Date: Tue, 18 Nov 2014 02:11:06 +0000 (UTC)
From: John McCormick via TowerTalk <towertalk@contesting.com>
To: "towertalk@contesting.com" <towertalk@contesting.com>
Subject: [TowerTalk] Rotor swap query
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It was bound to happen, although I wasn't expecting it so soon. I experienced a
rotor issue during the Sweepstakes contest last weekend when a visitor was
operating my station in a multi-operator effort. The Ham IV rotor is still
working, but the meter dial is stuck at southwest, even when the beam is
pointed in another direction. A ham buddy who is much more electrically savvy
helped me do some troubleshooting today and we are pretty convinced that the
potentiometer up in the rotor is not working properly. We also discovered that
the previous owner of the control box had removed the fuse that is supposed to
protect the potentiometer and metering circuitry.
The good news: I have a spare Ham IV rotor (purchased for this exact kind of
situation), so I can swap them out an make repairs to the one now up in the
tower. I also have a spare control box (we tried that as well today and it
produced the same southwest reading).
The bad news: I've never swapped out the rotor before and I don't have a gin
pole, something I plan to eventually acquire.
My question: What's the best procedure for swapping out the rotor? Will I be
able to lift up the mast and beam 18 inches and place it on a wooden brace in
the tower, while I make the swap, securing the base of the mast with some ropes
or wires to keep it from moving laterally? Am I foolish to even attempt this
without a gin pole, helping me lift the weight from the ground?
Some other specifics:
+ US Tower TX-455, with a KF7P work platform installed (cranks down to 22 feet,
but I don't have the tilt-over fixture at this point)
+ 5-element yagi (57 pounds)
+ WARC rotatable dipole (about 10 pounds)
+ 10-foot mast, 2-inch diameter (25 pounds)
+ one thrust bearing installed at top of tower
Thanks for any thoughts directly or through the list.
73s, John/N0FCD ( N0FCD@yahoo.com )
## Get the UST MRF....... aka mast raising fixture. I believe it will
work on all the ust towers. Then its safe and a snap..to raise the mast up a
ft to get the
rotor out. I would also temp install a heavy duty clamp around the mast... so
it sits on the top bearing. Then its perfectly safe to swap rotors. If you
do use a
gin pole, it doesn’t have to extend above the top of the tower very high. I
would use a cum-along between top of gin pole and mast..just above the top
bearing.
Either method will work, then its just a case of winching the mast + yagi up 1
foot. Most ust towers have a locking pin to pin the mast..when doing rotor
swaps etc,
so the mast is not rotating..while doing the rotor swap. Make sure the new
rotor is 100% tested good..on the ground.
Jim VE7RF
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