Wind chests

The four wind chests have in all 8+12+30+25=75 note valves (plus two spares in the melody chest, one in the counter melody). A note valve feeds a note channel, and in this channel a secondary set of  'register valves' controls which pipe ranks on the chest are actually blown. In the bass chest every note valve serves 2 pipes, in the accompaniment and counter melody chests 3, and in the melody chest 4.

Each note valve consists of a small 150 Ohm Reisner chest magnet (OSI #5501.32), in turn controlling a bigger pouch valve for air into one note channel. These pouches are from 75 mm diameter in the bass chest, down to 40 mm in the melody chest. This is about the same dimension as the inter note division along the chest, so the note valves as well as one of the pipe ranks had to be staggered a little in order to give enough room for the pouches.

Here is a section through the melody chest showing details for one note. The chest is basically a stack of 4 perforated boards (identifiable from the hatching directions) held together by 36 joining bolts and is easily (?) disassembled removing these. The top and bottom boards each are split into two 16 note sections while the air duct and the register pouch boards extend the total 1550 mm length of the chest.

  In the top board, below each pipe rank, is the set of register pouch valves, controlled in parallel. These work as pneumatic correspondents to sliders. In this drawing the second rank from left is enabled, its control channel is vented. The other three ranks are shown as cut off with their control channels under high (3 kPa) pressure. The outlet tubes protrude upwards and have slightly conical ends to match corresponding foot holes in the pipes.


The following photos show at right the top and bottom panels in place, at left in 'exploded' view. First seen from slightly above. At bottom the note valve pouches interlaced with the chest magnet windings. Middle a silicon tightened cloth forming the register pouches with little pallets, matching the top output copper tubes that accept the pipes. Between the small pallets are the white ends of the output tubes of the note valves.
And from slightly below: Here you see the lower valve tube ends that seat the pallets. At bottom parts of the chest magnets are visible, also part of their wiring.


These pictures reveal redundant features remaining from earlier attempts. One thing is that all pouches have a matching hole in the panels opposing the gluing surface. My original version did not have individual pouches - the whole pouch area was instead covered by big polyethylene sheets. Much simpler, but a bit sloppy to get under control. Also there were no chest magnets, the playing valve pouches were pneumatically remote operated. In the lower panels you can see the plugged holes after the bleed adjust screws, control tube nipples went in the opposite side. Abandoned that for reasons of repetition speed, in favor of electrical distribution.