[TowerTalk] Broken masts

[Jim Thomson]

Date: Thu, 6 May 2010 07:35:16 -0400
From: "D Calder" <towertalk at n4zkf.com>
Subject: Re: [TowerTalk] Loran Tower

http://www.n4zkf.com/files/Tower.jpg

Here is what happens. (the TV antenna in the foreground mounted to the
service drop isn't mine, it's my
idiot neighbor. It's 20 ft away it just doesn't look it in the pic)

If the A3S was mounted 2 inches above the tower instead of 2 feet, it
probably would have survived.
Doesn't matter, I don't use them anymore.

Dave n4zkf

## great pix.  What was the mast made from??    What OD, what wall thickness
and what yield strength, alloy etc.   I will add it to my  broken /bent mast pix
collection.   The last one I saw was of VE7SV's   contest station.. and the 402CD
was mounted abt 8-10' above the tower.   Huge windstorm.. and mast  folded
at a 90 deg angle.  Removing a bent mast is EXTREMELY DANGEROUS.  In some 
cases, a crane can't be brought in....to safely bring things down.  Even with a crane,
it's  dicey.   The correct mast is a helluva  lot cheaper than replacing ants, rotor's and 
crane costs.   Why spend $20K on ham gear.. then  cheap out on a mast?   The mast is
the most important part of the entire project.   The mast should be the last thing that fails. 

## The freebie  ARRL  mast software  will tell you all you want to know.. and uses the
latest EIA-222-F specs.  Just plug in the OD  of mast.. and wall thickness.. and the yield
strength in ksi.   Then XXX  square foot  for each ant... and also exact height  up the mast
for each ant.  Then enter a wind speed.  The wind speed you enter is a moot point, since the
software  will tell you at exactly what wind speed it breaks at.   What the software WON'T
do, is tell you what happens with an ice load. + wind.  

## BTW.. the local  franchised 'metal supermarkets'... across USA /canada.. all carry 1026
DOM  tubing.  It's all 75 ksi yield strength... and available in any OD.. and  a great  number
of wall thickness's.   They also sell 3 x diff kinds of zinc paint.. like  ZNC, galvcon, etc... in
both pint + gal containers.. and also spay bombs.  Pour the stuff down the inside of the tubing,
with both ends capped off,.. and teeter totter on a single saw horse.. rolling it back and forth.
Then paint outside.   It all has to be prepped 1st.  That's a last resort, if you can't get it hot
 dipped galvanized locally.   Array solutions also sells  quality masts.. like  87 ksi  1026 DOM
but the shipping cost are not cheap.  

## the right mast is still a lot cheaper than  destroyed ant's.  One of these days, somebody is gonna
snap off a heavy mast... and on the way down it's  going to take out phillystran /polygon guy wires,
which have minimal shear strength..and there goes the tower as well.  


Later........  Jim   VE7RF