[R-390] Cosmos PTO, spring-loaded linearizing core?

[Cecil Acuff]

Tim and Group,

        I can't tell you exactly how it works because I haven't torn mine 
down that far but I can tell you it does move the core.  First lets be sure 
you are looking at the right inductor...which you probably are.  With the 
covers off you should see the main inductor and two smaller ones on ceramic 
coil forms.  The one furthest from the main inductor is the end point 
inductor.  There should be one a bit closer to the main inductor.  The 
spring is probably hidden up inside the housing part that threads through 
the aluminum main framework of the pto.  You should be able to push the core 
easily I would think because the metal ring that rides the end of the core 
shaft is pretty thin I would think to be formed by the screws only in their 
little area and not the next on either side.  I haven't actually seen that 
part but I can't imagine the screws riding directly on the end of the shaft.

Anyway to cut to the chase what I did to verify function was to drop a 
plastic alignment tool through the hole in the rear end plate into the coil 
form for the that coil.  I marked a ring around the point where it 
intersected the end plate and I ran the pto from end to end and watched the 
movement of the alignment tool through that process.  It moves...mine didn't 
move more than probably 1/8 of an inch total...maybe not that much but it 
moved.  As long as yours is doing that I wouldn't sweat it....

Cecil....
----- Original Message ----- 
From: "Tim Shoppa" <shoppa_r390a at trailing-edge.com>
To: <r-390 at mailman.qth.net>
Sent: Sunday, February 26, 2006 6:52 PM
Subject: Re: [R-390] Cosmos PTO, spring-loaded linearizing core?


> Jim recommended:
>> Fix the wife some chicken soup, clean up the kitchen and get the kids
>> under control first.
>
> OK, made that much progress :-).
>
> But now I have more time to write my real question:
>
> How the heck is the linearization screws/plate/core/inductor supposed
> to work in real life?
>
> "In principle" it's a spring loaded thing such that the core follows
> the 40-some linearizing screws through the rotation.
>
> But this is what I find in my Cosmos:
>
> The linearizing inductor has a core in it.
> The core is on a leadscrew.
> The leadscrew goes through a threaded hole in the metal base of the
>  inductor.
> On the other side of the leadscrew is a plastic nub that, I presume,
>  is supposed to follow the 40-some screws.
>
> What I don't see:
>
> Any way for the nub to move the core in and out of the little linearizing
>  inductor.
>
> There's no spring. Nothing slides.
>
> Maybe, just maybe, the nub compresses/flexes the metal base such that
> the tiny corrections are made. But it doesn't seem likely.
>
> Maybe, just maybe, the pressurized nitrogen in the PTO provides the
> restoring force and the sliding is just the screw wiggling in its
> threads. But that doesn't seem likely either.
>
> Obviously my knowledge of how the linearizing is supposed to work has
> a huge gap in it, because I don't see how the screws move the nub
> or how the nub moves the little core.
>
> Can anyone PLEASE correct my mistaken reasoning here?
>
> Tim.
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