[TowerTalk] Rotor swap query

[Jim Thomson]

Date: Tue, 18 Nov 2014 02:11:06 +0000 (UTC)
From: John McCormick via TowerTalk <towertalk at contesting.com>
To: "towertalk at contesting.com" <towertalk at 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 at 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