive mind and make sure I'm doing this correctly. I'm not at work this weekend, but can provide a photo to better explain my idea. If there are any additional safety precautions that I should be aware of, such as secondary methods of securing the pipe in addition to the clamps, OR if there are better methods than what I'm currently thinking of, any advice is greatly appreciated.


    Thanks all!
     
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  2. SteveB

    SteveB Well-Known Member

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    50-75 lbs until somebody decides to add stuff.

    I wouldn’t be doing schedule 40 1.9” OD pipe for that span.

    What you describe calls for a truss solution.
     
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  3. RonHebbard

    RonHebbard Well-Known Member Premium Member

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    @stolympiakos Don't misconstrue me as any manor of authority having jurisdiction in your, or any other, area.
    Having said that, you're describing a method that's been used in the Hamilton Place Studio Theatre black box space since its construction in 1973 and hasn't failed yet. The studio is approximately a 75' x 75' black box with a flat (non-raked) patron's balcony approximately 8' wide within the 75' on all four sides leaving a span between opposite balcony rails of approximately 49 or 50'. From the flat floor surface of the balcony there are four permanently installed (Welded in place) ladders, one in each corner, leading up approximately another 8' to an overhead system of parallel catwalks criss-crossing the room in both directions. All of these parallel catwalks have 1.5" Schedule 40 iron handrails of two heights on both sides. Typically designers yoke work lights out from the upper hand rails and a myriad of other front lights, down lights, back lights and specials from a combination of the lower hand rails and standard boom arms up to 24" from the lower hand rails and any / all supporting verticals. In spite of the many positions and angles already available, it was less than a year before designers were doing exactly what you're proposing with approximately 12' lengths of 1.5" Schedule 40 iron (Never aluminum) pipe bridging across the gaps between handrails. Normally everything was kept in compression with the added pipes bearing down upon the supporting rails using a mixture of three types of clamps: Kee (Brand), Cheeseburroughs (Sp?) Roto-loks. [Not to be confused with coffin locks]
    I WON'T tell you I personally observed pipes added in compression and secured only with cotton tie-lines and / or duct tape.
    No, you won't see me putting that in print. (If you think I just did you're surely imagining things.)
    As to loads; In 1973 the originally supplied inventory was 20 Strand Pattern 223 eight inch 1 Kw fresnels and 20 Century Strand 6 x 9 500 Watt 'chimney-top' ellipsoidals with a dozen or so Century Strand scoops. Designers were always borrowing more fixtures from the Hamilton Place Great Hall main stage inventory and in less than two years revenue from the studio space was purchasing more and more fixtures.
    Here's another one of those things you'll never see me writing here.
    12' spans of 1.5" Schedule 40 iron pipe often had six or eight ellipsoidals hung from them and occasionally ten or twelve yoked up, out and down.
    I'd like to tell you every fixture was secured with its own safety.
    I will admit to seeing one safety looped over a pipe and serving two adjacent fixtures.
    I will DEFINITELY state this was in a time LONG prior to 'wigglers' and fixtures in excess of 30 pounds each.
    @stolympiakos Optimistically I've answered your query.
    Toodleoo!
    Ron Hebbard
     
  4. RickR

    RickR Well-Known Member

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    Schedule 80 pipe? More suitable for 12' spans and cheaper and easier to deal with than truss.

    I would also look for 2 connection points at each end of the bridge. Typical strength ratings for pipe assume "continuous spans"
     
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  5. RonHebbard

    RonHebbard Well-Known Member Premium Member

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    @stolympiakos @RickR

    Again writing with reference to the same venue and era; Further to attaching otherwise unsupported spans from more than one point at one or both ends:
    Sometimes (Approximately) 22' full lengths of Schedule 40 iron pipe were borrowed from the adjacent Great Hall main stage space on the condition their lengths were NOT to be altered (In the main space these were used for vertical side booms).
    Most often these pipes were installed from catwalk to catwalk as low as possible, rolled against, and clamped to adjacent 1.5" Schedule 40 iron vertical pipes supporting both the walking surface of the catwalks and both elevations of handrails. The pipes most commonly clamped against verticals on both sides of a catwalk, spanned across and similarly clamped against the verticals on both sides of the next catwalk over; this provided two attachment points at both ends of the pipe.
    One of the annoyances of this method was the trip hazards these pipes created where they crossed the foot paths which became even more annoying if / when tech's were in a hurry, scampering about in dim lighting and / or wearing street shoes and getting careless / forgetful. Bury the pipes in mounds of 12/3 type S, SO or SOW cable and pipes crossing the catwalks at approximately 2" above floor level were really annoying.
    Similarly annoying were pipes crossing the catwalks resting upon either of the two levels of horizontal handrails.
    When every stick of Schedule 40 iron pipe had been pressed into service, someone would install the one or two lengths of the much heavier Schedule 80 iron pipe that had been accumulated in error over the years.
    Continuing on with another couple of points you won't find me typing here:
    Shorter six or eight foot lengths of pipe were often clamped to both sides of one catwalk extending out 'divining board style' from one or both sides with more than one or two fixtures yoked below and to the sides of the 'diving boards'. I WON'T tell you four or five approximately 25 pound fixtures were often found secured to the 'diving boards'.
    Again, this would be done with 1.5" Schedule 40 or Schedule 80 iron but NEVER aluminum.
    It goes unsaid (but it's being typed here anyway) NEVER FORGET to check the integrity of what you're resting upon and clamping to; thoroughly inspect the integrity of all welds.
    Again I'm NOT any manner of engineer but I suggest steel is generally stronger in tension than compression and supporting / securing lengths from more than one point on more than one end is prudent.
    Overbuilding leads to sleeping better.
    Toodleoo!
    Ron Hebbard
     
