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  • Tomb💀Timetubetime@mastodon.social
    Sep 14, 2026, 1:38 AM

    it's the 70th anniversary of the IBM 305 RAMAC, the world's first hard drive! in celebration, here is a picture of a prototype RAMAC magnetic head.

    nickel-sized round magnetic head with a tiny rectangular pole piece in the middle. it is mounted in a two-axis gimbal so it can rotate to align perfectly with the surface of the hard disk. on the back is a connection for an air line.
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  • Tomb💀Timetubetime@mastodon.social
    Sep 14, 2026, 1:40 AM

    this head, unlike all the drive heads designed later, uses compressed air to float the head above the platter. a hose attaches to the nipple on the right and forces air through six tiny holes.

    closeup of the head, with the functional parts marked out: air holes, pole pieces, gap, gimbal pivots, air hose nipple.
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  • Tomb💀Timetubetime@mastodon.social
    Sep 14, 2026, 1:41 AM

    here's another prototype RAMAC head. this one has clear epoxy so you can see the internal structure.

    head being held up by one of the connecting wires by a thumb and forefinger. the gimbal mount is missing but there are pins where it would connect. the center is hollow, filled with yellow epoxy, and you can see red magnet wire wound around the pole pieces.
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  • Tomb💀Timetubetime@mastodon.social
    Sep 14, 2026, 1:42 AM

    if we zoom in very close you can see that the pole pieces have laminations just like a transformer. you can also see the copper windings.

    super closeup view showing the tiny metal pole pieces, the gap where the magnetic field concentrates, and some of the magnet wire windings.
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  • Mark J. BlairNF6X@oldbytes.space
    Sep 14, 2026, 4:17 PM

    @tubetime This makes me speculate that they assumed compressed air would be needed to fly the head, and then were surprised to find the head flying without it. Maybe the compressor failed, and the head didn't crash?

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  • argv[-1]argv_minus_one@mastodon.sdf.org
    Sep 14, 2026, 5:40 PM

    @NF6X @tubetime

    Maybe. It certainly isn't intuitively obvious that a spinning disk surface would generate its own air cushion. If I didn't already know that, then yeah, I would assume that an air pump or something would be needed to keep the head flying.

    By the way, that means a hard disk drive won't work in open space. No air.

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