Hello all,
Since this thread has turned into quality of the gearbox as much as the
pot replacement, thought I would share my experiences.
Almost exactly 10 years ago, I purchased a PST-71D for use with my full
size 4 ele 40 meter yagi. With 88 sq ft of capacity, thought this
should work fine. And, it did... at first.
The first problem I found during a mock up of the top ten feet of the
tower. The 3 foot piece of mast I installed wobbled terribly when I
rotated it. Turns out that the flat plate at the top of the output
shaft was NOT welded squarely to the shaft. It was off of 90 degrees by
4 degrees.
With the blessing of Jay, WX0B, (warranty) I machined this plate down to
where it was square with the shaft as it should be. ( Most of my
working life, I was involved with R&D engineering and design, so do this
was not a big deal for me.)
About 5 years ago, the pot failed, and as most of you now know, it's a
pain to replace since it's accessed thru the bottom of the gearbox.
Knowing that a massively heavy gearbox at 190 feet is nothing you really
want to deal with, we let it go and just visually pointed the antenna,
as it still turn fine. This antenna was part of a 2 antenna stack and
spent most of it's time on EU anyway.
Fast forward to last February.
When we attempted to turn the antenna to JA (by flashlight in the dark)
nothing happened. When the cold weather passed, we were able to pull it
down and replace it with a prop pitch gearbox. My first thought was
water had gotten into the motor end and seized up the bearings, since
the cover plate was a crappy design and never did fit quite right.
Because of this, I had added extra electrical tape around and around
this joint. The motor was not the problem.
When I took the cover plate off the bottom of the gearbox in order to
access the pot, I found the pot was heavily encrusted with 'stuff'.
Looked like it was a part off a sunken ship. Nasty. It was obvious
that this was caused by water.
The only way water could have gotten to this low point in the assembly
was to pass thru the gearbox.
Long story shorter, I poured water out of the gearbox. When I finally
got it apart, the tapered bearing at the far end of the worm gear was so
corroded and frozen, the bearing cage fell apart during disassembley.
The bearing on the motor end of the worm gear was intact but frozen in
place. Both of the larger bearings on either side of the wheel gear,
would move, but only with considerable effort. And, was only rough,
grinding movement at best.
This whole assembly could not have been any more corroded if it had been
stored in a bucket of water. Encrustations everywhere!
My gut feeling is that the seals never, ever actually contacted the
shaft. And, this is on top of the fact that there is a large disc on
top of the assembly, that acted as a water shield, or 'umbrella'.
As bad as it is, I'm reasonably sure I can fix it. /Assuming/, I can
finish getting it apart (it is still soaking in my parts washer...) *I
can repair the corroded, pitted main shaft with repair sleeves and
replace the bearings.
Bottom line for me is that I will never buy, or recommend this brand of
rotator again.
The manufacturing quality was pitiful. But, when I think about it hard,
I can not think of anything made in Italy that has been as advertised,
except for the food and *Gina Lollobrigida.* I think of high speed
rail
http://dutchreview.com/news/fyra-the-dutch-high-speed-rail-debacle/ and
Fiats.
Of course, you are welcome to your own opinions.
*
--
73 de Steve, NR4M
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