Hearing about the failure of Bob's Create rotor made me want to mention
something that others might want to think about before they perform
their next rotor replacement ...
I just took down the two original towers that were part of the old WA8ZDF
QTH in central Ohio. They had both been up since 1970. Both used W0MLY
modified prop pitch rotators, 1/2" wall, 2 1/2 OD 6061-T6 aluminum masts.
The 125 foot tower had a 5 element Telrex 20 meter and a 5 element Telrex
15 meter yagi. There have never been any failures of the rotor in any
kind of weather. The antennas are (were) pinned and clamped to the mast,
which in turn is pinned to the output shaft of the rotor with a Grade 8
stainless steel bolt.
After all those years of torque, that rotor pin bolt was looking a bit
fatigued, but it had yet to fail. I think the tower would have rusted
apart before that rotor ever failed ...
The moral of the story is (for me, anyway): prop pitches may be getting
harder to find, and more expensive to maintain, but unless you like to
change rotors in the middle of the contest season, there really isn't any
other way to turn large arrays.
-- Pat
WA8YVR
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