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?

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

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/

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?

What a gem of a site Thank you for sharing