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What's an order of magnitude among friends?

What's an order of magnitude among friends?

Posted Jan 31, 2013 20:51 UTC (Thu) by rgmoore (✭ supporter ✭, #75)
In reply to: What's an order of magnitude among friends? by drag
Parent article: Quotes of the week

Bullets are not known for their rugged construction; in many cases it's considered desirable if the bullet breaks up on impact so it can dump its kinetic energy more efficiently. Devices that are intended to operate at 72K RPM and above are certainly practical. Many of the machines I work with have turbomolecular pumps that operate in that speed range, and their diameter is larger than a disk drive so the force is larger as well. Similarly, ultracentrifuges operate at substantially higher speed than that- they can go above 100K RPM- without exploding. The thing they have in common is that they operate under vacuum to minimize friction. I suspect an ultra-high speed disk drive would need to do the same. As long as the vacuum is maintained, they would probably be pretty quiet. The motors would tend to give off a ~1200 Hz (e.g. 72K cycle per minute) whine.


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What's an order of magnitude among friends?

Posted Feb 2, 2013 18:25 UTC (Sat) by nix (subscriber, #2304) [Link]

The motors would tend to give off a ~1200 Hz (e.g. 72K cycle per minute) whine.
Right around the human hearing frequency optimum, and right in the range critical for comprehension of human speech.

What's an order of magnitude among friends?

Posted Feb 2, 2013 18:27 UTC (Sat) by Tet (subscriber, #5433) [Link]

they can go above 100K RPM- without exploding. The thing they have in common is that they operate under vacuum to minimize friction

You don't even need that. Most turbos routinely spin in excess of 100K RPM without needing a vacuum, and the Honda CX-500 had a turbo that spun at 200K RPM. Pretty insane, but it worked.

What's an order of magnitude among friends?

Posted Feb 8, 2013 0:16 UTC (Fri) by dfsmith (guest, #20302) [Link]

Did it work at 100kRPM for 5 years continuously?

What's an order of magnitude among friends?

Posted Feb 13, 2013 22:17 UTC (Wed) by Lennie (guest, #49641) [Link]

Western Digital says they are going to release Helium-based products 'soon'.

So this isn't an alien concept to producers of harddisks.

What's an order of magnitude among friends?

Posted Feb 14, 2013 17:58 UTC (Thu) by nix (subscriber, #2304) [Link]

Wow. How will they stop it leaking out in short order? (Hey, maybe they prefer that: if it leaks out in three years, you'll be *forced* to buy a new disk!)

What's an order of magnitude among friends?

Posted Feb 14, 2013 19:49 UTC (Thu) by Lennie (guest, #49641) [Link]

Arstechnica has an article with information about that:

http://arstechnica.com/information-technology/2012/09/hel...

The register mentions some more about the advantages and specifications:

http://www.theregister.co.uk/2013/01/08/wd_helium/

What's an order of magnitude among friends?

Posted Feb 15, 2013 18:13 UTC (Fri) by nix (subscriber, #2304) [Link]

Hm, they're saying it would *lengthen* drive lifespan. Obviously they think containment isn't that problematic, or is a solved problem, in which case I'm babbling about nothing (as usual).

What's an order of magnitude among friends?

Posted Feb 20, 2013 0:49 UTC (Wed) by man_ls (guest, #15091) [Link]

Helium is the second most inert of all gases so it is not hard to contain. Hydrogen (as said below) or even liquid helium (as you can read on the wikipedia) are harder. With helium gas you just seal the container and it just stays there, without condensing or interacting with the walls or other gases; it shouldn't be harder than creating a vacuum.

What's an order of magnitude among friends?

Posted Feb 21, 2013 21:11 UTC (Thu) by mikewd (subscriber, #46016) [Link]

"Helium is the second most inert of all gases so it is not hard to contain. Hydrogen (as said below) or even liquid helium (as you can read on the wikipedia) are harder. With helium gas you just seal the container and it just stays there, without condensing or interacting with the walls or other gases; it shouldn't be harder than creating a vacuum."

The problem is that the diffusion rate of helium through glass or epoxy and other glues and insulators can be quite high at room temperature (as a low temperature physicist well knows). So the container needs to be all metal with a soldered or welded seal.

Mike

What's an order of magnitude among friends?

Posted Feb 22, 2013 10:28 UTC (Fri) by khim (subscriber, #9252) [Link]

So the container needs to be all metal with a soldered or welded seal.

Well, we are talking HDDs here. They used "all metal" containers for decades now anyway. Usually they had some filters and were not welded shut, but that is minor change IMO.

What's an order of magnitude among friends?

Posted Feb 22, 2013 18:12 UTC (Fri) by magila (subscriber, #49627) [Link]

There are many openings in a hard drive which are currently sealed with epoxy or plastic/foil adhesives. The biggest is the seal between the top cover and the drive body but there are also many holes used during manufacturing. If you examine a hard drive's casing you can see where these have been sealed with circular stickers. Less visible are the openings for the spindle motor and servo/channel control lines.

Making all of these openings impermeable to He is not a minor change and will likely significantly increase the cost of the drive.

What's an order of magnitude among friends?

Posted Feb 14, 2013 23:43 UTC (Thu) by dlang (subscriber, #313) [Link]

Helium isn't that bad to contain. You are thinking of how hard it is to contain Hydrogen.


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