Robert Lindemann, the recently retired Vice President of SDP, designed the mechanical drive system that allows the gears to move properly. The motion is driven by an AC gearmotor inside of a large rectangular base, which rotates the smaller circular base on top. The two sprockets attached to the base are driven by bevel gears in mesh with a larger stationary bevel gear inside the base. The sprockets in turn drive the roller chain wrapped around the clear circular disks. The rotation of the circular disks about their center shaft is translated to the center gears inside, which in turn moves the entire geartrain.
If you are interested in learning more about kinetic sculptures in general, you can check out other Youtube videos on the subject at the SDP/SI home page at: http://www.sdp-si.com.