At 05:38 AM 9/15/2006, K7LXC@aol.com wrote:
>
>In a message dated 9/14/2006 5:27:50 P.M. Pacific Daylight Time,
>towertalk-request@contesting.com 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
>about.
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)
Jim,W6RMK
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|