Comments from KY3N:
_______________________________________________________________
----------
From: KY3N@aol.com[SMTP:KY3N@aol.com]
Sent: Thursday, September 26, 1996 11:59 PM
To: towertalk@contesting.com
Subject: Ham rotor U bolts
How many of you guys out there have broken the 1/4 ss U bolts on a Ham
series
rotor.? Most of you I bet. What about the mast turning in the clamp ? =
after
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 =
material
is not super strong (its min yield is around 36 Ksi or thereabouts and =
the
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 =
generally
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 =
two
pieces of stainless tend to 'weld' themselves together and you =
experience
extreme resistance to further tightening of the nut. Clamping the =
rotator
plate U-bolts on the Tailtwister rotator is a typical example. The way =
to
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 =
supply
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 =
U-bolts.
The 5/16 inch bolt solution may be a good one for this problem. The =
mast
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 =
causing
a trip up the tower to re-align the antenna direction. I am a bit =
reluctant
to drill a hold thru the mast and bolt it to the rotator top housing as =
this
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
jcarman@capecod.net or PacketCluster Node KB1H
--
FAQ on WWW: http://www.contesting.com/towertalkfaq.html
Submissions: towertalk@contesting.com
Administrative requests: towertalk-REQUEST@contesting.com
Problems: K7LXC@contesting.com
Sponsored by Akorn Access, Inc & KM9P
|