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[Towertalk] Mast Coupler

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Subject: [Towertalk] Mast Coupler
From: (Jim White)
Date: Wed, 11 Sep 2002 14:34:52 -0400
YES, and it does work.

W1CW built, and we have had installed for almost a decade now, a coupler 
based on the BMW flex disk... I bought ut from the local BMW dealer for 
about 50 bucks - believe the car it is for is a 50005 (that info is in 
Leason's book)... tried to find an equal from a generic source but no 
luck... ended up having to get the mil-spec version :-)

The rubber flex disk used was approx. 1 1/2" "thick" and had metal 
sleeves running through it - 8 I believe...

As my father installed it - it was used with a Create RC5B3, and has 
been in service since at the top of our highest tower.

The doughnut has half its metal sleeves bolted to a plate which is 
attached to the lower half of the mast to rotor clamp... and the other 
four bolts went up to a plate which anchored to the upper half of the 
mast to rotor clamp... the plates have voids on the far side of the 
active or bolted to space so that should it give under start/stop/wind 
stress the bolt head does not hit against the other plate (seem to 
remember the holes were made big enough that a socket could fit through 
them for tightening of the sleeve against the far plate.

The only problems this rotor has suffered are electrical (this is FL) - 
mechanical... note - although the load on it has been small so farm, 
thus far never has a consideration of mebbe this was a bad idea popped up!

Somewhere in my archives I have color photos of the assembly - should I 
ever find them I will scan them on the flatbed and make them available 
via e-mail attachment to those who are interested...Dad did a great job 
on it!

If it weren't 135 foot up in the air I would take a photo of it in place 
for you!


Jim, K4OJ

Dennis Mowers wrote:

> Has anyone built the shock absorbing mast coupler described in Leeson's
> "Physical Design of Yagi Antennas"?
> He describes a BMW "flex disc", used to isolate the drive shaft from the
> transmission.
> My local NAPA auto parts supplier shows nothing in their books for any
> year BMW.
> I will try BMW next.
> Has anyone ever seen one of these things?
> Dennis, K5YA
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