On 2009-05-01, Michael A. Terrell wrote:

"DoN. Nichols" wrote:

On 2009-04-30, Michael A. Terrell wrote:

[ ... ]

One of the Metrodata computers used a SMS 8" drive system that held
500K per disk.

O.K. Either SSDD, or DSSD depending.

SSDD soft sectored. I just found a few disks I saved, when we
scrapped the system.

O.K.

[ ... ]

The damn Shugart 801 drives ran 24/7 and wore out in
about two years. Every new drive had a different PC board, so we had to
make several phone calls to get the configuration data every time a
drive failed. The SMS design didn't lift the arm when it wasn't in use,

O.K. This makes it SSDD (Single Sided Double Density), since
the Double Sided drives moved one head against the other closing onto
the surface of the floppy. Those *might* have lasted longer in a clean
environment. (Of course, a bit after the Mt. St. Helens eruption, 8"
(and 5-1/4") floppies were having problems because of the airborne
abrasive dust which it spit out.


The system manager was an idiot. The door to the headend was about
three feet from the back door of the building, where the installers &
techs came and went. Then he decided to use the headend to store bulk
supplies, so you had guys covered with mud & dirt running in and out
several times a day.

Ouch!

so the felt pads would wear out. Then the arm would stick to the disk
and destroy the floppy.

Ouch! I *never* had an 8" floppy drive wear out -- but the OS
and controller lifted the heads when not actively reading or writing.


SMS built lousy equipment. I found out later it was designed as a
word processor for law offices, then they designed an interface board
for the old Motorola Exorcisor bus. that was why the drives didn't lift
the head, the typist was writing directly to the disk, on a continuous
basis.

Ouch!

I *did* have a DSDD 5-1/4" floppy drive die -- but from poor
design. The centering cpu was on a 1/4" shaft, running through two
shoulder style ball bearing assemblies, and secured by the drive pulley
slid onto the shaft, and then a central screw and washer tightened to
grip, followed by a glob of Glyptal to secure it.


Some 5.25" drives were extremely flimsy. I still have over 100 180K,
360K & 1.2 M 5.25" drives. I might even have a few 720K. I think they
made 720K drives for about two weeks, before switching to 360 RPM, and
calling them 1.2M.

I had one new Shugart 400 drive. That was their first SSSD 5.25"
design, and only had 35 tracks. I think I gave it away.

I started with two of those -- with the "phonograph" style head
positioning system. At least it made it resistant to damage by running
against the stops. :-)

Some of the early floppy envelopes only had a slot long enough
for the 35-track use, too.

[ ... ]

Somewhere I should have a pair of Teac 1/2 height 8" DSDD drives that
don't need 120 VAC.

Hmm .... there was also the one used in one of the systems which
had a voice-coil servo for head positioning, instead of a stepper motor.
I never had one, but I understand that while they were noticeably faster
on track-to-track seeks, the also needed to be re-aligned fairly often,
while the Shugarts were rock solid as far as alignment goes.

Now I remember who made the systems which used those drives. It
was a Chromemco system made for business use. Two of the drives, and
each drive would hold two floppies (but I think that the head
positioning servo moved both sets of heads together, so copying from
one area on one floppy to another area on the other floppy in the same
drive resulted in very slow operation. Better to work between drives
instead of between floppies on the same drive.

I think that the drives were made by PerSci -- yes, they were.

Enjoy,
DoN.

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