Re: magnets in HDs

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Dale Nassar by way of Terry Fritz <twftesla-at-qwest-dot-net>" <dnassar-at-i-55-dot-com>

The magnetic field is confined to the space between the two magnets--to 
make a parallel field--for the wire-wound end of the read-write head to 
intersect perpendicularly for maximum torque--did you notice the coils that 
pivot? one part of the coil is confined to one half of the magnet and the 
other part to the other half--also if you look at it you will see that the 
current flowing in these two parts of the coil are always traveling in 
opposite directions--it follows that the magnetic fields in opposite 
directions in each half of the pivot space.

Sometimes you see all four magnets--two on top and two on bottom--making 
the poles N-to-S from top to bottom on one side and S-to-N from top to 
bottom on the other side.  Sometimes the two magnets in the top and bottom 
are a solid piece,however it is easily shown that they DO alternate.

One more note:  I once showed a guy the power of this magnet and he said 
"Be sure this thing is about 50 yards from your computer"--of course it 
actually came from within a couple of inches from the internal drive platters!!

Generally It takes a LOT more magnetic exposure to erase a disk think most 
people think.  Take a regular (weak/everyday) magnet and test exposure 
times on a floppy disk--you'll be surprised at the determination of the 
data to remain intact!

»»dale nassar

At 09:23 PM 5/8/02 -0600, you wrote:
>Original poster: "BunnyKiller by way of Terry Fritz <twftesla-at-qwest-dot-net>" 
><bigfoo39-at-telocity-dot-com>
>
>Tesla list wrote:
>
> >Original poster: "Mr Gregory Peters by way of Terry Fritz
><twftesla-at-qwest-dot-net>" <s371034-at-student.uq.edu.au>
> >
> >After reading the post on magnets in hard drives, I was somewhat
> >skeptical - after all, don't magnets ERASE hard drives? Anyway, I
> >decided to pull apart an old 1 Gb SCSI hard drive I had lying around. It
> >was difficult to find, but there is definitely a strong magnet in there.
> >It is near where the read/write head "arm" connects to the HD chassis.
> >It seems to be in some sort of "anti-magnet" metal enclosure, as I could
> >not detect it at all with a screwdriver until I pulled it completely
> >apart. It is very strong. There was only one magnet in this drive, but I
> >reckon if I had two magnets I would not be able to pull them apart. The
> >magnet is arc shaped, about 1.3" long x 0.5" wide x 0.2" thick. I would
> >love to know what kind of magnet it is if anyone knows.
> >
> >Cheers,
> >
> >Greg Peters
> >Department of Earth Sciences,
> >University of Queensland, Australia
> >Phone: 0402 841 677
> >http://www.geocities-dot-com/gregjpeters
> >
> >
> >
> >
> >
> >
> >
>Hi Greg...
>
>these are Neodimium ( spelling) magnets...  they are some of the most
>potent magnets around...  If you had 2 of them and by accident put your
>finger between them, you would get a serious blood blister. They are
>POTENT little magnets....  quite capable of deflecting EMF and
>perminently damaging your computer screen from 12"...
>
>what I have always wondered is why you cant put a magnet back together
>once you break one in half.....  the joint is perfectly matched .....
>but it still repells each of the matching halves no matter how hard
>t\you try to press them back together....  :)
>
>Scot D