hosted on condor3913
 Mechanical Music Digest  Archives
You Are Not Logged In Login/Get New Account
Please Log In. Accounts are free!
Logged In users are granted additional features including a more current version of the Archives and a simplified process for submitting articles.
Home Archives Calendar Gallery Store Links Info
MMD > Archives > April 2005 > 2005.04.28 > 08Prev  Next

Causes of Air Leaks in Player Action Stack
By John A. Tuttle

Hi All,  Understanding a little bit about the theory of operation
of a player piano helps most people comprehend the problems they are
experiencing with the mechanism.

Leaky stacks are never the result of leaky pouches.  In fact, the
pouches could be removed from the stack and the leakage factor would
be virtually identical to that of a stack that had pouches which were
100% air-tight.  As it applies to the pouches, the only 'escape route'
for the vacuum is the signal tube which leads to the trackerbar.  And,
as long as the trackerbar is covered with a music roll, that escape
route is effectively closed.

Stack leakage is most often caused by leaky valves.  More often than
not, there is also a valve stem involved.  Most simply put, what
usually happens is that the air seal between the intake valve facing
and the valve stem deteriorates due primarily to corrosion.  In units
that do not have a valve facing with a hole in the middle (and a valve
stem passing through that hole), valve leakage is normally the result
of a poorly seating intake valve facing.  Also, in some cases it is
found that the intake valve seats are loose and leaking.  I refer to
this type of leakage as "static" leakage because it is present when
no notes are being played.

"Active" leakage involves a host of other components, including the
exhaust valve facing and exhaust valve seat, the air passage from the
valve chamber to the striker pneumatic, the seal between the tier and
the striker pneumatic, the wooden parts of the striker pneumatic, and
lastly the pneumatic cloth.

Getting back to the pouches, if they are leaking, the indication will
be that notes are reluctant to activate or they will not activate at
all when a perforation opens a note hole in the trackerbar.  This
happens because the atmosphere, which enters the pouch well via the
open hole in the trackerbar and inflates the pouch, is leaking into
the vacuum chamber (above the pouch), too fast for the pouch to develop
enough energy to 'push' the valve off its seat.

John A Tuttle
Brick, New Jersey, USA

(Message sent Thu 28 Apr 2005, 11:03:24 GMT, from time zone GMT-0400.)

Key Words in Subject:  Action, Air, Causes, Leaks, Player, Stack

Home    Archives    Calendar    Gallery    Store    Links    Info   

Enter text below to search the MMD Website with Google

CONTACT FORM: Click HERE to write to the editor, or to post a message about Mechanical Musical Instruments to the MMD

Unless otherwise noted, all opinions are those of the individual authors and may not represent those of the editors. Compilation copyright 1995-2023 by Jody Kravitz.

Please read our Republication Policy before copying information from or creating links to this web site.

Click HERE to contact the webmaster regarding problems with the website.

Please support publication of the MMD by donating online

Pay via PayPal

No PayPal account required

Translate This Page