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Ham rotor U bolts

To: <>
Subject: Ham rotor U bolts
From: (R. Jan Carman)
Date: Fri, 27 Sep 1996 17:22:55 -0400
Comments from KY3N:


Sent:   Thursday, September 26, 1996 11:59 PM
Subject:        Ham rotor U bolts

How many of you guys out there have broken  the 1/4 ss U bolts on a Ham
rotor.?  Most of you I bet. What about the mast turning in the clamp ? =
every wind storm I have a gob repositioning 5 or 6 yagi ants...

<snip remainder>


Your 5/16 inch U-bolt idea is a good one.  I have another suggestion you
should use for any stainless steel hardware that must be torqued down
hard.  Most stainless hardware you will find on rotators, antennas and
related equipment is 316 stainless (or it should be if its not).  This =
is not super strong (its min yield is around 36 Ksi or thereabouts and =
material can not be strengthened by heat treating, like the chrome-molly
steels can) but it is very resistant to corrosion, which is why it is =
used for outdoor use, particularly if you are very close to salt water =
as is
my station.

One of the characteristics of 316 stainless steel is that it galls =
easily.  This
means that when two pieces of the material are rubbed together under
high pressure, such as a nut being torqued down tightly on a bolt, the =
pieces of stainless tend to 'weld' themselves together and you =
extreme resistance to further tightening of the nut.  Clamping the =
plate U-bolts on the Tailtwister rotator is a typical example.  The way =
greatly reduce the galling problem is to coat the threads with a an
anti-seize compound prior to tightening the nuts.  The material I use is
Permatex Anti-Seize Lubricant.  This stuff comes in a 1 oz tube which is
convenient for top-of-tower use.  Just coat the u-bolt threads prior to=20
putting the nut on, and you will be able to torque the nuts down much
harder than without use of the compound.  It doesn't totally prevent the
galling probem, but goes a long way to helping you tighten the nuts much
harder.  You can get the Permatex Anti-Seize Lubricant at any auto =
store for about $2.50 a tube.

I would recommend use of this compound on any stainless steel hardware, =
particularly if you are using it to hold aluminum parts together such as =
antennas.  Aluminum tends to corrode rapidly in the presence of =
stainless steel producing aluminum oxide which is a white powder.  The =
anti-sieze compound helps to reduce this corrosion process.

Incidentally, I have not been able to totally eliminate the 'mast =
twisting in
the T2X rotator' problem, even with the anti-seize compound on the =
The 5/16 inch bolt solution may be a good one for this problem.  The =
I am using on my big tower is about 18 feet long, and supports a 205CA
Hy-Gain 20M monobander and a large, 7-element 6M yagi.  When we
get high winds here on Cape Cod (Hurricane Edouard is a good recent
example) the mast almost always twists in the rotator top housing =
a trip up the tower to re-align the antenna direction.  I am a bit =
to drill a hold thru the mast and bolt it to the rotator top housing as =
may cause pre-mature rotator failure.  I have never had a T2X last more
than 3 years here anyway before needing rebuilding.

73 de Jan, K5MA
West Falmouth, MA or PacketCluster Node KB1H

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