Memorex Disk Storage.

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What you are looking at weighs over 2 Hundredweight, one tenth of a ton.

This is just the disk drive, it does not include the electric motor that turned the disk,
or the power supplies, or the control logic, or the cabinet - framework, and enclosing panels.
The total weight must have been over 200 Kg

This is a photograph of a Memorex disk drive unit being repaired, as was too often the case.
At the bottom is a power supply and out of sight, a large electric motor that turned the pack of disks via a belt.
Above is control circuitry, and just visible a bit of the disk storage FRU itself.

The name of the engineer is Jack Morgan: he was one of our Customer Engineers for the Amdahl for many years.

Here is a view of the 8 disk platters, giving 14 recording surfaces, plus two servo surfaces.

This disk drive was really two disk drives. Although only one set of disks and motor and power supplies,
it had two head assemblies and electronic identities.

This is not a removeable disk! It is an FRU, (Field Replaceable Unit),
but its removal involved two people and quite some time. It was only removed if damaged.

Here is the two head assembly voice coils. The two voice coils are out of their magnetic enclosures
because the disk unit has been released to a position where it can be removed from the disk chassis.

Another significant aspect of this disk drive is that it moves the head assembly in a straight line
along a radius if the disk drive surfaces.This was the same for earlier disk drives.
This movement involved many bearings to keep the head assembly in place.
All of these bearings are prone to wear, this restricted the density of the track spacing.

This is an example of a linear voice coil actuator.

This is a rear view of the two magnets. The label reads:
CAUTION
UNIT WEIGHT
156 POUNDS
(71 KGS)

This disk drive was at the end of an era.

Up to here in order to store more data the drives were built larger,
and in order to go faster the driving force was more, which meant that the components were made stronger,
which meant the force needed to be larger, components stronger, ...

This spiralling up of force, weight, strength stopped in about 1985,
and this MEMOREX disk drive was typical of the behemoths that existed at the end.

In this photograph you can see that each of the two head assemblies had two heads per surface

The other significant fact of the MEMOREX disk drive was its thin film head.
Here you can see them and their reflection on each disk surface.

The thin film head was manufactured using a photolithographic process, the same as
was used to manufacture the semiconductor chips.
The thin film heads had very narrow and controlled head gap.
This enabled writing at greater densities and at closer track spacing.

This advertising artefact was given away in 1982 to promote MEMOREX disk drives.

As well as the enlarged photo of a thin film head it incorporated an actual thin film head
within the plastic, but it is hard to see. It is under the hn of Technology and above the word film.