The Art of Organ-building: A Comprehensive Historical, Theoretical, and Practical Treatise on the Tonal Appointment and Mechanical Construction of Concert-room, Church, and Chamber by George Ashdown Audsley

Author:George Ashdown Audsley
Language: eng
Format: epub
Publisher: Dover Publications, Inc.
Published: 2013-04-21T04:00:00+00:00

FIG. CCXLIV.

FIG. CCXLV.

From the above description, aided by the accompanying illustration, it is easy to realize that by the simple addition of similar parts in an adequate coupling-bar, and a diagonal disposition of coupling-tubes—after the usual manner indicated in Fig. CCXLV.—both Swell to Great sub and octave couplers can be introduced.

In the upper part of Fig. CCXLIV. is given a Transverse Section of the very efficient wind-chest pneumatic station above alluded to. We have a working model before us as we write, and can, accordingly, vouch for the marvelous sensitiveness and repetition of the appliance. In these respects it is the most satisfactory pneumatic station known to us. It may be described as follows: M is the general chamber, charged with organ-wind at all times while the Organ is being used. O is the diaphragm of the primary pneumatic, and N is the diaphragm of the secondary pneumatic. The former has the valve-stem W attached to it, carrying the disc-valve V in the manner indicated. This valve is a metallic disc of the thickness of an ordinary sheet of paper, or about inch; and the extent of its movement, within the cell formed by a perforated layer of six-sheet Bristol board, placed between the side U of the general chamber and the applied piece T, is also about inch. Accordingly, the cell formed by the perforated cardboard is only about inch: it communicates at top with the interior of the secondary pneumatic, through the duct 6; and at bottom with the valve-throat 7. The diaphragm N carries one end of the valve-stem X, on which are placed the twin disc-valves P and Q, commanding both ends of the valve-throat R, as clearly shown. This valve-throat communicates with the pneumatic channel S, which extends transversely under the compartments or stop-chambers of the associated wind-chest, and into which the ducts from the several pipe pneumatics enter, in the manner previously described in the Chapter on the Pneumatic Ventil Wind-chest. The pneumatic tube 4, from the Great Organ key pallet-box, communicates with the interior of the primary pneumatic, through the duct 8. All the other details of the appliance are so clearly shown as to require no description.

The action of the appliance is extremely simple. In the Section all the movable parts are shown in their relative positions when the corresponding manual key remains untouched. Under such a condition, the interiors of both the primary and secondary pneumatics are in communication with the open air, and the wind-chest pneumatic channel S is charged with the action-wind from the chamber A, the disc-valve P being drawn inward by the pressure of the wind on the inner surface of the diaphragm N; while all communication with the open air is shut off by the tightly closed disc-valve Q, as shown. Now, when the key is depressed, wind is admitted from the Great Organ key valve-box A into the pneumatic tube 4, and thence into the interior of the primary pneumatic. An equilibrium being established on

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