The 446 gyro is an all-welded, hermetic construction, capable of meeting performance requirements in extreme operating environments of vibration, shock, altitude, humidity and temperature. The heart of the gyro consists of a synchronous hysteresis motor whose high reliability is enhanced by preloaded inertial grade ball bearings and advanced lubricants. The spin motor assembly is dynamically balanced using state-of-the-art high precision balancing equipment and then run-in for a minimum of 96 hours to fully channel the lubricants. Instead of jewel bearings that yield a surface contact with the gimbal shaft, miniature high precision ball bearings are used to provide a point contact with the shaft reducing friction and drag. This enables precise alignment and axial positioning of the gimbal within the gyro case and for high performance applications radial play can be limited to 20 millionths of an inch. Dynamic characteristics of the gyro are maintained throughout the temperature range by means of a bellows-operated, variable-orifice, damping compensator. The compensator is a mechanical device and requires no power source. With an internal gimbal balancing device both g-sensitive and g-insensitive drift components can be precisely trimmed after final assembly. All gyros are temperature cycled from -65 deg F to +240 deg F for 48 hours to stress relieve all components and assure maximum drift stability.