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[TowerTalk] Rotator and Antenna Standards

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Subject: [TowerTalk] Rotator and Antenna Standards
From: (
Date: Mon, 1 Mar 1999 15:18:49 EST
>Question for the MEs out there -- how would you combine wind torque and
>measured inertia/momentum to produce a real number, that could be compared
>with rotating and braking torque specs to determine if a given rotator will
>do the job reliably?
>73, Pete Smith N4ZR

In trying to combine wind forces and starting torque needed to overcome
inertia, it would be relatively easy to look at the combination of the two
based on a set wind velocity (speed and direction) however there is the crux
the problem.  In looking at a wind speed, we are approximating the wind and
the often quoted 70 mph figure is a fastest mile wind which is currently being
phased out as all new wind data is based on 3-second gusts in which 90 mph is
the new base wind speed.  Even your previous 70 mph numbers had to use Gust
Effect factors to obtain wind forces.  So our wind forces which get
approximated as static forces are not static but dynamic.  In addition wind
can fluctuate greatly over a small area as well, in the national building
codes they have two different wind loads, one for an entire structure and
another for individual components of the structure.  All of this really boils
down to the fact that you can add the 'base' wind load torque created and the
required starting torque but I doubt this new number will mean anymore to real
world operation then the current 'K' factor which seems to be causing so many

-Bill King

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