Balancing cable weight on counterweight system.

Discussion in 'Scenery, Props, and Rigging' started by Zebulon1880, May 22, 2019.

  1. Zebulon1880

    Zebulon1880 Member

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    Last week I hung backdrops for a ballet at the Gallo Center For The Arts Rogers Opera House, Modesto, California. I was in flyhouse riggers heaven! This counterweight system is the most advanced I have ever seen. There are chains attached to the weight arbors that balance the cable weight making moving the pipes like a feather.
     

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  2. BillConnerFASTC

    BillConnerFASTC Well-Known Member

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    Cable weight compensation. A great feature. Near $1000/set with roller chain, my favorite method.
     
  3. derekleffew

    derekleffew Resident Curmudgeon Senior Team Premium Member

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    A couple of observations about the photo not related to compensating chains...
    1. I'm not sure I've ever seen pig with non-centered L&R notches for the tie rods. Opposite corners cut off, yes, but not "eccentric" weights. Is this common? In the olden days, Tiffen weights were cast iron, not steel and were narrower at the top, wider at the bottom. Does anyone still use cast iron weights?
    2. No 2" thick weights? Must take a long time to weight/un-weight. From a safety standpoint, is it better to have fewer, heaver weights or more, lighter weights? I can see arguments on both sides. Have were all heard the urban legend about the HS shop teacher who fabricated his own weights out of aluminum "so the girls could lift them"?
    3. Are there safety cable s around the tie-rod and stop collar ? Or is it some method to keep the spreader plate (s) up and out of the way while moving weights?
    4. Love the wooden belaying pin between 46 & 47, but any amount of rope would interfere with adjacent handles, wouldn't it?
     
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  4. RonHebbard

    RonHebbard Well-Known Member Premium Member

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    @Zebulon1880 Compensating chain; a cute trick initially developed and used by the elevator industry. Single width and double width GREASED roller chains can be workable. Serious chain manufacturers offer a line of welded link chains with their links all neatly oriented and encapsulated in molded rubber; these chains are listed by their weight per lineal foot, silent in operation, require zero greasing. are essentially maintenance free and tangle-free in operation.
    Up here north of Donald's walls, Canada's largest chain manufacturer lists their rubber encapsulated compensating chains in one of their specialty / niche products catalogs where they caught my interest decades ago prompting me to delve further into their applications and usage. An interesting product line.
    Toodleoo!
    Ron Hebbard
     
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  5. BillConnerFASTC

    BillConnerFASTC Well-Known Member

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    Looking close, not sure the weights are that offset. Paint and notches mislead.

    On thickness, I have gone to all 1" or whatever thickness is 25 pounds max trying to get closer to OSHA lifting regs.
     
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  6. RonHebbard

    RonHebbard Well-Known Member Premium Member

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    @Zebulon1880 This should link to a photo of meticulously aligned, welded link, rubber encapsulated, maintenance and tangle free, silently operating and non-greasy compensating chain.
    https://www.google.com/search?q=Dom...kKHTRCDT0Q9QEwB3oECAkQCg#imgrc=PSGGDP6jX-cbaM:
    Toodleoo!
    Ron Hebbard
     
  7. JAC

    JAC Active Member

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    Really interesting system, any idea who designed it? Not only are there compensating chains, but at first glance there appears to be an arbor well (unless the photo was taken at a gallery, not the deck), so this system should be a joy to use. But at second glance there appears to be an arbor stop at the floor level. Why would you do that?
     
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  8. RonHebbard

    RonHebbard Well-Known Member Premium Member

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    @JAC Locating the idlers in a basement well puts their operating noises below deck level. An idler well is also a popular location for space occupying / noisy motorized auxiliary hoists. The arbor stop likely stops the arbor before the system pipe hits the grid on it's upper travel and would be fitted in situations where extending the arbor's guide tracks into the basement effectively makes the guide tracks longer than the desired travel distance. I've probably not explained this very well; clear as mud, right?
    Toodleoo!
    Ron Hebbard
     
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  9. JAC

    JAC Active Member

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    I get it, Ron, but the whole point of an arbor well is to make up for the travel you lose to the length of the arbor, so that the batten can travel virtually from grid to deck. An arbor stop at deck level negates that.
     
  10. Calc

    Calc Active Member

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    Looks like cable tied to an ARC. Holds the spreader plates up, just like you guessed.

    They really are nifty little things. I picked up a few at USITT they a couple years ago when they came out, and they're worth every penny.
     
  11. derekleffew

    derekleffew Resident Curmudgeon Senior Team Premium Member

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    Ah yes, I think you're correct. I had forgotten about those, probably because I dismissed them initially: https://www.controlbooth.com/threads/arbor-rip-clip.41803/
     
  12. RonHebbard

    RonHebbard Well-Known Member Premium Member

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    @JAC That's not the sole purpose of an arbor well; while were chatting, in the majority of single and / or double purchase counter-weight systems stops are in place to limit a system pipe's low limit to a safe / convenient height above the deck, partially to place it at a convenient working height for attaching drops and masking and partially to permit hanging lights without them hitting the deck prior to loading the associated arbor. @BillConnerFASTC care to comment??
    Toodleoo!
    Ron Hebbard
     
  13. BillConnerFASTC

    BillConnerFASTC Well-Known Member

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    It's hard to know but with underhung and full walk on grid depending on loading bridge, arbor stops where they appear to be may permit maximum travel. Especially if top stop is near minimum below headblock and arbors not too tall. The walk in grid makes up for a lot. My style puts loading bridge lower, extends grid to head block beam for access, and then arbor uses all of pit depth - 12-14' below stage. Different, not necessarily better. I like head block access and access to arbor tops at lock rail. Makes it easier for and oldster like me to check lift line terminations.
     
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