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Spindle Tilt Reduction in Disk File

IP.com Disclosure Number: IPCOM000040742D
Original Publication Date: 1987-Dec-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 2 page(s) / 27K

Publishing Venue

IBM

Related People

Case, WJP: AUTHOR [+3]

Abstract

In a disk file with stacked multiple heads serving a disk stack mounted on a spindle, any tilt in that spindle means that some of the heads will be offset from their respective tracks on the disks causing data errors. To overcome this, the spindle is supported at each end by flanges, each of which may be heated to increase its length. The offset of each head is measured with respect to servo information on the corresponding disk, and averaged out to decide which of the two flange heaters should be driven via a feedback loop to give tilt correction. The figure shows a spindle, each end of which is mounted on a flange separated from the main body of the disk enclosure. The flanges are heated by small heaters. One heater or the other is used depending on the correction required.

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Spindle Tilt Reduction in Disk File

In a disk file with stacked multiple heads serving a disk stack mounted on a spindle, any tilt in that spindle means that some of the heads will be offset from their respective tracks on the disks causing data errors. To overcome this, the spindle is supported at each end by flanges, each of which may be heated to increase its length. The offset of each head is measured with respect to servo information on the corresponding disk, and averaged out to decide which of the two flange heaters should be driven via a feedback loop to give tilt correction. The figure shows a spindle, each end of which is mounted on a flange separated from the main body of the disk enclosure. The flanges are heated by small heaters. One heater or the other is used depending on the correction required. Any difference in temperature of the two flanges means that the expansion of the two flanges will be different. This gives rise to a compensating tilt of the spindle. With a temperature difference between the flanges, the relative motion of the ends of the flanges is: WL = L x WT x u where WL is the relative change of length of the flanges, L is the length of the flanges,

WT is the temperature difference of flanges (degrees C), and

u is the thermal coefficient of the flange material. (For aluminium u is 22.9E-6 per degree C) If L is 100 mm, then WL = .1 x WT x 22.9E-6 (Meters) If disk 7 is to be measured, and right hand flange is considered as moving (moti...