Patent ID: 7277258

Claim:
A magnetic recording disk drive having a rotatable magnetic recording disk and a recording head that reads data from and writes data to the disk, the disk drive comprising: a primary rotary actuator rotatable about an axis for moving the head across the disk; a secondary rotary actuator comprising a fixed portion attached to the primary actuator and a movable portion including the head, said movable portion having a center of rotation and a mass M and moment of inertia I z , the movable portion's center of rotation and the primary actuator's rotational axis being intersected by a line and the center of mass of the movable portion being located substantially on said line at a distance L from the primary actuator's rotational axis; and wherein said center of rotation is located along said line, said location being selected from the group consisting of (a) an optimal location, said optimal location being at a distance D from said center of mass, where D is approximately I z /(L*M); (b) a location between said optimal location and a distance 3X from said optimal location in a direction away from the primary actuator's rotational axis, where X is the assembly tolerance for the location of the center of rotation relative to the center of mass; and (c) a location between said optimal location and a distance 3X from said optimal location in a direction toward the primary actuator's rotational axis.