# Substituting tensioned wire rope for curtain track



## TEarlywine (Jun 2, 2011)

I have a P.M. trying to convince me that a tensioned wire rope and split-traveller on rings is a viable substitute to dead-hanging a curtain track from our fixed grid (we do not have fly or fixed battens to hang from). He says just set up 2 vertical pipes, floor to grid, OffSL-SR and stretch wire rope between them... "will be easier than hanging curtain track."  I say wire rope of any thickness will sag under its own weight, and even more with even a lightweight curtain on it, no matter how much we tension it ...not to mention the cost of securing and guide-lining the vertical pipes to handle the tension (and change of tension/weight as curtain is drawn in or out), etc. etc.

We're talking possibly 40'+ wide and approx 20' tall curtain (fabric weight from chiffon to painted drop to real drape is still in discussion).

Any advice on dealing with his idea (yes, I already tried dismissing/ignoring it), or more-specific facts or issues you have easily available to help me make my point would be greatly appreciated!


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## Footer (Jun 2, 2011)

Ouch. 40' is WAY to far for this to actually work. 5'... maybe. It is possible to get a peice of cable tensioned that tight, however, it requires very strong anchors and very strong winches. 1.5" sch. 40 is not even close to enough of an anchor. You would be looking at something more like a circus tightrope anchor, not just a turnbuckle. Yes, track is expensive, but this simply is not going to work. The curtain will never run correctly and it will pool on the floor as it passes through center. As far as formulas that can show what this will do, they are out there, though my books that have them in it are at work.


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## JBrennan (Jun 2, 2011)

Footer put it more elegantly, and your instincts are correct, it will sag, sag, sag.


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## derekleffew (Jun 2, 2011)

I agree with the above.

TEarlywine said:


> ...He says just set up 2 vertical pipes, floor to grid, OffSL-SR and stretch wire rope between them...


One of three things will happen before getting the cable satisfactorily taut:

The cable or an end termination will break.
The pipes will bend.
Either the top or bottom pipe anchorage will give way.


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## MPowers (Jun 2, 2011)

As everyone else has said, It won't work for your situation. 10' to 12' high and 12' to 15' between the ends, using a light weight curtain is about the maximum size that the "taut wire" system will work. In addition the taut wire system is prone to snagging, jerking and not smooth operation. If the PM in question needs advice, have them contact me directly. Your location makes it impractical for me to be a sales or install agent so my advice will be objective and unbiased.


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## TEarlywine (Jun 3, 2011)

MPowers said:


> As everyone else has said, It won't work for your situation. 10' to 12' high and 12' to 15' between the ends, using a light weight curtain is about the maximum size that the "taut wire" system will work. In addition the taut wire system is prone to snagging, jerking and not smooth operation. If the PM in question needs advice, have them contact me directly. Your location makes it impractical for me to be a sales or install agent so my advice will be objective and unbiased.


 
Thanks! I'm the house TD, so really the PM needs a swift kick in the rear for not trusting his TD. The joys of being part of Park & Rec


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## MPowers (Jun 3, 2011)

TEarlywine said:


> Thanks! I'm the house TD, so really the PM needs a swift kick in the rear for not trusting his TD. The joys of being part of Park & Rec


 
To paraphrase an old quote, "A Prophet is never respected in his own country." I have experienced the same thing during my career. It is especially true the younger you are. The outside "expert" often does not have to know any more than you, they just have to be from somewhere else, not just the "local boy"!


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## utilityman (Jun 28, 2011)

MPowers said:


> To paraphrase an old quote, "A Prophet is never respected in his own country." I have experienced the same thing during my career. It is especially true the younger you are. The outside "expert" often does not have to know any more than you, they just have to be from somewhere else, not just the "local boy"!


 
I'd have to think this through a little more, but had a thought that might make this work for something very lightweight with a meet-in-center traveller.

Use two cables rather than one. for the wire holding the stageleft to center curtain, anchor the stage right end of the cable higher than the stage left, such that it can account for some/most of the cable sag. do the opposite on the other side. This would cut the loads on each cable by 50pct? (probably not that simple, but more math than I can do quickly).

