[TowerTalk] Did I do something stupid?

[Russell Nelson]

Thanks for all the information.  You guys have a great community here.
I've gotten a lot of help from two local hams, and I'm CC'ing them on
this message so they'll get a pointer to the TowerTalk FAQ.  If you
want to see pictures of Mr. Bill taking down an 80' ROHN 25G tower
with only one set of permanent guys (plus some temporary rope guys),
they're at http://www.crynwr.com/~nelson/tower/.

K7LXC@aol.com writes:
 > In a message dated 99-02-22 09:23:12 EST, nelson@crynwr.com writes:
 > 
 > > I have a house bracket at about 16'.  It's screwed into three studs
 > >  with 4" lag bolts through about an inch of siding.
 > >  
 > >  No guys.
 > >  
 > >  Typical wind speed gusts to 40 MPH.  I have a 12' beam with 30 4"
 > >  diameter directors on a 1" pole.  It's on a 12" mast (which I've been
 > >  told is too short).
 > >  
 > >  Did I mention that I have no guys?  And no obvious place to run them
 > >  to, since the lot is narrow?
 > 
 >        What is the tower face width? What kind of legs and size? Are the lag
 > bolts simply screwed into the studs? What's the windload of your antenna(s)?

After I sent that message, I grovelled around on the FAQ at
http://www.contesting.com/towertalkfaq.html (thankfully, my question
wasn't in the FAQ :).  Seems like my tower is a ROHN 25G.  Curiously,
however, there are 6 bays per 10' section, not 7 as the ROHN web site
depicts.  Anyway, yes, the lag bolts are simply screwed into the
studs.  I was thinking about running several bolts through the wall to
a plate inside the building so the studs are in compression -- is this
much more advised?

Oh, by the way, the ROHN link on the FAQ is wrong.  It should be
http://www.rohnnet.com/commpro/Commpro.htm.

The windload seems to be (if I've calculated it right) about a square
foot.  It's a 12' x 1" pipe with 4" diameter reflectors made of 1/4"
material.  So, my naive calculation says that end-on the windload is
1/144 square foot (modulo turbulence :), and side-on it's 1 square
foot x 0.67 because it's a pipe plus 33 reflectors at 4" x 1/4" x 2
(because you ought to count both sides of the reflector) x 0.67 fudge
factor because they're circles.

So all told the windload seems to be about a square foot.  Even
missing the upper bracket I'd say that I'm safe enough.  According to
ROHN's specs, in a 70 MPH wind zone, with 44' of unsupported tower,
you can have 6.8 sq ft antenna.

-- 
-russ nelson <rn-sig@crynwr.com>  http://crynwr.com/~nelson
Crynwr supports Open Source(tm) Software| PGPok |   There is good evidence
521 Pleasant Valley Rd. | +1 315 268 1925 voice |   that freedom is the
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