NSK gyroscope special ultra-precision ball bearings (1) gyroscope and gyroscope special bearings Table 11 Types and applicable conditions of gyroscope special bearings Groove ball bearings, other special shape bearings Applicable conditions for example 12 000, 24 000 min-1 or 36 000 min-160 ~ 80 C in helium, 2 C swinging at room temperature ~ 80 C in silicone oil or in the atmosphere Input shaft gyro rotor 10,000 Gearbox output shaft Gimbal support bearing Rotor support bearing Rotating shaft (H) Spring or torque meter Shock absorber Figure 2 Types of gyroscopes 1 degree of freedom gyroscope rotor support bearing Gyroscopes Special-purpose ball bearings are used to detect the azimuth and angular velocity of aircraft, ships, etc. According to the detected movement direction and speed, they are structurally divided into 1-DOF and 2-DOF gyroscopes (see Figure 2) . Since the characteristics of the bearings used greatly affect the performance of the gyroscope, it is required to select the best quality products among the NSK ultra-precision miniature bearings. The bearings supporting the high-speed rotor shaft and its outer frame (gimbal) should have stable low friction torque. The main types and applicable conditions of rolling bearings for gyroscopes are shown in Table 11. The rotor and gimbal support bearings are mainly inch super-precision bearings, and their main dimensions and NSK representative models are shown in Table 12 (page B75). In addition, there are many special-shaped gyroscope bearings. (2) Characteristics of gyroscope bearing Special bearing for rotor Special bearing for gimbal Figure 4 An example of end cap ball bearing Figure 3 Oil quantity and torque Oil 1 drop r/min concentration 1% 1 drop concentration 0.5% 1 drop concentration 0.2% 1 Special bearings for drop rotors require extremely low torque and long-term stability in high-speed rotation, so oil-containing cages are often used. There is also a lubricating method in which solvent-dissolved lubricating oil is injected into the bearing, but since the friction torque is affected by the amount of oil, an appropriate concentration should be adjusted (see Figure 3). The oil quantity can be adjusted by centrifugal separation method to obtain stable torque. As for the bearing type, there are also special-shaped bearings in which the end cover and the outer ring are integrated (see Figure 4). The special bearing for the gimbal acts as the output shaft and must have low friction torque and vibration resistance characteristics. Table 13 lists the maximum starting torque of representative bearings. By finishing the raceway and special design of the cage, a lower starting torque can be obtained. In addition, in order to prevent fretting wear caused by external vibration, the surface coating is hardened on the raceway to improve the vibration resistance. The design parameters of the special bearing for rotor and gimbal are shown in Table 14.