I'll add my $0.02 here,
I have a Rohn 25 tower with the flat top adaptor on top. I have a TB-3
thrust bearing on the top plate, and a second one on a modified rotator
plate several feet below the top plate, followed by my rotor, located in the
middle of the top tower sections (this requires notching the Rohn AS-25
shelf to clear the diagonal brace on each side).
The rotor takes the weight of the mast and antennas, and the top bearing
keeps the mast centered, and helps intercept side wind loads.
I leave the mast clamp screws on the middle bearing loose for normal
operation. I plan to tighten them for two reasons only:
1) To hold the bottom of the mast if and when rotor replacement is
necessary
2) To hold the bottom of the mast more securely (in addition to the rotor)
if and when I decide to climb my mast to service the lightning rod/air
terminal, which is out of my reach from the top plate of the tower.
--...MARK_N1LO...--
_______________________________________________
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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