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MMD > Archives > November 1998 > 1998.11.22 > 03Prev  Next

Restoring Valves of 65/88-note Steinway Themodist
By Paul Manganaro

I have restored a few foot-pumped 65/88-note Steinway uprights through
the years.  You will find some of these mechanisms have a double-valve
action.  The primaries are located directly in back of the secondary
valves, unlike most units which have a separate primary chest.  The
only other player I can recall having a similar design was a Behning
(spelling?).  The Aeolian double-valve actions require many hours to
restore but they are worth the effort.

Due to the fact that these are early player mechanisms, check the valve
travel of the secondary valves.  I worked on two of these which had
valve travels set at 80 thousandths inch as the original factory
setting.  I recommend reducing the valve travel.

I do not want to enter into a discussion as to what valve travel is
best, but it is important to note that as a valve leaves its lower seat
it is leaking vacuum to the atmosphere until the valve is fully seated
on the top seat.  (The valve is forced to the top seat when the hole in
the tracker bar is open).  If the valve travel is set too low this will
not allow a closed pneumatic to open quickly enough to fall back to its
position at rest.

In other words: picture a key pneumatic that has just been activated
and is in the closed position.  When the hole in the tracker bar is
then closed, the pneumatic must fill with air in order to fall back to
it's open position.   Air is drawn through the upper seat of the valve,
and so if the valve is set too low, air flow is restricted and
therefore the pneumatic will be slow to fall back to rest.  This will
affect repetition.

Some mechanisms were designed with extremely shallow valve travel.
These settings should be observed and respected.  However I find it
more than acceptable to decrease valve travel, especially in this case
due to the fact that Aeolian learned in time that excessive travel was

As a general rule: I measure the travel of the stack valves before I
disassemble the mechanism.  If the valve travel is approximately 40
thousandths or greater, I reduce the travel to 37 thousandths plus or
minus 2.  I allow for the leather nap to compact.

Depending on the skin I am using I may set the travel a bit lower if
I feel the leather will compress after it has been played heavily.
I feel 33 thousandths is too low; however, I just restored a (late)
Duo-Art grand for someone who requested that I set the travel at
33 thousandths, and I must admit the piano worked very well.

In any case, with rare exception, valve travel in excess of 40 thou-
sandths will not be efficient.  These comments pertain to the stack
pneumatics.  Control pneumatics are not called for as often and also
are larger and so valve travel may be more generous.  Measure the
original travel before restoration.

I hope this has been helpful.  Apart from all the technical information
I hope you enjoy your piano.  My foot-pumper is still the center of my

Paul Manganaro

(Message sent Sun 22 Nov 1998, 16:41:01 GMT, from time zone GMT-0500.)

Key Words in Subject:  65/88-note, Restoring, Steinway, Themodist, Valves

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