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Re: [TowerTalk] Prosistel PST61 question

Subject: Re: [TowerTalk] Prosistel PST61 question
From: "Rroger (K8RI on TowerTalk)" <>
Date: Thu, 27 Jan 2011 22:17:58 -0500
List-post: <">>
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
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)
> 73,
> Andy
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