Sunday, August 6, 2017

Wrestling With Steel Guys

In an earlier post I mentioned that I am guying my big tower with steel. Although non-conductive guys eliminate interactions that can compromise antenna patterns they are more expensive. In my modelling of potential interactions I found that for my intended selection and placement of antennas there is a pattern of non-resonant lengths that is perfectly acceptable. Interactions among the antennas will likely be the greater concern.

Having selected steel I was faced with the perils and other difficulties in working with steel guys.

On the left you see a large reel of LDF4-50A Heliax. On the right is a much smaller reel of 5/16" 1x7 Grade 180 EHS guy strand. Their weights are similar (heavy!) and contain approximately the same length of cable. Both appear entirely innocent. Appearances are deceiving.

The Heliax is light and somewhat fragile. It is easy to handle provided you properly unreel it to avoid kinking.. The reel of guy strand is not light and it is not fragile. Indeed it is a serious hazard to your health, fortitude and sanity when not handled with extreme caution. That's no exaggeration.

The first thing to realize is that the guy strand is not comfortably coiled on that reel. Those coils hide an extraordinary amount of stored elastic energy. When released from the restraining staples the cable releases that stored energy as it rebounds to its resting state: straight.

My procedure for freeing the cable for use is to lightly hammer a pointed tool, such as an awl, between each staple and the cable to create space for the cable to move. It will stay coiled if you are careful not to go so far that the staple is ripped out of the wood reel by the cable.

With the staples loosened the cable is pulled back out of the first two staples. This isn't easy since the cable is pushing hard against the outside surface of the staples. It violently snaps to attention when exiting each staple. Take that as a warning!

Move off to one side of the reel when pushing the cable through the final staple. A long steel rod tapped with a hammer against the end of the cable is a good way of doing this. However you do it you should not have any part of your body between the sides of the reel. Alternatively use very strong vice grips on the cable and position the reel so that it can recoil. It can work but I don't like the risk since the reel recoil takes too long due to its weight, then if the pliers aren't quite tight enough the cable will whip back and around the reel at high speed.

When the cable emerges from the final staple the cable will kick backward as it unwinds and straightens. If you're in the way you will be hurt, perhaps badly. Stay out of the way.

Unreeling the guy cable for use can be done in several ways, provided you provide a barrier or other restraint so that the reel or cable doesn't get away from you and make a big mess. The risk of the cable whipping out and striking you remains right up until the reel is emptied.

Cutting and joining non-resonant lengths

EHS is not difficult to cut with the correct tool. For 5/16" guy strand I use ⅜" bolt cutters. The jaws are large and hard enough and the arms have enough mechanical advantage to enable anyone with average strength to cut 5/16" EHS.

If you don't have sufficient strength brace one arm of the tool against the ground and carefully push down on the other with two hands using your body weight. Open the jaws wide so you can push the EHS in deep for the greatest mechanical advantage.

Do this carefully! When the cable severs the two ends will spring away from the cutter if not restrained in some way. Make sure you're wearing skin and eye protection and do not place your body where the ends are likely to jump. Alternatively use clamps or heavy weights to restrain the cable. Standing on both sides of the cut with heavy duty work boots can work well if you can operate the cutters with your arms alone.

Watch out for the cut ends: they are hard and sharp. If the strand partially unravels during the cut -- a common occurrence -- wind them up again so they sit flat. Wear gloves since it's easy to pinch your skin doing this.

To minimize waste it is best to cut the longest non-resonant lengths first (43' in my case). This way when you reach the end of the reel you can cut the remnant into the needed short lengths. You'll also want to keep long lengths on hand for the variable length from the anchors to the linked set of non-resonant lengths.

The non-resonant lengths are joined with insulators and pre-forms. At each joint you need one insulator and two pre-forms. Since the portion of the pre-form from the insulator to the EHS is part of the segment length you should cut the EHS segments at least 6" less than the required length. A few inches either way is not critical so don't fuss over the measurement.

