Hi Dave,
It's not the torsional twist on the mast. I was up the tower when the wind
was blowing and saw the small movement back and forth on the rotator plate
itself. Since this noise started after replacing the clamshell mast clamp with
the more rigid K7NV tubular mast clamp, I'm beginning to wonder if the slight
movement in the rotator was always there due to gear play and maybe the sound
is due to an ever so slight misalignment of the rotator off center causing the
gears to make a kind of binding sound when they start to move. Perhaps the old
clamshell clamp had more flex so as not to apply as much twisting pressure on
the gears. It's just a thought.
73, Les
-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces@contesting.com] On Behalf Of David
Gilbert
Sent: Wednesday, May 26, 2021 10:28 PM
To: towertalk@contesting.com
Subject: Re: [TowerTalk] Mast slippage
Are you certain that what you are seeing isn't simply torsional twisting of the
mast itself? I have a 20 foot 2 inch diameter chromoly mast with
5 feet inside the tower, an Optibeam OB16-3 about 3 feet above the tower and an
OB2-40 about 10 feet above that ... all driven by a PST-71D with a homebrew
mast clamp similar to the one by K7NV. Granted that your 3 inch mast would
have less twist than my 2 inch mast, but under strong swirling winds I can see
the antennas swing back and forth and I know that it's just the mast twisting
because the upper OB2-40 twists a bit further than the lower OB16-3.
I used to have a PST-61D up there turning the same antennas and the winds did
indeed strip some teeth on the toothed gear, but that involved swings about +/-
20 degrees and was pretty obvious. I don't think there is enough slop in the
PST-17D gears to explain what you are seeing, and I'm pretty certain that there
is no clutch in the rotator since none is needed.
For what it may be worth ...
73,
Dave AB7E
On 5/26/2021 6:06 PM, Les Brown wrote:
> Hi guys,
> Last year, I reported mast slippage with my PST-71D clamshell mast clamp.
> Well, after replacing the clamshell clamp with the nice K7NV 3 inch
> mast clamp, no more mast slippage. However, the weak link now seems to
> be the rotator itself. In a strong wind, I hear a creaking sound as
> the rotator slips a couple of degrees one way then the other. Is this
> actually turning the gears all the way back to the worm gear or is
> there a clutch pad in the PST-71D that could be slipping?
> I have 2 Optibeams up top for a total of 44 square feet of wind
> load and the PST-71D is rated at 80 square feet.
> 73, Les VE3NNT
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