The increase in the track densities of disk drive systems has caused the sensitivity of the read/write head alignment to thermal expansions to be a primary design concern. A simple thermal model for predicting the transient temperature distributions and resulting thermal expansions within a disk drive has been developed to evaluate the feasibility of utilizing a thermal prediction code in the design process. Experimental measurements of the temperatures within an actual disk drive, including the radial temperature profile on the rotating disks, were made to compare with the model’s predictions. The air temperature in the gaps between corotating disks is nearly 10 percent warmer than air elsewhere within the disk-drive, and there is less than a 2 percent radial temperature variation along the disks. The steady-state temperatures within a disk-drive are very sensitive to slight changes in external heat transfer coefficient under free convection cooling. Thermal expansion predictions imply that thermal gradients along the hub caused by heat sources in the base and axial change in the arm position between neighboring disks are the major contributions to off-track errors.

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