[TowerTalk] Guy Anchor Safety was:Re: Screw Anchor Experience

[Pete Smith N4ZR]

This discussion prompted me to wonder why every ham installation but one 
that I have ever seen used only one anchor per direction, creating an 
opportunity for a single point failure to bring down the whole 
structure.  It would seem like a simple-enough fix to invest in another 
anchor and some more concrete, and anchor the top guy separately.

73, Pete N4ZR
Check out the Reverse Beacon Network at
http://reversebeacon.net,
blog at reversebeacon.blogspot.com.
For spots, please go to your favorite
ARC V6 or VE7CC DX cluster node.

On 6/18/2013 10:45 PM, K0DAN wrote:
> So the answer, it would seem, is to have any guy anchor (galvanized or 
> not) to not only be embedded in concrete, but in an elevated pier so 
> that the entire guy anchor is 100% above ground soil. If I were to do 
> another guyed tower (which is not my intention) I would do so...the 
> extra labor + materials to "shield" the anchor from soil is worth 
> it...at least based upon my circa 1998 tower disaster. YMMV.
>
> There are many very large commercial broadcast and land mobile 
> communications towers (guyed and self supporting) that have been up 
> for 50+ years. Certainly they are inspected and maintained on better 
> budgets than most ham installations, altho they beg the question of 
> what techniques make them successful (even though we know that some of 
> those big boys come down from time to time).
>
> 73
> Dan
> K0DAN
>
> -----Original Message----- From: Dick Green WC1M
> Sent: June 18, 2013 20:13
> To: 'K0DAN' ; N3AE
> Cc: towertalk at contesting.com
> Subject: RE: [TowerTalk] Screw Anchor Experience
>
> Any anchor that's exposed to soil is at risk of corrosion. Anchors 
> sunk in concrete are just as vulnerable because typically a good 
> portion of the anchor rod is not in the concrete -- it's in contract 
> with soil above the concrete footing. For example, Rohn spec calls for 
> my anchor footings to be poured in a 6-foot long by 3-foot wide hole 
> that's 4-feet deep. The concrete footings are only 18" deep, so 
> there's about 2.5 feet of soil that the anchor rod is in contact with. 
> Since the rod is set at an angle, probably 3-4 feet of the rod is in 
> contact with soil above the footing.
>
> The Rohn concrete anchor rods are very heavy duty, but just in case I 
> slathered several coats of roofing tar on the portions of the rod that 
> were above the concrete block.
>
> Regardless of the type of anchor rod you have, it's a really good idea 
> to inspect them every few years. That means digging down a bit to see 
> if there's corrosion.
>
> 73, Dick WC1M
>
>> -----Original Message-----
>> From: K0DAN [mailto:k0dan at comcast.net]
>> Sent: Tuesday, June 18, 2013 8:20 PM
>> To: N3AE
>> Cc: towertalk at contesting.com
>> Subject: Re: [TowerTalk] Screw Anchor Experience
>>
>> 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 at 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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