Still not the same as curtain track, but if you were hanging lightweight scrim, or a sheer, had strong anchor points and really oversized turnbuckles and rigging, and didn't have to worry about being perfectly even across the floor, it might work. Definitely would need to do the math to figure out the loads to make sure you build enough safety margin into the system.


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## JChenault (Jun 29, 2011)

A local group did something like this for a recent production. I was not intimately involved, but my memory is:
About a 35 foot span - drops 8 to 10 feet high. Very lightweight.
They stopped tensioning the wire when the support pipes started to bend / pull out of the wall.
Approx 6 inch sag in middle.

So could you do this - sure if you are willing to accept a substantial sag in the middle ( my guess would be three feet - but I have not done the math )


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## philhaney (Jul 8, 2011)

TEarlywine said:


> ...He says just set up 2 vertical pipes, floor to grid, OffSL-SR and stretch wire rope between them...


 

derekleffew said:


> One of three things will happen before getting the cable satisfactorily taut:
> 
> The cable or an end termination will break.
> The pipes will bend.
> Either the top or bottom pipe anchorage will give way.



And if you do get the cable satisfactorily taut, then and only then, you'll see the curtain rings still sitting on the table next to your tools...

But seriously folks, not a good idea (just dead hang the curtain track...)

Edit: With a cable rigged to support a curtain in this fashion, if you consider only the load on the cable at the low point of the sag plus the two fixed end points you're looking at a bridle. If you look it up in the Stage Rigging Handbook (somewhere around page 27 in the third edition) there is a diagram and a table describing the horizontal forces involved, whch pretty much negates the possibility of ever getting the cable taut enough...


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## Les (Jul 8, 2011)

JChenault said:


> They stopped tensioning the wire when the support pipes started to bend / pull out of the wall.



Ouch! They stopped too late!

I've used the same setup for a scrim. The anchors were vertical 8" structural I-beams from floor to grid. It worked ok - some pooling in the middle, a little jerky in operation, but overall not a 'terrible' outcome. 

I do not recommend this system though.
1.) It may be "easy" to set up, but what about taking it down?
2.) Many buildings don't have strong enough anchor points (as referenced by the quote above).
3.) Difficult to predict "how tight is too tight". 

I believe the installer of the system I used (no, it was not me) made sure to use strong components (aircraft cable, forged, closed eye-bolts, etc) but no formal calculations were made to determine load capacity or actual loading. It was one of those "it should be okay" situations. Overall, a traveler (or just a traverse) may be more expensive, but it will operate much more safely and reliably.

The taut wire system worked for approximately 5 years before its removal. I'm not sure how they did it -- that taut wire was taut!


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## shiben (Jul 9, 2011)

And the real fun comes when something breaks, and the cable whips across the room and slices someone in half, or flings a piece of metal thru a wall and embeds in someone's skull. That cable would need to have tens of tons of force on it... Even gigantic suspension bridges with massive cables sag when cars go over them, I doubt a tiny piece of aircraft cable would be ok... Now, you could do an el-cheapo system with a really long piece of pipe, do rings over that, secure it on drop-downs from the grid, and use that as your track... The tensioned cable seems a bit un-needed.


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## DuckJordan (Jul 9, 2011)

Just to keep the discussion alive what about spaces that dont have access to their grid? 

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## shiben (Jul 9, 2011)

DuckJordan said:


> Just to keep the discussion alive what about spaces that dont have access to their grid?
> 
> Sent from my ADR6300 using Tapatalk


 
Pipe and drape


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## DuckJordan (Jul 9, 2011)

Say its a pro opening of 50 wide by 30 tall.

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## shiben (Jul 9, 2011)

DuckJordan said:


> Say its a pro opening of 50 wide by 30 tall.
> 
> Sent from my ADR6300 using Tapatalk


 
I think your best option would be to find a way to access your grid. Otherwise, you could build a truss structure and secure it to the DS wall, and hang a traveler track off of that... Not really the best option, I dont think tho.


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## ejsandstrom (Jul 9, 2011)

The way we do it here is rings anchored to the wall and it is attached the wall on one side by looping through the eye and then connected to its self with those u bolt deals. In the other side is another eye bolt but we use a come along to tension the cable. The curtain is fairly light and never gets pulled but it does not sag, at least not enough to see. Its not the best way to do it but it works.


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