Ed, something to consider is a simple vector analysis. Lets say for
simplicity sake that there are 3 guys attached to a pivot point attached
to your anchor. Further lets assume equal tension in the three guys.
Lets further assume the center guy is dead on straight with the anchor.
Now if the angle between the center guy and the upper guy is equal to
the angle between the center guy and the lower guy the offset forces
cancel and the result is a straight pull as if all the force were
concentrated in the center guy.
There are an infinite number of combinations of tension and angles that
would similarly balance with offset forces canceling each other. If the
angle of a guy is greater than that of one opposing it at the same
anchor, an unbalanced version of the above 3 guy example, then the
tension might be adjusted to bring the resultant force (combined effect
of all the guys at a single anchor) into alignment with the anchor.
You have some latitude in adjusting guy tension so the above might work
for you if the total force on the anchor is not made to great while
trying to adjust the direction of the resultant force to align with the
anchor.
Patrick NJ5G
On 3/17/2015 12:04 PM, Ed G wrote:
I looked at the Hubbell link Shawn provided on the earth anchors, and
noticed this:
Note: If hand installed, holding capacity may be reduced by as much as 10%
to 20%. Capacity ratings apply to properly installed anchors only. Failure
to install within 5° of alignment with the guy load will significantly lower
strength.
I always knew the type of soil would affect holding capacity, but now I see
that with hand-installed anchors, and with anchors used to hold 2 or 3 guys
(where I am definitely exceeding the 5 degree load alignment spec)...I may
be way down from what I am estimating holding capacity to be.
So ignoring the lower capacity due to sandy soil here in Florida, I may be
losing 20% of capacity due to hand installing, and losing some unspecified
capacity (Hubbbell says "significantly reduced") because some of my guys are
pulling outside the 5 degree alignment. I'm starting to wonder how much if
any margin I have. Guess a more formal analysis may be warranted.
--Ed, N3CW--
Message: 2
Date: Tue, 17 Mar 2015 15:57:24 +0000 (UTC)
From: N3AE <n3ae@comcast.net>
To: TowerTalk <towertalk@contesting.com>
Subject: Re: [TowerTalk] Earth Anchors
Message-ID:
<1802192855.8625804.1426607844350.JavaMail.zimbra@comcast.net>
Content-Type: text/plain; charset=utf-8
The product you're looking for is likely on this page:
http://www.hubbellpowersystems.com/anchoring/no-wrench/
Perhaps a call to Hubbell's customer support line would get you info on a
local distributor.
OBTW...I put in three PS816's last year, by hand. What a job! Time of the
year, at least around here in Maryland, makes all the difference. Very moist
ground after the winter thaw is the best, i.e. NOW. In the summer with dry,
hard earth, forget it.
Good luck
Shawn
N3AE
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