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Tensioning Guy Wires

The following was grepped from the TowerTalk@Contesting.com mailing list from various authors. Thanks to MD Lowell, N1LO, for gathering this information.

Rohn specifies that guys should be tensioned to 10% of the breaking strength of the guy size that is recommended for a particular tower. One rule of thumb is 8% if the guy is out at 100% of tower height, 10% ifat 80% of tower height (standard Rohn drawings) and up to 15% if the anchor point is at 65% of tower height. You lose a lot of wind load in this last type of installation.

For Rohn 25, 3/16 EHS is recommended, having a breaking strength of 4,000 lb. Therefore, 400 lb tension is appropriate for Rohn 25 tower. The primary failure mode for Rohn 25 is in compression of the legs, so it is important not to over tension the guys, resulting in greater compression of the tower legs. 1/4 inch EHS is 6650 and tension should be 665 pounds for towers where 1/4 is specified by Rohn.

For Phillystran, there is some new information from the factory and it looks like it doesn't stretch as much as it 'relaxes'. What they recommend is that the Phillystran be initially tensioned to 15% of its ultimate breaking strength and then over time, it will 'relax' to the 10% desired tension. According to their chart, It goes from 15% down to 12% within about 10 hours and then finally reaching 10% within 30 days (a guess since their graph doesn't extend out that far).

The TIA-222 tower spec allows a tolerance of 1 part in 400 for tower alignment; that's 3 inches per 100 feet so your tower doesn't have to be perfectly plumb. Start with the bottom set of guys and an intermediate tension around 100 pounds, verify the plumb (or pull into plumb) using a long level (4-6 feet) and then adjust to the final tension. If all the guy anchors are at the same level, you only have to measure one guy; they should all be the same. Once you've got your intermediate tension and plumb, it doesn't take much travel in the turnbuckle to get to the final tension - maybe as little as 1 turn. Actually, using this method you don't need much turnbuckle to adjust. Going from 100# to 400# tension might be less than 6 turns of the TB, so there's not much problem with pulling the tower out of plumb. Move up to the next set and repeat until finished.

Use your arithmetic measurement for how long the guy should be and then make the piece of guy wire closest to the ground on that first one 10 feet too long. Since you are splicing the guys by insulating them this first one will give you a good feel for how close your arithmetic guesstimate is. i.e. ifyou have ten feet too much your math is one hell of a lot better than mine! I assume you are using a bolt cutters for cutting your EHS...they can be had cheap at flea markets...you have seen them they have the big long red handles and menacing black jaws. If you are using an AB Chance or similar anchor into the ground/concrete you have a closed eye that is your attachment point. You need to pass somethingthrough that eye which will act as a place for you to attach a comealong. Depending on the installation you use this will vary as you will need to try and avoid the actual guy wire's path as best you can. If you have an equalizer plate you can use an adjacent hole on the plate as an attachment point.

With the comealong and a Chicago grip (or another, second, guy grip applied several feet up the guy wire) moderately tension the guy wire. I say moderately so you don't pull the tower over or throw it out of plumb from the start. Once the guys are moderately taught check the tower for plumb, adjust the guy that needs to be tighter first and, if necessary, later on you can let out the far side guy(s). If you can tighten that first guy and bring the tower into plumb there is a good chance you will have also tightened the other guys in the process. If increased tension does not plumbize the tower, then you should consider letting out on the other guys. You will have a loose end pointing at your guy anchor with the comealong doing the work. I recommend you have a turnbuckle there as it will allow you to fine tune your adjustments later on. Start with the turnbuckle 3/4 out. With the force on the comealong, and the bottom side of the turnbuckle attached to your anchor you know how long the wild end of the cable needs to be. Cut it so that it corresponds to where it should end at the high side of the turnbuckle. Trim it, and marry it to the turnbuckle's upper end with a preformed guy grip. It should only take a couple of twists of the turnbuckle at this point to transfer the load off the comealong and onto the turnbuckle. It will take a couple of hits/misses for you to find how far up the guy wire to attach your comealong/Chicago grip so that you will not interfere with the turnbuckle, still be able to take up, and - be able to reach that upper point! Don't make it too high.

We have had great luck with using the Loos gauge as a method for equalizing the force on the guy wires. While it may not give an exact number it does give you a repeatable number, strive to have all your guys have equal tension (this assumes the end points are all the same distance from the base of the tower, of course). If you are going into an equalizer plate, remember that as the other upper guys attach to the plate it should want to change its angle with respect to the ground as the later guys attach to it. This creates a situation where the bottom set will be drawn tighter than when initially installed. The best way to handle this is to compensate for it by having several inches of extra take up on the lower turnbuckle when it is originally installed so that they can be backed out as the upper guys tighten, allowing the eq plate to rotate. I encourage you to purchase a Chicago-Grip (the Florida Rednecks call it a Pork Chop...when you see it you will know why) - this device when used with the comealong makes the job of tightening the guy wires no big deal. Having a second person is a big plus on this job as you can really zip from one to the other with one guy in charge of attaching the hardware and the other in charge of tightening, etc.....I recommend a Dad!

After you have done the first level (assuming you took my advice and got that pork chop - don't leave home without it) you will zip through the subsequent guy levels. If you are a member of a club you might wanna encourage the club to buy a pork chop for all the members to use. We have used these techniques successfully, repeatedly. Oh yeah, one other thing - the pork chop is a great way to grab the lower end of your tram line when you are putting up your antennas....but, we will wait for you to askabout that in a month or so :-)

Using preforms, you do not cut the turnbuckle end of the guy wire at all. Just let it lay on the ground or coil it up if you like. Only when you are sure your tower has grown tall enough would you cut the excess length with bolt cutters.

Make sure you put a cable, or one of the long ends through all the turnbuckles to prevent them from loosening. Also, loop a cable through all of the thimbles (in a circle) in case one of the turnbuckles breaks. If you are afraid of vandalism, you should put the loop through the centers of the turnbuckles as well, rather than the loose end serving this purpose. The advantage of using the loose end, is that tightening of the turnbuckles requires less time, since no cable clamps need be removed.

To tighten the guys, I use a preform about 6' up each guy wire and a come along attached to the preform (lever end of come-along). The cable end of the come-along hooks at a convenient place on the anchor or equalizer plate. Make sure the tower is vertical to the first set of guys via 4' level (what I use) or plumb bob (never tried this). Then, as long as the first part of the tower is vertical, you can site up the legs to see which way you need to go with the rest of the guys. There will be interaction between adjustments of sets of guys.