(Simplex advertisement courtesy of Art Reblitz.)

(Photograph courtesy of Dick Hack.)

Interior view of National automatic piano #348. At a quick glance this National piano might seem to be the usual fare, but the most glaring difference is the pneumatic stack, which for this particular piano is a Simplex stack, instead of the more commonly found National built stack. Moreover, the vacuum expression controls on the left stack foot and the spill valve setup are very different. The Simplex stack uses a balance-beam design for vacuum regulation, which is built into and is an integral part of the left-side stack foot. The large spill valve for the Simplex system is completely separate from the vacuum expression system and is mounted front and center on the front cover of the stack. The spill valve consists of a simple poppet type valve that is lifted by a cam operated lever arrangement that is part of the Rewind/Play mode control system. When the spill valve is popped open it immediately vents the vacuum throughout the entire player system, so that no piano notes or control valves are functional during the rewind and roll changing operations.

(Photograph courtesy of Bob Gilson.)

Spill valve on the front cover of the Simplex stack in National automatic piano #348. The spill valve in this photograph is shown in the raised, open position, and is lifted open by a wooden cam follower lever arrangement that is part of the Rewind/Play mode control system. The long valve stem passes down through an eyelet affixed near the rear end of the aforementioned cam follower lever, where hex nuts on the threaded valve stem allow for exact vertical positioning of the stem in relation to the horizontal position of the cam follower. This vertical adjustment affects the amount and accuracy of the spill valve lift provided.

All National pianos are different from most coin pianos in that they do not have vacuum reservoirs to dump when the spill valves opens. Consequently, when the spill valve pops open the vacuum is discharged almost instantly—as long as the spill valve capacity is greater than the volume of air forcefully moving through the system while the pump is in operation, which is anytime the electric motor that powers the player systems is powered on and working.

(Photograph courtesy of Bob Gilson.)

Simplex vacuum expression control components in National automatic piano #348. Simplex stacks—at least those installed in National pianos—utilize a balance-beam type of soft/loud vacuum expression control system, which is embedded into the left-side front foot of the stack. The regulated spill valve at one end of the balance-beam and the beam's pivot casting are located on the foot, while the lock and cancel pneumatics that influence the opposite end of the balance-beam are mounted on the "keybed" shelf, in front of the stack foot. The larger lock pneumatic increases the tension trying to hold the spill valve closed, in turn increasing the vacuum level in the system (piano loud). Once the locking pneumatic has fully collapsed it is latched in the downward position, until the locking latch is released by the cancel pneumatic (piano soft). The separate medium sized pneumatic to the right of the balance-beam related components is used to trip the Rewind/Play mode camshaft into the Rewind/Roll Changing mode position, which occurs when the rewind pallet valve falls into the cutout at the end of the music roll.

(Photograph courtesy of Dick Hack.)

Front side of a Simplex stack removed from a junked National piano. Here is a Simplex stack laid bare in all of its tarnished glory. The large rubber tube at left is meant to be connected to the tune indicator, mounted in the upper left part of the piano case. The large hole at center, and surrounded by what remains of some packing leather, is where the spill valve would normally be attached. All of the little scraggly stubs of cutoff rubber tracker bar tubing still dangling along the bottom edge of the stack are stuck on short brass nipples pressed into a removable wooden header. By simply removing this single header none of the tracker bar tubing needs to be otherwise disconnected when removing the stack. Along the top side of the stack is a wooden rail with 65 wooden flanges, each with a wooden finger attached that swivels on a pin pushed through the flange. At the far end of the finger is a brass capstan screw for adjusting the individual player action parts to the piano action.

(Photograph courtesy of Dick Hack.)

Loose Simplex vacuum spill valve from a junked National piano. The valve assembly is screwed tightly to the front cover of the Simplex stack. Remnants of tattered packing leather are visible around the large hole bored into the side. Below the wooden valve block is the long metal valve stem, which is threaded except for the segment that slides up and down through the valve block. At the bottom of the valve block is a brass washer against which rests a coiled compression spring, with the opposite end of the spring pushing down against a metal nut, which keeps the spill valve closed, unless intentionally lifted by a cam operated lever that is a function of the Rewind/Play mode control system. At the bottom of the valve stem are two more metal hex nuts tightened against each other to lock them in place. Below the pair of nuts, the tip of the valve stem sits in an eyelet affixed to the aforementioned cam operated lever. Barely peeking out from the front side of the valve block is a tarnished brass elbow, but for what is unknown. Maybe it was connected to a little valve unit for a "Dancing Man" retrofit, for which what may be the only known example came from the same junked out National piano.

