David R Brooks wrote:
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...

what sort of drives were these?