The "rotational" logic version was suggested to me as a way to implement a computer by a mechanical engineer in ~2004. He claimed that such a "boolean calculato

The "rotational" logic version was suggested to me as a way to implement a computer by a mechanical engineer in ~2004. He claimed that such a "boolean calculator" had been initially designed as an alternative to the first electromechanical computers during WW2 — trading off speed for reliability. The design he suggested used spur-gear differentials for all parts of the computer, including the one-way gear (using a free-spinning axle and a pall). Using a single "element" (analogous to the transistor) simplifies design & implementation. (The one-way gear shown in the video has failure modes that the one-way spur-gear mitigates to a great extent.) I've always wanted to build one out of wood and brass. A rotational mechanical computer will work in a way that a "push-pull" mechanical computer will never do, at scale. The main take-away is to understand that — like a transistor — the rotation is "saturating": you keep turning, but the state doesn't change after a given "settle" time. For "push-pull" the mechanical computer will never truly saturate (friction; compression; ...), and the larger scale components will fail to propagate their "signal". Once you've got that you need "saturation", then you'll find that there's "saturating" mechanisms all around you! Consider a cup with a hole in its bottom: if the incoming water is less than the outflow, the cup will drain. But, let's say you have two incoming streams such that their sum fills the cup faster than it drains: now the cup will fill up. If the cup is a counter-weight to a funnel, you've got an implementation of an nand-gate: the cup controls whether or not a continuously fed stream of water goes to the next cup, but the water going into the cup only controls its saturating behavior. I've always imagined a Japanese-style bamboo garden very slowly performing calculations [1]. [1] http://cdn.home-designing.com/wp-content/uploads/2013/08/japanese-bamboo-water-feature-21.jpg http://cdn.home-designing.com/wp-content/uploads/2013/08/jap...