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MMD > Archives > January 1998 > 1998.01.18 > 09Prev  Next

Help for Standard Action Valves
By Roger Waring

Hi group -- I have a problem with a restored Autopiano stack and would
appreciate some advice. The problem is this: it is hard to pump.

Some background information:

It is a Standard deck, nothing fancy.  I have replaced all valve
facings and tested the valves individually, prior to reassembly with
the pouch board.  They seem all right: they sit level and have correct
travel.  I tested the assembled chest with a household vacuum with half
of the suction supply hole uncovered to simulate light pumping.
Response by all pneumatics was snappy.  All 88 lifted together without
problem.  I did not have the upper action (the head) assembled at this

I have recovered all motors, bellows and pumps and they all perform
satisfactorily.  I have replaced all gaskets.  The cutoff motor and
associated bypass/retard-accelerate controls work fine.  So does the
wind motor,  although I have one question about the governor.  The
tracker bar is OK and its associated tubing is clear of any
obstructions.  There are now no leaks in the system that I can detect.

This is what happens:

If I pump lightly or moderately the roll runs but does not play.  If
I set to rewind I get very fast rewind: lots of power with very light
pumping.  This suggests to me that the lower action is okay.  If I set
tempo to 0 and play/rewind to play I get some resistance, but not
great.  I think I hear air movement inside the chest.  If I set
play/rewind to play and pump very hard things happen.  The valves
suddenly seat and I get resistance.  I can then ease off a little and
the roll will play, but not sweetly -- the wind motor seems to run a
little irregularly.

If I ease off too much I lose it altogether.  This suggests to me one
of two possible causes: either my valve leather (calf) is not good
enough to seal without strong persuasion, or the valves are being held
off their inside seats a little.  I have set the valve buttons to clear
the edge of the chest by 1/16".  Maybe it is something else that I do
not have the experience to recognise.

Question:  Can someone suggest a simple test for the latter possible
cause?  What do members think is the most likely cause?  Should I
re-leather?  If so, with what?

The wind motor governor is of the type that has a horizontal, front
mounted, externally adjustable spring hooked up to an internal,
medium-sized  pneumatic.  It has no screw-in externally adjustable

The wind motor speeds up/slows down a little with hard/soft pumping.
I checked the inside mechanism and everything seemed in order.  Maybe
the cause is simply due to my main problem but any advice is welcome.

Thank you to all who took the trouble to read this far!

Yours frustratedly

Roger Waring

(Message sent Mon 19 Jan 1998, 06:39:16 GMT, from time zone GMT-0800.)

Key Words in Subject:  Action, Help, Standard, Valves

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