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Long masts, winches

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Subject: Long masts, winches
From: (rattmann)
Date: Thu, 12 Dec 1996 12:06:01 -0800
About the mast:  Erect the first 30 feet of tower and guy it off.  Put your
gin pole at the top of it. Then, use the pole to help you erect another 30
feet (3 sections) of tower RIGHT NEXT TO THE MAIN TOWER.  Tie the two towers
tightly together with good ropes in several places.  Now move your gin pole
to the top of the temporary tower.  Add one more section to the temporary
tower, so now it is 40 feet high.  Move the gin pole to the 40-foot point.
The top of the gin pole is now 'way above the top of the permanent 30-ft
tower.  You can now tie the gin pole rope to your lifting clamp on the long
mast WELL ABOVE the center of gravity, and lift it safely into position over
the tower.  Lower it into the tower, down to the concrete base where it can
sit.  Then dismantle the temporary tower, and finish building the main tower.

When your top bearing is installed, you can pull the mast up the inside of
the tower.  A long chrome-moly mast is very heavy, so the lifting should not
be done by people.  You should use a winch at this point, and proceed slowly.

With the winch mounted near the base of the tower (waist height), run the
cable up the outside of the tower face to NEAR the top.  Attach a wire-rope
pulley to the tower a couple of feet below the top bearing.  Now run the
wire rope down the inside of the tower, to pick up the mast (do not run the
cable down through the bearing!!).  I recommend a very strong mast clamp
with appropriate lifting-eye.  Set the clamp at about six or eight feet down
from the top of the mast, keeping it well above C.G.  While you climb along
the tower (belted on) to guide the mast and keep it (and the clamp), from
hanging up on tower braces, brackets, etc. the winch operator lifts the mast
slowly and safely. I would use only a hand winch for this operation.  Power
winches can do damage and hurt people in an application like this, where
things tend to get hung-up.  With a hand winch, you are safer!

As the mast nears the tower top, guide the mast-top into the bearing.  Keep
raising until the top is about 4 feet out of the bearing, and then put a
mast clamp above the bearing to hold it in place.  Now you can put on the
first beam and its truss.

You can detatch the lifting cable if you want, and use a come-along-- good
for "local control"-- to raise the mast and beam up high enough to receive
the next antenna, after sliding the clamp down lower on the mast.  Or, you
can continue using the winch to raise the mast if you have a ground person.
I've done it both ways. One of my 140-ft towers has a 27-ft chrome-moly mast
in it, installed as described.

If you insist on a powered winch, you should remote-control it through a
long cable so that you-- on the tower, where the action is-- have
instantaneous control of the switch.  Even brief delays in communication to
another winch operator can bring disastrous results!

73, Glenn K6NA

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