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[TowerTalk] How to raise mast?

To: <towertalk@contesting.com>
Subject: [TowerTalk] How to raise mast?
From: djl@andlev.com (Dan Levin)
Date: Mon, 09 Jul 2001 16:02:56 -0700 (PST)
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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