Aeolian-Skinner chest question

[beel m]

I'm ashamed to say that I probably should know the answer, but don't...
What is the purpose of the primaries, since the chest has individual pneumatics?
Thanks to anyone who can clear this up for me. :-)
R, Bill Miller

[Menschenstimme]

This is only a guess on my part - but here goes:

The primaries are for stop control/selection rather than having a 61-note switch. But this may be only for straight stops with no duplexing nor unification. Sorry I am not more technical.

[Guest]

Think about it as a matrix, or a grid. Each note of each stop sits on the point where two perpendicular lines of the grid intersect. In order to play just the particular notes of the particular stops that you want, you have to remove both lines of the grid under that note.

Stop actions effect one axis of the grid, note actions (primaries) effect the other axis. If you turn on 8' Diapason and play F#1, only the F#1 of the diapason plays. In an Æolian-Skinner organ, the signal that effects both axes of the grid is electrical. Also understand that in my description the grid or matrix is just a metaphor for the actual mechanism. There isn't an actual grid inside an Æolian-Skinner chest.

(In a tracker organ, the whole windchest is one big grid and it is purely mechanical.)

So in an Æolian-Skinner organ there will be a wire for every note on the keyboard, and one wire for every stop. In an 8-rank 61-note chest that means the whole thing only needs 69 individual wires to the chest.

In a unit chest, there is no primary or stop action, just a magnet and a note pouch under every pipe. so that 8-rank 61-note chest would take 488 individual wires.

Does that help make sense of it or just confuse it?

I'm ashamed to say that I probably should know the answer, but don't...
What is the purpose of the primaries, since the chest has individual pneumatics?
Thanks to anyone who can clear this up for me. :-)
R, Bill Miller

[pictureroll]

Primaries are for fast repetition of note action.

[Terpodion]

Adam makes good points about "Pitman" windchests being thought of as a matrix. The individual pouches (pneumatics) under each pipe have no electrical connection with the keys in such a chest. The primary is connected to the keys via the "magnets" - which are electro-mechanical valves. These cause larger pneumatics to open in the primary. It is these which connect to the individual pouches via a channel. At the other end of this channel are the individual note pouches - the pneumatics. The pouches collapse when the primary opens, allowing pressurized air to "dump" out of the channel. In between, controling the flow of air in the channel are the pitman, which are controlled by the stop action. When they are open and the stop is on, the channels can dump air. When they are closed and the stop is off, the channel can not dump. Please don't ask exactly how they work, it's .... complicated.

[beel m]

Thanks, guys!
Bill

[pictureroll]

Is this a single stop chest or a multi stop chest?