Lower Center Section of the
Hupfeld Helios III/39 Orchestrion

Front view of the centrally located six-station music roll changing device. To the right is the tempo regulated wind-motor drive mechanism that propels music rolls in the forward direction over the tracker bar. Main power for the roll changer comes directly from the feeder pump crankshaft, by means of a roller chain and sprocket that interfaces with a geared right-angle drive, which is barely visible below the wind-motor. At the left side is the register control unit, with its row of individual draw-knob controls.

Rear view of the roll-changer mechanism. To the left is the wind-motor, with the double-acting motor pneumatics visible. To the right is the backside of the register control unit. In the forefront are the bundles of lead tubing that connect the main valve stack with the roll-changer's tracker bar, and that also connect the main stack with pipe chests and other components scattered throughout the chassis of the instrument.

Backside of the register control unit. Visible are some of the many lock and cancel pneumatic operators that are activated by special control perforations in the music roll. Automatic operation of the various musical voices can be overridden on an individual basis by engaging clever locking levers on the front side of the register unit. These locking levers enable the machine's operator to force any musical effect to be permanently on or off as desired.

Front view of the (blue colored) feeder pumps at the case bottom. The pump consists of three pairs of upper and lower bellows that are connected to a crankshaft rotating at 44 RPM and that is powered by a flat-belt running over a heavy 39-inch diameter cast iron pulley on the backside of the instrument. All six bellows develop wind-pressure, while only the bottom three bellows develop vacuum. At the left is the electrical cut-off switch, which is interconnected with certain functions on the roll-changer.