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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