In a recent digest, Lee Walker cited page 142 of my book, "Player Piano
Servicing and Rebuilding," as saying the clearance between the pouches
and valves in a Standard action should be 1/8". That isn't what I
meant to say.
In discussing the secondary valve buttons, the text says "... usually
the buttons protrude 1/8" beyond the rim of the valve board, with the
valves held against the inside seats." The accompanying illustration
6-133 shows a 6" straightedge resting on the valve buttons, with the
valves being held against the inside seats, and with an 1/8" gap
between the straightedge and the rim of the secondary valve board.
That means the buttons will hang down about 1/8" into the valve wells
when the pouch board is reattached to the valve board. After restoring
many Standard player actions in the 1970s, I found this to provide
adequate gap between pouches and buttons.
However, in "Questions and Answers from Standard Player Monthly," the
answer to question 179 is "By holding the valve stem with a pair of
pliers, turn button in or out in the direction it should go. By
placing straight edge in front of button and by pulling forward it
should pass the straight edge 1/16th of an inch. This will give you
distance of 1/16th inch between pouch and button when pouch board is
placed on." (Reprints of this and other Standard player action
literature are available from John Tuttle.)
If the Standard factory is saying that the secondary buttons should
stick out beyond the rim 1/16", which provides 1/16" clearance, then my
description has them sticking out too far and touching the pouches.
This would be true in a piano where the pouch wells are only 1/8" deep,
including the thickness of the pouch leather in the bottom of the well.
My memory is that the pouch wells are sometimes deeper. If the pouches
have about 3/16" dish across the whole diameter of the buttons, then my
1/8" overhang would hold true. If the wells are only 1/8" deep, then
the 1/16" overhang should work.
I'm interested to read more feedback in MMDigest regarding pouch well
depth in a variety of 3-tier and 2-tier Standard and Autopiano actions.
If the wells are much deeper than necessary, and if the pouches are
dished all the way to the bottom of the wells, the pouches will have
less power than if they have only moderate dish. For most primary
pouches, I like to have a little less than 1/16" clearance to the valve
In general, it's better to have a little too much clearance than not
enough. In time, and with a lot of playing, the pouch will form itself
around the bottom of the button, creating a little "donut" shape bulge
in the leather. That donut of just a little extra leather will shrink
or expand with humidity changes, allowing the valve to seat properly
even when the pouch gets a little tighter.
I'm speaking only of pouch leather here, as that is what Standard and
Autopiano used in most or all of their actions. With any material, the
more a player piano is played, the better it will continue to work. We
also have the advantage today that most of our homes are air-conditioned
(i.e., dehumidified) in areas of the country that have very high humidity
in the summer so our restored player pianos have fewer problems than
many did in the 1920s with more extreme seasonal humidity changes.
On an associated subject, one original Standard or Autopiano manual
recommends 1/32" primary valve travel and 1/16" secondary travel.
I always thought 1/16" travel was too much for any player piano valve,
so we set the secondaries to about .040" to .042". With too little
travel, if the leather expands when the humidity rises the flow of air
in and out of the pneumatic will be constricted, causing the pneumatics
to play and repeat poorly. With too much travel, the valves will be a
little noisier but the pneumatics will still work positively.