I am not even sure that torque means much. All of the rotator issues that
I have had (broken gears, worn keyways, failed potentiometers, etc)
occured while the station was QRT.
I currently use a small and a medium prop pitch. The small has a 9576:1
gear ratio and the medium has a 7063:1 ratio. It is possible that the
small one has the same or more torque than the medium. Which one is less
likely to break, I would guess the medium. I think you would be happy
switching to prop pitch rotator and Green Heron controller.
John KK9A
To: towertalk@contesting.com
Subject: Re: [TowerTalk] Rotator Choice for Larger Yagi
From: David Gilbert <xdavid@cis-broadband.com>
Date: Tue, 3 May 2016 11:14:23 -0700
In my opinion, and in general, turning/braking torque as a spec makes more
sense than surface area. In theory, with normal winds, surface area of a
perfectly balanced antenna would have little to do with with how strong a
rotator would be required to turn it. Mass and length would be far more
relevant.
However, in my somewhat unique case, balance and mass of the antenna isn't
all that relevant ... but rated torque of the rotator still is. I live on
a hillside that blocks the normal flow of wind, and I get these monster
swirlers that roar down the hillside as the wind is forced to come around
the ridge line. I've measured them at over 100 mph on a clear day and I
watched one literally lift my 16 year old son about two feet off the
ground. When one of those hits my tower straight on the forces on the boom
ADD UP and put incredible torque on the rotator. I have a PST-61D with
stripped gears to prove it, and the total surface area of my antennas
(OB16-3 and OB2-40) is less than 20 sq ft. The gears were stripped while
in a resting state.
I was going to upgrade to a PST-71D or even PST-110D, but WA7NB's litany
of woe with two different PST-110D's (Hall effect pulse detector issues, I
think) has me leaning more toward a prop pitch. The gears on the Smart GE
2500 NS Rotator by Giovannini look totally awesome but it appears to use
an AC motor, and that would involve a permit process I'm not anxious to
pursue.
At the moment I'm still considering what I'm going to do.
73,
Dave AB7E
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