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

[David Wise]

Caveat: I have linearized one Collins R-390A corrector plate PTO.

I can't remember the range of correction.  There is a very real
limit on rate of change of correction.  If there's a valley, it
has to be wider than the follower, or it will never touch bottom.
The plates slide individually quite well, as each pair is separated
by a thin stationary finger.  A thumbnail is a pretty good tool
for sliding individual plates.  Just thin enough and stiff enough,
and always handy :)

Dave

> -----Original Message-----
> From: r-390-bounces at mailman.qth.net
> [mailto:r-390-bounces at mailman.qth.net]On Behalf Of Tim Shoppa
> Sent: Thursday, March 02, 2006 7:58 AM
> To: r-390 at mailman.qth.net
> Subject: [R-390] Corrector plate PTO's, was Re: Another "Close to
> Perfect"R-390a
> 
> 
> > 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.
> __