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For Henry Cook -- The easiest way I can suggest for you to remake
accordion pneumatics for a Duo-Art is to buy a set of spacers from
Player Piano company. They only cost a few dollars and will give
you practically all the information you need.
Just cut squares of hard wood slightly larger than the spacers and
after drilling each to take nipples, cover them with thin leather
so each of the spacers is progressively thinner than the previous one,
that is, each of the compartments will be smaller (thinner) than the
previous one. Before you seal the final side, the spacers can be
removed from the pneumatics.
You should also get a copy of the 1927 Duo-Art service manual. You
can most likely also get that from player piano company. It has
illustrations of the pneumatics if you are not sure what they are
supposed to look like. Be sure to seal the leather!