[ADXA] rotator mast pinning

[J. Setcer]

The rotor is a Ham IV. with a tail bracket on it. The tower was homemade by
a local welder. He welded a mast stub to that plate under my elbow there.
[image: IMG_1021.JPG]

On Sun, Sep 8, 2024 at 4:32 AM Stan Stockton <wa5rtg at gmail.com> wrote:

> I am curious about the picture.  What model of rotator are you standing on
> and how is that pipe that comes out the bottom of the rotator secured to a
> plate below?  I’ve never seen a rotator suspended between two flat plates
> on a tower with mast material above and below the rotator.
>
> Stan, K5GO
>
> On Sep 7, 2024, at 7:45 PM, J. Setcer <j.setcer at gmail.com> wrote:
>
> 
> <IMG_1030.JPG>
>
> Dennis,   Do you mean THAT antenna? I hated & hated that antenna!
> I never did figure out if we even had the elements in the right order.
> Different owner's Manuals had different configs.
>
> But NO. The Mast was not Pinned, just Good & tight. I trusted the rotor
> enough to stand on it.
> - QJ
> ---
>
> On Sat, Sep 7, 2024 at 6:55 PM Dennis Schaefer <dennisw5rz at gmail.com>
> wrote:
>
>> After my comment about pinning the mast, I thought I should research the
>> issue again since I’m getting ready to swap out a rotator.   I have to say
>> right up front that in the last 35 years or so, I have never gone up the
>> tower to correct an aiming error.   With rotator repairs and several
>> antenna change-outs during that time, making  sure the mast clamps were
>> properly tightened every few years did the job.
>>
>> I read lots of comments, many in the old tower talk forum, where the big
>> dogs hung out.  The word most often associated with NOT pinning the mast
>> was “nuisance” or “inconvenience”.  The words most often associated with
>> pinning the mast was “catastrophic failure”.    A reason often given for
>> pinning the mast was “Yaesu said to do it”.
>>
>> I understand that catastrophic failure caused by pinning  is rare and
>> unlikely, but brake wedge failure and bell housing damage were often
>> mentioned.  This would probably only occur with a very large and/or
>> unbalanced antenna.   The problem is that big antennas  exert more torque
>> and are more likely to cause slippage.  Pinning the mast might be
>>  necessary for those really big antennas.  You’re going to spend time and
>> money maintaining a large antenna system anyway.
>>
>> My antennas have usually been relatively small tribanders, except for the
>> Mosley PRO-57, which was a little larger.  My C-3 has been trouble free and
>> slippage free for over 20 years and I don’t expect any problems.  If I had
>> a 30 foot boom, I would anticipate problems, such as more rotator failure,
>> weather damage, sheared mast pin bolts, etc.  That’s one reason I stick
>> with smaller antennas.
>>
>> This article seems sensible:
>> https://ve3vn.blogspot.com/2022/02/hy-gain-rotator-mast-slippage.html
>>
>> I just remembered something - At our club station, we had a KLM KT-34XA,
>> which was a pretty big tribander.  (about a 36 foot boom and very
>> unbalanced).  We found a bunch of ball bearings on the ground from its
>> Ham-4 after some wind.  I don’t remember if the mast was pinned, or just
>> good and tight, but it did not slip, and there was catastrophic damage to
>> the rotator.  Would it have helped if the mast had slipped?  Maybe, maybe
>> not.
>>
>> I’m not trying to change anyone’s mind, or soliciting comments or
>> arguments - it’s like politics, everyone has their minds made up.  By all
>> means, do what you are comfortable with.   I just did this research to
>> refresh my knowledge and wanted to share my thoughts.   I learn a lot from
>> ADXA members and seldom have anything technical to contribute.
>>
>> 73,
>> Dennis/RZ
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