At 05:05 PM 3/1/2000 , Tobin Copley wrote:
I believe Lief may be referring to the '10"' (actually 250mm, so a little
less) floppy drives manufactured under the Ubermodernwerk brand

"Supermodernfactory?"  Was it housed in the Trabby plant?

  and sold only in East Germany for about a year, around 1981, if I
recall.  They were single-sided, half-density, and held 22K of data.

Kewl!

They were discontinued due to design problems and poor manufacturing
quality control.

Just like the 2/3-height 5 1/4" BASF drives I helped build.  Interesting
example there of engineering myopia -- the original Shugart 8" had an
H-frame to clamp the disk when you shoved the drive door down.  When they
started making 5 1/4 drives, everybody did the same.  BASF essentially
folded the mechanism in half to get a 2/3 height drive, but the leverage
was incredible and the puck too shallow to center properly.  There matters
stood until some bright spark at Tandon thought of using a rotating cam to
operate the clamp.  They came out with a half-height 8", and within a year
everybody was building half-height 5 1/4 drives too.  That worked, unlike
the BASF units.

  The drive units were plagued with problems; for example, the vacuum tubes
used in them were of poor quality, and the drive motor created a
considerable magnetic field itself, often erasing data as the drive spun.

Gee, at 22K per disk they could have used a pencil and eraser...prolly
would have taken the heat better too.  What size tubes, do you know?  Did
they use a stepper?  How many tubes?  How big was it physically?  Where can
I get one?

>As a matter of fact, I have a pile of these old 250mm disks, which I
>acquired through a surplus outfit here.  The tight, lint-free weave of the
>disks' battleship grey canvas fabric protective cover

Canvas?  Canvas?? Oi vey.  I would just *love* to see one.

>Just thought I'd help clarify the discussion regarding the 10"
>drives.  Nice to see that Lief isn't the only listee with an interest in
>early computer hardware!

Amazing.  Obviously the Deutsche Methode inaction (or is it "in action?").

:)
david

David Beierl - Providence, RI
  http://pws.prserv.net/synergy/Vanagon/
'84 Westy "Dutiful Passage"
'85 GL "Poor Relation"