[R-390] Corrector plate PTO's, was Re: Another "Close to Perfect" R-390a

[Tim Shoppa]

> The R-389 PTO is type 70H-1 (not 70H-2  or 70H-12).  It makes FIFTY
turns 
> not 10 turns end to end. It is rumored to have been the most difficult
PTO 
> Collins ever made. I assume that they were all made at Collins, not 
> contracted out.

I just googled for "R-389" and PTO and found Don Reave's pictures
of the internals of a 70H-1. Except for the corrector plate stack
it looks a lot like the innards of my 390A Cosmos PTO's (some
of the parts look to be identical or at least the same series) and
elements of the chassis look very similar too (including those
dessicant packs even!)

Silly questions about corrector plates (my very limited experience
is with Cosmos-style PTO's):

What's the typical "range" of correction? It looks like a little
less than 1/4 of a turn is max (although typical seems to be far less
and obviously
you can't go too far from one correction plate to the other.)

Are the plates "slidable" to the correction, or is each correction plate
machined to provide exactly that correction? If they're slidable it
looks like it'd be tricky to slide one without disturbing others in the
stack... If they're not slidable it would seem that re-linearizing
would require either a machine shop or a large supply of
assorted corrector plates.

Tim.