(Photograph courtesy of Dana Johnson.)

Aluminum frame rotary box pump in National piano #7524. The chain sprocket on the front side drives the worm gear clutch sprocket above it (located on the "keybed" area shelf of the piano). The large diameter rubber hose goes from the pump inlet to the pneumatic stack, and provides a vacuum source for the entire player system. The horizontal shaft (at photograph top), with a chain sprocket at its left end, is used to synchronize the tune indicator selector wheel with the rotational position of the revolver magazine. The belt pulley used with this pump is made of wood, with a die-cast center hub to securely clamp it to the pump crankshaft.

(Photograph courtesy of Dana Johnson.)

Front view of aluminum frame rotary box pump from National piano #7823. The hollow cast aluminum box framework is probably the most outstanding feature of this rotary box pump. The exterior framework is a single aluminum casting, hollowed out to provide an air passageway that connects each of the four bellows with the pump inlet pipe. The bellows are fastened to the frame by six wood screws, making it easy to remove a troublesome unit and repair it and/or the internal inlet flap valves. On the movable leaf of each of the four bellows is a long leather strip of valve leather that covers a row of holes bored through the board, which acts as an exhaust valve to expel air trapped within the bellows when pushed into the closed position.

On the front and back side of the pump framework is a horizontal cast aluminum strut that supports a bronze crankshaft bearing, with both struts working together to hold the crankshaft centered within the surrounding aluminum framework. The crankshaft has a single throw, on which is a bearing housing with four protruding flanges. Fastened onto each of the flanges, using two cap-screws, is a short length of rubberized canvas belting, which essentially serves as a flexible connecting rod between the crankshaft and the individual bellows.

(Photograph courtesy of Dana Johnson.)

Rear view of aluminum frame rotary box pump from National piano #7823. The most prominent thing visible here is the 15" outside diameter wooden belt pulley. At its center is a die-cast hub with a setscrew to securely clamp the hub to the crankshaft. Curiously, on the forward edge of the hub there appears to be a groove suitable for use as another, but tiny, belt pulley. It is currently unknown whether, or not, National ever made use of this "extra" but very small hub pulley. Although not a sure and fast rule, it seems that wooden pulleys tend to be associated with the aluminum frame rotary pumps, while metal pulleys are more likely to be seen on the wood frame reciprocating pumps.

(Photograph courtesy of David Krall.)

Rotary pump from a National built Welte pipe organ roll changer unit. This beautifully restored National rotary pump provides the vacuum supply for the roll changer mechanism, which has 10 music roll stations fastened to a long endless chain arranged vertically in a steel framework. Each roll station has its own take-up spool and feed spool chucks for a Welte pipe organ roll. The aluminum castings for this pump are almost identical to the late rotary style pumps used in National coin pianos, the difference being some additional mounting lugs on the top surface of the aluminum box frame to accommodate a wooden platform on which was mounted an electric motor.

(Photograph courtesy of David Krall.)

Pulley side of a rotary pump from a National built Welte pipe organ roll changer unit. The drive pulley for this National rotary pump is cast iron, instead of the sheet metal or wooden pulleys used for the rotary pumps installed in National coin pianos. The sweepingly curved spokes serve to relieve cracking of the spoke attachment points during cooling of the poured metal. The vacuum inlet pipe is at top right, and is closely connected by rubber tubing to control devices mounted on the pump's topside wooden platform. An electric motor to power the pump will be installed on the platform to the left of the inlet pipe.

(Photograph courtesy of David Krall.)

Two National built Welte pipe organ roll changers side-by-side, on display in the Organ Room, at the House on the Rock, Spring Green, Wisconsin. A National rotary pump is located on the right side of each roll changer mechanism. The rotary pump appears to have an unused topside mounting platform, while the pump at far right has an electric motor atop its wooden platform. Each roll changers holds 10 Welte pipe organ rolls, which can be remotely selected as may be desired.

The photograph date is unknown. The Organ Room was completed during the 1980s, before the passing in 1989 of Alex Jordan, Jr., who was the creator of the House on the Rock.