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I'm looking at redoing our stair railing and going with a more modern look with cable rails. 'Proper' cable rails, however, seem to all come from perhaps one factory. All the options I can find look exactly the same and fall into roughly the same ballpark prices.

For the 5'-ish span we're looking at, I can get a kit that includes two pivoted ends, the turnbuckle and 5' of cable. If I want 6 cables, I get six. At about $40 a kit, that's about $240. Not a crazy price, but got me thinking as to why I'd need 6 individual cables. Why couldn't I just get one cable and weave it in and out?

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The idea would be to use only two eye-bolts for the entire set of rails. I'd then weave the one cable in and out of both ends and add one turnbuckle somewhere in the middle.

As you can see, this is a lot cheaper--especially when you put it into the context of say a full deck installation.

The idea would be something like this:

enter image description here

(Illustration just to show the 'weaving' concept. If I were to do this, I'd route the ends through curved channels so that the cable wasn't attempting to make a full 90 degree turn at any one point.)

However, I never see it done this way. I can't find any examples using just one cable--all cable railings I see use individual cables and attachments for each line.

Question: Is there a reason for this other than perhaps habit/preferred aesthetics? Is there a structural/installation aspect I'm maybe not considering?

UPDATE:

After more web surfing, I came across this blog post where they had the same idea I had--at least in terms of using off-the-shelf hardware:

enter image description here

Note the turnbuckles are almost closed, so even with one turnbuckle per-cable, a lot of slack needs to be taken out to make it taught. MIGHT Be doable with one cable on my short interior run, but anything bigger, I suppose it does make sense to go with one turnbuckle per cable.

That said, I personally think it looks great--but, admittedly, likely best as an outdoor solution on a large deck. It's probably a bit too 'industrial' for my interior short-run.

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I doubt you'll be able to drill curved channels that enable the wires to pull straight and tight. –  Matt Sep 24 '13 at 2:28
    
It's not a lot of money to do it properly with the official stuff. But I think you'd get away with eyes and turn buckles on each wire. rather than looping it through the posts so many times. I'm sure that would get quite stuck. –  Matt Sep 24 '13 at 2:31
    
@matt in this case, it's not, but if we're talking a large deck with stairs, the price gets rather large with the 'official' hardware. Note that even the 'official' hardware does tend to allow 45 degree bends around corners, so it seems that bending the cable isn't unheard of. –  DA01 Sep 24 '13 at 3:23
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I think the cables look like some type of civil engineering project. Cable - not pretty. Turnbuckles - Ugly. Standard hardware lag screw type eye bolts - Too weak and will tend to start opening up when the cable is taut enough to be a safety restraint. This last point is one reason that "real cable railing ties" use clevis type ends with a cross pin. –  Michael Karas Sep 24 '13 at 6:04
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In general, make sure that your top rail can support the force that the 6 cables are going to put on it. Assume from your diagram that the upper support is bombproof. You're going to have a lot of force tending to tip over the lower post. You'll need a beefy railing to counteract it. –  Chris Cudmore Sep 24 '13 at 17:08
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3 Answers

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I have it! 4" cable pulleys (used in garage doors)

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You put them on the inside, (no post grooving) The 4" diameter means the spacing between strands will be perfect, the tensioning will be uniform, with no kinking.

You just offset the opposite pulleys down by 4".

enter image description here

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hey....that's an unique idea! And I like the look of it! –  DA01 Sep 24 '13 at 15:50
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Keep in mind that you'll be doubling the force where it ties into the wood. You'll need beefy eyes with a coarse thread. Or even better, eye bolts that go right through the wood and are attached with nuts and washers. –  Chris Cudmore Sep 24 '13 at 16:07
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Tension in the rope is assumed to be constant throughout. Look at your lower right pulley. There is a force of 2 T pulling it to the left. Therefore, there needs to be a force of 2 T pulling it to the right. Otherwise, F = MA -> A = F/M will result in rapid acceleration to the left. –  Chris Cudmore Sep 24 '13 at 16:37
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@ChrisCudmore Agreed, pulley tension is 2T, eyelet (endpoints) tension is 1T –  HerrBag Sep 24 '13 at 17:00
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@ChrisCudmore this would probably be a good, separate question, but: I've always learned that lag bolts provide more strength (in terms of resisting pull-out) than through-bolts (the theory being more thread is in contact with the wood in a lag bolt than there is thread in contact with the nut in a through-bolt) –  DA01 Sep 24 '13 at 17:12
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I dont know how you would make curved channels. But anything short of installing pulleys in the posts I don't think the wires would be tight enough. With the codes 4" maximum opening the wires need to be extremely tight to prevent a child from spreading the wires apart.

Plus the turnbuckle and screw eye contradicts the clean lines of the wire.

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For the curved channels, I'm thinking some drilling at various angles. Alternatively, I could build up the posts as by sandwiching some cut-out plywood in between dimensional lumber. I agree about the turnbuckle and screw eyes not being a look for everyone...and I wonder if that's just not the reason right there. Personally, though, cable railing is industrial looking to begin with, so wouldn't mind the extra hardware showing (that said, I could also hide the end points BEHIND the posts...I have to think about that a bit more...) –  DA01 Sep 24 '13 at 0:19
    
I fully agree with Justin's answer. "Weaving" the cable is a non-starter. You will never be able to get it tight enough!! –  Michael Karas Sep 24 '13 at 5:56
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Let me emphasize that again. Never! This taken from practical experience if working with small 'aircraft' type cables. –  Michael Karas Sep 24 '13 at 5:59
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Just speculating, but one single cable provides a single point of failure. That fact alone probably excites lawyers enough to prevent such products from being widely produced, let alone marketed.

Also, the friction at the posts will be quite high at the range of tension needed to stabilize the cable making it quite difficult to transmit the tension throughout the array.

With all the cable tension coming from one point, there will have to be quite a bit of cable stretching to compensate for at the turnbuckle. Either it will have to be extra long, or an installation tensioner will be needed to get in the ball park of turnbuckle adjustability.

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hrm...'lawyers' are always a likely scenario for why things aren't done. I don't know that I'd personally be that worried, as braided cable is pretty strong. I agree that there'd be more 'stretch' to deal with, so installation labor is probably a viable reason it's not done a whole lot either. –  DA01 Sep 24 '13 at 0:16
    
@DA01 also weaving the cable will put bends in it, which can weaken it –  ratchet freak Sep 24 '13 at 11:18
    
If someone falls against a railing and one baluster breaks, the two on either side of it can help bear the load. When a single woven cable breaks (and that means the eyelet pullin out of the wood, an end splice failing, etc.), you are hoping the friction on the weaving will slow down the failure of the whole thing. While it is a low likelihood event, safety is the primary criteria for railing construction. (And yes, I am a recovering lawyer.) –  bib Sep 24 '13 at 14:15
    
@ratchetfreak the commercial systems allow bends (45 degrees) so I don't know if it'd weaken it all that much. A 90 degree bend would be bad, though. –  DA01 Sep 24 '13 at 14:18
    
@bib I agree in theory, though do note that this is aircraft cable. It's has a tensile strength of 10,000+ pounds. (Granted, there's always multiple points of hardware failure in a system like this). It's a valid warning, though. Good point. –  DA01 Sep 24 '13 at 14:19
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