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Re: To bang or not to bang

sfahey wrote:

  To: Tristan Mumford
  Re: To bang or not to bang
  By: Tristan Mumford to comp.sys.apple2 on Fri Aug 31 2007 11:01 am

 > My other option is to use an Atlas-8 drive I have. What sets it aside from
 > the Apple 5.25 is it has headbang protection. Ie no rattle-rattle. However
 > using this I would need to drop a floppy controller card into my IIgs,
 > which would mean a drop to 1MHz during transfers. (Or does the IIgs do that
 > anyway with smartport devices?).

It probably does the same thing as your Apple drive; it's just quieter about
it, because it's likely a direct drive mechanism instead of a belt-driven one.


The seek mechanism of the Apple full-height drive is a big (>2") cam
with a spiral track on it.  It makes a good "speaker" when it is
vibrated against the stop by the stepper motor driving it.

The track 0 stop is adjusted a fraction of a track outside track 0
so that only the stepper motor alignment determines the track 0 cam
position. When the drive is stepped out "beyond" track 0, the cam
moves this fractional track before hitting the stop, and this movement
is what creates the classic noise.

Half-height drives don't use a cam--they are usually split-band driven
from a small cylinder about 1/2" in diameter.  In general, there is less
moving to generate sound when seeking.  They also often incorporate a
track 0 sensor that interlocks with "seek out" so that they ignore
attempts to seek out past track 0.  Otherwise, the seek mechanism would
put stress on the split band, the head carriage, the rails, and the
track 0 carriage stop if it were "banged".

Since the track 0 stop on a full-height drive is a mechanical interlock
on the cam itself, only the cam and the stepper motor are affected by
"overstepping", and they easily tolerate the moderate torques produced
by the stepper.

-michael

NadaPong: Network game demo for Apple II computers!
Home page:  http://members.aol.com/MJMahon/

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