3.5" floppy failure mode? Hub not attched to media.

[Chuck Guzis]

On 02/28/2015 02:57 PM, Eric Smith wrote:

> I haven't seen this OEM manual, but OEM manuals rarely explain in
> detail how everything works and (for the purpose of this discussion)
> why.  OEM manuals are intended to explain how to use the drive, and
> the details of the operation of the track following servo are not
> necessary for that.

Well, again, I have my doubts.

Take early 100 tpi drives, for example, say the Micropolis 1015 SS drives.

Initially, they did not "spin" the disk as the door was being closed, 
which could cause the disk hub clamp to severely mangle the early DSDD 
disks--and this was before the reinforcing rings appeared.  We ran into 
the problem quite often, with the wrinkled hub area.  While a severely 
mis-registered clamp would cause read errors, I don't think we ever lost 
data by simply carefully re-clamping the disk in the drive.

Note that the early Micropolis units did not use the Shugart "epanding 
cone" clamp, but rather one of their own design that consisted of a 
projecting hub piece that fit a recessed piece on the other side of the 
drive, sandwiching the media between the two.  What do you suppose that 
the mis-registration would have been in that case?

I've got several Drivetek drives, including the later Kodak versions, 
and I can't ever recall seeing the "flag" on the fine positioner move 
once the drive was on-track.  So, while it may have been possible to 
compensate for eccentricity, I'm not aware that it was done.

Since neither you nor I are willing to spend the time to investigate 
real-world samples, I think the discussion is academic at best.

--Chuck