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Old September 14th 05, 12:27 AM
Marshall Goldblatt
 
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Default How to weather-seal an upside down Tailtwister rotor?

Hello all,

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?

73, Marshall - W4EMB



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Old September 14th 05, 12:51 AM
Dan/W4NTI
 
Posts: n/a
Default


"Marshall Goldblatt" wrote in message
...
Hello all,

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?

73, Marshall - W4EMB



Maybe ... get some axle grease, or RTV sealant would be better, perhaps.
Both should peal off reasonable well.

One other thing I am concerned with tho. I always heard that the rotar
must be kept in a vertical position or the grease would drain out of the
bearings? Wives tale ??? I don't know. But I always keep mine vertical
when stored.

Dan/W4NTI


  #3   Report Post  
Old September 14th 05, 02:25 AM
Bob Bob
 
Posts: n/a
Default

One of the tricks I learnt early on with RTV sealant in medical
ultrasound water tanks is if you wet the surfaces with water and a
detergent wetting agent the sealant wont actually adhere to the
prewetted surface. Kind of handy if you wanted to force the sealant into
a clearance slot and remove it later.

Or was it oil? Damn I cant remember! I know kerosene is used to pre the
surface for better adhesion...

How about paper/masking tape over the gaps and spraying with that gluggy
sealant you use on sink drains?

Probably not very useful thoughts, sorry!

Cheers Bob W5/VK2YQA

Dan/W4NTI wrote:


Maybe ... get some axle grease, or RTV sealant would be better, perhaps.
Both should peal off reasonable well.

One other thing I am concerned with tho. I always heard that the rotar
must be kept in a vertical position or the grease would drain out of the
bearings? Wives tale ??? I don't know. But I always keep mine vertical
when stored.

Dan/W4NTI


  #4   Report Post  
Old September 14th 05, 02:40 AM
Marshall Goldblatt
 
Posts: n/a
Default

Dan/W4NTI wrote:
"Marshall Goldblatt" wrote in message
...

Hello all,

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?

73, Marshall - W4EMB




Maybe ... get some axle grease, or RTV sealant would be better, perhaps.
Both should peal off reasonable well.

One other thing I am concerned with tho. I always heard that the rotar
must be kept in a vertical position or the grease would drain out of the
bearings? Wives tale ??? I don't know. But I always keep mine vertical
when stored.


Don't know about that, but there's no way to keep the rotor vertical
when lowering a foldover tower... In any case, it's been folded over
(for long periods) many times, and I've never noticed a bearing problem.
  #5   Report Post  
Old September 14th 05, 02:44 AM
LRod
 
Posts: n/a
Default

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


  #6   Report Post  
Old September 16th 05, 06:04 AM
Brian Kelly
 
Posts: n/a
Default


Marshall Goldblatt wrote:
Dan/W4NTI wrote:
"Marshall Goldblatt" wrote in message
...

Hello all,

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.


Fold the tower then cut the rotator loose and store it indoors . . . ??


w3rv


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?

73, Marshall - W4EMB




Maybe ... get some axle grease, or RTV sealant would be better, perhaps.
Both should peal off reasonable well.

One other thing I am concerned with tho. I always heard that the rotar
must be kept in a vertical position or the grease would drain out of the
bearings? Wives tale ??? I don't know. But I always keep mine vertical
when stored.


Don't know about that, but there's no way to keep the rotor vertical
when lowering a foldover tower... In any case, it's been folded over
(for long periods) many times, and I've never noticed a bearing problem.


  #7   Report Post  
Old September 16th 05, 03:59 PM
John Ferrell
 
Posts: n/a
Default

I am not sure I understand the question. I think you have the rotator
upside down on the tower at the moment. If it went through some
weather, it is probably full of water now. The way I would handle the
problem is to remove the rotator from the mount and hang it on the
tower (clothes hanger wire) right side up. I would hang it there for a
few days to drain & dry out. When it comes time to reinstall the
antennas, test the rotator for proper operation. Chances are that it
will be OK. If you seal it tight, the moisture will be sealed in.
These things are intended to be able to breathe!

If removing/replacing the rotator is a major hassle, I would either
send it to one of the maintenance guys or put up a new one & sell the
old one on ebay WITH the explanation. There are lots of us who have
setups that are easy to change.

If the rotator must be left in the inverted position outside for an
extended time I would wrap it in black landscape plastic and duct tape
to prevent more water from entering while leaving the bottom of the
plastic open to dry out.

On Tue, 13 Sep 2005 20:25:25 -0500, Bob Bob wrote:

One of the tricks I learnt early on with RTV sealant in medical
ultrasound water tanks is if you wet the surfaces with water and a
detergent wetting agent the sealant wont actually adhere to the
prewetted surface. Kind of handy if you wanted to force the sealant into
a clearance slot and remove it later.

Or was it oil? Damn I cant remember! I know kerosene is used to pre the
surface for better adhesion...

How about paper/masking tape over the gaps and spraying with that gluggy
sealant you use on sink drains?

Probably not very useful thoughts, sorry!

Cheers Bob W5/VK2YQA

Dan/W4NTI wrote:


Maybe ... get some axle grease, or RTV sealant would be better, perhaps.
Both should peal off reasonable well.

One other thing I am concerned with tho. I always heard that the rotar
must be kept in a vertical position or the grease would drain out of the
bearings? Wives tale ??? I don't know. But I always keep mine vertical
when stored.

