Late Type 5 "Unitype" Pneumatic Stack
in Seeburg Coin Pianos

Late Unitype stack made by Pratt-Read.

(Photograph courtesy of Art Reblitz)

The unmistakable very late one-tier stack from Seeburg Greyhound #166,227, made in 1928. With the tiny unit pneumatics screwed to a common rail, the one-tier stack has been found to date only in very late Greyhound pianos featuring the dog race gambling attachment. The pneumatics face the front of the piano, and each pneumatic has a partition inside to allow the cloth to have two sets of neat folds instead of one wrinkled mess. This stack was made by Pratt-Read, a major maker of player piano actions, as well as one of the largest suppliers of keyboards in the U.S. It was known as a “Unitype” stack, and was sold on the merits of using less wood and weighing less than a usual piano stack. Why Seeburg turned to an outside supplier near the very end of piano production remains unknown, unless the Pratt-Read stacks cost less than building them “in house” for the last few months of piano production. Ordinary 2-tier stacks also fit in the Greyhound cabinet, so the Unitype stack wasn’t used just for its small size. This Greyhound is #166,227, made in 1928.

Unitype stack from Seeburg Greyhound made in late 1928.

(Photograph courtesy of Dana Johnson)

The Unitype stack from Seeburg Greyhound #166,275, also made in late 1928. The “spoons” attached to the tops of the pneumatics lift the piano wippens when the pneumatics collapse. The bleeds are in the capped rail under the mounting rail.

Left side view of complete Unitype valve/pneumatic assembly.

(Photograph courtesy of Bill Kavouras and Art Reblitz)

Left side view of one unit pneumatic before disassembly, from Greyhound #166,275. The “spoon” attached to the top of the pneumatic lifts the piano wippen when the pneumatic collapses. The brass elbow connects to the tracker bar tube. One long screw attaches the unit to the mounting rail.

Left side exploded view of Unitype valve/pneumatic assembly.

(Photograph courtesy of Bill Kavouras and Art Reblitz)

Left side of the unit pneumatic with the outer seal cloth, pneumatic, and valve removed, showing the vacuum valve seat. The operation of this valve and pouch are different from any other pneumatic mechanism, as described in the caption for the Unitype patent drawing.

Left side exploded view of Unitype valve/pneumatic assembly.

(Photograph courtesy of Bill Kavouras and Art Reblitz)

Right side of the unit pneumatic with the pouch retainer, pouch, and valve removed, showing the atmosphere valve seat.

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