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Re: [TowerTalk] Screw Anchor Question

To: towertalk@contesting.com
Subject: Re: [TowerTalk] Screw Anchor Question
From: Mike <k4gmh@arrl.net>
Date: Mon, 16 Jan 2006 16:31:44 -0500
List-post: <mailto:towertalk@contesting.com>
Hello,

Regarding the ability of screw in anchors to hold - An eighty foot 
pine tree fell across one set of guys on my 130 foot tower in 
hurricane Isabel.  The tower was guyed by three sets of 4 levels of 
Phylistran (4000 lb) guys, each set to a single screw in 
anchor.  Three of the guys in one set were broken by the tree.  (Yes, 
the tower and ant. were turned in to a bunch of steel and aluminum 
pretzels.)  The screw in anchor for that set of guys looked like it 
hadn't budged.  The soil has a lot of clay in it and the tower had 
been up for 4 years.

Please consider the above as one data point in making your decision 
as YMMV always applies.

At 08:38 AM 1/16/2006, Pete Smith wrote:
>Not to mention that you do not have the typical ham single-point 
>failure risk , with all the guys in one plane attached to the same anchor!
>
>73, Pete
>
>At 08:19 AM 1/16/2006, Dennis OConnor wrote:
> > I have two towers, 130' lightly loaded and 150' with LARGE 
> antenna loads - way, way beyond Rohns data for 25G...   They are 
> installed with screw anchors into sandy ground... They have been up 
> more than ten years without any incident or evidence of failure... 
> Storms with recorded gusts to 89 mph have happened over those 
> years... In Michigan we have freeze thaw cycles up the bungees...
> >
> >So why does it work for this clueless ham?
> >Well, ol clueless here designed and installed it so that there is 
> a separate anchor for every 60 feet of tower, i.e. only two guys 
> per anchor... And the steepest guy angle to any anchor is 45 
> degrees, while it's lower mate is roughly 30 degrees... My 
> suspicion is that the tower sections will bow enough to gyrate and 
> twist the tower down before the guy anchors will pull 
> out...  Limiting the load to each screw by keeping the guy wire 
> angle low, is the key in my book...
> >
> >denny
> >
> >
> >
> >
> >
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         73,
         Mike, K4GMH 
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