pgboswell

Thanks a lot, dang! That's ok - it's been super interesting to read what other people have to say without being a part of the conversation.

Yeah, good question. My first attempts were with fluids: water and air. Water doesn't work very well because there's a lot of resistance to flow unless the pipes are large in diameter. It's not practical for anything but the simplest of circuits. So I went with air for a long time before I realized it had no chance, either - when it compresses and decompresses, it heats and cools, and that energy is lost to the surroundings. It makes horribly inefficient circuits. It's also hard to seal moving parts without adding an unacceptable amount of friction. And finally, you still can't see air moving through a circuit.

So I stepped back and thought about how to do it mechanically. But the hardest part of a mechanical circuit is the absolute simplest part in electronics: the junction. That is, where electricity flows in one wire and splits along two wires. How do you make chain or a belt split? Not only that, but it has to follow Kirchoff's law: the sum of currents leaving the junction must equal the current entering the junction. I finally realized that's what a differential gear arrangement does, and planetary gears are a sort of differential arrangement that would work perfectly for this. It was very, very hard to make the mechanical junction so that it had low resistance while under load, but I eventually got it. Once I had that, I knew it would all work.

Yup. I actually tried making an analog of electronics with water and air first. Water didn't work very well because of the high resistance. Air didn't work very well because of it's compressibility - each time it compresses and decompresses, there's serious hysteresis and you lose a ton of energy.The trickiest part to make in a mechanical version is the simplest part in electronics - the junction: Where one wire splits into two wires. I spent a lot of time trying to figure out how to do that with anything besides a fluid or a gas. Fortunately, planetary gear systems do the trick. Once I got that working, everything fell into place. Using a junction, you can easily make parallel circuits. Capacitors are just torsion springs in the spintronics model.

I think there's space for two spintronics. They are different enough that I don't think anyone will get confused.

This is very interesting. Why would they be faster?

For sure - at least with the parts in their current form. A simple flip-flop takes up a minimum space of about 30 cm x 30 cm. But I wonder how small these parts could get. Like, what if spintronics was invented in the 19th century instead of the 21st century? Would Moore's law have applied to mechanical transistors?

Thanks so much for the kind words.

Ha ha! Thanks so much!

Hey cool! I made this. It's fun to see it here on Hacker News!