Likewise, I use two thrust bearings and unlike others here, I use the thrust
bearings to support all the weight of the antenna system which is
substantial. Probably on the order of 600#, give or take. They maybe crude,
but I think they are far more rugged at supporting weight than most rotors
such as the tail twister and HDR 200s and 300s.
In all the years I've used the ROHN thrust bearings I've never had one
fail.OTOH, prior to the PST61 rotors suffered very short life spans.
Nothing would hold that system including the big Hygain HDR 300s. I use the
plural as I went through two of them in almost as many weeks.
One thing about using two thrust bearins, or even one for that matter. The
mast is clamped in the bearing(s) and rotor. The mast changes length with
temperature. To reduce bending moment the mast should extend below the top
of the tower about as far as it extends above the top. If the mast is
Aluminum it will expand and contract much more than the steel tower and can
put tremendous strain on the top of the rotor, in either, or both pushing
and pulling. With Aluminum masts in Aluminum towers and steel masts in
steel towers the differential should be minimal.
Roger Halstead (K8RI, EN73 & ARRL Life Member)
N833R, World's Oldest Debonair (S# CD-2)
www.rogerhalstead.com
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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