How to construct a cable bundle - Page 1
Forum section: electronics / projects

author: Cicada
author_rank: Regular Contributor
timestamp: February 18, 2021, 08:38:28 am
content: HiI need to build a cable assembly with 3 x RG58 and 1 x 4-twisted-pairs cable like the one shown in the attached picture bundle.jpg.The cable will be enclosed in a braided nylon sleeve as shown. The 4-twisted-pairs cable diameter is just a bit bigger than the RG58's diameter.The problem I have is a lack of experience in building these types of cable assemblies. I know a little bit about cable construction i.e. the importance of cable layups, cable fillers, circle packing etc. as discussed on page 7-1 in this document.https://www.nationalwire.com/pdf/cat07_design_guideV10.pdfOne thing mentioned in the document is the helical (spiral) winding of "wires in a bundle" and "bundles in a cable assembly". As far as I can gather helical winding, on average, exposes each cable in a bundle to equal amounts of compression and extension as the cable is coiled up. Thus allowing the cable to be coiled up neatly.Now I have tried to implement this helix construction in my cable bundle assembly. I have spiraled (helix, see attached photo spiral.jpg) the cables clockwise and anticlockwise. But I still have the problem that I can't coil up the cable assembly without kinks when I use the seemingly standard over-under method as described in this video.I am able to coil the bundle using over-under method when the cables in the bundle are not spiraled.I have rolled up the clockwise spiraled cable bundle using a method as shown in this video by twisting the bundle in my left hand anti-clockwise.https://youtu.be/PfqIm_R2zywThis might be a modified version of the over-under method but it is too challenging for my spatially challenged brain to confirm that.MY QUESTIONWhat are the considerations that should take into account when building such a cable, i.e should I spiral or should I go straight?It seems that spiraling does not work. What is the standard way of building such cables?Any other comments or sources of information are welcomed.PS. The braided sleeve shown in bundle.jpg was put on too tight. I plan to make the cable sleeve fit less tight onto the bundle before cable tying the sleeve to the cable at each end. Will then fit heat shrink over the cable ties. This will make the cable assembly bend easier for coil up.ThanksCicada.

author: nctnico
author_rank: Super Contributor
timestamp: February 18, 2021, 08:36:37 pm
content: Do yourself a favour and buy glue lined heatshrink tubing and get rid of the tieraps. It looks nicer and won't clamp the wires inside the cables together probably making it easier to roll up. I don't bother with under/over I just roll / unroll cables.

author: ajb
author_rank: Super Contributor
timestamp: February 18, 2021, 10:03:43 pm
content: That document is about cable assemblies, where wires are put together into a single molded jacket, what you're doing is looming, where you combine multiple separate cables into a bundle that is held together by additional hardware. Don't spiral in both directions for bundles like this, especially with only five cables. That will make the loom stiffer and harder to coil and lumpy besides. If you want a spiral, just pick one direction and spiral them that way.Cable looms are made all the time for live events, where cables of all different types are combined into bundles so they can be dropped onto truss and quickly plugged into equipment. Generally they're just laid straight and banded with tape (good quality vinyl or rubber electrical tape, usually) every couple of feet and they hold up fine for months-long tours getting coiled into and out of cases every couple days. If you're going to sleeve the bundle, you may not even need to band it, but it can help in the case that the sleeving is loose and would allow the cables to flop around inside.Over-under vs half-twist is a hotly argued topic among people who coil and uncoil cables for a living. What you're doing in your video clip is a little hard to follow due to the number of times you turn the bundle around, but you don't want to do half-twist on both sides of the coil, that will be liable to turn into a whole lot of knots when you go to deploy it. Even regular over-under can have that problem if you're not careful when opening the coil, which is why a lot of people prefer half-twist. Either method of coiling really requires responding to what the cable wants to do--the whole point is to avoid twisting the cable as it's coiled, so a cable (assuming it's in good condition) will fight you if you try to coil it wrong. If you can find yourself a nice fabric-reinforced flexible rubber hose, like the kinds used for good quality air tool lines, that would be a great thing to practice with, as it's not too stiff against bending but very resistant to axial twist.Edit to add:If you do twist the cables around each other, it's important to ensure that each cable is not itself twisted. I don't really know how to explain this, but when twisting the cables around each other the ends sort of need to orbit around each other without rotating. Maybe look at videos of rope-making for the idea, the individual strands that go into a twisted rope are revolved around each other without themselves rotating (or sometimes with a slight counter-rotation so the spiral stays tight when the rope is allowed to go slack).

author: vk6zgo
author_rank: Super Contributor
timestamp: February 19, 2021, 03:49:59 am
content: Don't wind the cables into a spiral, it is very rarely, if ever done in Broadcasting or Comms work in my experience.Each cable is complete in itself, it simply occupies fairly close quarters with other cables.By spiralling them, you are simply adding physical stresses to the cables.As for winding them up, OB crews use a method where they lay cables on the ground in a "figure 8" manner, then after the figure is completed, grasp the "8" by its middle, bring the outer parts of the loops together, & tie both off.When you need to use them, you can normally reverse the actions & pull the "start end" straight out, without causing tangles.That said, it is easier to describe than to learn in practice!I hadn't done much such work when I first encountered this, as I came from a job where we either were feeding fresh cable off a reel, or for shorter lengths, just rolling them around our arm, so I was never all that good at it!

author: Cicada
author_rank: Regular Contributor
timestamp: February 19, 2021, 09:52:29 am
content: Quote from: nctnico on February 18, 2021, 08:36:37 pmThanks for this tip. I looked at a youtube video regarding this and you are correct. This will look much nicer.

author: Cicada
author_rank: Regular Contributor
timestamp: February 19, 2021, 10:04:36 am
content: Quote from: ajb on February 18, 2021, 10:03:43 pmThanks. Tried it now. I would say it is a bit better. I have fitted the braided sleeve a bit looser on the second cable. Not so loose that the cable can flop around inside. The cable is now generally a bit easier to coil up but still a bit wonky/lumpy here and there. But is ok.Quote from: ajb on February 18, 2021, 10:03:43 pmWill tryQuote from: ajb on February 18, 2021, 10:03:43 pmI suppose you mean one of the 2 actions depicted in the attached pictures.Thanks

author: Cicada
author_rank: Regular Contributor
timestamp: February 19, 2021, 10:08:23 am
content: Quote from: vk6zgo on February 19, 2021, 03:49:59 amThanks. I also begin to believe that this is the right view.Quote from: vk6zgo on February 19, 2021, 03:49:59 amI think your explanation is clear enough. I can picture what you describe. This sounds like a really neat idea, especially for a long and maybe thicker cable. This might emulate the over-under or half twist method.