Hi Eric and MMD!  I was skimming the MMD and was halfway through your
post in 030216 and suddenly realized that you had partially addressed
the question I had raised two days earlier in 030214 about the missing
spring in one of my Ampico A crescendo units.

I agree completely with your remarks concerning air tightness of the
crescendo pneumatic (the same is also true of the spring pneumatic to
which it is connected).  I test by joining the two small nipples with
a piece of tracker bar tubing, close the pneumatic fully and then block
the larger nipple with a finger.  Mine take over 5 minutes to open to
the point that the pallet valve begins to activate.  Incidentally, new
pouches and valve leathers were installed everywhere.  The pouches were
sealed with a thin solution of Dow Corning 111 silicone grease as
recommended by Craig Brougher.

My two units behave in exactly the same way.  The "tss tss tss" sound
is the same for both with a frequency of about 2 per second.  Since one
has the small spring, and the other does not it, appears that the spring
makes no difference at all.  So I am back to my original question:
What is the purpose of the spring?  Ampico obviously thought it did
something.

Is it possible that the spring was installed to guard against the pouch
tightening up in very dry conditions which would tend to lift the valve
thus causing the piano to play loudly all the time?  Just a thought.

Regards
John Johns
Ottawa, Canada