Make sure it all fits. I could have gone with 3" moly masts but then my thrust
bearings, rotors, boom to mast plates, etc would all have to be changed to
accommodate the larger mast. Your installation may require the 3" mast if you
are going above the top of the tower by 15'. The 2" moly mast weighs about 180
lbs if I remember right. (22' long x 2" OD). With a 10' gin pole you can grab
it just above the center of gravity and I usually pull it up with a tractor.
At the top you may have to give it a little lift to put it in the thrust
bearing at the top of the tower. Depends on mast length and where above the
center of gravity you grab the mast.
I have pulled them up through the tower (tilted up the first two sections with
the mast laying inside it) and installed them from the outside of the
completed tower, which was easier than pulling the mast up through the tower.
Be sure to run the load numbers. An antenna mounted up a mast 15' exerts a lot
more force on the mast at the top of the tower. Depending on the tower, the
next weak link might not be the mast but the top section of tower itself.
On my installation I put the top yagi in place, with a foot or two of the mast
sticking out of the tower. Then I jacked the mast up with a come-a-long and
installed the rotor to hold it in place (rotor is 10' or so inside the tower).
Then placed the lower yagi in place. I have done this with ground crew and by
my lonesome. Have to really think it out when you do it by yourself to
minimize the trips up the tower.
It takes a lot of equipment, shackles, come-a-longs, rope, pulleys, gin-pole,
snatch blocks, etc. I bought all that stuff and only use it about once a
decade.
Earl
N8SS
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