[TowerTalk] Trig Question
Bill Hider, N3RR
n3rr@erols.com
Sun, 20 Sep 1998 11:56:58 +0100
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Rick,
You have given us a trick question of sorts. See my answers imbedded in your
original below:
Rick Bullon wrote:
> I need some help doing some calculations for a tower. It has been over
> 30 years since I took trig in school and I can't remember my formulas.
> The tower is going to be 70 ft Rohn 25 guyed as per the Rohn book, 70
> mph wind area guy wires at 32' and 65' guyed at 56' from tower base it
> will right now have a TH 6 tribander on it.
> My questions are
> 1. With 2 of the guy points on the property line how far is it from the
> property line to the tower?
You said the guy point was 56 feet from the tower base, so why isn't that
the answer? - That's the trick part.
> ( I need this measurement so I can figure
> the postion of the 3rd guy point to see if the proposed site is big
> enough)
You need a plot plan to scale and make a to-scale "shrimp boat" of you guy
wire situation and position the shrimp
boat on your plot plan and visually see the answer to this. The shrimp
boat, as I call it, is a cut out in a star shape,
with three radii, each 56 feet long (to scale) with an angle of 120 degrees
between each of the three arms.
> 2. Will elevating the guy points make the guys wires longer or shorter?
> and if so by how much? ( XYL requires elevaterd guy points)
Elevating the guy points will allow you to bring the point of penetration of
the guy anchors with the ground CLOSER (less than 56 feet) to the tower,thus
DECREASING the length of the guys. Alternatively, by keeping the location
of the guy points at 56 feet from the tower
and elevating the guy anchors, you will be decreasing their length, but
"virtually" increasing the guying % and thus causing your installation to be
more stable.
As far as "how much", that is a trig question and depends on how high you
elevate the guy wires.
> I seem to remember reading on here that "I" beams were stronger than
> round pipe for elevated guy points right or wrong?
Well, maybe. It depends on the size of each for comparison.
> Do I need to use an equlizer plate for this setup or is that over
> kill?
Doing things right is never overkill.
By the way, the nature of your questions indicates to me that you need more
help than you will receive over this reflector. By this, I mean that
you ought to be creating drawings of each situation above and using trig to
evaluate each option. Since we can't see your plot plan, we are limited in
what we can
offer you. Furthermore, by the nature of your questions, I am concerned
that you will proceed with a design and implementation based on our answers
to your questions. Please do not do this. Obtain professional if not
qualified and experienced LOCAL amateur radio operators to help you. The
questions you are asking are very basic and critical to the safety of your
installation. They should not be treated so casually as to expect this
reflector to be able to guide you at-a-distance since you admit you don't
know the basic geometry and trigonometry of your situation, such basic
knowledge, in my view, is a requirement for someone owning and operating an
amateur radio tower system.
See my website: http://www.erols.com/n3rr
73,
Bill, N3RR
> thanks
> Rick Bullon
> KC5AJX
>
>
> ______________________________________________________
> Get Your Private, Free Email at http://www.hotmail.com
>
> --
> FAQ on WWW: http://www.contesting.com/towertalkfaq.html
> Submissions: towertalk@contesting.com
> Administrative requests: towertalk-REQUEST@contesting.com
> Problems: owner-towertalk@contesting.com
> Search: http://www.contesting.com/km9p/search.htm
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Rick,
<P><FONT COLOR="#3366FF">You have given us a trick question of sorts. See
my answers imbedded in your original below:</FONT>
<P>Rick Bullon wrote:
<BLOCKQUOTE TYPE=CITE> I need some help doing some calculations for
a tower. It has been over
<BR>30 years since I took trig in school and I can't remember my formulas.
<BR> The tower is going to be 70 ft Rohn 25 guyed as per the Rohn
book, 70
<BR>mph wind area guy wires at 32' and 65' guyed at 56' from tower
base it
<BR>will right now have a TH 6 tribander on it.
