Beams/towers

[K7LXC at aol.com]

In a message dated 96-02-10 09:49:30 EST, you write:

<< I didnt realize that there was such a small wind load capability
difference between <25G and 45G--  45G feels like climbing a ROCK compared to
25G to me--- Why is <55G so much stronger?

   Yes,  I was surprised by those numbers myself and decided to look into it.
 Tower legs take all the up and down forces so I compared the specs:

         25G  1.25" OD     16 guage thick
         45G  1.25" OC     14 guage thick
         55G  1.5" OD       11 guage thick

You can see that the 25G and 45G legs are directly related strength-wise
since they are the same OD.  The 55G legs are almost 17% bigger OD with
thicker walled steel.  Increasing the thickness of 25G and 45G legs is pretty
incremental until you increase the OD as in the 55G.  Interesting exercise.

<I need to get that Rohn catalog - great stuff in there - lost mine years ago
- but zeoxed <pages I need from supplier when I installed my 25G - yep -- 25G
when I knew it should <have been 45!!!  

  Get the Rohn catalog from your Rohn dealer or direct from Rohn
(309-697-4400); there are 2 versions, Consumer Products and Commercial
Products - the consumer one has BX and the commercial one doesn't.  They're
$10.00 with a $10.00 rebate.

<I saved some bucks but its just a matter of time that I will pay the
price--- My  25G is <70ft high - mounted in 1 yd concrete, house braket at
12ft, and three sets of guys with <tork bars and equalization plates at
anchors--- 3/16" Rohn with insulators on the two <lower set of guys and 3/16
Philly Stran on top -- whats on this??
<I hate to tell you!!!  get ready for this ----A HS 20ft mast with a
cushcraft 10M 4 elm <beam on top - 10ft down a Force 12 15M 4 elm beam driven
by a Yaesu G1000SDX <and about 10ft below all of that just below the rotor
plate a Tic-Ring with a Force 12 <20M 4 elm yagi on a 30ft boom -- I chose
the force 12 antennas due to their <comparativly less wind loading -----  Oh
well --- It all sayed up in the close call <Hurricanes this summer -- 65MPH
winds--- I think the beams would have blown away <at 80 or above---

   Well, yes your tower is overloaded - Rohn spec says 8.0 sq ft. at 110 MPH
(9.8 @ 90 MPH.)  But they only call for 2 sets of guys of  3/16" EHS at that
wind speed so you have ample guying!  I think your QTH is in Jackson County,
it is a 100 MPH TIA-222-E wind zone; but you already knew that.  Like I said,
when you speed, you don't always get a speeding ticket. Keep your homeowner's
insurance paid up (check into a special rider for your tower system) and have
fun in the meantime! 

73, Steve  K7LXC

     "Up The Tower"    now appears in CQ Contest magazine