    Last edited: Aug 12, 2018
  6. gafftaper

    gafftaper Senior Team Senior Team Fight Leukemia

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    Calling our resident riggers @porkchop and/or @What Rigger? for an opinion on the safety of this.
     
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  7. porkchop

    porkchop Well-Known Member

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    The span and load don't particularly bother me. @RickR makes a good point with wanting more than one connection point per side. Keep the cheeseboroughs in compression and I'd say you've at least got a reasonable idea. My question is 1) How are you going to get the fixtures and necessary cabling safely out where you want them on the pipe, 2) what are you going to do with them once they're out there, and lastly 3) how are you going to get them back safely? Hanging a single source 4 within arms reach of the catwalk might not be bad, but if you're trying to hang a moving light half way between the catwalks then I have some serious questions. Also if you do this, remember the pipe wants to roll so keep the yoke pointed down.
     
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  8. RonHebbard

    RonHebbard Well-Known Member Premium Member

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    @stolympiakos @RickR and @porkchop Writing in agreement and FULL support:
    Another one of those things I WON'T write here expands upon how IDIOTS were dealing with @porkchop 's very valid concerns in the aforementioned Studio venue in 1973. Designers were taking a 20' section of a standard 40', grade 1 or 2, 'home duty' rated aluminum ladder, lying it horizontal and flat spanning the gaps between the floors and / or handrails of parallel catwalks then crawling out on their hands and knees to hang, cable, color and focus lamps. In some instances, IDIOTS were lying down flat on the ladder. at least spreading their weight out, to reach as low and / or far out as possible before either continuing to the next catwalk or crawling back to where they came from. Safeties, color frames, cut colors, donuts, shutters, gobos and gobo holders were often dropped and others would either climb up a 12' wood or aluminum ladder and stand on the top stretching up to hand whatever'd been dropped, or perhaps an extra fixture and / or 'two-fer' into the hands of the IDIOT kneeling or lying on the ladder.
    Non-trussed, 20' sections of flat aluminum ladders are MOST DEFINITELY neither rated nor intended to be operated, loaded and stressed in such a manor. I'm pleased to write I never had any part in misusing the ladders in this manner but I will say I was all too often the junior IA member from the adjacent Great Hall crew having to retrieve items borrowed from the Great Hall for a three week run and NOT returned post a late Sunday evening strike in time for a Monday morning 8:00 a.m. load-in.
    Bah! Humbug!! Phuquin' IDIOTS!!! @gafftaper @RickR and @porkchop you have my full support and I thank you for raising and clarifying your very valid concerns and issues.
    EDITED: To remove an inadvertently repeated word.
    Toodleoo!
    Ron Hebbard
     
    Last edited: Aug 12, 2018
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  9. egilson1

    egilson1 Well-Known Member Premium Member

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    Why speculate when we have data.
    The attached image
    is from JR Clancy and shows loading data for 1.5” schedule 40 & 80 pipe.

    As others mentioned keeping the cheeseboroughs in compression only helps.

    If you are likely never to move this pipe, then I recommend something like the mega-gridlock from The Light Source. By using nylock nuts you don’t need to check the connection as often.

    Ethan
     

    Attached Files:

    Last edited by a moderator: Aug 12, 2018
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  10. BillConnerFASTC

    BillConnerFASTC Well-Known Member

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    Man that is weird. I went to same (Clancy) app when I read this last night and I get different results than you. (I don't have a clue how to get a screenshot of my phone so I photographed it.) MIne says copyright 2016. Could no find a version.

    upload_2018-8-12_12-26-7.png
     
  11. RickR

    RickR Well-Known Member

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    Last edited: Aug 12, 2018
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  12. BillConnerFASTC

    BillConnerFASTC Well-Known Member

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    I don't question his accuracy or the conditions, just the app results. And what I posted actually matches the pdf Rick posted. So like I said, man, this is weird. (Yes, the non-continuous changes it, but not a lot.) My results are the same as the pdf.

