Automatic Musical Company
Vacuum and Combination Pumps

(Photograph courtesy of Terry Barnes)

Early rotary vacuum pump and other mechanisms below the keybed in an Automatic Musical Company coin piano (Mandolin Piano, Haddorff #27096). To the right of the pump the vacuum reservoir is partially visible and is fastened to the side of the case. The motor, while old, is not original to this instrument.

(Photograph courtesy of Terry Barnes)

An early 3-lobe rotary pump in the bottom of Automatic Mandolin Piano #27096. The vacuum reservoir is to the right of the pump, with its spill valve and any noise muffled by the protective wooden cover near its bottom edge. The rotary pump consists of three individual bellows physically connected together by flanged cast iron brackets, the bottom one of which also has risers that support crankshaft bearings. Brass oil cups were installed to help keep the main crank bearings oiled. Connected to the upper left iron bracket is a spring loaded motor-to-pump round leather belt idler. Connected to the upper right bracket is a two belt idler arrangement for the pump-to-roll mechanism round leather belt. Each lobe of the pump is interconnected by rubber tubing, which is in turn connected to the vacuum reservoir.

(Photograph courtesy of Terry Barnes)

Close-up of one bellows unit in Automatic Mandolin Piano #27096. The exhaust valve straps are clearly visible on the outside of the movable bellows board surface; the internal intake valve straps are, of course, not visible. Notice the rigid, inflexible mounting of the connecting rod to the bellows board. Alignment of the movable bellows boards is entirely dependent on the crankshaft connecting rod and the bellows cloth or leather covering on each individual bellows unit. In contrast, rotary pump designs of the 1920s (such as those of Seeburg and Nelson-Wiggen) used a four lobe design where each bellows was hinged on one side and connected to the crankshaft by a flexible flap of leather or heavy belting, instead of being free floating as is the above pictured pump. Both designs were durable with proper maintenance.

(Photograph courtesy of Terry Barnes)

Rear view of the early 3-lobe rotary pump removed from the bottom of Automatic Mandolin Piano #27096. The white leather strips on the bellows are patches. At the back end of the crankshaft (just in front of the brass oil cup) is a round leather belt pulley that is used to power the music roll drive mechanism. The leather belt goes from the small crankshaft pulley and is then threaded around the two spring loaded wooden idlers at the left side of the picture, and then up to the roll feed drive mechanism fastened to the underside of the keybed.

(Photograph courtesy of Terry Barnes)

Side view of the early 3-lobe rotary pump that has been removed from the bottom of Automatic Mandolin Piano #27096. The white leather strips on the bellows are patches. At the back end of the crankshaft is a round leather belt pulley that is used to power the music roll drive mechanism.

(Photograph courtesy of Terry Barnes)

Close-up of the crankshaft area of the early 3-lobe rotary pump from Automatic Mandolin Piano  #27096. Notice the odd, wide single throw on the crankshaft. The connecting rod for each bellows attaches to an intermediary cast iron split-yoke bearing assembly that rides on the single crank, and for which an oil fitting is visible on the top side. The connecting rod for the bellows on the right side (as viewed from the large front pulley side) is different that the other two in that it is notched so that when it is screwed tight to the split-yoke bearing it is firmly fixed and cannot rotate on the attaching machine screw. This keeps the split bearing assembly properly oriented and from spinning out of alignment in relation to the other two bellows. The connecting rod for the other two bellows attach by means of a shoulder screw on which the connecting rod can rotate. At the back end of the crankshaft (at picture left) is a round leather belt pulley that is used to power the music roll transport mechanism.

(Photograph courtesy of Terry Barnes)

The large vacuum reservoir in Automatic Mandolin Piano #27096. With the vacuum pump removed the large vacuum reservoir is easily accessible. It is screwed into the side of the piano case to the right of the pump and below the keybed. The spill valve muffler box has been removed so that the normally covered valve is visible. Of the two large brass nipples at the top, one connects to the rotary pump and the other to the pneumatic stack.

(Photograph courtesy of John Rutoskey)

Transitional combination pump in Automatic Musical Company piano #20634 with symmetrical metal pipes, made in 1907. It was impractical to use the early 3-bellows pump for both vacuum and pressure because the moveable boards were not hinged to the stationary boards, guided only by the connecting rods and relying on the stiffness of the leather or cloth covering for stability. If that pump had been used for pressure and vacuum, the connecting rods would have pushed the bellows out of line as they collapsed and forced air into a pressure reservoir. In this vertical 4-bellows pump, the bellows and connecting rods have enough stability to handle both vacuum and pressure. This is the direct predecessor of the horizontal pump used in Link pianos with bellows that slide left and right on guides.

(Photograph courtesy of  John Rutoskey)

Pressure reservoir in Automatic piano with pipes and 4-bellows vertical action pump shown in the previous picture.