Ok, next issue in my tower project is raising the
mast and installing the antennas (I plan to install
the tower, a 72' Trylon, with a crane). For those
who are curious, my cable with stand-off's idea for a
safety system has been replaced with a more
traditional cable + trolley system, since the cable
is the same price and the trolley turns out not to be
too expensive.
But back to the question at hand. Suppose that you
had a 72' tower, and you wanted to install a 24'
chrome-moly mast (~18 feet sticking out) and three
antennas. How would you do it?
Seems to me that there are three obvious approaches:
1) Use the crane to do it all. Upsides: fast.
Downsides: the antennas have to be ready when the
tower goes up, someone has to ride the crane to bolt
on the antennas, the crane has to be taller (~90'
reach instead of ~50' reach since it now has to reach
to top of the mast, not just above the center of
gravity of the tower), expensive (additional crane
time, bigger crane), not reproducible for maintence.
2) Pre-install the mast in the tower, raise the whole
thing with the crane, then install steps on the mast
and climb the mast to install the antennas using a
rope and pulley to raise them. Upsides: cheaper,
reproducible for maintenence, antennas go on
whenever. Downsides: someone has to climb the mast
and work while perched on it (that someone would be
me :-).
3) Use two thrust bearings or similar, install the
mast in the tower with ~3' sticking out pre-raising
of the tower. Once the tower is up, climb the tower,
install the top antenna, winch the mast up a few
feet, install the next antenna, winch the mast up a
few feet, install the next antenna, etc. Upsides:
All of those of #2 above, plus no climbing of the
spindly 2" mast. Downsides: Mechanical issues of
keeping the mast vertical while installing the
antennas (before it is seated in the rotor at the
end).
Thoughts - suggestions?
Thanks!
***dan, K6IF
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