[ Jon Page wrote in 101008 MMDigest:
> What is the consensus on the overall measurement of Duo-Art
> accordion expression pneumatics when fully open?

I am not sure I understand what is wanted since the question really
does not have any bearing on either rebuilding or adjusting the
accordions.  However, if you add up the thickness of each of the five
blocks plus the spacing between them, you come up with 3-5/16 inches.

The difference between fully open and fully closed is 15/16 of an inch.
Applying all the possible combinations of opening of the four
pneumatics results in fifteen different gradations of 1/16 inch each.

 -- Duo-Art Accordions Dimensions --

The Blocks

There are five 3 inch by 3 inch maple separating blocks in each
accordion.  For purposes of identification, call the top one #1, the
bottom one #5.

The top block (no. 1) is 1/4 inch thick.  No. 2, no. 3, and no. 4 are
3/8 inch thick.  No. 5 is 1/2 inch thick.

Blocks 2, 3, 4 are fitted with a 7/32 inch OD X 1-1/4 inch long brass
nipple through their front edges.  Block 5 (bottom) is similarly
fitted with a 5/16 inch OD nipple.

If you face the edge with the nipple, on the left edge there is a maple
piece 1/2 inch wide by 3 inches long.  On no. 1 it is 1/4 inch thick,
on 2 through 4 it is 5/16 inch thick.  Each of these has an adjusting
screw near each end.  On the opposite side there is a similar piece
except that it is 1 1/4 long and centered on the side.  It has only one
adjusting screw.

I find that there is frequently confusion about the spacing and
adjustment of the accordions, and I think the reason for this confusion
may be in part the illustration in the Duo-Art Service Manual.  The
drawing seems to show the spacing between the blocks;  however, if you
look closely, you see the word "Collapse" above the dimensions.  This
is not the distance between the blocks when open but the distance that
that section of the pneumatic should collapse when vacuum is applied.
The distance between the blocks is actually 1/8 inch wider than the
collapse distance.   The following shows the two dimensions for each of
the four pneumatics:

The spacing between the blocks:

  Between no. 1 and no. 2: 3/16 inch
  Between no. 2 and no. 3: 1/4 inch
  Between no. 3 and no. 4: 3/8 inch
  Between no. 4 and no. 5: 5/8 inch

This is the thickness you should make your spacers to insert between
the blocks while recovering.    The amount each closes will be shown
below.

The amount each pneumatic collapses:

  Gradation 1.  Between no. 1 and no. 2: 1/16 inch
  Gradation 2.  Between no. 2 and no. 3: 1/8 inch
  Gradation 4.  Between no. 3 and no. 4: 1/4 inch
  Gradation 8.  Between no. 4 and no. 5: 1/2 inch

These distances should be set carefully by turning the adjusting
screws.

I can furnish more details on the construction of the accordions if
anyone is interested.

Dave Geissinger