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MMD > Archives > May 2013 > 2013.05.26 > 06Prev  Next


Player Piano Valve Design Parameters
By Timothy L'Amoureux

Why is there no lag in a longer tube than a short tube when triggering
a pneumatic valve?  My guess is that it's an "unbalancing" act.  You
can topple a clown perched on a wire with either a one-foot stick or
a 30-foot stick and get the same simultaneous result; he just needs to
be de-stabilized to fall.  Same with a pneumatic valve.

I think the confusion comes from thinking about the issue in this way:

If one takes a one foot-long-tube, large enough in diameter to fit a
single marble, and another thirty-foot-tube of the same diameter and
places a marble in the end of each tube and then lets them both go at
the same time. The marble in the one foot-long-tube will reach the end
much sooner than that of the thirty-foot-long tube.

This is where the confusion comes into play.

Place the two tubes on level ground and fill each tube completely full
of marbles from left to right.  Now push one more marble into the right
end of each tube.  The left end will release one marble at the same
rate of speed and velocity regardless of length of the tube.

This is a simple visual illustration of what the tracker tubing is
performing invisibly, pneumatically to simultaneously trigger the
pouch, regardless of tubing length.

The tracker tube is under vacuum supplied by the tiny bleed and needs
only to be unbalanced to trigger the pouch regardless of the tubing
length. (of course this has to be a reasonable length piece of tubing
I would think you might have a problem if your tracker tubing was, say,
a mile long).

I have always found that the shorter the tracker tubing, the more
reliable the operation.  But in theory, the length of the tubing should
not matter.

Did I get this right?  Pretty close?  It was fun writing, anyway!

Tim L'Amoureux


(Message sent Sun 26 May 2013, 21:32:33 GMT, from time zone GMT-0400.)

Key Words in Subject:  Design, Parameters, Piano, Player, Valve

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