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Re: [TowerTalk] Rotator Choice for Larger Yagi

To: "towertalk@contesting.com" <towertalk@contesting.com>
Subject: Re: [TowerTalk] Rotator Choice for Larger Yagi
From: Máximo EA1DDO_HK1H <ea1ddo@hotmail.com>
Date: Wed, 4 May 2016 12:44:57 +0000
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
Hi,

Prosistel and others use to provide an option called "torsionally  flexible  
jaw coupling".
You can see how it looks, at CN2R: 
http://cn2r.net/cn2r/Photo/Station/Installation/Yagi%20installation%2080/slides/80-160%20rotator.JPG
It is the yellow stuff.

Smart Rotators from Giovannini comes as default, with those absorbers.

73, Maximo


> From: dj7ww@t-online.de
> To: towertalk@contesting.com
> Date: Wed, 4 May 2016 08:57:40 +0200
> Subject: Re: [TowerTalk] Rotator Choice for Larger Yagi
> 
> I used that product:
> 
> http://www.centa.info/?show=products&c=&nr=32
> 
> 73
> Peter, DJ7WW
> 
> 
> 
> 
> -----Original Message-----
> From: TowerTalk [mailto:towertalk-bounces@contesting.com] On Behalf Of Jim
> Thomson
> Sent: Mittwoch, 4. Mai 2016 05:41
> To: towertalk@contesting.com
> Subject: [TowerTalk] Rotator Choice for Larger Yagi
> 
> Date: Tue, 3 May 2016 19:05:25 -0700
> From: Jerry Gardner <jerryw6uv@gmail.com>
> To: Bob K6UJ <k6uj@pacbell.net>
> Cc: towertalk@contesting.com
> Subject: Re: [TowerTalk] Rotator Choice for Larger Yagi
> 
> Interesting, Not being a "car guy" I've never heard of flex discs. Do you
> have any more info, perhaps a few links to websites describing them and how
> they can be used as part of an antenna/rotator system?
> 
> 73,
> Jerry
> 
> ##  The  BMW  flex disc is well documented in leesons book,   physical
> design of yagis...now out of print.  It was a $25 part, available at any 
> BMW dealer,  looks like a giant rubber doughnut...without the hole in the
> middle,
> lol,   and had  4 x threaded studs imbedded into the rubber.... at each end.
> IE:  4  on each end.  The 4 at the front end are offset from the  4 at the
> back end,
> 
> ##  I believe BMW used the rubber flex coupler, in line with the driveshaft
> on their cars.
> It has just enough flex in it, when twisted in either direction, to absorb
> tq. 
> 
> ##  For rotor use, its mounted vertical of course, sandwiched between 2 x al
> plates.
> I think leeson then used a huge chunk of 90 deg angle AL, on both the top
> and bottom
> al plates , bolted.   Then the long ant mas was U bolted to the upper angle
> AL. 
> Then a real short, 1 ft long  piece of pipe /tubing  was U bolted to the
> lower
> angle al.  ( which in turn is bolted to the bottom plate).   Bottom end of
> this 12 inch long
> piece of pipe /tubing was inserted into the rotor in the normal fashion. 
> 
> ##  It worked superb, and provided  just enough isolation, so when yagi is
> at rest, and winds blowing,
> the rubber flex disc absorbed the shock, vibration etc, so the teeth in the
> rotor final gear don't get trashed. 
> IE:  the rubber flex disc absorbed a lot of the gear chatter / backlash.
> The disc will also absorb the initial hit
> of tq, both starting..and stopping.   These days, most rotors have  ramp up
> and ramp down, so that part of it
> is not a big issue. 
> 
> ##  sad part of all this is... M2 in fact did make their version of this
> disc assy, with heavy duty steel plates, and
> the same finish as their m2 oem drive plate assy.  The M2 version used no
> angle al pieces at all,  and the simple 
> sandwich was just bolted to the oem m2 drive plate. Oem m2  mast clamp was
> then bolted to the upper steel plate.
> 
> ##  m2  stopped making the optional rubber doughnut isolation assy. They
> told me, it was cuz  folks...were not doing regular
> maintenance on the assy.   IE: the bolts that held the sandwich assy, would
> work loose.   Also the 8 x threaded  BMW 
> studs would also work loose.   Seems silly to me, since  blue loctite, or
> even red loctite would have solved that issue.
> I pleaded with them at the time I bought the pair of OR-2800  rotors to
> reconsider, and start making it again..but
> to no avail.   Their version was superb. Built like a tank. 
> 
> ##   For automotive applications,  the same 8 x  threaded  BMW studs were
> always installed with blue loctite ! 
> AFAIK, the BMW flex rubber couplings are still readily available.   Yaesu
> offered an optional rubber pad for their
> big rotors, that was installed between the base of their rotor and the
> mating steel triangular rotor plate in the tower.
> The pad does little good,  since it has its isolation at the wrong end of
> the rotor. 
> 
> Jim   VE7RF   
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