Wednesday, May 9, 2012

Mechanical Computers

Some people are surprised to find out that computers can be built from mechanical operations without any electronics.  I would like to some day implement a mechanical computer that can do things people would recognize, like word processing and other things - but getting these things to operate faster than ~10hertz can be tricky.  In addition, if an invalid instruction is programmed into the mechanical processor then it is possible to damage the computer, possibly taking months to repair.  (ouch!)

Here's an example of Charles Babbage's difference engine (invented in the early 1800's), reconstructed with legos, which can be seen operating in a video below.  The difference engine can calculate polynomial functions with sufficient accuracy to approximate non-polynomial functions like logarithm or square root.  These could then be used in a table to look up the approximate results of the function for a certain input.  Considering that slide rules were in common use as recently as the 70's, the difference engine was really ahead of its time.

Perhaps best of all, mechanical computers make mechanical noise - perfect for providing that steampunk atmosphere!

P.S. That picture is from The Guild.  The episode and show are definitely worth watching :-D


  1. If it's parts were as small as transistors in microchips:

    Mechanical memory would be durable replacement for flash memory in a hybrid where transistor controlled electric motors push and pull nanoscale switches. Cheaper version would be writable once, and possibly could be erased by turning it 90 degrees or shaking, so it might not be usable other than maybe for readyBoost and swap.

    FPGAs would benefit from such mechanical parts.

    Mechanical computer would work in owen, fire or in a space probe made to work in the surface of Venus.
    Aircraft black boxes one use.

    Mechanical memory could be read with x-ray microscope.

    Stands storage and radiation especially well, but may be difficult to do so, that dropping it, would not cause reboot and wipe of memory.

    May work best in vacuum or helium, because of lesser air resistance. Or maybe not, because even air and other gases have some lubrication effects...

    Closest thing to a mechanical digital camera would involve array of metal spikes expanding in heat.

    If it were in macroscale:

    Analog to digital and digital to analog converter i.e. system to turn a wheel to a precise position might be usefull.

    Some kind of mechanical computer would look cute in a shop window. 3D printing would probably be the best method to make it.

  2. For decades, cash register machines were mechanical calculators.

    In a way, a mechanical clock is doing some computation. It is bit strange how common new mechanical clocks are even today. I wonder, if there is even usb connectable mechanical clock...

    Metal key turning in a lock is bit like computation.

    If one tries to think one purpose for some type of actual mechanical computing machine where it might be advantageous that it's parts are just big enough that they can be seen by naked eye, I guess that purpose would relate to security and encryption keys. For example, a 1024 bit public key would be encoded as holes to a metal disk or metal sheet, and done something in front of a group of people... Voting machines possible (another) use, with or without it relating to encryptions...

  3. good to see that machine and parts as these backs me to my earlier life...
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