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MMD > Archives > March 1999 > 1999.03.01 > 08Prev  Next


Pouch On Early Ampico Air Motor Governor
By Craig Brougher

Terry Smythe is wondering about the pouch on the Ampico governor: It
should be made of heavy pouch leather, well sealed with pure silicone
grease, talcumed, and a bleed placed in line with it to the treble end
of the stack (if those nipples are even provided).

But there is another (and better, more direct and more effective) way
to tube up this pouch.  I have never hooked up one to the treble side
of the stack, but instead, to the pump pressure.  When you hook it to
pump pressure, it will always have a pull proportional to the pump.
Since the only time it is needed is when the pump is amplified, anyway,
I see no reason to connect it to the treble stack unless perfect
originality is foremost and there is a nipple provided.  Sometimes
there are no nipples, even though you have that particular governor.

Either crescendo bellows operate the amplifier pneumatic.  As Stoddard
said years ago: "Why have two crescendo bellows when they are joined at
the hip, anyway?"  And if Ampico rolls ever used the bass crescendo to
amplify the pump instead, then you'll catch them by connecting it to
the pump vacuum.

But, you say, "That would cause it to pull at all times, much harder
than it would normally pull."  True.  That's what your spring adjust-
ment is for.  And if you want to see how much difference it makes in
governor speed, do this little test:

After you have it set, run the test roll for tempo and clock it.
Then once you have the tempo perfectly adjusted, pinch off the pouch
tube and run it again.  Take the difference and figure the percentage.
Now, run the tempo test the third time, but this time with one of the
crescendo input pairs open, so the amplifier is closed.  The speed
should be close to the same as it was on normal.  Finally, if you have
problems, connect that same tube over to treble stack and reregulate,
then perform the tests again.  I think you'll find you have the same
differences.

In my presentation on the Ampico system in Charlotte NC, I showed how
the crescendo bellows and the amplifier bellows track.  The closure
rates are (or should be) exactly the same.  As the crescendo starts,
so does the amplifier.  When the crescendo is fully closed, then at
that very instant, so also is the amplifier.  That is why the pouch
on the governor does just as well hooked to the pump, even though the
changes seen in the stack are greater, the governor doesn't see those
fluctuations until a certain threshold is reached.  (You have to have
a certain percentage of force from the pouch before the air motor
responds.)

Besides, the whole thing is very academic, anyway.  Keeping the
trackerbar polished and clean works wonders for trackerbar clamping,
and there is no real way to automatically adjust any governor to sense
the effects of a grungy trackerbar.  It's basically just a gimcrack to
give the piano another talking point for the sales force, I think.

Craig Brougher


(Message sent Mon 1 Mar 1999, 14:31:04 GMT, from time zone GMT-0600.)

Key Words in Subject:  Air, Ampico, Early, Governor, Motor, Pouch

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