On 5/29/2013 9:01 PM, K8RI wrote:
Which is why I always chuckle when someone, apparently thinking of their
tower as some sort of rigid rod (sorry about that :-)), agonizes over
their rotator brake.
Now mine never did that. You could just feel it in the tower when it
started or stopped and it was a big antenna...as far as UHF, TV antennas
go<:-))
On a 45G the gate will likely be 2 feet long. If that's the case,
multiply the weight of the antenna by two for the off center leverage in
foot pounds. How fast it decelerates, or accelerates will give the force
in Gs. So you then multiply the leverage in ft lbs by Gs to get the
twisting force on the tower. Ever get an antenna rotating on a shaft
and then try to stop the rotation by gripping the shaft, or just hold
one against the wind. Be careful, you can lose a lot of hide doing this
experiment.
My point was that towers that are tall relative to their face width, as
many guyed ham towers are, act like rotational springs, thereby saving
rotator brake wedges to a large degree. The towers seem to handle it OK,
though some recent analysis has sounded the warning bells.
-Steve K8LX
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