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Re: [TowerTalk] Add on 3" mast brake?

To: towertalk@contesting.com
Subject: Re: [TowerTalk] Add on 3" mast brake?
From: Leeson <leeson@earthlink.net>
Reply-to: leeson@earthlink.net
Date: Mon, 14 Nov 2022 20:04:39 -0800
List-post: <mailto:towertalk@contesting.com>
I do two things here on windy ridge: when the power's off I use relays to put a short circuit across the DC motor in the prop pitches and also the TIC Ring (2-motor). A DC motor with shorted terminals acts as a brake all by itself.

Also, I use the bigger BMW rubber coupling ("flexdisc" or "guibo") from the 750il and 850ci, PN 26-22-1-229-065. Kurt made me a lovely adapter plate setup for the prop pitch from my drawings.

A while ago, I did an rough analysis of the rotating forces from wind shear and vortices, and am convinced that even a completely symmetrical antenna will suffer from the resulting buffeting.

To keep the shaft and gear together in various rotators, I use green 600-series Loctite bearing retainer between the gear and the shaft (609 or 638 for really tough situations). That keeps the key from giving way on the shaft and causing play.

Dave

On 11/14/22 7:07 PM, john@kk9a.com wrote:
Yes the larger prop pitch motors have a lower gear ratio but the gear box is
larger and considerably heavier so I assume it is stronger.  I am not sure
if the medium has any more turning torque than the small or how resistance
to back turning compares. Most rotators made for ham radio do not hold up
well for medium to large antennas so you have a tough problem.

I wonder who (if anyone) is working on prop pitch motors these days?

John KK9A




Grant Saviers KZ1W wrote:

<snip> The small PP I had from K7NV showed a surprising amount of backlash,
more than Kurt thought it should have.  He also commented that the small
unit has the highest total gear reduction and thus the most resistance to
turning.  I have a medium PP that needs rebuilt, but am not sure I want to
get into it and where would I get parts?

Grant KZ1W

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