Disk drive including a balancing element with first and second cavities and a cylindrical portion disposed about a spindle motor hub

1. A disk drive comprising:

a disk drive base;

a spindle motor rotatably coupled to the disk drive base, the spindle motor including a spindle motor hub defining an axis of rotation;

a disk disposed about the spindle motor hub, the disk including a disk inner diameter biased against the spindle motor hub at a contact location of the spindle motor hub; and

a balancing element including:

a cylindrical portion disposed about the spindle motor hub;

a first cavity defining a first cavity centroid, the first cavity centroid disposed on a same side of the axis of rotation as the contact location; and

a second cavity defining a second cavity centroid, the second cavity centroid disposed on a side of the axis of rotation opposite the first cavity centroid, the second cavity centroid being spaced apart from the first cavity centroid in a direction along the axis of rotation.

2. The disk drive of claim 1 wherein the axis of rotation and the contact location defined an alignment plane, the first cavity centroid and the second cavity centroid each are disposed within 20 degrees of the alignment plane about the axis of rotation.

3. The disk drive of claim 1 wherein the second cavity centroid is closer to the contact location along the axis of rotation than the first cavity centroid.

4. The disk drive of claim 1 wherein the balancing element includes an upper surface disposed away from the disk, the balancing element further includes an outer periphery with respect to the axis of rotation, and the first cavity is disposed along the outer periphery at the upper surface.

5. The disk drive of claim 4 wherein the first cavity is open at the upper surface and the outer periphery.

6. The disk drive of claim 4 wherein the second cavity is open at the outer periphery.

7. The disk drive of claim 1 wherein the balancing element includes a lower surface disposed towards the disk, the second cavity is open at the lower surface.

8. The disk drive of claim 7 wherein the second cavity is closed at the outer periphery.

9. The disk drive of claim 7 wherein the balancing element includes an upper surface disposed away from the disk, the second cavity is a hole extending through the balancing element between the upper surface and the lower surface.

10. The disk drive of claim 7 wherein the second cavity defines a uniform diameter between the upper surface and the lower surface.

11. The disk drive of claim 7 wherein the second cavity defines a non-uniform diameter between the upper surface and the lower surface.

12. The disk drive of claim 1 wherein the second cavity is a contiguous cavity with the second cavity centroid within the second cavity.

13. The disk drive of claim 1 wherein the second cavity is a split cavity that includes a plurality of voids.

14. The disk drive of claim 13 wherein the plurality of voids are symmetrically angularly spaced about the axis of rotation from the alignment plane.

15. The disk drive of claim 13 wherein the second cavity centroid, considering all voids together, is located outside of any one of the voids.

16. The disk drive of claim 1 wherein the balancing element is a disk clamp.

17. The disk drive of claim 1 wherein the cylindrical portion comprises an entirety of the balancing element.

18. The disk drive of claim 17 wherein the balancing element is a spacer ring.

19. The disk drive of claim 18 further comprises a disk clamp, wherein the spacer ring is disposed adjacent a disk clamp and the disk is the only disk of the disk drive.