On Tue, 13 Sep 2005 19:27:20 -0400, Marshall Goldblatt
wrote:

I have a Tailtwister (TX-2) rotor mounted on a Rohn 25 foldover tower.
While the tower itself appears to have survived intact, hurricane
Katrina snapped the mast and destroyed the antennas. I need to fold the
tower over to work in it, and likely leave it folded over for a fairly
extended period. This will leave the top of the tower and the rotor
upside down. Unfortunately, it is still the rainy season here, and the
last time I needed to do this, rain water got into the rotor and settled
in the bell, causing rust and other corrosion damage inside the rotor,
because it is only weather protected when it is upright. I would like
to seal the rotor to prevent this from happening again, but none of the
ideas I've had so far (wrapping it in plastic garbage bags, using duct
tape, using sealing foam) are usable, either because they don't seal
well enough to keep water out or because stuff may get up inside the
rotor where I can't get it out.

So, does anyone have any suggestions?

First off, there are at least two rotor repair vendors whom you should
contact for ideas; Craig's and RotorDoc (I think those are the
names--a web search should yield results).

Secondly, with some experience with HAM type rotors I would suggest
that the two principle entries for moisture are at the cable
attachment point (either a terminal strip or an Amphenol connector,
depending on vintage or whether you modified it), and the space
between the fixed portion of the rotor (the part with the cable
attachment) and the black rotating part.

The cable attachment point will be trickier, but you may be able to
get good results with gobs of plumber's putty. What you want to avoid,
particularly if you have a terminal strip, is glopping it up with
silicone sealant or Coax-Seal. You will rue the day you ever tried
either if you use it on a terminal strip. The spaces around the
attachment into the non-rotating part need to be sealed, too.

You might also have success with plumber's putty at the opening
between the moving and non-moving parts. Just roll it up and stuff it
in.

I would follow that up with some sort of shroud. The garbage bag/duct
tape method you mentioned seems like a really good idea. I would have
been inclined to think it sufficient without any extra caulking. Don't
be concerned about "stuff [that] may get up inside the rotor where I
can't get it out." See below.

As far as Dan's warning about the grease, I think he's right about the
"old-wive's tale." The rotator turns at 1 RPM. Even if the grease did
run out of the races (there are two in the T2X), you can certainly run
the rotator at least a limited amount of time without concern until
you get to it, not to mention that fact that there will be a film of
it that will stay on regardless of position.

What many people ignore is the instruction right in the manual
regarding grease, and it calls for very little. It's not a wheel
bearing. Since you're almost certainly going to want to take it apart
for a cleanup after all of your other repairs are completed, you can
take care of any missing grease (and "stuff") then.

There are two kinds of hams: those who have had bearings on the floor
and those who have never taken apart a HAM style rotor. But, even if
you don't get 'em all back in, you'll be okay. When you talk to one or
the other of the rotor repair guys, order a pack of extra balls.
You'll need 'em sooner or later anyway. Think of the fun you'll have
telling people you ordered extra balls.

Here's a tip: the bearings are held in a plastic carrier. Whatever you
do, when you lift the carrier out, do NOT attempt to straighten the
carrier into any bigger diameter than the race it rests in. In fact,
keep the ends of the carrier overlapped. That is the secret to keeping
the bearings off the floor. It's not foolproof, but it'll certainly
reduce your adventure significantly. I can't tell you how many rotor
invasions I had to perform to learn that.

I hope your Rohn 25 isn't one of the ones that folds over halfway up
with a significant boom to crank it over. Those things are killers. I
had a friend in Oswego, IL, who broke his arm when repairing his after
it went over during the Plainfield tornado. The kit for 45 is MUCH
stronger.

Good luck on all of your recovery.

Rod
K4QG

--
LRod

Master Woodbutcher and seasoned termite

Shamelessly whoring my website since 1999

http://www.woodbutcher.net

Proud participant of rec.woodworking since February, 1997