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Comment by mnw21cam | Hacker News Reader

It's missing capacitors and inductors.

Did you know - a boost switching regulator was used to pump water up to the top of a garden in Victorian times. The regulator uses the water pipe analogy to electricity, except electricity hadn't really been invented then. The system uses an inductor (a long straight pipe, where the water has momentum), and a switch (a flap that closes and opens regularly), with a diode (one-way valve) and a capacitor (a container with a pressurised air cavity). https://en.wikipedia.org/wiki/Hydraulic_ram

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Acoustics is a more direct parallel, and even uses the same unit- the acoustic Ohm. The hydraulic Ohm also exists, but is not really used.

Helmholtz resonators[1] are used to provide capacitive acoustic impedance in a gas system. Archetypically a beautiful hollow copper sphere. Ported subwoofers use the same formulas, as do some types of automotive exhaust. Exhausts use a long pipe and cylindrical section to form a low-pass filter, which transforms the individual exhaust bursts of an engine into a smooth continuous flow. Two stroke exhausts[2] are band-pass filters that improve compression by putting backpressure on the engine at the correct time.

[1]: https://en.wikipedia.org/wiki/Helmholtz_resonance

[2]: https://en.wikipedia.org/wiki/Expansion_chamber#/media/File:...

Electrics, Acoustics, Hydraulics, Mechanics, ... They are all mathematical duals of each other. Just the terminology is different in each field (pun?). James Clerk Maxwell, who wrote down the fundamental equations for electromagnetism, also worked in acoustics.

https://acousticstoday.org/past-issues/james-clerk-maxwell-a...

Check out Spintronics, it's a game/kit for building mechanical analogs for electric circuits. It's coming out sometime this year from the same team that made Turing Tumble.

https://www.kickstarter.com/projects/upperstory/spintronics-...

Has anyone tried Turing Tumble? Would you recommend it? Thinking about getting it for an upcoming bday for one of my kids.

It is nice, and the things you can do are amazing. As an adult I enjoyed playing it.

My 9 year old brother found it quickly too hard though.

I bought it and explained to my kids (7 and 3) that it's "daddy's game" and they can watch me play it but can't play it without me. My 7 year old daughter helped me up through about the first 1/3rd of the game but then quickly it became too hard.

It does a good job of introducing concepts slowly but they are in fact hard concepts if you're new to them. It is actually a bit of a challenge for adults too.

Mechanically, the game is good but a bit finicky to set each piece in place. That means the time between "I think I know what to do" and testing it out is a bit too long. Overall, I find it pretty fun though. (I also backed the spintronics kickstarter)

Thanks for that, this looks indeed like a fantastic educational game (previous discussion [0]). Seems there is a similar game to building "computers" [1] as well.

[0] https://news.ycombinator.com/item?id=27222457

[1] https://www.turingtumble.com/

Thank you. Stuyding the hydraulic version really helped prepare me to understand the electrical version. I've been wanting to understand how boost converters work for a while, so this was super useful and interesting!

> The system uses an inductor (a long straight pipe, where the water has momentum),

How would you model mutual inductance in other circuits?

A hydraulic cylinder connecting the systems would work. It maps voltage (pressure) between two disconnected systems through a ratio of windings (piston area). It only creates flow when there is a change in voltage (pressure) and current (flow), and if the circuit is open on the induced side then the transfer of energy is limited to the capacitance (compressibility) in the circuit.

Yes, that's always been my favourite hydraulic-electrical analogy!

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