Millihertz 5 Mechanical Computer (2022) | Hacker News Reader

Millihertz 5 Mechanical Computer (2022)

srimech.com

95 pointsgene-h18 comments

I've always wanted to build (distinct) mechanical computers out of the following kinds of elements:

1. Spur-gear differential; and,

2. Shishi-odoshi.

Both of these are saturating mechanical devices that can be used to build NAND gates; the latter, I think, would be very pleasing, if exceedingly slow.

For the spur-gear differential, you'd need to up-scale the output by a factor of 2 (since the output is half-speed), and use a locking wedge to build a one-way gear out of one of the spur-gear differentials. However, it has the nice property that the logic is made entirely out of a single element: the spur-gear differential.

Similarly, for the shishi-odoshi: you're going to have to do a bit of analysis (drilling a hole in the bottom part of the bamboo ladle), to figure out the in-flow and out-flow to build the basic AND gate, and then balancing out the NOT gate, to build your basic NAND. This is, obviously, very finicky; but, I supposed, that'd be quite a bit of the charm of a Zen computer garden?

A shishi-odoshi ALU would be amazing to see…and hear too.

I love that idea.

I wanna run my neural net on shishi-odoshi.

Has any computer been built out of spur-gear differentials? Like maybe some sort of adder circuit, not necessarily a full instruction executing computer. The only uses I could find was what seems to me like the differentials being part of some sort of analogue computer.

Spur gear differentials are naturally adders (with carry!); so, traditionally they've only ever been used for analogue logic. They're overly complicated for digital logic: you need two spur gears to build a single gate (NAND) to perform a single binary operation. If you want any sort of reasonable lash characteristics you're going to need ~60 teeth. At that point, two 60 teeth spur gears give you a 3600-valued adder. That'd take something like 300+ spur gears in binary: it just doesn't make any damn sense.

I think the last time I looked at this, if I used the cast spur gears available I needed a staged approach to "start" the computer and a 1100 hp motor to run it.

> a 1100 hp motor to run it

Oh, ye that sounds impractical. A really big truck engine more or less.

Convincing Mrs. thechao that we needed to drop 80000$ on a blown V8 to build a 4b 3 function calculator didn't workout, BTW.

Well I want to be on your side but I think one need to keep the dreams not within grasp but at least in sight.

A huge steam engine might be the ticket, that'll solve your starting torque problem

I built some logic gates using water and a 3D printed "seesaw" that tilts to the left or right: https://byronknoll.blogspot.com/2022/06/water-computer.html

Beautiful! Thank you!

the shishi-odoshu seems like the more promising avenue. The key question in mechanical computing is never designing gates, its designing power amplifiers.

I just smile hearing the term "Millihertz Computer". I'd love it if building and designing mechanical and analog computers grew as a hobby/educational activity as I find them both fascinating and somehow satisfying.

Also, this 1950s Naval Training film explaining the fundamentals of how mechanical fire control computers work to solve complex problems is excellent. https://www.youtube.com/watch?v=s1i-dnAH9Y4

I was incredibly surprised to find that this actually is a computer. Normally when you hear about a "computer" constructed in an unusual medium, it turns out to just be a binary adder or an analogue computer. I've learned to expect disappointment.

About 8 years ago I visited TU Chemnitz and they had a lab making similar things to this. It wasn't clear to me what the goal was, but it was very cool nonetheless.

Is anyone going to produce a proof-of-concept Analytical Engine?

Will robots (which will hopefully soon be available) be able to do it?

This brings to mind two stories: Exhalation by Ted Chiang (short story), and the Three Body Problem (specifically the human computer) by Cixin Liu (novel length).

Exhalation really gets me thinking about what it means to be sentient & self-aware. If the neurons in our brains could, even in theory, be simulated by logic gates then, equally in theory, a Turing machine could be sentient. I can even imagine a bunch of rocks being sentient: https://xkcd.com/505/

What a gem of a site Thank you for sharing

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