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[TowerTalk] Flex coupling for rotators

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Subject: [TowerTalk] Flex coupling for rotators
From: VE6JY Don Moman" < (VE6JY Don Moman)
Date: Tue, 3 Jul 2001 16:18:49 +0100
I always make a point of having the mast rest a 1/2 inch above the "floor"
of the rotor.  It is easily held there by the locking collar on the bearing
and a backup U clamp or something even heavier.  At least with any rotor
that the side clamp comes off, it is an easy matter just to slide the rotor
to the side and out.

K7LXC wrote:
>     I'm not sure what kind of antenna load you're carrying but if it's a
> or similar and your windspeeds are also moderate, that'll work.
> I've never seen pinning a mast with a thru-bolt work for very long. With a
> moderate antenna torque load (say something with a boom 24' or longer) and
> moderate windspeeds (70 MPH), the bolt will eventually elongate the bolt
> holes and then the bolt breaks. There's just too much slop in this
> to be useful.

They certainly can elongate and cause problems, esp with aluminum masts.
However I use the pinning technique quite a bit as it is simple and cheap
and the first thing that came to mind. It can work fine - example:
I have a driveshaft for the log periodic - 60+ boom length, weighs over 1000
pounds - that has been pinned for years (over 10) without any problems or
even loosening.  Nothing fancy - 2 3/8 OD pipe (2" Sked 40 steel) with an
insert of 2" solid rod going about 6" into each side. 2 1/2" grade 5 bolts
thru each side, drilled 90 deg to each other.

Other techniques to help keep the "sloppies" out of the bolt holes:
.... use a tap and thread the hole.
.... use roll pins / spring pins instead of bolts.

73 Don

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