hanging wire gauge strength distance requirements/details? - Page 1
Forum section: electronics / general

author: coppercone2
author_rank: Super Contributor
timestamp: March 07, 2023, 10:34:46 pm
content: Does anyone have like a table about wire and supports? I.e. maximum distance that some gauge of wire of various strand configurations (even litz) or solid conductor of various materials can be strung before there is a problem, possibly with data relating to wind load, ice/water load, temperature, etc. Maybe a handbook or text book about the matter. Like maybe the research that power companies did to figure out how to optimize distribution wire on poles. I assume this might be some ancient literature from the 1800's.I thought it might exist somewhere in a ARRL handbook, or maybe someone that knows about the history of telegraphs or power poles or telephones might know.I kinda wanted to know generally where support wires and stuff being necessary. It would suck to find it out in the field after a design is made.I am interested in antenna but it must be relevant to communication cables and power distribution also. This seems like one of those things that can work for a while and fail eventually if done wrong.Also interested in wire rope, which is alot stronger, and that is probobly a form of mechanical engineering, just a general overview... looking to over build not design a budget crane.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: March 08, 2023, 04:09:06 am
content: Attached is a couple of pages from the Lineman and Cablemans Handbook McGraw Hill, 1964. It gives enough data to get wind and ice loading for US locations, and you can probably guess or extrapolate to Canada. Once you have loads per unit length you can plug them into the catenary equation and get tensile loads to compare with the strength of your possible cable materials. The handbook didn't go into the latter phase, and the tables provided were for wires suitable for carrying 100s of amps and up. Not very useful for your application.

author: coppercone2
author_rank: Super Contributor
timestamp: March 08, 2023, 05:14:09 am
content: can a thin wire still develop such a thick ice layer? I guess so. And can't you get even more load from icicles ?AWG 8 is still damn big

author: CatalinaWOW
author_rank: Super Contributor
timestamp: March 08, 2023, 05:52:19 am
content: The only limit on how thick the ice can become on a thin wire is its breaking strength. I haven't actually run numbers but I suspect that these ice loads do put a moderately large minimum size requirement on the wire.How often the ice gets to a given thickness is complex and why they simplified into zones. Basically they are saying if you allow for this condition you can legally establish that you did due diligence. It doesn't mean they are the maximum possible thicknesses or wind speeds.For the last decade I have lived in the medium zone on the map. In the last decade I have only seen significant icing on wires a couple of times. And never seen a quarter inch. So it is a pretty conservative standard even before they add the factor of two at the end.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: March 09, 2023, 05:17:36 am
content: Coppercone, I got fascinated by your question and put together a spreadsheet to do some of the calculations. After playing around with a variety of values the problem doesn't seem too bad. There are some things to think about.1. How much sag are you willing to have. In my personal experience with long wire antennas (mostly when I was a teenager and didn't worry about details, just put it up and use it) I allowed a lot of sag, and performance was always adequate for me. I can't say whether less sag would have been noticeably better, I never experimented. Based on some rough theoretical guesswork you will probably not notice sags less than 5-10% of the span.2. It is common to use trees as hanging points for long wire antennas. Unfortunately they present a lot of area to the wind and move back and forth a lot. This can cause broken antenna wires and/or temporary ground touches as the sag grows. One solution for this is to tension the far end of the wire with a weight connected to the end of the antenna through a pulley. This has the benefit of fixing the maximum tension in the wire, regardless of shrinkage due to temperature, tree motion, wind loads or anything else.3. How hard are you willing to pull on the wire during installation? While there seem to be solutions for very modest sag that are comfortably within the strength of the wire, they can require 100 lb or more of pull. Not something I would feel good about while up on a ladder.

author: coppercone2
author_rank: Super Contributor
timestamp: March 09, 2023, 05:25:59 am
content: Yeah Taught steel cables snapping are a hazard. Not sure how much better copper is, but for some reason I imagine getting smacked with a copper braid over a kevlar wire is going to be much better then getting smacked with a stainless wire rope. Always keep people nearby in mind too, not just the setup guy. Big wires will decapitate you if they snap I heard.. but that is cranes, but it would not take much I think to cut open the neck. Part of the reason why I am doing research too. And as always, eye injuries are no joke, even from thin wiresThere is probobly a diameter under which there is little threat for wire rope, but I don't know what it is.I am kinda thinking for temporary installations a fiber rope of some kind of going to be much more acceptable, especially if its taught.Also something that randomly came to mind is hanging a pulley on the pole with a weight to keep it taught. Maybe the strain on the wire would be more consistent that way, but I know nothing of the practice, and of course ice would fuck that up big time, it would need a brake of some kind when it goes into 'overload' tension from ice or wind.Trees are even more chaotic because branches can break.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: March 09, 2023, 06:14:19 am
content: Quote from: coppercone2 on March 09, 2023, 05:25:59 amCables become dangerous when they snap under 1000s of pounds of load. If you are pulling this, and attaching to un-guyed poles you won't be running those levels of tension. I suspect just a couple hundred pounds at most. If you are still concerned lossy cables/wires are the secret. A steel cable is high Q, it releases its stored energy quickly. A nylon rope not so fast and the lower Q means at least part of it is lost. Of course there are always trades. Because the nylon rope will stretch a lot further it can widen the danger zone.A pulley on the pole is what I suggested in thought 2. Ice and dirt problems can be resolved with a small shelter box around the pully and downweight. Often a piece of 4 inch or larger PVC pipe is used to shelter the down weight and cable. It can make trees viable. Appropriate pruning can keep the chances of branches coming down under control.

author: coppercone2
author_rank: Super Contributor
timestamp: March 09, 2023, 06:27:31 am
content: Oh yeah I missed it because I got excited about hazards. I was thinking that losing an eye to 40$ of materials that would bring in cuban propaganda and evangalists as very ironic, there has to be a better reason to get injured lol, maybe technical repairs on the roof satellite to facilitate access to pornography (1980s?)

author: CatalinaWOW
author_rank: Super Contributor
timestamp: March 09, 2023, 03:45:57 pm
content: I suggest you run the spreadsheet with your intended spans and look at the numbers. I think you will find there is little to worry about if you don't try for 100 meter spans and/or use a high power winch to apply tension. Climbing the ladder is likely to be the primary risk.If you are still worried do a ground level test with your intended wire size and tension. Either rig up a remote release or just cut it while wearing goggles and gloves. In all likelihood you will find this test uneventful.Rather than a sickle of death beheading everyone for dozens of meters, the biggest hazard from a failed antenna will be tripping over the downed wire.

author: coppercone2
author_rank: Super Contributor
timestamp: March 09, 2023, 06:29:54 pm
content: haha yeah, I am probobly just traumatized by hollywood.Ladders are difficult IMO, you need alot of experience to use that, its never setup correctly, I did get the thing for the ladder so it rests on the roof instead of the gutter though, expensive. Trusting those gutter screws with your bones while cleaningalmost every time you see a ladder used outside, its propped up against a tin can, literally.https://www.amazon.com/Glesam-Ladder-Stabilizer-Accessory-Standoff/dp/B0BFGSMP93/ref=sr_1_22?crid=1A5XMHL941C1M&keywords=ladder+stabilizer&qid=1678386776&s=hi&sprefix=ladder+stabilizer%2Ctools%2C102&sr=1-22