(Photograph courtesy of Dana Johnson.)

Wood frame reciprocating vacuum pump in National piano #7125. The pump fits rather snugly in its left side compartment, and is actually notched out on the front left hand corner so as to fit around the piano case interior structure. The chain sprocket on the front side of the pump drives the worm gear clutch sprocket above it (located on the "keybed" area shelf). The worm gear clutch sprocket delivers motive power to not only the camshaft worm gears, but also to anything else requiring rotational power located on the right hand side of the "keybed" area. The large diameter rubber hose goes from the pump inlet to the pneumatic stack, and is the source of vacuum 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 position of the revolver magazine.

(Photograph courtesy of Art Reblitz.)

Front view of a wood frame reciprocating vacuum pump. For most coin piano applications this view would represent the rear of the pump, because the belt pulley is normally located front and center. Not for National pianos, however. The belt pulley is always mounted on the rear end of the crankshaft. The chain sprocket on the front side of the crankshaft is used to supply motive power to all needy components in the "keybed" area of the piano. The large metal belt pulley is necessarily on the back side of the pump, because the drive belt must go behind the revolver magazine and over to the electric motor located on the opposite side of the piano. It is an inconvenient setup for servicing the leather belt, but a necessary one in this instance. Note the cutout in the framework on the front left corner of the pump, which weakens the pump framework, but is necessarily there to accommodate the interior structural design of the piano case—an indicator of how limited the space is for the vacuum pump, The vacuum inlet hose connection at top left connects to the pneumatic stack.

(Photograph courtesy of Art Reblitz.)

Rear view of a wood frame reciprocating vacuum pump. Here the large metal belt pulley and the associated belt idler pulley are prominently visible. The belt pulley is fitted with a large die-cast hub with a setscrew used to clamp it securely to the crankshaft. The belt idler puller has a tension spring connected to the top of the pump framework, pulling the idler up, so as to keep an even tension on the leather belt as it stretches out due to age and sustained use.

(Photograph courtesy of Art Reblitz.)

Top view of a wood frame reciprocating vacuum pump. This plan view clearly illustrates the layout of the pump, with the vacuum inlet connection sticking up at far left, the crankshaft at top center, and the four bellows affixed to the floor of the wooden framework. The side-by-side pair of bellows on the left side face the opposing pair of bellows on the right. On either side of the crankshaft there are two metal bars threaded on each end. Using hex nuts and washers to spatially secure the bars to both of the wooden beams, the lateral position of the two horizontal bearing support boards are kept parallel, the bars stabilizing and preventing the wooden structure from flexing sideways under stress.

(Photograph courtesy of Dana Johnson.)

Crankshaft and connecting rods in wood frame reciprocating pump. Notice how the crankshaft is made. Each throw is made up of separate blocks of steel that have been drilled at both ends to accept a short length of steel shaft. The shaft is probably a press fit into the steel block, and then firmly held from rotating with a tapered pin, which looks like they were hammered into place until blunted and seated with great force. This crankshaft assembly work was probably done in a jig that held all of the separate pieces in position when the holes for the tapered pins were drilled, and then tapered with a reamer. With the brutal hammering the head of each tapered pins appears to have taken it is probably the case that none of them ever worked loose.

Of the connecting rods, the three on the left side are of the original die-cast type, with the one connecting rod on the right appearing to be a bronze replacement. The fitting on the top of each die-cast connecting rod is there to hold oil for lubrication. The oily felt washers, located at the lower bearing end of each of the connecting rods, provides a "reservoir" of oil for longer lasting lubrication. It looks as though the second connecting rod from the left has a piece of shim stock on the visible side between the connecting rod and the bearing cap, apparently to provide some extra clearance for the bearing surface.

(Photograph courtesy of Dana Johnson.)

Vacuum bellows in wood frame reciprocating pump. Here the bellows detail becomes apparent. At left is a side-by-side pair of bellows, which face another pair of identical bellows on the right. Each of the four little bellows are covered with durable bellows cloth—an airtight sandwich consisting of heavy duty outer layers of twill cloth covering a rubberized center core. The leather exhaust valve flaps on the top of each of the bellows lay over holes cleanly bored through the movable leaf, so that air trapped inside the bellows can be easily expelled when the movable leaf is pushed down. When the movable leaf is pulled up, creating a vacuum, the exhaust flaps seal tightly against the holes in the top of the movable leaf,

(Photograph courtesy of Dana Johnson.)

Bottom side of a wood frame reciprocating pump. When viewed from the front bottom side of the pump, the bottom air passageways connecting the four bellows to the vacuum inlet pipe can be seen. The vacuum inlet pipe is at left in the area with the thinner wood channeling. Notice that each of the bellows are fastened to the bottom floor by only four wood screws, making it relatively east to remove one of the units to get to and repair a faulty intake valve flap.

(Photograph courtesy of Dana Johnson.)

Connecting rod and bellows bearing cleat for a wood frame reciprocating pump. At top is a connecting rod with its bearing cap to the right. Below the connecting rod (and to the left) is the bearing cleat that screws onto the movable leaf for each of the four vacuum bellows. When assembled, a short shaft is inserted into the hole going through the cleat, which shaft also passes loosely though the end bearing for the connecting rod. The connecting rod and its crankshaft bearing cap are held together by machine screws. The purpose of the thick felt washer at the left end of the connecting rod is to act as an oil reservoir for the cleat bearing attached to a movable bellows leaf.