    And, I seem to recall that ETC cast iron clamps The Light SOurces Mega Clamp, and some others fit on 2" pipe. Plenty of Legacy c-clamps out there that don't . That would be the sure way to solve it, depending on the annoyance caused by your inventory.

    PS - I'd feel safe with 1 1/2 schedule 40 and just keep an eye on the load. 20 PLF is a lot of units - and there is a 5 to 1 or 8 to 1 design factor in that chart IIRC.

    upload_2018-8-12_13-0-26.png
     
  13. MPowers

    MPowers Well-Known Member

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    A couple of minor points . 1. Steel is equal in strength whether in tension or compression. That's what supports skyscrapers. 2. Re: two attachment points at each end. someone mentioned keeping them both in compression. The attachment point on the outer end of the pipe would have to be above the pipe as the first attachment point will act as a fulcrum when weight is placed along the main span of the pipe.
     
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  14. RonHebbard

    RonHebbard Well-Known Member Premium Member

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    @MPowers Your mention of supporting skyscrapers harkens back to my apprenticeship days. I'dve sworn a structural PEng pointed out to me in passing that the upper chords of prefabricated welded steel girders spanning across a structure were intentionally wider and thicker than the angles used to fabricate the lower chords due the upper chord being in compression versus the lower chord operating in tension. We weren't having any manner of university level discussion, I was merely a lowly electrical construction and maintenance apprentice on a full bore unionized project. I'd pointed the visiting structural PEng towards a location or person he was seeking and he imparted a little wisdom in return. It made sense to me when he explained it and scribbled an explanatory sketch on the back of one of the prints I was working from. All these years I've recalled and believed him.
    Toodleoo!
    Ron Hebbard
     
  15. stolympiakos

    stolympiakos Member

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    Luckily we have a 2 man lift that we can use to hang these. We'll go into rep in that space for as long as I'm here, so once they're set, they're set. Nothing is getting added or removed without me knowing or being in the space to approve it.

    Man, there is some incredibly valuable knowledge on this board, and I'm so lucky to be a part of it.

    From what it sounds like, going Sch 80 is a little better for the span, but if I HAVE to go Sch 40 and I keep an eye on it and don't move it, I'm likely fine...? Obviously there's more to it, but at its base level this is essentially what I'm hearing.

    Also, for clarity, these would not be moving light hang positions. Each fixture would weigh no more than 20 lbs on average.
     
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  16. BillConnerFASTC

    BillConnerFASTC Well-Known Member

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    Good clamps tightened and you'll be fine with 1 1/2 " schedule 40 imho, especially if the aded pipe is on top of its anchor point.
     
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  17. egilson1

    egilson1 Well-Known Member Premium Member

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    @BillConnerFASTC it appears Clancy released a Second app called IRigging Tools to replace the original IRigging App. The second one was updated more recently and I would suspect they revised the numbers.

    Proof you should always update your data!

    I would mention another thought about the OP. Label the position with it’s capacity. Laminated signage can be DIY, and will help reduce (not eliminate) the chance of overloading by someone who is ill informed.

    Ethan


    71ED2A9F-2E76-49B6-AFD6-CCF8EB7B76B2.png
     
    Last edited: Aug 13, 2018
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  18. RickR

    RickR Well-Known Member

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    I second the notion of labeling. Smart & cheap are a great combination.

    30lbs per foot is roughly S4 ERS packed as tightly as possible all the way along a pipe. I think that's a great basis for permanent battens. 20lbs per foot is having them be a bit over 12" appart and reasonable for "light duty" positions.
     
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  19. BillConnerFASTC

    BillConnerFASTC Well-Known Member

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    I agree with the warning signage. And KISS - just have it say "8 LIGHTS MAX". The basic S4 - tungsten and 19-50 degrees -is listed at 14 pounds (includes ETC clamp; shipping weight is 20) and 12" is awfully tight: handle to handle is over 10" and shutter to shutter out is over 13". LED is near twice the weight - over 24 at least with clamp and lens tube - so maybe these area all LED. I just rarely think units less than 18" on center - so 8 @ 15 pounds is around 10 plf - which even old and new clancy chart say OK to. Its hard to get to 30 plf with lights, even LEDs. And then there is that (at least) 5:1 factor. And dead hung there is no impact load like there is for a batten on counterweight where the forces may triple at high speed. And Steve could always run a chain or wire rope through all the yokes - or the pipe - if concerned.
     
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  20. MNicolai

    MNicolai Well-Known Member Fight Leukemia

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    In that vein, probably not a bad idea to drop a batten clamp or equivalent to each end of the pipe and safety up to structure or to the catwalk rails. More so for if/when pipes are being moved around and positioned with the added benefit of being a safety once the pipes are installed and clamped into place.
     
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