The Almost Useless Machine

We all know, we should use more renewable energy. Here is my contribution. Use solar power if you want to cut 20mm wooden rods. And plan ahead because it may take a while.

This little machine uses a so called solar engine to drive the motor. This solar engine is able to collect tiny amounts of energy over time and stores it in large capacitors. When the voltage reaches a certain level, it opens up and uses all the stored energy at once to drive a motor. These engines were used to drive tiny BEAM-bots and were quite popular a while ago. A lot of information can be found at on how to build them and how they work.



The machine works fine. That is … most of the time. Sometimes the solar engine locks up in the state where it dumps all the energy to the motor. It works like this:

  • The two solar panels charge the capacitors until they reach ~2.85 V.
  • The 1381 drives the transistor open and the motor starts turning
  • The voltage drops until 1.1V, the motor stops turning
  • Now there maybe a balance between the solar panels to provide enough current to hold the voltage and the motor on the other hand, not consuming enough.

In the video, there was bright sun light. With that, the machine runs quite well, even without having to pause to collect more sun light. In that condition, I’m quite sure, it would have worked without the solar engine.

To solve that, there are a couple of other solar engines on the BEAM wiki, that I can try, even if most of them were not designed for this high power use case. If someone has any tipps or hints, please add a comment below.

Links and Downloads


  1. Great contraption!
    You should offer it as a kit, I bet there are many people who would be interested (me included).
    (Same for the 2 euro machine.)


  2. take a while, how long, even in full sun? looks like there’s very little pressure on the blade, might take months?


  3. Brilliant! I have to build one… and thanks for the link to BEAM wiki, I didn’t even know this was a Thing.


  4. hi from Frankfurt,

    can you give a tipp how to create/construct this gears you use? i am a portal cnc newbie and would love to are able to create this by my own.
    cool project ;)



  5. I’d definitely buy this in a kit. You could test the waters by making a kickstarter project.


  6. I’d buy it as a kit, or constructed. It would be the coolest gift for my dad.


  7. Awesome just Awesome !!! Really cool display would love a kit of this this is just too great !!

    keep up all your cool projects


  8. So this could power what kind of water pump? :) Seriouslky, though, it might power an Archemedes’ Screw well enough to pump some water before it evaporates :)


Comments are closed.