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Compensation

Discussion in 'Question of the Day' started by derekleffew, Aug 11, 2016.

  1. derekleffew

    derekleffew Resident Curmudgeon Senior Team Premium Member

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    "What is the purpose of compensating chain in a counterweight fly system; Compensating chain NOT trim chain?"
    Compensating for what?

    Suggested by a member. You, too, can play along--submit questions to any moderator. Students only for one week please.
     
  2. np18358

    np18358 Active Member

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    To compensate for the weight of the additional length of lift lines as the batten flies in. The chain attaches to the bottom of the arbor on one side and the wall on the other.
     
  3. josh88

    josh88 Remarkably Tired. Fight Leukemia

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    Chains have to support their families too. You think its doing all that work for free? Too many chains have taken unpaid internships and it needs to end! Compensate them damn it!
     
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  4. StradivariusBone

    StradivariusBone Well-Known Member Fight Leukemia

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    There's also compensating cables too. We are unfortunate enough to employ two such devices in our building for our electrics.
     
  5. RonHebbard

    RonHebbard Well-Known Member Premium Member

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    Hi Strad'; Compensating cables in the sense of the lightly tensioned / each link correctly oriented in relation to it's mates, black neoprene jacketed compensating chains normally found in the specialty products sections of traditional wire and cable manufacturers' literature and site and often found swag-ing quietly and tangle free below trendy exposed elevator cabs?
    A few decades back, when manufacturers were still promoting their products to appropriate contractors via 3" and 4" thick binders, I remember leafing through a thin "specialty products" section tucked in the midst of a thick 'Canada Wire & Cable' binder and thinking to myself: "Why on earth are Canada Wire & Cable marketing welded link chain in a molded black neoprene jacket, in three different sizes, designated by their "weight per lineal foot?" My query continued to nag my thoughts for weeks to no avail and, as this was prior to the internet, Google, and convenient ready access to the world of data on everyone's desk; years passed until one day, by pure happen-chance, I found my self staring at a shining example of the product's application. My then employer had dispatched me from southern Ontario to a trendy hotel tower in the midst of NYC for a few days to supervise the installation of the electrical aspects of some major pieces of automated scenery into one of the larger Broadway theaters.
    Centered in the hotel's multi story lobby, was a circle of six or seven elevators as somewhat of an architectural feature of the lobby's decor. At ground level, they were only accessible from one common entrance where you entered a smaller circular sub-lobby and were encircled by a ring of traditional looking elevator doors with the normal arrangement of call buttons, indicators and arrival chimes. When you entered from the street at ground level, you didn't initially see the elevator lobby, or any collection of elevator doors and waiting guests but you couldn't miss the towering central core rising up ten or so stories surrounded by six or seven small, dark circular enclosures scurrying up and down the central core's walls.
    The little traveling 'pods' were the architecturally designed exteriors of the actual elevator cabs with their lower halves in a tasteful dark finish and their upper halves swathed in a dark-tinted, one-way see through material shielding the cab's occupants from the stares of the collected masses below while simultaneously affording the riders a fabulous view of the lobby and its decor as they ascended approximately ten floors until the view disappeared when you vanished into a more or less normal elevator shaft.
    Being the 'techno-nerd' I've always been, I spent more of my free time staring up at the cabs than any other human being in the heart of broadway. I was fascinated by the extremely neat displays of chunky "cables" hanging down from on high then 'U-turning' upwards to the undersides of their related cabs.
    First pass through the lobby: Hmm ... Dang neat installation. Matching lengths, all hanging straight with nary a twist or ripple. Near zero side to side sway. Real pretty! Almost a work of art.
    Second pass: Hmm . . Six or eight cables per cab. Low voltage control. Power for door actuator, interior lights and fan. Comms cable for the mandatory telephone. But what the heck are those other, identically matching diameter, cables for?
    Third pass: WHAT ARE THOSE OTHER CABLES FOR???
    One day it kicked in: "Hey you dummy! You've been staring at those black neoprene jacketed, welded-link, chains marketed by their weight per lineal foot for DAYS without realizing what you're looking at!!! Those aren't additional multi-conductor copper electrical cables. THOSE are traveling compensating chains cleverly disguised to match the look of the other cables and to keep them from clanking, rattling and tangling!

    Yeah. It still fascinates and amazes me how something I've wondered about in the back of mind for years can suddenly gel in an instant when I've dang near forgotten / basically given up on ever solving the mystery.
    With apologies for yet another of my "TLDR" posts.
    To tag this back to the beginning.
    Strad': Is this what you meant when you wrote: "There's also compensating cables too." or were you referencing back to Mr. Bill's mention of circulating loops of varying gauge stranded lift lines?
    Toodleoo!
    Ron Hebbard.
     
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  6. RonHebbard

    RonHebbard Well-Known Member Premium Member

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    Unfortunate in what sense?
    Toodleoo!
    Ron Hebbard.
     
  7. StradivariusBone

    StradivariusBone Well-Known Member Fight Leukemia

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    Our electrics are these pseudo-tri-truss monstrosities that have baskets on top that collect the multicable as they move up and down. The multi cable itself is sheathed in 10' sections of PVC so it sort of folds up on itself into the baskets. The truss assemblies weigh about 1200# and instead of the elegant chain assembly that most everyone else has, we have two 3/4" GAC cables that are basically positioned opposite to the purchase lines. As the arbor travels down, the 3/4" GAC rolls over a block on the back of the t-track and it's weight is transferred to the arbor. Theoretically it changes the weight on the arbor in proportion to the amount of copper carried in the truss baskets. In reality it introduces a number of other failure points in the system and increases the drag on an already heavy lineset.

    I have another thread on here about my 1st electric which is still not working right. We think it's some issue with the headblock being out of alignment, but I can't get any traction from our school district to repair it. Anyway, it's a frustrating system when there are so many other theatres with significantly better methods in place.
     
  8. RonHebbard

    RonHebbard Well-Known Member Premium Member

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    Commenting specifically on your multi-cables. I've seen this approach forcing your cables to serve as a series of 180 degree hinges between a series of sheathed straight lengths thus creating a series of over-flexed / over-stressed potential failure points and that's just your electrical multi's before you get to the rest of the problems with your installation.
    Thanks for elaborating Strad'
    Toodleoo!
    Ron Hebbard.
     
  9. StradivariusBone

    StradivariusBone Well-Known Member Fight Leukemia

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    Bingo. Our sister theatre with the same design has already gone through the process of replacing bad cables. I figure it's only a matter of time for us. Fortunately it doesn't get moved often since it takes three techs pulling to get it anywhere.
     
  10. RonHebbard

    RonHebbard Well-Known Member Premium Member

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    And that's when it's "balanced". Then you fly it in, add a dozen fixtures, and need to add more counter-weight.
    Again: You have my sympathies.
    Toodleoo!
    Ron Hebbard.
     

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