Includes encoder and position sensor. Speed (revolutions/sec.) depends on the size and weight on the bearing. Moment of Intertia Using an aluminum disc of 210 mm in diameter, 8.5 mm thick, weighing 1kg, and with an engine with 10 Nmm torque, will take 3.5 seconds to reach 1 revolution per second. If the disc is 100 mm in diameter, 37 mm thick, and the same weight (1 Kg), it will take 0.8 seconds to reach 1 revolution per second.