Jon,
I really like this "steel and rubber sandwich" :-) design right on the
Orion mast plate.
Your reasoning makes sense to me.
Plus, looking at the picture, it just looks right, hihi.
It would be simpler to fabricate this arrangement too.
Bob
K6UJ
On 5/4/16 1:25 PM, Jon Pearl - W4ABC wrote:
Thanks for posting that, Bob! I was just gonna say...
I've been reading and researching different couplers as I'm making my
way down through part of today's emails and I started to do some
re-thinking on the subject. I started to ask myself if there might be
some advantage to moving a flexible coupler down, directly onto the
top of the Orion mast plate rather than placing it up above the
rotator's mast clamp where it would be forced to deal with more axial
forces. From my own reasoning, (and I may be wrong) viewing this
picture http://www.its.caltech.edu/~w6ue/KT/OR-2800-2.jpg leads me to
draw some conclusions:
* No three fingered drive shaft ends need to be incorporated into the
design to attach to the flexible coupler.
* Axial loads are shifted downward, closer to the rotator.
* Full mast and antenna weight can be applied to the flexible coupler
as its distortion is limited to a small amount of sag - held in
check by the OR-2800's OEM mast plate. It's essentially a steel and
rubber sandwich.
The issue of loose nuts and bolts is an interesting one as you're
attempting to tighten the pair over a compressible rubber donut. Why
don't they come loose and fall off of automobiles? It may still come
down to the presence of annoying axial loads as Grant has eluded to.
73,
Jon Pearl - W4ABC
www.w4abc.com
On 5/4/2016 1:25 PM, Bob K6UJ wrote:
Grant,
From what I read their main function is to dampen the torsional shock
loads.
Here is what Mercedes Benz says:
"The flexible discs serve two functions on the vehicle. Primarily to
absorb excessive torsional shock applied to the drive shaft under
hard acceleration and deceleration. They also isolate the drive
shaft from vibration while still transferring power from the
transmission to the differential. "
Jon, W4ABC brought up an interesting consideration. Unless they are
isolated from the
axial load involving the mast and antennas the disc will be
supporting the load. Will they do their
dampening job when they are supporting a load ? Doesn't sound like
they would.
In my case I will be supporting 99% of the load from the thrust
bearing above. So probably not a concern.
Lastly found this interesting post from the Tower Talk archives.
Seems the bolts coming loose is a
common issue.
73,
Bob
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
athttp://www.its.caltech.edu/~w6ue/antenna-pictures.html
<http://www.its.caltech.edu/%7Ew6ue/antenna-pictures.html>
73 de Mike, W4EF.............
Bob
K6UJ
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