Ernie Sty wrote:
A guy I know bid on an old non-working hard drive. It was big, something
like ten inches by maybe 18 inches by three inches. I asked him why he
wanted it, and he said he'd show me.

A few days later, the display on my CRT started wobbling. The guy was
holding a magnet a good six feet away from my monitor and rotating it
slightly. Needless to say, he got it out of the hard drive. He had to use
a ball joint separator to get the two magnets apart. Each one was about the
size of two decks of cards, if I recall correctly.

I never found out what the strength of those magnets was. He soon made the
mistake of holding one in each hand. They got too close together and in a
split second they had collided, nipping off a little of the skin from his
fingers in the process. I figure he's really lucky that's all that
happened. I can think of a number of ways it could have been worse.

He brought in the now-stuck-together magnets and surprisingly (to me,
anyway) their magnetic pull for other objects was very weak, like they were
each absorbing the magnetism of the other. I asked if he was going to try
to separate them, and he said no, and showed me that they were both cracked.

I think he was, too, a little.

Anyway, that's all the experience I've had with what were to me monstrously
powerful magnets.


I once worked as a service tech on drives like that. Those magnets
probably came out of the head positioner, which is a *righteous* linear
motor. There might have been a nice DRO-like glass scale to go with it.
We were severely warned to keep hands out of that thing when the power
cord was in. If it detected a low-speed fault (like, the power fails), a
crowbar SCR dumped the 48V supply cap. into that motor coil, to drag the
heads off the disk instanter. You really did not want fingers in the way
of that...