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title: K'nex Adding Machine
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# K'nex Adding Machine

This is a project I did my freshmen year of high school. 100% for fun, I built a binary half-adder using mechanical logic gates constructed out of K'nex. If you know what that means, good for you! If not, you can watch this lovely video. (Keep in mind this is from 2004.) The logic gate designs for the NOT and AND gates are my own. (The design for the OR gate is, as they say in patent lingo, "obvious to a person having ordinary skill in that field".)

Some statistics about the video:
- It has generated over *70,000 views* and had a steady viewership!
  ![graph of YouTube views since 2007](./KnexViews.png)
- It was on the *front page* of Google search results for "mechanical logic gates" for some years.
- For many years, it was the top YouTube search result for "mechanical logic gates". *Update 2013/07: It's dropped to #3. There are a whole bunch of new videos related to the field too!*

<iframe width="560" height="315" src="https://www.youtube.com/embed/3vXlQZvS-nM" frameborder="0" allowfullscreen></iframe>

*Video of my mechanical adding machine constructed in 2004*

At the time this was uploaded, there was very little material on the Internet on mechanical logic gates. There were a few Lego designs using rotating shafts, but that was it. **This work is completely unique;** ~~as far as I know, no one has built anything using these logic gate designs before or since.~~ *Update: My work was cited in a [project proposal](https://mechalogic.wordpress.com/about/) by some Carnegie Mellon University students.* I think I made a significant dent in the field of mechanical logic gates.

The top hit for "mechanical logic gates" (http://goldfish.ikaruga.co.uk/logic.html) includes a link to my video. I suggested the owner add that link, because there was so little information on mechanical logic gates at the time. Since then, more people have constructed binary adders using mechanical logic. However, my machine is still special because it is reversible - most designs I have seen since require marbles falling or some other process that must be manually reset.