Winchester head

Hard-disc drive heads are subjected to a heavier use and therefore need a different design in order to prevent wear and extend the useful life of both the disc and the head. Hard-disc drive heads (also known as Winchester heads) make no physical contact with the hard disc. They are designed to fly very close to the disc, supported by the air flow resulting from the disc rotation. Fig. 5.18. The magnetic element in Winchester heads is usually a Mn-Zn ferrite. 

As with any analytical method, the ability to extract semiquantitative or quantitative information is the ultimate challenge. Generally, static SIMS is not used in this mode, but one application where static SIMS has been used successfully to provide quantitative data is in the accurate determination of the coverage of fluropolymer lubricants. These compounds provide the lubrication for Winchester-type hard disks and are direaly related to ultimate performance. If the lubricant is either too thick or too thin, catastrophic head crashes can occur. 

Information obtained from visits to various munitions factories suggests that manufacturers will use whatever is available at the time, from whatever source, to complete an order, provided that it meets the required ballistics performance and produces no residues that are injurious to the gun. During the war years, shortage of material meant many variations in materials used in manufacture. For these reasons it is unwise to make assumptions about ammunition components and composition, even for the same caliber and manufacturer, as they could vary from batch to batch. The differences between ammunition with the same head stamp can be seen in Table 21.3 for Winchester Western in. 38 Special and. 357 Magnum calibers and in Figure 21.2 for. 30 Ml caliber VE 54 FI and VE 2-61 S. 

Mass data storage represents something of a problem. Floppy discs are probably inadvisable under the severe conditions at sea (vibration, large motion, dirty air, etc.). Some forms of data storage that do appear desirable are Winchester discs (if head crashes can be avoided), digital tape recorders, electronic memory systems (protected from power interruptions), or bubble memories (a bubble memory for the Apple II has become available commercially). 

Winchester discs are molded as blanks in engineering plastics, usually General Electric s Ultem polyetherimide, then coated with an epoxy-ferric oxide layer. The main requirement in manufacturing these discs is absolute flatness because the magnetic read/write head moves only 8-20 microinches above the disc surface and is spinning at a high speed of 3,600 rpm. Any microscopic bump can thus cause damage to both the disc and head. 

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