A Purely Mechanical Useless Machine Prototype

Many of the people that enjoy this site are probably people that have seen video of “The Most Useless Machine.”  Pretty neat, of course, a switch is flipped, and a finger rises up to turn itself off.  This generally uses a circuit that is reversed when the switch is flipped.  Being a mechanical engineer, at some point I thought that this could be done without using any electronics.  The video below is my prototype of this clockwork useless machine concept:

This is my first attempt at any sort of clockwork, and my Zen Toolworks CNC router was immensely helpful (here’s one of my latest posts on it).  It’s really great to be able to design something on Draftsight (AutoCAD clone, see my review), and just feed it to my router through CAMBam.  Getting this router has really opened up lots of possibilities for me.

mechanical useless machine MDFThe concept behind this machine is that a driving wheel, driven by a weight on a string, pushes and pulls a linkage that rotates the “finger” approximately 90 degrees up and then down.  This finger then pushes the switch back into place, which mechanically pushes the middle linkage down, stopping the driving wheel each time when the “finger” is down.

As seen tin the video, the switch is stopped from rotating too far by nails in both the “on” and “off” state.  This causes the middle linkage, reminiscent of an escapement in clock making, to stop the driving wheel when the finger is down.

The device isn’t really all that complicated, and in reality, the finger doesn’t reverse itself by turning the switch the other direction.  The finger would go down either way and just keep going in and out until the weight unwound the string attached to the driving wheel.  This wasn’t a particularly easy build though, since there were quite a few parts that had to be just the right length or shape.

mechanical clockwork useless machineAs of now, it’s just a prototype, but hopefully I can develop it into something really cool.  The things that need some work are getting enough force out of the finger to lift the lid on a box correctly, so it will pop out, and slowing down the motion a bit to make things more visible.  These things seem like they could work against each other, so it will take some thought.  Also, a better method of winding the string would be extremely helpful as well.  Right now, one has to remove the assembly from the box and wind it by hand.


Before searching around, I wasn’t sure if there was another “useless machine” that was purely mechanical.  The one in the video below is made from Legos, so I though I would include it for your viewing pleasure:

Be sure to check back or subscribe to see if I ever get this prototype’s kinks worked out!  Also, you may want to check out my “Even More Useless Machine” that is a converted air freshener that opens a door part way when it sees light.  Pretty useless.


  1. A Clockwork Useless Machine Prototype - Hack a Day - pingback on May 8, 2012 at 7:02 am
  2. I think both this and your tiny useless machine are fantastic.

  3. Hai! Can I find a lay-out / drawing of this for diy?

    • Hi, I don’t have the drawings in a very refined form that you could just cut out or 3D print. Here’s one of the drawings that I have, but I’m not sure if it’s everything or the final design. I’ve got another one with some random modified parts, so I think that was the first try, then I cut out a bunch more to try until it worked.

      It’s been a while since I made it though!

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