(Photograph courtesy of Dick Hack.)

Backside view of treble end of a Simplex stack taken from a junked National piano. Here the 3-tiers of Simplex unit pneumatics that populate the entire treble and mid-section portion of the stack are easily discerned. The unit pneumatics are attached using adjustable pitman wires to the flanged fingers running along the top of the stack. The end block at left is supportive only, with no special channeling or function.

(Photograph courtesy of Dick Hack.)

Backside view of bass end of a Simplex stack taken from a junked National piano. The bass side of the stack holds a mixture of unit valves and unit pneumatics. The first 5 positions, counting from the far right side, are unit valves used for control functions. Each of these control valves has a brass elbow on the rear end of the unit valve's back side extension, instead of a pneumatic to play a piano note. Position 20 is also a control valve, snuggled into the spacing break between the bass and mid-range piano section notes, which is connected to and triggered by the rewind pallet valve when it falls into the cutout at the end of the music roll. All other bass positions are occupied by unit pneumatics. To the left of the position 20 unit valve (on the other side of the spacing break) is the mid-range piano note section populated with nothing but unit pneumatics. Notice that the structural end block at far right is much wider than the end block on the treble end of the stack (see previous image). This is because this end block (at the bass end) is channeled to supply vacuum to the front side of the trunk board, to which each of the unit valve assemblies is attached.

(Photograph courtesy of Dick Hack.)

Closeup view of Simplex unit pneumatics. This intimate look at the unit pneumatics on the treble end of a junked Simplex stack shows how the pitman rods are attached to the pneumatics. At the end of the movable leaf for each pneumatic there is a cupped and slotted metal flange. The metal rods with the leather nuts spaced sufficiently apart can be easily slipped in or out of the cupped receptacle, but when the nuts are snug they keep the pitman rods securely in place, but still free to flex as the movable leaf moves up and down when playing piano notes. For the one pneumatic with the torn rubber cloth, the interior of the air evacuation hole and thin saw cut passageway to the valve chamber are visible. While hard to discern, there is a circular saw cut made on one side of the fixed, non-movable part of the unit pneumatic, which serves to connect to the easily visible bored hole with the valve chamber itself.

(Photograph courtesy of Dick Hack.)

Simplex stack from a junked National piano standing on its treble end. Upright amidst boxes and other spare parts in a workshop storage closet is the working side of a junked Simplex stack. At top it is easy to see the air channel detail on the underside of the bass end's structural wood block. It is this surface that sits atop and mates with the stack foot, with its built-in balance-beam vacuum expression control. This view also gives a splendid look at the first five unit valves used for control purposes. Positions 6 through 19 are populated with unit pneumatics, and position 20, on the bottom row and partially visible to the carefully observant eye, is home to another unit valve, which, in this instance, would normally be connected to and triggered by the rewind pallet valve when it falls into the cutout at the end of the music roll.

(Photograph courtesy of Dick Hack.)

Left side foot (with vacuum level controls) for a Simplex pneumatic stack. This loose stack foot and its associated expression controls were removed from a junked out National piano. The wooden boot-shaped component at right is a crucial part of the vacuum distribution system. The dark colored wood block at top center is the fitting used to connect to the vacuum pump. The stack foot has channeling that connects the vacuum supply to the regulated spill valve and to the large opening on the top side of the foot. This flat surface, with the large vacuum port (and two much smaller holes for long bolts that tie the foot to the stack) mates with the matching opening in the bottom of the stack (see previous photograph). To make the joint air-tight a leather packing gasket is inserted between the two mating surfaces. The paired lock and cancel pneumatics (on the separate mounting board at left) determine the tension applied to the left end of the balance-beam, which, in turn, determines the tension applied to the spill valve at the other end. The higher the tension applied to the spill valve, the higher the vacuum level in the player system (and the louder the piano notes will be played).