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MMD > Archives > March 2009 > 2009.03.11 > 06Prev  Next

Adjusting Valve Travel for Consistent Flow Rate
By Paul Manganaro

Hello John, Thanks for writing.  I posted in 090307 MMDigest saying
a few thousandths may not make a difference in performance but it
will help the life of the restoration because it conserves vacuum.

Yes, I was talking about the fraction of a second it takes for the
valve button to travel from the bottom seat to the top (not the valve
seats leaking).  It is important to find a travel setting in which the
valve operates properly without excess travel that will spend vacuum

I have a lot of information on the page from my web site about valves,
I suggest you read it over.  I explain in text and diagrams how too
little travel will prevent the pneumatic from repeating properly and
too much travel waists vacuum.  This is generally true for single valve
systems and secondary valves.

I work on primary valves in the last part of this page:

As a young man, I was determined to learn how to get every one of my
foot-pumped players to pump as easily as possible.  After a few years,
I had learned so much from speaking with other restorers, and through
the practical experience of restoring dozens of foot pumpers, that I
was able to turn out players that were very easy to pump.

I think my experience with foot-pumped players was a great advantage
in understanding the important aspects of restoration.  If a person is
experienced in restoring electric pianos such as reproducing pianos or
coin pianos, it may be difficult for that person to understand how much
vacuum loss is taking place in various parts of the pneumatic system.

When I was restoring foot pumpers every day, I could tell after a few
simple tests on the bench that the piano was going to pump well.  The
most dramatic real life lesson in setting valve travel was working on
a few early (about 1909) Aeolian foot pumpers in which the valves were
set at 80 thousandths from the factory (sometimes these units used
primary valves but I'm talking about single valves or the secondary
valve settings).

In 1975 I thought it was too presumptuous of me to have known better
than the Aeolian factory and so I left the travel alone.  The piano
used a lot of vacuum and so after that I cut the travel down to
40 thousandths on similar units and they worked great.  Cutting the
valve travel down just a few thousandths in the Ampico for example may
not be as dramatic but it does cut down on the loss of vacuum.

Learning how to work on valves of all kinds and shellacking the
interior wood channels are two ways to start with a solid, air tight
system that will last a long time.   I hope this has been helpful.

Paul Manganaro

(Message sent Wed 11 Mar 2009, 02:47:05 GMT, from time zone GMT-0400.)

Key Words in Subject:  Adjusting, Consistent, Flow, Rate, Travel, Valve

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