The disk on which the magnetic data is stored are mounted on the motor with spacer rings in between them. The ball bearings are visible above and below the copper coil windings. A representative ball bearing is shown below. The motor bearings are lubricated for life by only milligrams of grease. The disk on which the magnetic data is stored are mounted on the motor with spacer rings in between them.
Ball bearings for disk drive motor.
These bearings are lubricated by a few milligrams of grease. The grease is mostly synthetic ester oils such as those shown below. The oil is held in place by a soap thickener, which imparts a temperature independent yield stress. Since the greases last many years during normal operation, accelerated tests were developed for bench-scale study of grease oxidation chemistry to develop the stabilizing additive systems. Example UV and NMR spectra are shown below.