Trinity College, Hartford.  Austin Organ, 1971.

The Austin Universal Windchest

Pneumatics | Key Action | Stop Action | Unit Action
Video Files

Introduction

Instruments made by Austin Organs Inc. of Hartford Connecticut employ a unique type of electro-pneumatic windchest. The Universal Air Chesttm was developed in 1893 by Englishman John T. Austin while he was employed at Farand & Votey, Detroit. Following the success of instruments built to his designs, he founded the Austin Organ Company in 1898. The firm, in the form of its successor, Austin Organs Inc., has continued to build instruments using their patented designs since that time. 76

The term universal is used in describing these chests because the wind in the chest is contained in a single chamber. The mechanism is attached directly to the topboard, and the wind in the "universal" chest is always available to any pipe on the chest through opening its associated valve. There is no need for wind to travel through a channel to reach the pipe. Within the scope of this definition, an electro-mechanical windchest can also be considered a type of "universal" windchest. Austin chests, however, are distinguished from other types by the type of mechanism used in their actions and occasionally by their size.

Austin Universal Chests are usually made sufficiently deep to allow easy access to the action, which is attached to the underside of the top board. In many cases, the chest is made deep enough to allow a technician to stand inside the windchest when it is being used. From the interior, all parts of the action are visible and accessible.

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Pneumatics | Key Action | Stop Action | Unit Action
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Pneumatics

Austin chests use two different types of pneumatic valves in their actions. The two types differ primarily in the shape of the bellows which provides the motion needed to accomplish the action:

Both types of pneumatic valve are made as small units which contain

Animated Austin Bellows DrawingThe diagram to the right illustrates the action in a rectangular bellows used to control the key action. The green shape is the magnet, as seen from the side. When the magnet is activated, it attracts an armature, and that movement opens a small channel, exhausting its wind. This channel leads to a small chamber, and a pouch then collapses, moving a the rod and seal (red in the diagram) and opening a second channel. As the rod and seal open the second channel, its wind is exhausted, and the rectangular bellows (yellow in the diagram) collapses. As in other types of electro-pneumatic action, the channel opened by the magnet is very small so that a strong magnet is not required. The rod and seal - - moved by the pneumatic action of the first pouch - - can then open a larger channel which exhausts enough wind to move the bellows.

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Pneumatics | Key Action | Stop Action | Unit Action
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Key Action

In the Universal Air Chest, each bellows that is controlled by a key from the console has a wooden tracker attached to it. Through the course of its length, small vertical rods are attached to the tracker, and these are in turn attached to padded metal pallets, which control access of organ wind to individual pipes.

Animated Austin Key Action: Stop OnThe way the motion of the tracker opens a pallet is illustrated in the diagram to the left, where both tracker and vertical bar are colored green. The small pale aqua rectangle above the point marked B is the metal stop action bar, shown in cross-section from the end in this view. In the position shown, the stop is on. The pallet is shown in cross section as a red rectangle and is attached to the vertical bar at point B by a metal frame, also shown in red. Although the framework of the pallet crosses the vertical bar at point A in this diagram, the two components are not attached to one another there. As the bellows collapses, and the tracker moves to the right, the vertical rod pivots at point A. This motion pulls open the pallet, and air can exit the chest through the hole in the topboard.

Austin Key Action: Stop OffWhen the stop is turned off, the metal rod has the position shown in the diagram to the right. In this case, as the bellows is exhausted and the tracker is pulled to the right, the vertical bar pivots at point B, the only place where the pallet framework and the vertical bar are attached. No force is exerted on the pallet and its framework, the hole in the topboard is not opened, and the pipe above it cannot sound.

Austin Key Action Photo The photograph to the left is of a corner of the interior of an Austin Universal Chest. 80 In this view, five key action units (marked "A"), each of which consists of a bellows at the top and a magnet and valve below, are visible along one side of the chest. Each of the key bellows has a tracker attached to it (B), and short vertical rods extend upwards from the trackers. At C, along the adjoining wall of the chest, is the first of a row of stop action units.

Austin Pallet PhotoThe photograph to the right shows a slightly different view of a similar set of key action units. In this view,


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Pneumatics | Key Action | Stop Action | Unit Action
Video Files

Stop Action

Animated Austin Stop ActionIn the photograph immediately above, the dark line that runs slightly up and to the right (between the pallet and the vertical rod), is a metal bar that forms part of the stop action of the organ. The motion of the stop action is represented graphically in the diagram to the right. The metal bar, as seen from the side, is illustrated by a light aqua rectangle. The darker shape connects it to a wedge-shaped bellows shown in yellow. As the wind is exhausted from the bellows, the L-shaped connector pivots at the point marked A. The metal rod then pivots at the point marked B, and its lower edge is raised toward the front as the rod rolls along it top edge.

Austin Stop Action Photo. Stop Off.The photograph to the left shows one of these units in the off position. The bellows is inflated, and the point at which the connecting rod pivots is marked A, as in the diagram above.

Austin Stop Action Photo. Stop On.The photograph to the right shows the same stop unit in the on position. The bellows has been exhausted of wind and is collapsed. The metal bar has pivoted at the point marked B, and it is in its raised position. The stop controlled by this unit (an 8' Bourdon) is "on," and motion by any tracker that crosses the stop action would cause a pipe to sound.

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Pneumatics | Key Action | Stop Action | Unit Action
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Unit Action

In a so-called "straight" chest, a separate unit is not required for each pipe. A single unit controls the action for each stop, and each key also controls a unit. If a manual chest has 61 notes and ten stops, 71 different units are built. The trackers for each key action unit run perpendicular to the metal stop rods, and a pallet is located at each point at which a tracker crosses a stop rod. The Austin chest is also suited to unit actions, in which a separate action unit is required for each pipe.

The photographs below show an Austin unit-action pallet and bellows. The pallet is attached directly to the side of a wedge-shaped bellows that moves when wind is exhausted from it. The first photograph shows the bellows inflated and the pallet closed. The second shows the same bellows deflated and the pallet open.

Austin Unit Action: Closed Austin Unit Action: Open

Because trackers and stop rods are not used in the unit action, these units can be placed at any point on a chest. They are often used for pedal stops when large pipes must be placed apart from the rest of a rank. As in other types of unit actions that use electrical switching, control of the specific action-unit by both stop controls and keys is governed by a system of precise electrical switches.

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Pneumatics | Key Action Stop Action | Unit Action
Video Files

Video Files of Austin Action

Two short films of the Austin Electro-Pneumatic Action are available. Both films were made inside a Universal Air Chest and show portions of the action in motion. The films were made in the same chest that was used for the photographs above.
  1. A film of a pallet and stop bar in motion.
  2. A short film of a unit-action bellows and pallet in motion.

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Pneumatics | Key Action | Stop Action | Unit Action
Video Files


© 1998 James H. Cook