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Home // Hobbies // Electronics // Vintage Mainframe Hard Disk Clock

Vintage Mainframe Hard Disk Clock

Clock with HubMany people are turning old hard disks into clocks. They disassemble old disk drives and put a clock mechanism behind the mirrored disc platter. They’re using 3½” disks, so they end up with itty bitty little clocks. I wanted something big enough to hang on the wall and retro enough to satisfy my nostalgia for the computers of my youth.

A disk pack for mainframe computers in the 1970s

In the 1960s and 70s, mainframes and minicomputers used removable disk packs. Each pack was a stack of several 14” disks. I had the joy of using these disks on a Honeywell 200 computer at my first job.

I bought two old 14” disks via the Internet. I wanted the clock’s numerals to echo the vintage computing theme, so I rendered them in the old Magnetic Ink Character Recognition (MICR) font, which was widely recognized as “computer numbers” in the 1970s and which can still be found on checks today. I sent the rendering off to Ponoko to have them laser cut out of black acrylic.

The MICR digits

The MICR digits

One of the disks had a metal hub in the center, the other didn’t. For the disk with the metal hub, I needed to drill a 5/16” hole to mount the clock mechanism. For the disk without a hub, I needed something to fill the empty space and to hold the clock mechanism. On eBay, I bought a vintage printed circuit board for a Digital Equipment Corp. PDP-11 (an asynchronous multiplexer board, for those who care), drilled a hole for the clock mechanism’s shaft, and glued the disk to it.

The end result is two beautiful clocks worthy of an aging geek with a mid-life crisis. Which do you think looks better? Vote for one or the other below!

Clock with HubClock with PCB

Which clock looks better?

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Posted in Electronics, Featured, Hobbies and tagged as , ,

11 Comments

  • Are the platters shiny? Shiny is best.

  • How about using the arms that carried the read-write heads, or replicas thereof, as hands? I’ve just used an H200 disk platter to stand a water butt on in the garden. Perhaps a matching sundial would be an idea, the head assembly arm being the gnomon.

  • was that whole stack only 200MB?

    • My wife recently got a new cell phone. She put in a 4GB SD card and asked me “so what is this, just a little bit of flash memory?”

      She had to listen to me rant about how 4GB “is not a little bit!!” and my first floppy disk was 80K and my first hard disk was 5MB and my first computer was 16K etc. etc. etc.

    • Yes, “only” 200MB, in an era of 800/1600 bits per inch tape (typical 9-track reel-to-reel tape was ~50MB according to sources on the ‘net) and 256kB of RAM.

      [Yes, that's kB with a 1024. Often mis-typed as KiB, for those who don't realize addressing is in powers of 2]

      Kids these days .. :-)

  • They are indeed gorgeous, nice build!

  • The first one is easier to fit in a general location than the second which calls for nostalgia, also the plated one is easier to remove dust, but it seems colder than the one with circuits. I voted for the second one (score is 40% – 60%).
    BTW, you can use the dip switch to set the alarm.
    And to keep them used as they are used to you may rotate the disks to show the time (use 2 for a clock).

  • Sweet project. I think the one with the metal hub LOOKS best, but the one with the circuit board takes it for coolness.

    I once knew a junk dealer with a semi-working PDP-11. I sure wish I had that monster now…

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