Lots of questions. Here's what I did on my 110' Rohn 55G tower:
1. I fully tightened each guy set immediately after installing the guys, so
that the tower was plumb and properly tensioned at each level before I added
more sections above. My reasoning was somewhat specific to my installation:
1) My tower sits on a pier pin, so the lower sections needed to be
well-tensioned to prevent tipping and rotating, 2) I have Phillystran guys
with EHS leaders at the bottom, so the tower moves a bit more with the more
flexible Phillystran than with the more rigid EHS (even at full tension),
and I was more comfortable climbing the partially-erected tower when the
guys were fully tensioned, and 3) 55G sections are 100 lbs each, which puts
some force on the tower as each section is raised -- things moved around a
lot less with the guys fully tensioned.
2. Per Rohn spec, guys were tensioned to 10% of breaking strength which is
about 670 lbs for the gauge of Phillystran (6700 lb) and EHS (1/4") I used.
With Phillystran guys, you have to initially tension them to 15% of breaking
strength because they will relax somewhat during the first few hours or
days. In my case, when overtensioned to the manufacturer's spec (about 1000
lbs), all nine cables relaxed to almost exactly the correct tension. With
EHS guys, you would just tension to the final spec of 10%.
3. You need at least one come-along and one Klein grip to do the job. The
come-along is attached to the equalizer plate or guy anchor, and the
come-along cable is extended and attached to the guy cable with the Klein
grip. It's possible to use cable clamps to attach the come-along cable to
the guy cable, but I don't like that method because it's more time-consuming
and potentially can damage the cable (the clamps have to be tight enough to
hold under significant tension, but not so tight as to dig into the cable.)
Klein grips are expensive, but worth every penny.
4. I happened to have two come-alongs when I started my project, so I
purchased a third so I could tension each of the three cables in a set at
the same time. You don't need a super-expensive heavy-duty come-along. Just
a good-quality unit with rated load of at least 2x the target tension for
the cables. I purchased one high-quality Klein grip from Champion Radio, and
was planning on using cable clamps for the other two guys. Luckily, a local
ham was getting out of the rigging business and sold me two large Klein
grips for $25 each -- an incredible bargain. Three come-alongs and three
Klein grips made it a snap to tension the guys, and eliminated any need to
unwrap the Preform guy grips (see below.)
5. I also used a Loos tension gauge from Champion radio. This tool is
indispensible for tensioning guys. A great feature is that it can be snapped
onto the cable during tensioning rather than having to be placed in line,
like you would have to do with a dynamometer. An in line gauge is OK when
you're doing the initial tensioning, but isn't practical after you install
the turnbuckles. A Loos gauge can be used at any time. Loos gauges are
actually made for stainless steel wire rope used in boating, so the
calibration of the dial isn't correct for EHS. I think there's a conversion
chart in the manual, or maybe K7LXC publishes one. I used a Dillon
Dynamometer in line with the first cable to calibrate my Loos gauge. My
numbers were a little different than the manual or 'LXC's but not too far
off.
6. With the luxury of three separate come-alongs, all I had to do was go
from guy-to-guy, adding a little tension at a time to keep the tensions
equal and the tower as plumb as possible. For each rotation around the guys,
I simple cranked the come-along the same number of clicks. Eventually, I got
a sense of how much tension would result from how many clicks. I had the
dynamometer in line on one guy and use the Loos gauge on the other two. It
didn't take a lot of running around from guy-to-guy to hit a given level of
tension -- one or two rotations max. I checked the plumb of the tower after
each rotation. This made it easy to keep the tower plumb as the tension
increased. I don't recall exactly, but I probably iterated three or four
times, starting with 200-400 lbs of tension, then 600 lbs or so, then maybe
800 lbs or so.
7. Once tension was within a couple hundred lbs of the final target, I
installed the turnbuckles and Preform guy grips. Before installing, I
unscrewed the turnbuckles almost all the way, leaving about an inch or so of
screw exposed at each end. I wrapped the grips about 2/3 of the way so I
could remove them if more adjustment with the come-along was needed. Then I
used the turnbuckles to achieve final tension (you need a long, heavy-duty
screw driver for this.) I used the same process, going from guy to guy
turning the turnbuckles the same amount and checking tension with the Loos
gauge. In between guys, I checked plumb on the tower, compensating as
needed. After all three guys were at the right tension, I checked plumb
again and made any necessary adjustments. It didn't take a lot of back and
forth, because I had been checking plumb all through the process. I wrapped
the guy grips almost to the end, leaving just enough to be able to unwrap in
case adjustments were needed after the Phillystran relaxed. That wasn't
necessary, so a few days after installation I finished wrapping the guy
grips.
8. I had a long level to check plumb, which was useful mostly for plumbing
the bottom four sections. As the tower got taller, it was more effective to
sight up the legs and face of the tower. It's easy to tell when the sections
are not in line with each other. I got very close to plumb this way. I used
a transit level for the final check and it was so close I didn't have to
make any adjustments.
9. The procedure would be a bit more involved if you have only one
come-along and Klein grip. Since I haven't done it, someone else should
comment. I imagine you would have to install and partially wrap the guy grip
after tensioning a cable, leaving enough of the grip unwrapped so you can
remove it if additional tensioning with the come-along is needed. That would
mean you'd have to minimize the iterations because the grips can only be
unwrapped 2-3 times before you have to replace them. I'm interested to hear
how the experts do it.
Hope this is helpful.
73, Dick WC1M
> -----Original Message-----
> From: STEPHEN L SALA [mailto:k7awb@msn.com]
> Sent: Friday, September 12, 2008 5:01 PM
> To: towertalk@contesting.com
> Subject: [TowerTalk] pulling guy lines tightly
>
> I now have two sets of guys wire slightly loose on my new Rohn 45 (70
> feet going to 90 feet) and one set on my new Rohn 25 (35 feet going to
> 105 feet) with the remaining guy sets already made. In what order do
> I tighten them? Since I will have three sets of guys on each tower
> with a three-hole equalization plate at the end of the guy rod, do you
> tighten the lower set to 400 lb or so and then the 2nd set and go back
> and forth? or do you do them lightly (maybe 200 lb until the final
> set is up)?
> What happens when I try to tighten the top set at the top of the
> towers? For each set, how many iterations do you have to do going
> around the tower to get the tower vertical going guy wire to guy wire?
> What kind of error will I have using a 4 foot level at read plumbness?
> Should I use a comealong to pull the wires tightly?
> Stephen L. Sala (Steve) K7AWB Nine Mile Falls, WA DN17es
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