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MMD > Archives > October 2001 > 2001.10.31 > 13Prev  Next


Ampico B Rewind Problems
By Craig Brougher

It is important to get things correct, and while I appreciate
Robbie's comments to clarify things, this particular clarification
is incorrect:

>[ Using a restriction at the top seat of valve "D" makes the system
>[ unbalanced and quite susceptible to the effects of stray leakage
>[ at the pneumatics and at the valve seat.  Better is the separate
>[ #65 and #67 bleeds at the pneumatic nipples, as shown in the
>[ drawings.  Valves A, D and C are ordinary "inside" valves with
>[ a large bleed and no ball check.  -- Robbie

Well, let me put it this way.  There are three valves on the valve
block in the Ampico B drawer.  A and D are the top valves (Reroll and
Repeat, with the black felt covers on them), and the bottom valve is
labeled C (the repeat arming valve), which is the one you will often
find the cardboard on with the small relief hole in it.  D never has
cardboard.  If it does, then someone got them mixed up.

As far as their not having ball bleeds in them, I have seen it both
ways.  Sometimes they do, and sometimes they don't, but usually, the
only one that never has a ball bleed is C.  A and D usually have ball
bleeds.

With those minor exceptions, Robbie is right. :-)

Regarding the "restriction in the line," there are two restrictions.
One is a #67 bleed that slows the shut off of the electrical switch
pneumatic, giving the repeat time to function.  The other is a #65
bleed supplying a bit of pump supply to both pallet #1 and #5 to slow
down the electric motor when the roll has 15 turns left to go.

I don't understand how a restriction might cause an unstable valve,
since neither restriction are in the pouch circuits of any valve.

 [ Sorry, I used a poor expression.  The valve is stable but the
 [ pneumatics it controls aren't.  If only one bleed is used, such
 [ as at the valve seat, then equal suction is applied to both the
 [ reroll pneumatic and to the shutoff pneumatic.  Therefore the
 [ bleed aperture is a compromise, and the one or the other pneumatic
 [ suffers.  -- Robbie

Regarding the paralleling of 5B and 1B with 5T and 1T, this can be
done on Ampico A's without a problem (although it isn't necessary, for
certain reasons that I covered in my seminar at the MBSI convention in
Charlotte), and also as mentioned by Ken Vinen.  However, if you wish,
you can parallel 1B and 1T together in the Ampico B, but do not
parallel the fast crescendos together (as in the model A).  The line
will be doubly bled and the pump pressure is always greater, and will
stop the action of the fast crescendo valve, instead of doubling its
effectiveness.

Just remember, basically, there is no reason to crescendo the treble
and not crescendo the bass, or vice versa, so the crescendos worked
together anyway.  Anytime you crescendo one or the other, and the
brilliant is on, you raise pump pressure to both.  As Charles Stoddard
said early-on, "They are joined at the hip anyway."

So while Ampico rolls looked as though their crescendos were perfectly
separate, in operation they were analogous and simultaneous.  I have
never recorded over 3/4" difference between them at 20," which is
immaterial.

Craig Brougher


(Message sent Wed 31 Oct 2001, 15:25:37 GMT, from time zone GMT-0800.)

Key Words in Subject:  Ampico, B, Problems, Rewind

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