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Re: [TowerTalk] ma550 question - Yikes!

Subject: Re: [TowerTalk] ma550 question - Yikes!
From: Jim Lux <>
Date: Fri, 15 Sep 2006 06:50:03 -0700
List-post: <>
At 05:38 AM 9/15/2006, wrote:
>In a message dated 9/14/2006 5:27:50 P.M. Pacific Daylight Time,
> writes:
> >  I wouldn't want to depend on the "automatic lowering" system  to
>protect me and/or my neighbors either, but ... it HAS been  done...with
>a building permit.  I know a ham that has an MA850 with a  MonstIR on
>top.  His neighbor's property is probably < 50 feet from  his tower
>base.  He was required to install an "automatic lowering"  system that
>would guarantee that it was nested any time the windspeed was  > (I
>think) 25mph.  I was shocked when I heard that the city ok'd  this, but
>it has been done :-)
>         How did it ever get calc'ed  out for a 225# antenna?!? I'm shocked
>too. It must not be a stock MA850 or  there's something going on we 
>don't know

If he has an "auto lowering system" set at 25 mi/hr, then the bending 
loads are going to be fairly small.

Then, it's just a matter of the dead lift of the antenna mass, and 
for most non-guyed towers I've seen the numbers for (which isn't a 
huge number, granted), the antenna mass isn't the limiting factor. 
(for a guyed tower, where buckling is the failure mode, this isn't 
necessarily the case)

Cylinders are pretty strong in compression; Heck, an aluminum beer 
can (<0.001" wall) will support 225 pounds vertical load (until it buckles)



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