I won't give a lesson on attaching pre-forms since I am not an expert. What I will tell you is that it takes some muscle, hand protection and a clean surface. Don't do it on grass or dirt! The only grit you want between the grip and cable is that with which the grip is coated. Foreign material will reduce the strength of the joint. I did most of the work in the garage then moved to the gravel driveway when the length required more space.

The larger the insulator the farther out the wrap begins. The pre-forms have helpful paint markings. The inner one should only be used for thimble terminations. The outer one is for insulators, but you can sometimes start the wrap sooner depending on the insulator. I did that for 502 size insulators while the 504 lined up pretty well with the outer paint mark. Don't force the wrap since you could add unwanted stress to the pre-form and insulator.

Eventually the guys will start coming together. It takes time and should not be rushed. Take a break if you get tired. Fatigue causes mistakes and injury. The most common risk in my experience is pinching fingers while wrapping the pre-form around the EHS. Most dangerous are the start and end of the wrap. Holding the thimble or insulator down with a work boot or gripped in a work bench helps to hold everything in place when you begin the wrap.

Coil the guys and put them out of reach

The relaxed coil diameter for the 5/16" EHS I am using is about 5' to 6'. Don't force it into smaller diameter coils for storage and carrying since you'll need restraints to prevent accidents. You'll also discover that the completed guys are heavy. A 500' reel of 5/16" EHS weighs approximately 120 lb so you can see that even a short 6' length is not an inconsiderable weight. Insulators and pre-forms add even more weight. When fully assembled a guy for my tower can weigh up to 100 lb.

If you need to temporarily store the completed guys put them where people and pets won't tangle with them. Curious children can quite easily hurt themselves. Not only are the ends sharp they will easily tangle feet when you try to step over and around them when they're lying on the ground.

Attaching guys to the tower and anchors

Thimbles are used to terminate guys at the tower and the anchor. They allow the pre-forms to maintain their shape and therefore their strength. Since pre-forms are wider than the guy strand for which they're made the proper thimbles are typically one size larger. For example, for my 5/16" guy strand the thimbles should be at least ⅜".

Don't go larger unless you must since larger sizes are more difficult to use (more force required to spread and close) and may be a tight fit in turnbuckle eyes and some brands of guy station. Thimbles made for pre-forms are thicker, deeper and larger radius than those for more flexible aircraft cable. They should also be hot-dip galvanized to last a long time outdoors.

Since as I write this I don't have thimbles in hand the above picture is of a used ¼" guy termination that I have in junk pile. I have lots of used guys broken into non-resonant lengths, but I am guying with entirely new hardware and guy strand. This is not because the old guys are unsafe but rather to ensure maximum longevity. Galvanizing isn't forever.

Work, work, work

Constructing non-resonant steel guys is hard work and there is potential for injury. The guys are also heavy and therefore difficult to carry, lift and attach at height. For these reasons many hams are happy to pay more for fibreglass or kevlar guys.

Even then the bottom segments of non-conductive guys are typically made from EHS to minimize risk of damage, whether accidental or deliberate. Break a guy and the tower will fail.

As of now the first set of guys is ready to go. The other 3 sets are partially complete. I am delaying the rest of the cuts until the first set is installed so that I can minimize waste once the long lengths from the non-resonant upper sections to the anchors are cut to the actual required length. Making guys is tedious work so I make it more palatable by doing a little at a time.

One thing I've realized is that I will almost certainly need another 500' reel. Since the 2,000' in the 4 reels I have is too close to the total length I'll need any amount of waste will cause a shortfall. That's okay since I can use for the rest of the 5th reel in the future. Reel remnants can be used to make short non-resonance lengths for a future tower. Yes, I do have another tall tower in my plan.

Next steps

The tower is currently two sections high. Additional work was necessary once the gin pole and lifting method were tested and found wanting. Other issues have also cropped up. I'll talk about these in later articles since all of it is relevant to anyone contemplating putting up a guyed tower.

And I still have 8 sections to paint. I am hopeful of getting the tower completed this month.

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