I have a MonstIR turned by a K7NV "small" prop pitch. I don't
know how big your Yagi is, but mine has full size elements
(70 feet long) on a 36 foot boom.
I have been having the beam turn a bit during high winds.
It never occurred to me that the prop pitch could be free
wheeling. I assumed it was either the mast slipping in
the prop pitch clamp or the boom slipping on the mast.
The K7NV has probably the best mast clamp ever made.
Also I have a Slipp-Nott on the boom to mast plate.
Now that I think about it, the free wheeling theory
makes some sense.
This raises the question: how did you determine that
the slipping was due to the rotor gears, as opposed
to the rotor to mast clamp or the mast to boom plate?
Thinking out loud here (a bad habit of mine), should
I leave the rotor control box turned on all the time,
especially on windy days, with the rotor parked at zero
degrees azimuth. AFAIK, the display on the box will
indicate any free wheeling of the prop pitch, but will
do nothing if the mast is slipping. So far, I usually
turn it off when not on the air (or during a 160 meter
contest, hi) and I am assuming it is completely off
and wouldn't record free wheeling. The box is a legacy
Green Heron (still works great after 15 years).
73
Rick N6RK
On 5/22/2020 9:29 AM, Stan Stockton wrote:
I have an extra large prop pitch that has been turning a large 40m Yagi for
13.5 years. Unfortunately the gear reduction on the extra large prop pitch is
only 5830-1 instead of 9576-1 for the small one. I am guessing the small prop
pitch would hold it. At any rate, although it does a fine job of turning the
antenna, and would hold most any antenna you could imagine, the prop pitch has
never been able to hold this antenna in place. I've probably replaced the coax
jumper between the hardline at the top of the tower and the hardline on the
boom a dozen times after big winds.
I know that mounting the prop pitch outside the tower with the proper gears and
chain I could make it hold the antenna. What I would prefer is to install a
brake of some kind that would stop the shaft coming out of the bottom of the
motor to keep it from turning. I would think the torque would be small. I
haven't tried it but want to think I might hold that antenna in place with my
fingers on the shaft coming out the bottom of the motor??
Anyway, the question is this. Does anyone have an idea for an off the shelf product that
could be adapted to stop that shaft when I wanted to "park" the antenna or
after it is rotated with a delay?
Thanks... Stan, K5GO
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