[TowerTalk] Swinging gate antenna mounts

[K8RI]

On 5/29/2013 7:57 PM, Steve Maki wrote:
> On 5/29/2013 3:52 PM, Cqtestk4xs at aol.com wrote:
>
>> Been doing swinging arms for years...
>>
>> Make sure the tower face is set in such a way as to allow the rotation in
>> the direction you want.  You can make a model of this on a piece of
>> acetate
>> over a drawing.  It makes it easier to visualize.
>>
>> Make an effort to place the mount just above a set of guys as  sidemounts
>> really tend to torque a tower.  Ask anyone who has ever  been on a tower
>> with a large beam sidemounted, and then had someone in the shack
>> rotate the
>> beam.  Even without hitting the brake on the rotor it can be
>> uh...exciting.
>
> 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.

73

Roger (K8RI)

>
> -Steve K8LX
>
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