>From this thread it seems that long term endurance of screw anchors ranges
from poor to excellent, both in terms of their anchor capabilities as well
as their tendency to corrode over time.
Here, in central Missouri near the MO/KS state line, the soil is about
6'-12" of nice black dirt, below which is at least 10-15 feet of pretty hard
clay (when very wet the clay turns to a mud-like substance, but thick &
heavy; when dry, it is hard and brittle). Before development, much of this
land was either prairie and/or cattle raising, depending on how close to
civilized areas.
I have no idea of the pH of the soil (other than that 15 years of soil +
seasonal moisture + galvanized screw anchors led to major deterioration and
eventual failure of mine). During installation, it was a booger to get the
anchors drilled in, and they were solid and strong. The tower NEVER moved or
wobbled; retensioning of guywires never was necessary due to anchors
"floating", occasional retensioning only due to stretch of the wires
themselves It was a great installation. But, once that slow, hidden galvanic
action went past a critical point, BOOM!
Just as there are charts for average soil conditions, wind loading, etc.,
it'd be interesting to see if there are regional averages for soil pH.
Perhaps pH varies too much within small geographic areas to make
generalizations of any use.
Whatever the case, those using screw anchors should consider soil
compaction, water contect, and soil acidity/alkalinity versus the ham's need
for load bearing and estimated life cycle.
Good luck all, and may your screw anchors not turn on you!
73
Dan
K0DAN
It would be interesting to learn
----- Original Message -----
From: "K8RI on Tower talk" <k8ri-tower@charter.net>
To: "Phil Camera" <kb9cry@comcast.net>; <towertalk@contesting.com>
Sent: Monday, January 16, 2006 1:24 AM
Subject: Re: [TowerTalk] Screw Anchor Question
>
> ----- Original Message -----
> From: "Phil Camera" <kb9cry@comcast.net>
> To: <towertalk@contesting.com>
> Sent: Sunday, January 15, 2006 7:45 PM
> Subject: Re: [TowerTalk] Screw Anchor Question
>
>
> > Don't take this personally, but IMHO screw anchors are only to be used
> > for a temporary installation.
> > A 70 ft. tower is a sizable structure and needs adequate anchors,
> > meaning, anchors that have concrete holding them in place.
> > Yes, you should be concerned about the anchor in question, as well as
> > the others.
> > If you get Zero rain, and I mean none, then your anchors may last. But,
>
> We get quite a bit of rain around here, but screw anchors seem to last
> forever. 20, 30 years and you still see no corosion. OTOH you don't want
> to plant them near a marsh. I think a lot depends on the PH of the soil.
> You see a lot of lime sperad on farm land that was once swamp.
>
> > if your location gets any kind of rain, then that soil can become very
> > soupy and won't hold worth squat.
>
> Again, it depends on how much rain and what kind of soil, but for me, I'd
> not use screw anchors except in an emergency or it they were the only
viable
> method available. (or on a small tower)
>
> Roger Halstead (K8RI and ARRL 40 year Life Member)
> N833R - World's oldest Debonair CD-2
> www.rogerhalstead.com
>
> > I'd seriously rethink your installation. Gd Luck and be safe, Phil
> > KB9CRY
> >
> > _______________________________________________
> >
> >
> >
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> >
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