Alignment disks, and the creation thereof

[Roy J. Tellason]

On Wednesday 11 February 2009 08:13:15 pm Fred Cisin wrote:
> > > The problem comes if you want 2 offset tracks say 180 drgrees out of
> > > phase (so one is at its innerpost point when the other is at the
> > > outermost point). Aligning the media to the offset hub accurately to do
> > > that would be 'interesting'.
>
> On Wed, 11 Feb 2009, Roy J. Tellason wrote:
> > Didn't the Lisa have floppy drives with heads on opposite sides of the
> > spindle?  :-)
>
> the "twiggy" drive.  Apparently, not all 5.25" diskettes had thumbprints
> on the media, so they added an extra access slot where your thumb would go
> 600 Oerstedt media, 96TPI???
>
> There are 8 possible ways to put a 5.25" diskette into the drive, without
> damaging it.  Did the Lisa have two sets of heads, or was the extra access
> slot there just to double the odds that the position in which it was
> inserted would work?

It's been a while,  but my recollection is that they had two heads and each 
had a pressure pad on the other side of the disk...

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