[TowerTalk] Swinging gate antenna mounts

[Steve Maki]

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