In a message dated 7/14/2007 8:46:00 A.M. Pacific Daylight Time,
towertalk-request@contesting.com writes:
> The tower will still move but it is not twisting as in winding up to a
point
of possible fracture. The commercial site over on the next hill had 140' of
45G with the base buried in concrete and a bunch of sticks on it. After
about 15 years the bottom section fractured. The tower didnt collapse but
they replaced it with 55G on the same pad but drilled it for a pin.
There is practically no movement of a tower at the base. Any torquing of
the tower due to wind forces is pretty much absorbed by the upper part of
the tower - it doesn't really twist the whole structure uniformly. A typical
ham tower with a big 40M antenna will definitely move at the top but not at
the
bottom.
I'm surmising that the aforementioned failure was due to lack of leg
moisture drainage resulting in a freezing split leg and subsequent failure.
Of course big loads and big wind torque forces are pretty much
eliminated with six-way guying using a star bracket.
Cheers,
Steve K7LXC
TOWER TECH
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