On Apr 19, 2004, at 4:51 PM, Clark Martin wrote:
That is true about the disk and magnets except for the fact that there are two very powerful sets of magnets INSIDE the drive, the head positioning motor and spindle motor.
HDD's haven't had head positioning motors in a very long time. Instead they use a coil actuating system which is much faster in response.
I know about voice coil positioners, I was using motor in the basic sense which it is.
They also require very strong magnets forming the static field that the coil moves through, far stronger than the ones in motors.
I have a number of those magnets from both desktop and laptop drives. The desktop magnets are enormously strong: strong enough that when they're attached to the side of a metal desk you need to slide them off instead of pulling them off.
If you need to magnet a half-ream of paper to your refrigerator these are the ones to get!
The magnets in laptops are correspondingly smaller and less 'attractive' still they require some effort to remove from a metal desk drawer.
Moreover, we have a number of hard drives operating within about ten feet of a 300 MhZ NMR spectrophotopmeter, fields strong enough that we have to leave our wallets in a box in another room, or our credit cards get erased. The computers hum along just fine.
Strong enough to suck keys right out of your hand. I worked at Varian PAID on their NMR spectrometers. Superconducting DC permanent magnets. We also had some huge honk'in old fashioned DC magnets and huge honk'in permanent magnets. These could stick your refrigerator to a wall if you wanted.
-- Clark Martin Redwood City, CA, USA Macintosh / Internet Consulting
"I'm a designated driver on the Information Super Highway"
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