Rodgers' Piano Restorations
The Best Piano Rebuilding in the Business
9091 Ox Bow Rd.   North East, PA 16428
814-725-2665 weekday afternoons from 1 pm to 9 pm EST

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How a Player Piano Works

First, we learn about the valve and pneumatic.

Picture #1

The first thing to understand when learning how a player piano works is the action of air pressure.  Look at Picture #1.  You will see that there is a line that is labeled "Pouch."  This picture is a cross section of a player piano valve.  The pouch is actually a round disc of very thin leather which is glued into the valve block.  This pouch acts like a balloon.  When you apply air vacuum to the area above the pouch and normal air pressure beneath, it sucks the pouch into the position shown above. 

Picture #2

In picture #2 you see the position the pouch ends up in when vacuum is underneath the pouch.

Picture #3

Picture #3 is more detailed to show you how the principal explained above takes shape in a player piano.  The shaded areas are areas that are under suction.  The unshaded areas are under normal air pressure.  Suction is supplied to the valve through the channel labeled "Suction."  The bleed (see Pictures #1 and #2) allows this air suction to be continued down under the pouch as well as being above it.  The action of the air causes the pouch to drop down and also causes the valve to be sucked down against a seat that blocks the suction off from the areas above.

Picture #4

In Picture #4 we see what happens when a hole in the player piano roll crosses over one of the signal tubes.  Air is allowed to rush up the tube and under the pouch.  The size of the bleed hole is so much smaller than the size of the signal tube that the suction cannot be maintained underneath the pouch.  This causes the air pressure under the pouch to increase thus pushing the pouch up or inflating it.   The action of the pouch forces the valve body up against the upper seat.   (Called the outside seat.)  With the valve blocking the outside air and also uncovering the lower (or inside) seat the suction is allowed to pass on to the pneumatic.   This causes the pneumatic to be sucked shut. 

The pneumatic is a simple device made up of two identical rectangles of wood.  These two pieces of wood are hinged to each other at one end.   Then, with the pieces held so that they form the shape of a "V" air tight cloth is glued all around their perimeter.  The pneumatic is attached to the action of the piano so that when it is sucked shut the note it is connected to will play.  The loudness of the note will depend on the intensity of the vacuum pressure at the time the valve is activated.

Next:  The Bellows