The wind motor uses plenty of suction, alright.  The suction loss of
having ten tracker bar holes open is very little _if_ the pneumatics
have good airtight cloth, _and_ the glue joint with the deck is solid,
and the top valve leather is airtight.

The greatest loss of suction in a tight system is during the time
(milliseconds) when the valve is in motion from the bottom seat to the
top seat.  This is particularly noticeable when fast arpeggios or
marimba chords are being played.

The amount of valve travel is a huge part of the leakage if it is too
wide.  Once the valve reaches the top of its travel it should no longer
lose suction except for the amount through the bleeds under the pouches.
Player piano valves should travel about .035" and no more than .040" in
order to lose less suction and to repeat fast.  A few stacks use less
travel than that but 90% use .035" travel.

Too little valve travel (less than .031") will slow repetition or
attack of the note and too much travel (over .050") will cause too much
air loss, make noise, and greatly lower stack pressure during passages
with many repeated notes operating.

This problem is shown off by the Aeolian plastic valve block stacks
where the valve travel may be as wide as .150".  When rebuilding those
blocks using leather, and actually regulating them to .035" travel,
they can play soft and loud almost as well as a reproducer.

Doug L. Bullock
St. Louis, Missouri
http://thepianoworld.com/