[TowerTalk] Rohn 55G Tower Damage, etc.

[Keith Dutson]

Your tower is not bent.  The two guys now holding it firmly are pulling it
out of line.  Your EHS is not stretched either.  You can reuse it as-is.
Same for the turnbuckle.

You don't need clamps to hold the EHS.  If the EHS slipped in the grip, it
was either defective or had been removed at least once then re-installed.
This is assuming the color code on the grip is yellow.  Just buy a new grip
and replace the one that slipped.  Re-tension the guys and you are good to
go.

73, Keith NM5G

-----Original Message-----
From: towertalk-bounces at contesting.com
[mailto:towertalk-bounces at contesting.com] On Behalf Of N9EN at VOYAGER.NET
Sent: Sunday, October 02, 2005 6:46 AM
To: TOWERTALK
Cc: SMC
Subject: [TowerTalk] Rohn 55G Tower Damage, etc.

Hello all,

On Tuesday, Sept. 15, a thunderstorm with very high winds rolled through the
northern IL area, where my QTH is lo- cated. Our neighbors to the west of us
lost 2 mature oak trees in their front yard - they were about 12" diameter
and just snapped off above the base. Our yard was filled with debris,
including large branches from one of our larger ma- ple trees.

After the storm subsided, I glanced up at the stack of yagi antennas on the
top of a 76' high Rohn 55G tower. The antennas lloked like they were still
in place so I didn't pay any more attention to them, until the next day,
when I happened to notice that the top antenna had half of its driven
element broken.

The damaged antenna was a home-made copy of a KLM 3-el. 30 meter yagi and
the insulator that held the element on the boom had broken. My wife came
home later and as I was out in the "back woods" unloading a pick-up truck
full of storm debris, she came by and I told her that my antenna had a
broken element.

She looked at the stack of antennas from where we were standing and said
that she didn't see any broken antenna, so we walked into the middle of the
back yard so that she could get a look from a different angle. She then saw
that the element was broken and as she was looking at the antennas and
tower, she said to me that the whole tower appeared to be bent.

I took a closer look myself and sure enough, the tower did appear to be
bent! I then walked to the guy wire anchor in the back yard and found that
the 2 sets of guy wires were very loose. Neither of the turnbuckles had
loosened up and all of the Big Grips looked normal. So I am assuming that
the 1/4" EHS guy wires stretched under the load from the high winds.

I had originally installed the tower for the previous home- owner about 10
years ago. We put it up as a 100' tower, with the guy anchors 80 feet out
from the base; all of the guy anchors and the tower base installed according
to the specs in the Rohn catalog, complete with the re-bar assemblies in all
anchors and the tower base.

I had taken his antennas and tower down for him before we realized that my
wife and I were going to be buying the house from him and his wife. After we
moved in, I decided that I'd only go up 76' (with 4' of tower in the
concrete base). I installed 7 sections of 55G on top of the section coming
out of the concrete and used Rohn 1/4" EHS guy wire, Big Grips and forged,
galvanized
1/2"-11 x 12" turnbuckles.

I had 3 antennas on the top of the tower, using an "IIX"
ladder mast. Just above the top plate of the tower was a HyGain TH7 for 10,
15 & 20 meters. 5-1/2' above that was a little 3-el. CushCraft A3-WS yagi
for 12 & 17 meters and 5-1/2' above the A3-WS was the home-made copy of the
KLM 30M-3 yagi, a 3-el. monoband yagi for 30 meters.

A couple days after the storm, I took a 24" long brass- bound mahogany
contractor's level and checked the tower at various points, to see how far
it was now out of plumb. At the section coming out of the concrete, it was
off approx. 1/16" (in 24"), just above the lower set of guy wires, it was
off about 3/16" and just above the top set of guy wires, it was off about
1/4".

So now I have a bent 76' high Rohn 55G tower with an antenna that is in need
of repair. I am going to replace the top set of guy wires with 5/16" EHS and
I will replace the turnbuckles for that set of guy wires with forged,
galvanized 5/8"-11 x 12" ones. I am not going to use Big Grips on the new
guy wires; I'll use 2 forged wire rope clips (Crosby Clips) per turn-back
and serve the 7 in- dividual strands, as the Rohn catalog suggests. I'll
also replace the lower set of guy wires with new 1/4" EHS material.

In the past, I had never worried too much about high winds; I figured that
nothing short of a direct hit from a tornado would cause any significant
damage to my towers. Boy, was I WRONG! Live & learn, I guess...

73 de Brad, N9EN

@ (Storm-Damaged) Radio Free Roscoe (IL) [tm]...






_______________________________________________

See: http://www.mscomputer.com  for "Self Supporting Towers", "Wireless
Weather Stations", and lot's more.  Call Toll Free, 1-800-333-9041 with any
questions and ask for Sherman, W2FLA.

_______________________________________________
TowerTalk mailing list
TowerTalk at contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk