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Re: [TowerTalk] Screw Anchor Experience

To: "N3AE" <n3ae@comcast.net>
Subject: Re: [TowerTalk] Screw Anchor Experience
From: "K0DAN" <k0dan@comcast.net>
Date: Tue, 18 Jun 2013 19:19:54 -0500
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
Hi Shawn...

I had screw anchors which I think I purchased from Texas Tower. They were 
probably manufactured by Rohn or some other well-known tower mfgr.

IRC they were 4” augers on 4’ 3/4” (or 1”?) rod, all galvanized. They met the 
tower mfgr (TriEx) spec. They were installed (with difficulty) into local soil 
here near Kansas City. Which is about 2’ of topsoil on top of packed clay. I do 
not know the pH of the soil. 

The tower was a 72’ crank up (HW series if IIRC) was triple guyed and was not 
overloaded. All was fine for 15+ years when one night we had thunderstorms and 
50 MPH wind gusts (the tower was spec’d for 70 MPH), I was on the air at the 
time, and suddenly all the signals went down 50dB. I turned the rotor and it 
would only turn about 10 degrees. WTF? I went outside and to my horror, saw the 
tower lying over in the trees! If you ever want a gut-wrenching sight, that is 
it.

Later investigation showed that one guy anchor and failed, causing the 
equalizer plate and all attached guywires to slingshot in the direction of the 
wires; the remaining two anchors kept tension on the tower, pulling it in the 
direction bisecting the angle of the two remaining guys (50’ trees).

The antennas were destroyed, and the tower sections sufficiently bent that I 
did not want to attempt to repair them. 

The cause of the anchor failure was long term corrosion (galvanic action) from 
soil working on galvanized anchors. The 3/4” anchor rod and shrunk down to the 
diameter of a pencil, and probably pulled apart like soft taffy when then wind 
load was high enough.

Based on my experience I do not think screw anchors are a good long-term guy 
wire anchor at all. For short term, probably fine, but despite what Texas 
Towers told me, they are NOT permanent. 

However if you drilled and belled footings for the guy anchors, filled them 
with concrete, and then inserted the screw anchors, I think you’d be OK. Ask 
the tower mfgr or a civil engineer or M.E., not me. With galvanized encased in 
concrete, I think there would not be the exposure to chemical reaction. 

It is also possible that your local soil is not reactive and what happened to 
me is not a risk at your QTH. You will have to ask people wiser than I.

I have photos of the crashed tower and failed guy anchor. Someone on this 
reflector (maybe the fellow who wrote”Up The Tower”?) was looking for this 
stuff a few years ago, and I promised them to him but I lost my note and never 
followed through.

Good luck and 73

Dan
K0DAN

From: N3AE 
Sent: June 18, 2013 17:16
To: k0dan@comcast.net 
Subject: Screw Anchor Experience


Dan,



I was reading your recent post in TowerTalk regarding thoughts on a new tower 
for KR5DX.   You mentioned a failure you experienced with a screw-in guy 
anchor.  Wondering if you could share some info on that, like the type on 
anchor, auger diameter, depth and a description of your soil type.  



Obviously I'm considering a screw-in anchor here for a tower (EZ-Way).   This 
tower came from a local who had it guyed using screw anchors and it held up 
fine for 15+ years, including hurricanes and tropical storms.  I've been basing 
my plans on published info from companies like A.B. Chance and Hubble Power 
Systems.   See http://www.hubbellpowersystems.com/anchoring/no-wrench/



tnx



Shawn - N3AE

Southern Maryland
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