27 Jan
2014
27 Jan
'14
4:35 p.m.
Many of the analog ones were made with two
tones. One would be 1 cycle off per revolution.
The space between the two tones would be the center
of the tracks.
No need to make an eccentric spindle.
If you want to make an eccentric, it is easy
if you saw the end off and make a center hole
slightly large and connect it back tot he spindle
with a screw.
Dwight
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Date: Sun, 26 Jan 2014 15:18:18 -0800
From: cclist at sydex.com
To:
Subject: Re: 1541 Alignment disk
On 01/26/2014 12:53 PM, Tony Duell wrote:
I think machining the drive hub to give the rigth
degree of sccentricity
would be non-trivial.
Were I do go about this, I'd probably start by gluing a thin shim (a few
mills) into the cup of a Shugart-style clamp arrangement. Most drives
still use this. The "cone" has flexible fingers, so it should matter
for thin shims. Failing that, you'd probably have to separate the cup
from the spindle and tinker some with the shaft hole.
I did wonder if you could modify the positioner
circuitry. Most floppy
drives use stepper motors, and as is well-know, if you feed carefully
controleld currents into the windings you can 'micro step' them, you can
get them to settle between their normal positions. I wonder if you could
feed sutiable signals in to wobble the headjust enoguh (synchronised wit
hthe spindle rotation) to write the eccntric track.
In the case of 5.25" "megafloppy" drives, such as the Drivetek, that
would be almost trivial, once you got into the drive MCU firmware That
is, if the "fine" stepper could move quickly enough.
--Chuck