Concerning the covering of Duo-Art accordion pneumatics with valve
leather instead of pneumatic cloth, I agree that's a good point.
I should have thought it.

However, the extra space between the accordion boards is necessary.
According to the Duo-Art literature, the sections must have motion
Of 1/2", 1/4", 1/8", and 1/16" respectively. If there is no extra
allowance, the covering would be smashed flat when the sections
collapse, certainly not desirable, and the motion would be reduced
by the thickness of the covering.

Each movable board has two "wings" that attach to it outside the
covering. The wings have adjusting screws with flat, hexagonal heads.
When the boards collapse, the screw heads butt against felt pads of
the adjacent board's wings, limiting the closure.

I measured the gap on the original uncovered accordion, and they
limited each closure to approximately 1/8". That's why I added the
1/8" to each space.

After I covered the boards and attached the reworked wings to them;
the screws fairly closely, but not perfectly, set the travel of each
one to the desired amount of travel (1/2" to 1/8") for each section.
I readjusted the three screws of each board to get it as nearly correct
travel as possible.

The finished total height of the completed collapsed accordion measured
2.387". The extended height is 3.329", a difference of .942" of
available motion. The ideal difference should be 1/2" + 1/4" + 1/8" +
1/16" = 15/16", that is, 0.938". That 0.004" difference from optimum
is as close as I could get it repeatably.

Kermit Hobbs