Double Punching Diskettes
cclist at sydex.com
Sun Nov 26 16:42:21 CST 2006
On 26 Nov 2006 at 13:16, Fred Cisin wrote:
> The "deluxe" models of both had a peg and donut for putting on
> center hub reinforcers. EARLY DD 5.25" needed them. And then
> they stopped putting them on with the HD disks.
IIRC, it wasn't the diskettes so much as the clamping arrangements on
the drives (Shugart had the most reliable system, but sued anyone who
tried to copy it). It was quite awhile before someone figured out
that turning the spindle motor on when a diskette was inserted so as
to center the hub in the clamping setup was a stroke of genius. I've
got some old Micropolis single-sided drives that will mangle a hub in
fewer than 10 insertions.
A few HD manufacturers put the hub reinforcement on their disks early
on. I didn't think it did any harm, but it didn't help either and
I recall getting a very angry call from a customer who said that
CopyQM was making unreliable 5.25" DSDD copies--that he'd make and
verify a copy and then found it couldn't be read by another machine.
What he didn't mention is that he was using the PolyPak equivalent of
diskettes--no-name mail-order cheapest possible. I asked him to send
a few of the failures our way and we'd have a look at them.
It turns out that whatever bit of machinery that was used to apply
reinforcing rings had applied TWO to each side, each ring being
slightly offset from the other. The diskettes would never center on
the hub the same between any two insertions. After I pointed this
little tidbit out to him, the complaints stopped.
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