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[TowerTalk] Stuck Rotator

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Subject: [TowerTalk] Stuck Rotator
From: "K8RI on TowerTalk" <>
Date: Tue, 25 Jul 2006 16:23:08 -0400
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Several times I have mentioned the rotator sticking over the past few years. 
The previous winter (04) I discovered the TB-3 thrust bearing had worn to 
the point that the upper race was setting on the lower casting and 
preventing the whole works from turning.  Loosening the centering bolts in 
the bearings allowed the mast to turn and things appeared to be fine... 
until late this past winter (05).  It started sticking again, but the 
weather was not favorable for tower work for a while and this has been a 
very busy Spring and early Summer.

Sunday I managed to get a couple of go-fers for help and 
tackled the antennas and rotator.  (There really wasn't a lot for the 
go-fers to do except lower the rotator, go-fer forgotten tools, and act as 
safety observers which is reason enough)

I loosened the rotator to mast clamp and then using a come-along, raised the 
mast.  I then tightened the thrust bearing bolts to hold the mast and took 
out the rotator.

The next step was to go back up on top and cut as much of the pigtails loose 
from the mast as I could reach. Then it was back to the come-along to lower 
the mast.  I managed to lower it *almost* enough to get at the 6-meter beam 
before running out of loose pigtails.  Unfortunately that was where I ran 
out of steam. At my age I'm not quite as durable as I was just 5 or 6 years 

So we anchored things in place. Next time I hope to get the 6-meter beam to 
the top of the tower and the 144/440 beams removed.

Taking that big rotator apart (PST-61) can be messy if you don't have a big 
bucket under it.  We did and it was still messy, but the bucket kept the 
mess to a minimum.  Other than the lube looked like black paint the interior 
looked pretty good at first glance. First glance also told me that is 
rotator certainly has no relation to the spur gear rotators most of us are 
familiar with.  That thing is *massive* inside.  Not only are the output 
worm gear and worm gear wheel massive, the end bearings are taper roller 
bearings that bear a close resemblance to wheel bearings.  It is rated to 
support almost one ton and has about 16,500 inch pounds of torque, but I 

The bottom bearing, although dirty appeared to be in good shape. However 
getting to the top bearing revealed a gooey, grainy, black mess.  The top 
seal had failed and that bearing had almost disintegrated.  Much of the 
retainer had dissolved and broken into parts.  The only thing holding the 
rollers in some places were the inner and outer races.  It was these pieces 
of retainer getting under the rollers, or the rollers sliding out of place 
that was causing the rotator to bind up.

The distributor (Jay) has been very helpful in getting this thing apart. 
I've now reached the point where it's time for a hydraulic press to get the 
shaft out of the gear and the top bearing off.  IF I don't brake anything 
the only parts needed will be the two bearings and oil seals.

That big bronze gear appears to have been cast onto the steel inner support. 
As the bronze gear is thicker than the support it means supporting the steel 
flange rather than the brass when pressing out the shaft.  The whole works 
has been soaking in PB blaster for the last two days.

If any one is interested AND has a high speed internet connection there are 
three LARGE high resolution photos of the insides at  I emphasized the large as they are 
about 750K each.  Maybe I'll get a chance to replace them with 800 X 600 
images which are only about 100K each.

BTW my address has changed and the only accepted sender to this one is the 
reflector.  Direct replies/e-mails should go to an address on my home page. 
Sorry about the round about method, but the old address here was getting 
more spam every day.

Roger Halstead (K8RI and ARRL 40 year Life Member)
N833R - World's oldest Debonair CD-2 


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