Hello MMD.  I have encountered three Aeolian cross valves in the pedal
power governor of my Half Duo-Art upright.  I would be grateful for
any advice about the correct travel for these valves.

Rather stupidly, I had dismantled two of the valves before I thought to
measure their in-situ travel.  The remaining valve had a travel of 0.7
mm, or 0.028".  This is a good deal less than the 0.040" recommended
for Aeolian valves by Art Reblitz in "Player Piano - Servicing and
Rebuilding".

I'll admit that my measuring technique was rather crude.  I used a
powerful lens and a millimeter scale while blowing gently into a rubber
tube attached to the pouch nipple.  But I don't believe I was 0.012"
in error.  I seem to recall reading somewhere that cross valves were
intended to produce greater air flow than a conventional valve of the
same size, so this may be a reason for the smaller travel -- if I'm
remembering correctly.

When I set up valve travel in actions I've worked on previously, I used
a travelling microscope that was available at my workplace.  But that
isn't readily available now.  I have also used a dial gage, but I have
reservations about that method.

The gages I used had a spring-loaded plunger.  The force exerted by the
plunger would surely have compressed the lower leather facing in the
valve's down state, and reduced the force exerted by the upper facing
when the valve was in the up state.  That's why I switched to the
microscope, using about 7" water positive pressure under each pouch,
since everything else was at atmospheric pressure.  Comments about this
would be welcome, too.

John Phillips in Hobart, Tasmania