On 1/27/2011 10:17 PM, Rroger (K8RI on TowerTalk) wrote:
I should have gone out to the shop and looked instead of relying on an
My rotator does have the two section base, but the bottom flange is
connected with 4 8mm studs. (Photo 32)
I did not take those out during disassembly as it was not necessary and
those things were tight.
Too bad that end shell doesn't have spaces to double the number of
bolts. A new end cap could be machined out of solid Aluminum alloy of
the proper hardness, but that might be a bit pricey.
As for antenna load, here's what I was turning.
So, I think what I have on that page will most likely be identical to
what you have.
If the bolts/studs are sheared and the bottom plate is in good enough
shape you can use new bolts except for the hole that has been enlarged.
The "thread inserts" can be used. They come under a number of names,
with Heli-coil probably being the oldest name. The steel thread inserts
will be much stronger than the original threaded Aluminum.
The mating surfaces between the base and bottom plate should be clean,
dry, AND flat.
If the rotator is exposed to "salt air" then the points where the joints
are exposed should be painted over to keep out water and salt. A little
corrosion can really weaken the holding ability of this part.
Sorry about the misdirection.
> On 1/27/2011 8:55 PM, Andy GD0TEP wrote:
>> Hi to the group,
>> My PST61 recently failed. It appears that the mighty large rotator has what
>> IMHO is a inherent weakness, this being the way the rotator is bolted to the
>> bottom mounting casting. Mine is only a couple of years old but has had
>> little use, but the four M8 machine screws that hold the two halves of the
>> assembly have sheared off. As a picture is 1,000 words, have a look here:
>> I was wondering if anyone on here has ever taken one of these rotators apart
>> before? I'm currently trying to acquire information on how to dismantle the
>> rotator from Prosistel in Italy, but so far, no joy.
> Rebuilding the old style PST-61 http://www.rogerhalstead.com/Gears.htm
> Looking at the photos should tell you if this PST-61 is close to being
> like yours.
> They may have some differences but so far I've been told the new and old
> housing are similar.
> Externally that PST-61 sure looks different than the one I took apart.
> On the link above photos 25 through 30 give a good look at the side of
> the PST-61 showing the bottom casting bolted to the body. I believe it
> uses 9 M6 Allen Cap screws. The only 4 bolt holes are on the top of
> mine. The base is part of a casting that bolts to the body. The seals
> and bearings should be available at most automotive stores although you
> might have to settle for a single lip instead of double. OTOH I don't
> know what you have available there.
> The new ones have a DC motor that is longer and smaller in diameter than
> the AC motor. The few with the DC motor I've seen were very much like
> the one shown being repaired. The AC motor and be mounted vertically or
> horizontally (left or right). You'll note I used white Lithium grease
> instead of the original gear lube. I understand they have gone to using
> the grease instead of gear lube.
> "It appears" that the top plate which does have the 4 M8 bolt holes
> (Photo 19) has been used as the bottom plate with a casting mounted to
> it, replacing one piece with two. If that is what happened you *might*
> be able to replace the two pieces with the one...IF it will fit the body
> of yours.
>> It's a little worrying that such a mighty rotator relies on four M8 screws,
>> and as each half of the castings have no castellations or other such
>> fixings, the 4 screws have to take ALL of the rotator torque.
> It appears the screws may not have been torqued down, or were soft. A
> grade 5 M8 can hold a lot of force in the shear mode. OTOH the ones
> I've seen with the one part base all use 9 M6 SS Allen Cap screws. Then
> again it's possible they sell/sold a slightly different model over here.
> The positive side is you are a lot closer to France than I am. I found,
> getting parts from the factory took a very long time and that big brass
> worm gear wheel is expensive. (Photo 16)
>> Anyone with some info to hand?
> If I can be of help let me know.
> Roger (K8RI)
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