<BR>My questions are
<BR> 1. With 2 of the guy points on the property line how far is it
from the
<BR>property line to the tower?</BLOCKQUOTE>
<FONT COLOR="#3366FF">You said the guy point was 56 feet from the tower
base, so why isn't that the answer? - That's the trick part.</FONT>
<BLOCKQUOTE TYPE=CITE>( I need this measurement so I can figure
<BR>the postion of the 3rd guy point to see if the proposed site is big
<BR>enough)</BLOCKQUOTE>
<FONT COLOR="#3366FF">You need a plot plan to scale and make a to-scale
"shrimp boat" of you guy wire situation and position the shrimp</FONT>
<BR><FONT COLOR="#3366FF">boat on your plot plan and visually see the answer
to this. The shrimp boat, as I call it, is a cut out in a star shape,</FONT>
<BR><FONT COLOR="#3366FF">with three radii, each 56 feet long (to scale)
with an angle of 120 degrees between each of the three arms.</FONT>
<BLOCKQUOTE TYPE=CITE>
<P> 2. Will elevating the guy points make the guys wires longer or
shorter?
<BR>and if so by how much? ( XYL requires elevaterd guy points)</BLOCKQUOTE>
<FONT COLOR="#3366FF">Elevating the guy points will allow you to bring
the point of penetration of the guy anchors with the ground CLOSER (less
than 56 feet) to the tower,</FONT><FONT COLOR="#3366FF">thus DECREASING
the length of the guys. Alternatively, by keeping the location of
the guy points at 56 feet from the tower</FONT>
<BR><FONT COLOR="#3366FF">and elevating the guy anchors, you will be decreasing
their length, but "virtually" increasing the guying % and thus causing
your installation to be more stable.</FONT><FONT COLOR="#3366FF"></FONT>
<P><FONT COLOR="#3366FF">As far as "how much", that is a trig question
and depends on how high you elevate the guy wires.</FONT>
<BLOCKQUOTE TYPE=CITE>
<P> I seem to remember reading on here that "I" beams were stronger
than
<BR>round pipe for elevated guy points right or wrong?</BLOCKQUOTE>
<FONT COLOR="#3366FF">Well, maybe. It depends on the size of each
for comparison.</FONT>
<BLOCKQUOTE TYPE=CITE>
<P> Do I need to use an equlizer plate for this setup or is that
over
<BR>kill?</BLOCKQUOTE>
<FONT COLOR="#3366FF">Doing things right is never overkill.</FONT><FONT COLOR="#3366FF"></FONT>
<P><FONT COLOR="#3366FF">By the way, the nature of your questions
indicates to me that you need more help than you will receive over this
reflector. By this, I mean that</FONT>
<BR><FONT COLOR="#3366FF">you ought to be creating drawings of each situation
above and using trig to evaluate each option. Since we can't see
your plot plan, we are limited in what we can</FONT>
<BR><FONT COLOR="#3366FF">offer you. Furthermore, by the nature of
your questions, I am concerned that you will proceed with a design and
implementation based on our answers to your questions. Please do not do
this. Obtain professional if not qualified and experienced
LOCAL amateur radio operators to help you. The questions you are
asking are very basic and critical to the safety of your installation.
They should not be treated so casually as to expect this reflector to be
able to guide you at-a-distance since you admit you don't know the basic
geometry and trigonometry of your situation, such basic knowledge, in my
view, is a requirement for someone owning and operating an amateur radio
tower system.</FONT><FONT COLOR="#3366FF"></FONT>
<P><FONT COLOR="#3366FF">See my website: <A HREF="http://www.erols.com/n3rr">http://www.erols.com/n3rr</A></FONT>
<P>73,
<P>Bill, N3RR
<BLOCKQUOTE TYPE=CITE>
<P> thanks
<BR>Rick Bullon
<BR>KC5AJX
<BR>
<P>______________________________________________________
<BR>Get Your Private, Free Email at <A HREF="http://www.hotmail.com">http://www.hotmail.com</A>
<P>--
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<BR>Submissions:
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<BR>Administrative requests: towertalk-REQUEST@contesting.com
<BR>Problems:
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FAQ on WWW: http://www.contesting.com/towertalkfaq.html
Submissions: towertalk@contesting.com
Administrative requests: towertalk-REQUEST@contesting.com
Problems: owner-towertalk@contesting.com
Search: http://www.contesting.com/km9p/search.htm