To: rolls@foxtail.com

Hello again -- it's me with the asthmatic grind-organ again.  After more
testing and observing, and cranking and listening, I conclude that:

(1) The bellows, not the chest, are leaky -- but not in any particular
place that I can identify so far.  (I have not yet removed the case).
If I blow back into the bellows through the wind-trunk hose, I have to
exhale fairly fast to keep the reservoir from closing.  Yet no air leaks
can be heard or felt.  It's more like a porosity problem, or perhaps the
internal flap valves to the feeders, though I can feel no wind escaping
through the little intake holes along the center board's edge.

(2) The pipe-voicing problems, and a lot of the wind loss, turn out to be
valves that intermittently seat wrongly while their notes are sounding.
They seem to seal okay when the note is silent, but upon playing, the
relief side of the double-acting valve sometimes goes crooked and fails
to seal.  This leaks enough air to drop the pressure to the smaller
melody pipes and make them sound flat and weak, although the next time
that note sounds it may play better.

These are double-acting valves, much like a player piano stack valve but
upside down and inside out.  When a tracker bar hole opens, the pouch not
only pulls the pressure valve disk off its seat, admitting air to the
pipe -- but also pulls a relief valve dangling under the chest up so it
seals the hole through which the valve stem passes.  Unlike a player action,
there is no cross guide -- the relief disk just hangs under the chest on
the metal valve stem.

So sometimes when a note speaks, the pouch pulls the pressure disk off
its seat not straight up, but one side first.  This tilts the valve stem
and causes the lower (relief valve) disk to contact the bottom of the
chest first on one edge.  As the pouch continues to pull the valve stem
up, the bottom disk's edge sticks on the chest bottom and refuses to
slide over a tiny bit towards the center to let the lower disk seal the
hole.  Hence the loss of pressure.

It appears that some sort of re-design of the valve system is needed:
perhaps add guides, or smaller bottom disks, or replace the bottom disks
with small hard rubber cones that will always self-center and seat
properly?  I'll bet Raffin uses guides...

Mike Knudsen