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[TowerTalk] Single Base for 45g and 25g?

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Subject: [TowerTalk] Single Base for 45g and 25g?
From: (Stan or Patricia Griffiths)
Date: Fri, 30 Mar 2001 14:42:02 -0800

Jerry Keller wrote:

> Anyone know how much wind load 50 feet of guyed 45G will handle?

You ask a very complex question, Jerry.  It depends on LOTS of variables:

1.  How many sets of guys?
2.  What size of guy wire?
3.  Is the tower going to support long boom antennas with lots of torque applied
to the tower during startup and braking?
4.  Is the tower guyed to resist the torque?
5.  What is the wind speed?
6.  What kind of icing do you expect?
7.  I am sure there are other questions to address, too . . .

For a simple answer, I can show you a page in the current Rohn Catalog (Drawing
#C850498R1) that says such a tower will support 94 Square Feet.  But it also
says the antenna is a 10 foot diameter mesh dish . . .  So, you see, this is
probably not the right answer for you.  The other simple examples Rohn gives in
their catalogs are obviously  not designed with a guying configuration that will
give you the maximum wind load for a 50 foot tower.  I have never seen an
engineered tower designed for maximum windload for a given height.  It would be
a very interesting problem for a professional engineer and the design and
windload he comes up with would be even more interesting . . .

So, Hank, KR7X, do you want to do an exercise for us?  Given a free hand, how
would you guy 50 feet of Rohn 45 to handle MAXIMUM wind load?  You pick the wind
speed (100 mph would be nice).  You pick the number of sets of guys and
placement on the tower.  You pick the guy wire size.  You pick the base design.
You pick the anchor design.  What will be the most likely failure point in your
final design?   My guess is that it will hold an AMAZING load if you design for
maximum load and use lots of big guy wires on it . . . it will be a LOT more
than Rohn has ever hinted at in any of their example designs shown in their
catalogs.  The key here is to have a professional engineer do the design work .
. .


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