24 Sep
2005
24 Sep
'05
9:24 a.m.
On Sat, 24 Sep 2005, Chuck Guzis wrote:
> Portable Smith Corona word processors used a 2.8" drive that worked the
> heads via a follower than ran in a spiral groove molded into a plastic
> disk that was driven by the spindle motor through a clutch. Basically,
> pulsing the clutch caused the head to move in a continuous spiral
> pattern from the beginning of the diskette to the end. Sort of a
> windshield-wiper auto-completion mechanism. You could read or write the
> entire diskette (about 60K (MFM), if memory serves), but nothing less
> than that. A gutless wonder if there ever was one. It was actually pretty
> robust.
On Sat, 24 Sep 2005, Vintage Computer Festival wrote:
Apple Disk ][ drives used a similar mechanism.
Yes, and no.
Shugart SA390 (used for Apple ][ disk drives), and the Shugart SA400
(used in TRS-80 and others) used a spiral groove on a disc for head
positioning.
(definitiely NOT a helical lead screw as Dick used to claim -
only helical lead screw that I saw on 5.25" was Micropolis).
It was a real joy when the MPI B51 came out with a split band
positioner, and later the Tandons.
The Shugart was with a separate stepper turning the cam.
I believe that Chuck is referring to a a similar mechanism connected
to the SPINDLE motor, resulting in a spiral track! instead of the
usual series of concentric circles for tracks.
--
Grumpy Ol' Fred cisin at xenosoft.com