As a general case, older hard drives also rotate at between 1/2 and 1/3 the
speed of today's and may be using a larger platter (further reducing the
relative speed of the platter under the head).  Both of these factors will
reduce the ability of the platter to suck the head down while it is spinning
and require that the drive be able to operate with a greater gap between the
platter and the drive.   In addition, they probably have a lower data
density on the platter itself providing a greater amount of redundancy of
'signal' to the head when it is reading from the platter.  

Without knowing what the actual drives being compared are, I can't state
that these are definite factors but the generalization for the technology
based on age are valid.

Andrew

-----Original Message-----
From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On
Behalf Of Ralph Reed
Sent: July 5, 2004 6:33 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Into the blue again :-)


  The hard drive is "sealed" but it probably has a tiny hole some where just
like an eustation tube. That would prevent the deformation.  The older one
probably works to a higher altitude because the gap between head and the
disk surface is greater. I  have been told that this actually has to do with
the  airfoil on the head. As the platter spins up to speed the head drops
down on its cushion of air.



  ----- Original Message -----
  From: "Haywire" <haywire@telus.net>
  To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
  Sent: Monday, July 05, 2004 12:16 AM
  Subject: [FlyRotary] Re: Into the blue again :-)


  > > All hard drives have a spinning platter with a read/write head riding
a
  > > cushion of air just above it.  Go to 10,300' and there isn't much of a
  > > cushion left.  The head will fall into the platter turning at 7500 or
  > > 10000 rpm.  I think you'll be lucky if the drive ever works again.
  > >
  >
  > Hi Ernest;
  > Another theory I heard is that the disc case is sealed so that at the
lower
  > pressure it deforms the case enough that the heads are no longer aligned
and
  > that by drilling a very small vent hole into the hard disc case this can
be
  > alleviated. No evidence to back it up but it is something to consider.
  > However, I ran the system recovery disc's and everything is working
again
  > although I lost allot of data, but I've been thinking for quite sometime
  > that I should reformat my drive anyway. I just wish that I'd gotten
around
  > to backing up more data.
  > Last night I loaded Jepp FlightMap onto this old Toshiba and I took this
  > flying today all the way up to 15,300' and had absolutely no problems at
  > all. It worked very well and in some ways is more appropriate to the
task.
  > It only requires 12vdc versus the 19vdc for the Sony so can be wired
direct
  > to ships power rather than the inverter/power supply that I used to have
to
  > mess with. It's only real drawback is the screen is nowhere near as good
as
  > the Sony, however I'm likely going to add a small external screen in the
  > allowing this to be slid into it's storage slot under the panel. It
sounds
  > complicated but it's not really and it gives a great moving map display
  > along with a few thousand MP3's as it also inputs to the intercom.
  > I wrote down alot of performance figures during our flights today but I
  > forgot them in the plane so will post them tomorrow if I get in early
  > enough. After 11.1 hours flying this weekend I'm a little tired and
since
  > it's after midnight, I'll post in more detail tomorrow.
  > But I need to add that today was full of adventure for my plane as we
  > rolled it, looped it, flew it to 15,300' and did some rough field
landings
  > with never so much as a hiccup.
  > I'll try to answer other e-mails regarding fuel system & prop tomorrow.
  >
  > S. Todd Bartrim
  > Turbo 13B
  > RV-9endurance
  > C-FSTB
  > http://www3.telus.net/haywire/RV-9/C-FSTB.htm
  >
  >          "Whatever you vividly imagine, Ardently desire, Sincerely
believe
  > in, Enthusiastically act upon, Must inevitably come to pass".
  >
  >
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  >
  > >>  Homepage:  http://www.flyrotary.com/
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