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AXN-RXN was contracted by Andy Cavotorta to handle the mechanical engineering and fabrication for Bjork's Gravity Flower musical pendulum sculpture. This computer controlled moving sculpture plays a pre-programmed melody that accompanies Bjork during her Biophilia performance. All four harps work in-sync with each other to create a singular musical piece. A wooden structure houses a sub-frame containing the main timing motor and pivot bearings. This timing motor begins to rock the pendulum back-and-forth until it hits its target amplitude and period. It then counteracts the frictional forces over the duration of the musical performance.

 

A secondary electric motor is located on the bottom of the harp. This motor controls the orientation of the harp as it swings past the plucking element at the nadir of it's swing. To pluck a certain note, the motor indexes the barrel-harp so that the desired string is in line with the stationary pick. As the pendulum swings by the pick, it pluck the harp string. Immediately after this pluck, the computer indexes the harp to the next string in the sequence.

 

One interesting challenge was to sonically isolate the harp from all the other vibrations in the system. In order to only hear the harp's strings and sound board resonate, all the other vibrations from bearings, bushings, motors and support structures had to be removed in order for them not be picked up by the acoustic microphones. Custom mounting hubs were designed to house layers of specific sound-deadening materials so that there was not a direct connection between the harp and the surrounding mechanical system.