On Fri, 02 May 2014 21:32:05 +0100, Vir Campestris
wrote:

On 01/05/2014 23:56, Dave Plowman (News) wrote:
I'd ask then why they chose that size? No reason not to make it bigger if
a longer time was needed/possible. Remember it was a completely fresh
concept.

It meant the drive was the same size as the then-standard half-height 5
1/4 inch hard discs and floppies.I know of no other reason for the disc
size.

Incidentally one of the reasons why 5 1/4 floppies held as much as 8
inch was that one limit is the way the disc changes size with humidity!

Andy

True but you still had the same problem since the track pitch was
also scaled down requiring finer absolute indenting accuracy of the
head stepper drive. They got around this by including a suitable
length of the base material used by the floppy disks themselves as
part of the head carriage assembly which meant the changes due to
humidity levels were cancelled out.

Obviously, putting a floppy disk in the drive that had been stored in
a location with a different humdity level to that of the drive could
throw this temporarily out of alignment but this was rare on account
the disks were usually stored in the same room as the computer.
--
Regards, J B Good