[TowerTalk] Yaesu GA-3000 tower absorber

[Michael Tope]

Hi Jim,

Warren, KE6LEA and I built one these flex-disc shock mount for one of the towers 
at the Caltech Amateur Radio Club. We used a Mercedes-Benz Flex Disc (a.k.a. 
Hardy Disc) coupled on one end to the output spindle of an M-Squared Orion 
OR-2800 rotator, and a homebrew steel mast clamp flange on the other. The system 
is used to turn a KLM 4el 40M yagi and KT-34XA both with the heavy duty
boom options (~ 300 lbs of antenna). Our first inspection of the installation
earlier in the summer revealed that several of the grade 8 flange bolts had fallen
out of the steel flange, so we added a set of grade 8 jam nuts to each of the 
6 flange bolts. After getting a considerable workout in Sweepstakes and CQ WW,
I need to go back up the tower sometime soon and inspect all the hardware
to see if anything has loosened. 

You can see pictures of the setup at http://www.its.caltech.edu/~w6ue/antenna-pictures.html

73 de Mike, W4EF.............


----- Original Message ----- 
From: <K7LXC@aol.com>
To: <n7us@arrl.net>; <towertalk@contesting.com>
Sent: Monday, December 11, 2000 9:32 PM
Subject: Re: [TowerTalk] Yaesu GA-3000 tower absorber


> In a message dated 12/11/00 7:33:15 PM Pacific Standard Time, n7us@arrl.net 
> writes:
> 
> > Has anyone used one of these things and, if so, what do you think??  They
> >  are shown on p. 141 of the Fall/Winter AES catalog.  It looks to me to be a
> >  two-plate sandwich with big rubber grommets/bumpers in between.  I'm
> >  assuming it mounts below a rotor to minimize the torque on a tower.
> >  
> >  They aren't cheap (compared to what??) at $120 for the one for the
> >  G1000/G-2800 (I have the latter rotor).  I'm thinking it's good insurance
> >  against wind damage to the tower.  In my case, I'll have a C-31XR above the
> >  tower top and a F-12 MAG 340 toward the top of a 20' chrome-molly mast.  
> The
> >  tower is a US Tower HDX-589MDPL.  (Used to have a TW-33XL 3L WARC antenna 
> on
> >  it too in NM, but the tower was only up 49' there.)
> 
>     Dave Leeson, W6NL, ex-W6QHS, started using BMW parts to absorb rotational 
> shocks a bunch of years ago. One or two companies introduced them but they 
> wouldn't hold together so they fell out of favor. When I was at Hy-Gain, 
> Roger Cox felt that using one would increase rotator capacity by about 25%.
> 
>     I don't know anything about the one you mentioned. 
> 
> Cheers,   Steve    K7LXC
> Tower Tech 
> 
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