[thechao]

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?

[byronknoll]

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

[thechao]

Beautiful! Thank you!

[hnlmorg]

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

I love that idea.

[blackhaz]

I wanna run my neural net on shishi-odoshi.

[rightbyte]

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.

[thechao]

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.

[jcgrillo]

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

[rightbyte]

> a 1100 hp motor to run it

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

[thechao]

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

[rightbyte]

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.

[QuadmasterXLII]

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