C
CJT
I think he knows what it means. But it didn't fit the context.Seymour said:
F
Folkert Rienstra
Al Dykes said:
Yeah, Huh!
And fix your newsclient, you are spreading reply addresses
all around the internet for any virus and spam spreaders to see.
D
Dorothy Bradbury
I think the 10,000ft altitude is for reasons of air density:
o At altitude you will move the same cfm of air
o However due to lower density the mass of air moved is less
For 10,000ft that reduction in actual mass of air is large.
Whilst the drive has a max temp of say 52 or 55oC, some
components on the PCB have a higher temperature - such as
motor drive ic's. So whilst the drive may be in spec, you can
have components out of spec. A drive tends to have a spec
airflow in m/sec over its surface - which is your m^3 through
a particularly cross-sectional area. You would have to adapt
the m/sec airflow for that at your an altitude, eg, 10,000-ft.
I think there may be something in the head flying over the disc,
but you'd have to perhaps dig someone out of IBM Almaden.
At really high altitude, you're talking about aviation integration,
and that brings into play other design factors - re ruggedness,
sealed NEMA enclosures, ability to withstand fogging, things
like condensation, shock, vibration, and lots of other nasties.
Could also be a more practical reason for a 10,000ft limit:
o Argument may be head-flying or cooling re air mass/density
o Argument could equally be one of not testing to say 75,000ft
Exactly how many users are going to be operating a hard drive in
an unpressurised aircraft at altitudes above 10,000ft? Sit on top
of a U2 operating your laptop with the wind in your hair?
That could be a real bad hair day.
Still, it would be interesting to know what the spec is for a laptop
disk - you could want to email someone from the top of Everest.
"Honey, I think I left the gas on - could you just pop home & check?".
In that instance I'm sure an explorer reported that HD didn't work.
Either that or he'd forgotten to charge the battery... ...
o At altitude you will move the same cfm of air
o However due to lower density the mass of air moved is less
For 10,000ft that reduction in actual mass of air is large.
Whilst the drive has a max temp of say 52 or 55oC, some
components on the PCB have a higher temperature - such as
motor drive ic's. So whilst the drive may be in spec, you can
have components out of spec. A drive tends to have a spec
airflow in m/sec over its surface - which is your m^3 through
a particularly cross-sectional area. You would have to adapt
the m/sec airflow for that at your an altitude, eg, 10,000-ft.
I think there may be something in the head flying over the disc,
but you'd have to perhaps dig someone out of IBM Almaden.
At really high altitude, you're talking about aviation integration,
and that brings into play other design factors - re ruggedness,
sealed NEMA enclosures, ability to withstand fogging, things
like condensation, shock, vibration, and lots of other nasties.
Could also be a more practical reason for a 10,000ft limit:
o Argument may be head-flying or cooling re air mass/density
o Argument could equally be one of not testing to say 75,000ft
Exactly how many users are going to be operating a hard drive in
an unpressurised aircraft at altitudes above 10,000ft? Sit on top
of a U2 operating your laptop with the wind in your hair?
That could be a real bad hair day.
Still, it would be interesting to know what the spec is for a laptop
disk - you could want to email someone from the top of Everest.
"Honey, I think I left the gas on - could you just pop home & check?".
In that instance I'm sure an explorer reported that HD didn't work.
Either that or he'd forgotten to charge the battery... ...
P
Peter
My application was a deep sub-sea project at very high pressures. I
can guess that at high pressure the air will turn to liquid and that
will certainly stop the drive working. And in a vacuum the head will
simply scrape over the surface of the disc as there will be no
aerodynamic behavior at all. Somewhere in the middle a disc drive
operates within spec.
can guess that at high pressure the air will turn to liquid and that
will certainly stop the drive working. And in a vacuum the head will
simply scrape over the surface of the disc as there will be no
aerodynamic behavior at all. Somewhere in the middle a disc drive
operates within spec.
L
lars
Actually 10,000 ft is not extreme altitude. Quite a few people
live at that level.
When trekking in Nepal I have done emails in Internet cafés
(satellite), at Namche Bazaar, which is at some 12,000 ft. They
had some fairly new desktops and at least one well used
Thinkpad. I am sure the HD´s were just plain ordinary.
I also know that at Everest Base Camp, abt 18,000 ft, the
expedition base camp crews send out emails daily.
If I remember correctly it is mentioned in the book "Into Thin
Air" (great book!), that a jet set American female climber had
porters lug her Thinkpads, and quite a supply of batteries,
almost all the way to the top of Everest. At least to camp 7,
at some 25,000 ft, so that she could write her diary in style.
I believe that at 18,000 ft the air is about half as dense as
at sea level. It seems to be enough for a lap top.
Lars
Stockholm
live at that level.
When trekking in Nepal I have done emails in Internet cafés
(satellite), at Namche Bazaar, which is at some 12,000 ft. They
had some fairly new desktops and at least one well used
Thinkpad. I am sure the HD´s were just plain ordinary.
I also know that at Everest Base Camp, abt 18,000 ft, the
expedition base camp crews send out emails daily.
If I remember correctly it is mentioned in the book "Into Thin
Air" (great book!), that a jet set American female climber had
porters lug her Thinkpads, and quite a supply of batteries,
almost all the way to the top of Everest. At least to camp 7,
at some 25,000 ft, so that she could write her diary in style.
I believe that at 18,000 ft the air is about half as dense as
at sea level. It seems to be enough for a lap top.
Exactly how many users are going to be operating a hard drive in
an unpressurised aircraft at altitudes above 10,000ft? Sit on top
of a U2 operating your laptop with the wind in your hair?
That could be a real bad hair day.
Still, it would be interesting to know what the spec is for a laptop
disk - you could want to email someone from the top of Everest.
"Honey, I think I left the gas on - could you just pop home & check?".
In that instance I'm sure an explorer reported that HD didn't work.
Either that or he'd forgotten to charge the battery... ...
Lars
Stockholm
D
dg
You may be able to use a flash memory drive of some kind. I don't know the
operating specs of them but I would guess that they may be more tolerant to
more extreme pressure levels. While they won't have issues with
aerodynamics of a head passing over a platter, they might have some other
limitation.
--Dan
operating specs of them but I would guess that they may be more tolerant to
more extreme pressure levels. While they won't have issues with
aerodynamics of a head passing over a platter, they might have some other
limitation.
--Dan
J
J. Clarke
Peter said:
If you're going to be designing systems to work at high pressure, you need
to familiarize yourself with the physics of the situation before you do
anything.
Air will not liquefy at _any_ pressure until the temperature gets below the
critical temperature of one of its components, and the critical
temperatures for all the major components of air are more than 100C below
the freezing point of sea water.
When you are doing engineering, do not _guess_.
At that kind of pressure I doubt that the sealed mil-spec drives would hold
up--while they'll take some pressure they aren't designed for those levels.
You need to either make a pressure vessel to hold the drives or you need to
go to an alternative technology that is not dependent on a specific range
of air pressures.