[TowerTalk] Unconventional Tower Installation

[tony_brock-fisher@agilent.com]

I have just such an installation. I had a ham/engineer work out the details.
My case:

78 feet of Rohn 45; three sets of guys (overkill) at 22, 44, and 66 feet.
Two sets are anchored 56 feet from the base; the third set is only 30 feet.
The 56 foot guys are 1/4 inch; the 30 foot guy is 5/16" EHS. all base sizes
were increased to the 4B spec. One of the 56 foot anchors is on a down
slope, about 10 feet lower in grade than the other. The anchor was placed so
as to keep the angle on the middle guy wire at nominal.

My guess is that your proposed installation is possible, but that like
myself you will have to spend some $$$ with an engineer to get plans that a
building inspector will accept.

-Tony, K1KP

-----Original Message-----
From: Kurt Andress [mailto:K7NV@contesting.com]
Sent: Thursday, June 01, 2000 4:12 PM
To: Bob Allen; towertalk@contesting.com
Subject: Re: [TowerTalk] Unconventional Tower Installation



Bob Allen wrote:
> 
> I have a question regarding the guying of a tower that will not be the
> "ideal" installation.  The tower will be placed behind the house next to a
> place where the hill was dug out to level for the foundation.  From there,
> the land slopes upward with a medium slope.  On a 60 foot tower, the Rohn
> book says to place the guy anchors 48 feet from the tower.  In my case,
one
> of them will have to be placed at only 30 feet.  The other two could be
> placed 48 feet away, but since the ground is not level, they will not be
at
> ground level, but higher, and therefore shorter than what the book says.
> If one is only 30 feet away, should all of them be the same, or can you
> have one at 30 and two at 48?  And what about the fact that the guy
anchors
> will be at different heights?
> 
> Any help with this would be appreciated.
> 
> 73,
> Bob
> KK5MI

Bob,
Since I saw no answer posted for this....here's a condensed response.

The anchor distance from the tower can be viewed as establishing an
angle (in a vertical plane) between the tower and the guys. This
relationship is fundamentally significant in determining how the entire
system behaves. 
You are trying to produce a variable terrain equivalent for the flat
terrain recommendation of the manufacturer. 

The goal is to place all anchors at equally spaced radial
locations to maintain the recommended 120 Deg radial angles (for 3 way
guyed towers) between the guys and at locations along the terrain that
produce the same vertical angles between the tower and each of the guys
as those presented by the flat ground scenario the manufacturer has
recommended. 

Properly placed anchors on other than flat ground should be at different
straight line (horizontal) distances from the tower.

Your particular solution is probably best dealt with by laying out your
selected radial anchor directions, then measuring the elevations along
those lines with a transit and then computing the proper locations with
a little trigonometry. 
Anchors that are uphill from the tower will be closer, those downhill
will be further from the tower to obtain the same tower to guy
relationship. 

Some very simple guyed tower analytical observations have been presented
at: http://www.freeyellow.com/members3/yagistress/	

Select the "Guyed Tower Study" link, you might find some of it
interesting reading.

-- 
73, Kurt, K7NV

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