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MMD > Archives > April 2011 > 2011.04.07 > 04Prev  Next


Ampico A Music Plays Too Slow
By Jim Heyworth

[ Douglas Heckrotte wrote in 110405 MMDigest:

> I'd expect that there is some control associated with the pneumatic
> so that uniform vacuum is applied to the Tempo slide.

Hi Folks,  It's a while since I have had my Ampico A governor apart
but I recall that its vacuum regulator is extremely simple.

In the Ampico A governor, unregulated suction is connected directly to
the inside of the governor pneumatic through a round hole in the _top_
of the pneumatic.  A rounded pad is centered on the _bottom_ board right
under the hole.  When unregulated suction is applied through the hole,
the pad under it on the bottom board is drawn up and would occlude it
if the regulator spring were not holding it back.

The regulator spring on the bottom board opposes this upward pull until
the vacuum level determined by the spring tension is reached inside the
pneumatic and the pad covers the hole cutting down the supply.  Thus
the spring tension regulates the suction inside the governor pneumatic
which is applied under the keyhole of the Tempo slide.

Air enters the governor pneumatic from the air motor through the Tempo-
adjust keyhole causing the governor bottom board to float and maintain
the desired vacuum inside the pneumatic.  This constant now-regulated
vacuum allows a controlled amount of air to be drawn from the air motor
through the open portion of the keyhole which is adjusted by the Tempo
slide.

I hope this isn't too convoluted.

Because your problem is the motor running too slow it is also very
important to check that _every_ connection in and to the air motor
between the suction pump via the governor is tight.  It takes very
little to throw the whole thing off.

I had what seems to be almost exactly your problem last year and all
connections were visibly tight.  But there was one on the unregulated
suction very near the pump that turned out to be a teeny bit leaky.
That's all it took!

Best regards,
Jim Heyworth,
Sechelt, B.C., Canada


(Message sent Thu 7 Apr 2011, 04:44:27 GMT, from time zone GMT-0700.)

Key Words in Subject:  Ampico, Music, Plays, Slow, Too

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