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Manager - AB7RG
Manager Notes

Choosing Guy Wire

Created by TowerTalk Mail Reflector on 2000-06-18
The following was gathered from posts to the TowerTalk mail reflector by Mark K1LO

3/16" type EHS galvanized wire works well. Preforms, or ?dead ends? are the most reliable and easiest way to terminate the guys. Old type cable clamps are cheaper but tend to loosen with age as the joint forms itself to the cable after tightening. Use thimbles at ALL terminations. Although the tower leg gives you a nice convenient radius for the preforms, this technique does nothing for the wind induced torque that will try to twist your tower down. This is the function of the guy assemblies; to add torque resistance. There is a specified size of thimble for each part of the guy wire system; i.e. 3/16" preform grip takes a 7/16 to 3/8 inch thimble. BTW, the 'seat diameter' (which is the distance/radius required) for a 3/16" preform is one inch minimum. Since 25G is 1.25 inch OD, it does give an acceptable seat diameter for installing the preform grip directly on the leg.

Moving along, you'll need to use thimbles when using the guy assemblies but they are smaller diameter than the legs and you shouldn't have as much trouble getting the thimbles over them. There are different kinds of thimbles. Many are teardrop-shaped; these are the ones that you'll have to open up when installing them. Check with your local suppliers; there are also thimbles that are U-shaped with enough clearance in the mouth that you should have a minimum of fuss installing them. Yes, the whole process is tedious but just think how well you'll sleep nights knowing you did everything correctly.

1/4" EHS guy cable is rated at 6700#. 3/16 EHS is rated at 3990 pound strength.

Phillystran is a non-conducting guy wire material made out of aramid fiber and is like Kevlar - strong and lightweight. It comes in different diameters and strengths. It appears Texas Towers may be the only Phillystran supplier in the ham market.

HPTG1200I - 1200 pound strength (545 kg), .19 inch diameter (4.8 mm)
HPTG2100I - 2100 pound (953 kg), .24 inch dia., (6.1 mm)
HPTG4000I - 4000 pound (1816 kg), .30 inch dia., (7.6 mm)
HPTG6700I - 6700 pound (3,042 kg), .37 inch dia., (9.4 mm)

Phillystran consists of a Kevlar fiber core and a PVC jacket. The purpose of the jacket is: 1) protect the cable from abrasion during installation, 2) prevent moisture from wicking into the core and 3) most importantly, protect the core from UV damage. Phillystran has only been manufactured since 1974 so thus far the longest service life of the product has been 23 years. No one knows how long it'll last past that because it hasn't been around long enough. 40-50 years? Maybe. The service life may also be related to the region and environment; the more UV, heat, wind, etc. may have an impact on how long it retains its characteristics. Some of the oldest Phillystran (with the old jacket material) is still being used in southern Florida. In places the jacket has disappeared and the core is out in the Florida sun. After 23 years in this worst case scenario, it still retains 75% of its rated tensile strength.

Bottom line? It'll last a long time and is a worthwhile investment particularly if you're planning on having a populated tower/antenna system and want to minimize any potential interaction problems. You need to use factory pre-formed guy grips for the bigger sizes but for boom trusses using the smallest size, cable clamps are okay. It is a commercial product and its PVC jacket gives abrasion and UV resistance so that its service life is probably 20 years or longer. Phillystran can be terminated with a special preformed grip made by Preformed Products.

Although it entails two more guy ends and hence, ups the cost per guy, it seems like the EHS pigtail at both ends of a Phillystrand guy is a nice inexpensive comfort margin. I am thinking in terms of tool buckets, climbing belts and the like bouncing off Philly as a potential source of problem, if you bump into EHS who cares!
(The cost of your installation in Phillystran must be compared to the total cost in the EHS installation, not only in hardware, but in your time as well. In my case, I compared the total cost of the Philly to the EHS with insulators, clamps, thimbles, and estimated my time in assembling all of that. I just didn't have the time to do all the measuring, cutting, and assembly and get the tower up before contest season. The total cost difference was not significant in my small tower installation (70' Rohn 25) so I went with the Phillystran. No regrets. Tail pieces 'pigtails' of EHS at the groud end of the Philly are highly recommended. -ed.)
EHS guy wire has a different twist than wire rope, and requires preforms made for that specific type of wire.

Using Rohn's guy assemblies (not torque arms) allows a secure attachment for the guys (as opposed, for example, having them looped around the legs where you have the forces being held by the diagonal welds). Imagine a force big enough to pull the leg out, bending it and possibly breaking a weld or two. This would not happen with a guy assembly. The guy assemblies allow the forces to be spread across the faces of the tower instead of just a leg. (See 'big force' above.) The guy assembly allows Rohn towers to comply with the TIA-222-E structural tower standards. Lack of guy assembly makes them non-compliant and probably has an impact on their rated wind load figures as well. Rohn came out with the current product to upgrade to one of the recent TIA-222 revisions. When they did their calculations, they found the "old" torque arms really didn't contribute anything to the torsional resistance of the tower. What they did do was keep the twist down as it was being climbed. They discontinued the old product but hams put up such a fuss that they re-introduced them. If you use the current guy attachments and tension the guy wires properly, there's not much need to have the old torque arms installed.

As far as down below and sizes that fit, etc.....what we use at the equalizer plate IS the turnbuckle. The lower end eye of the turnbuckle is sandwiched between the equalizer plates.

This is nice in that it "freezes" the lower end of the turnbuckle from rotation. When you are done tensioning everything you just need to "freeze" the top half of the turnbuckle and the center of the turnbuckle which can be accomplished with a single loop of cable through those two. Watch the combination of bolt size that the equalizer plate uses with eye size on the turnbuckle, make sure the eye is big enough to handle that diameter bolt. This will present the top end of the turnbuckle as what you need to actually connect the guy to. A simple thimble through the eye of the turnbuckle, I prefer them to jaw type as there is fewer things to go wrong [K.I.S.S.], and a preformed end and you are good to go!

Cutting EHS cable can be difficult without bolt cutters. One method is to use a hand grinder. Tape the place where you want to make the cut and it'll zing through it in less than 10 seconds. The tape keeps the strands from unraveling after its cut. If you don't have a hand grinder, you can use a steel-cutting aggregate blade in your skill saw. They only run four or five bucks. BE REAL CAREFUL - use eye protection when doing this because you'll be throwing sparks all over the place. This method also works for cutting concrete rebar. Another method is to use a steel ?cold chisel?. Place the guy wire across any metal surface, put the chisel on the wire and strike with a 2 lb or bigger hammer. Wear safety glasses! (Bolt cutters are the way to do this! -ed.)

Choosing Guy Wire
I'm researching the use of Kevlar as guy material for a 40' 25G tower. This article has caused me to give second thought to using Phillystrand.

The main problem it seems is the tendency of Phillystrand to elongate (stretch) when stressed. The problem is analyzed toward the end of the article. I note that the study was done on a 100' tower basis but the basic premise of elongation needs to be considered.

Anyone else have information about the subject???