Dan/W4NTI



  #8   Report Post  
Old September 16th 05, 04:41 PM
Ted Goldblatt
 
Posts: n/a
Default

John Ferrell wrote:

I am not sure I understand the question. I think you have the rotator
upside down on the tower at the moment. If it went through some
weather, it is probably full of water now. The way I would handle the
problem is to remove the rotator from the mount and hang it on the
tower (clothes hanger wire) right side up. I would hang it there for a
few days to drain & dry out. When it comes time to reinstall the
antennas, test the rotator for proper operation. Chances are that it
will be OK. If you seal it tight, the moisture will be sealed in.
These things are intended to be able to breathe!


The tower is currently up (the mast broke above the rotor, so all the
antennas are dangling by their feedlines, but the tower itself is OK)
and the rotor is in its normal upright position. It will be upside down
when the tower is folded over to work on. As far as I know, the rotor
is fine right now.

If removing/replacing the rotator is a major hassle, I would either
send it to one of the maintenance guys or put up a new one & sell the
old one on ebay WITH the explanation. There are lots of us who have
setups that are easy to change.


Don't understand this. Yes, removing/replacing the rotor is a hassle,
largely because it has to be done with the unit upside down, and
standing at the top of a ladder. But that isn't the issue here - in
fact, there is no obvious reason to remove the rotor at all, since it
seems intact. Just remove the stub of the broken mast from the thrust
bearing and put a new one in. The issue is that while that is done, and
the new antennas are mounted, and new (or repaired) feedlines are run,
and all the antennas are tuned, the tower will need to be folded over,
with the rotor mounted, and these steps will almost certainly take
several days. Because of availability of helpers reasons, this will
likely have to be on weekends, meaning the tower will be folded (and the
rotor inverted) for a period of at least 1 to 2 weeks.

If the rotator must be left in the inverted position outside for an
extended time I would wrap it in black landscape plastic and duct tape
to prevent more water from entering while leaving the bottom of the
plastic open to dry out.


I have done this in the past, but because of the way the rotor is
mounted on the Rohn tower, it isn't possible to seal it very well this
way - I was looking for suggestions for better ways of weatherproofing
it for this period.

Marshall

  #9   Report Post  
Old September 16th 05, 05:18 PM
Ted Goldblatt
 
Posts: n/a
Default

LRod wrote:

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).


Have used both over the years (at least one and perhaps both on this
particular rotor :-)). I don't believe that either had specific
suggestions for this problem.

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 unit has a terminal strip, but this was "remoted" via a short cable
the last time one of the rotor repair vendors overhauled it, and the
point that the cable exits was heavily sealed. (This was done because
the terminal strip is blocked by the Rohn rotor mounting plate.) The
space between the fixed and rotating parts is the one of concern.

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'd have some concern about some of the putty getting into the bell of
the rotor, where it could cause problems. I'm currently thinking of
using tape (perhaps just masking tape) to cover the opening, and then
covering this with sealing foam or something else. The tape would be to
prevent any of the sealer from entering the bell.

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.


Just garbage bags and duct tape isn't really sufficient (or hasn't been
in the past) because the way the rotor is mounted on the Rohn (seems
to?) preclude wrapping it well without gaps that let rain in.

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.


Haven't ever had (noticeable?) problems with loss of grease.

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.


Actually, no plans to take it apart (hence the concern about "stuff"
getting in). It was overhauled after tower damage _last_ year (not
directly hurricane related, but...). As far as I know, there are no
current problems with the rotor, so if at all possible, I had planned on
leaving it mounted, and just replacing the mast and other thing above.

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.


Well aware of bearing on the floor :-)...

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.


It indeed _is_ a half-way up fold-over. No other style works in the
location (well, at one time in the distant past, I had a crank down,
fold over at the base tower, but current versions of such either won't
fit the space or won't fit the budget...) Have had it and folded it
over many times for many years without problems (lost it in hurricane
Andrew, but no problems for 10 years before or after that). However,
have lost the hinge section a couple of times in the last few years -
once because a wind gust spun it sideways while it was being cranked up,
and once because the boom got caught in a guy without our noticing while
it was being cranked up. I'm a lot more concerned (and careful) about
it now than in earlier years, but (for the above reasons) don't expect
to do anything about it if it can be avoided. We've avoided injury by
keeping well clear while it is going up and down, and (trying to)
control rotation by using guide ropes well to the side and out of the
path. The 45 _is_ much stronger, but it would be difficult to fit, and
would require replacing the entire tower, which is effort and expense
that isn't viable right now.

Good luck on all of your recovery.


Thanks!

Marshall
  #10   Report Post  
Old September 17th 05, 02:28 PM
John Ferrell
 
Posts: n/a
Default

Now I understand!
I this case I would get some of the soft rope like window putty from
the hardware store to seal up the rotator while it was vulnerable. I
have not bought any for years, I assume it is still available. Play
Dough does not work well, it either shrinks and falls out or hardens.

On Fri, 16 Sep 2005 11:41:56 -0400, Ted Goldblatt
wrote:



I have done this in the past, but because of the way the rotor is
mounted on the Rohn tower, it isn't possible to seal it very well this
way - I was looking for suggestions for better ways of weatherproofing
it for this period.

Marshall




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