Hi Bob and Jim,
There's a whole bunch of videos on Youtube on their typical use, but
these two get to the point pretty quickly with some good close-ups:
https://www.youtube.com/watch?v=4yCxhyTlysw &
https://www.youtube.com/watch?v=v71KGSCjBrQ
Bob - as to your prior question in the earlier email, I would imagine
any decent driveshaft shop could come up with 3 bolt flanges to weld
onto whatever you could drag into their shop and do so concentrically.
In searching, I see that there are also 4 bolt models of flanges and
flex joints. I would think that the 6 bolt versions would provide more
cushion for rotator purposes as there is more rubber between the bolts.
I have a question about the use of one of these devices, though.
Would it be possible or more likely *wise* to allow the weight of a mast
and antennas to come to rest directly on the flex joint, compressing it
(distorting it) between its two flanges? Its primary function in
automotive use is to reduce vibration through the regularly anticipated
twist of a drive shaft, not to be heavily compressed between the
transmission and pumpkin. I wouldn't mind trying one of these flex
joints, but I would hate to have to use a bearing shelf, collar and
bearing to hold the weight of the mast and antennas off of the joint.
73,
Jon Pearl - W4ABC
www.w4abc.com
On 5/4/2016 12:21 AM, Bob K6UJ wrote:
Jim,
Thanks for the good background info on the flex discs for our ant masts.
I used to have Leesons book. Wish I still had it to check out his BMW
flex disc
configuration. I had to chuckle about M2 backing away from the flex
discs. They have
been used on automotive drive shafts for a long time, and as you said
the locktite
for the studs is standard procedure.
Bob
K6UJ
On 5/3/16 8:40 PM, Jim Thomson wrote:
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
_______________________________________________
---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|