I am hoping that maybe some of the Ampico B specialists who read
this list might be willing to answer a couple of questions I have.

After the roll winds onto the take up spool far enough to cause
the pallet valve to turn on the vacuum to the stack, and before the
roll starts playing, I will often get what seems to be a resonant
oscillation in the pump spill value unit which I believe to be at about
four times the pump speed and therefore in sync with the pulses from
the four pump bellows.

It's quite noisy at times, like it's knocking up against a stop.
At other vacuum levels, such as the higher vacuum level that exists
during reroll or when the crescendo raises the vacuum level, the
oscillation doesn't occur.  I can often hear it come and go during soft
play sections with few notes going.  At other times the piano will go
through periods when it doesn't occur at all at any vacuum level.

Possibly the weather may have something to do with it.  Changing the
spill valve spring didn't get rid of it.  Does anybody have any ex-
perience with this phenomenon or know how to deal with it?  It seems
like it would eventually cause excessive wear.

My other question is, about what size and length should the muffler
tubes carrying atmosphere to the wind chest spill valves be?  I think
at least some of the later Ampico B's came out of the factory with
tracker bar size tubing fitted into the larger tubes off the unit spill
valve nipples.

These were then strung out across about 3/4 the width of the stack.
I've also seen some with just the short lengths of the larger tubing
in use.  How is this supposed to be done?  Whether the tubes are sized
down and long or not doesn't seem to affect the playing.  I do wonder
if the lesser air flow I'm getting with the long, sized-down tube runs
may be a factor in the pump spill valve oscillation.

Regards,

Dick Merchant
Carlsbad, NM

 [ Suck on the hose to the pump spill pneumatic; the pneumatic must
 [ be airtight or problems will arise.   -- Robbie