I opted for using two small gear motors installed in the sensor
support arms to motorize the spinners. The motors themselves are
quite pricey (around $130 each). I ordered them from MicroMo
at: www.micromo.com. These eight millimeter motors with a
256:1 gear ratio, bring the RPMs down to around 30 RPMs at six volts.
If you order from MicroMo order the motor with the gearhead:
Installation was quite easy. Using the sensor support arms, I drilled
an eight-millimeter hole into the vertical section of the support
arm for the motor to sit in.
And then another smaller one-eighth-inch hole for the connecting
wires to the motor. Install the wires first, before connecting them
to the motor.