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MMD > Archives > December 1997 > 1997.12.11 > 09Prev  Next


Neoprene Valve Facings Collect Dust
By John A. Tuttle

Hi All,  This article was stimulated by the recent postings regarding
increasing the valve gap to improve performance.

I had occasion to revisit a customers player piano in Cape May, NJ a
few days ago for a general tuning and minor repair.  Upon arriving, I
ran the test roll and noticed a number of leaking exhaust valves.

Having rebuilt the valves myself, I was somewhat annoyed at the leakage
and began investigating (at my expense).  It didn't take long to find
the problem.  It was two-fold.

First, I noticed a build-up of dust on the exhaust face.  When I took
my small brush to clean it off, I noticed something strange.  As I
pulled the brush away, I saw the dust particles 'race' back to the
facing.  It was rather dry in the home and so I surmised that the
Neoprene facing had a static charge.  Then I tried 'puffing' air (from
my mouth) onto the facing.  That seemed to neutralize the charge and
clean off the facing.  However, I realized before starting that blowing
into the valve chamber in such a manner would only serve to blow the
dust deeper into the valve chamber.  So, in essence, it was a lose-lose
situation.

Secondly, I noticed that the valve gap seemed a little shallow.  So I
removed the valve cap (the player action is similar to a Gulbransen in
that regard) and reset the gap to about .042 in.  (actually I simply
removed a .010 punching that was under the exhaust facing which had
been used for reducing the gap to .032, which is where I used to set
valves some 10 years ago.)

Once everything was back together, the valve worked flawlessly but it
left me wondering.  If I had set all the valves to .042 in, thus
providing more room for the air to rush back into the note bellow,
would it reduce the amount of dust buildup on the exhaust face?  And
would increasing the gap actually change the velocity of the valve and
thereby create a better seal?

To be sure, I have long since stopped using Neoprene (sponge) valve
facings and I will be less surprised by the buildup I always see on the
plastic Aeolian block valves, especially in homes where there is a
smoker.

Just thought some of you might find this info interesting.  And if my
questions can be answered, I would certainly be interested, even if
just for information's sake.  Although I can't realistically check my
theory, if the valve gap is increased by 20+%, the incoming air will
not have to travel as fast and might reduce the amount of static
charge?

Musically,
John A. Tuttle


Key Words in Subject:  Collect, Dust, Facings, Neoprene, Valve

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