Hi Stan,
My small PP moves a bit more back and forth in heavy wind, but does not
drift. I think that is the backlash in the large gear reduction.
Talking to K7NV about this he mentioned the advantage of the smaller PP,
which is what I have.
Here are some "off the top" ideas, I've not seen an off-the-shelf
product but one might exist
Maybe try to modify a motorcycle drum (or maybe disk) brake. Use
standard brake shoes with a HD solenoid to actuate the brake. (would
need power all the time) Although it would be better to have push and
pull motion. One downside is the positive feedback in drum brakes so
"reverse" may be needed to get a release after high "forward" torque.
An easier idea is a band brake, a car drum inside out. Assuming there is
enough shaft to hold a disk (cast iron preferable). It has no positive
feedback so takes more actuating force. Short stroke linear actuators
are available with lots of force, run on 12v or 24v. (a lot on ebay,
check if it has power off load capability).
Here is a possibility,
https://www.coxreels.com/band-brake-heavy-duty_8_28_1423.html
Some googling turned up https://knottbrake.com/categories/band-brakes/
A fair amount of work, but so is climbing the tower a dozen times....
Grant KZ1W
On 5/22/2020 09:29, 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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