When computer memory was big iron

This picture on Gizmodo shows an ancient hard drive being taken in for cleaning. The drive weighed in the neighborhood of 100 pounds, the platter weighed about 35 pounds by itself and spun at 3600 RPMs, so the centrifugal force was significant.

It held, at most, a megabyte or two of memory -- a fraction of what is held in USB pens that slip into your pocket or onto your keychain now.

Here is the comment of someone who worked on these machines:

The picture is of a fixed-head disk, very similar to a Borroughs unit I had the pleasure of disassembling (in 1975) after a catastrophic head crash .... It took me 3 days to whittle it down to nuts and bolts, and the platter weighed 18 pounds. The hub upon which the platter was mounted was phosphor bronze, and weighed an additional 17 pounds. So imagine the inertia of 35 pounds spinning at 3600 RPM. It had electric brakes, because if you just switched off the power, it would spin for a loooong time. ... It held a few megabytes at most, if I recall correctly (a similar unit was used as a swap disk on the PDP-10, so it would have held 256K or so).