Instead of the BJT that is shown in the article, these act more like MOSFETs; and in fact, the "water analogy of electricity" translates quite well, since the "gate" has no current flow besides the tiny amount of "leakage" past the seals, and the volume of the actuating chamber and its return spring acts like the gate capacitance.
This is just to clear the OUT hose, so it will be ready for the next cycle. If this wasn't done, the WT could block in the "Logical One" in some circumstances.
...and that corresponds to the "high-Z" state, which along with the "capacitance" of the circuit would actually be usefully analogous to dynamic CMOS.
One more remark from someone who has worked with hydraulics before: the valve drawn in the diagram is known as a spool valve, and usually for diverting the flow of fluid, the chambers would be so arranged that they don't create any forces on the valve spool --- see how pressure on the "VCC" or "GND" ports would act on the land and tend to push the valve? In practice a "balanced spool" design is used, where the pressure of the controlled fluid is balanced on both ends:
Mechanical (esp 3D) and Chemical systems are so complex that modeling the results of highly simplified systems is often almost impossible, results are nonlinear and mixed with "unrelated" inputs and prior state, and thus results are "chaotic" and unpredictable. That's not usually what you want to base a complex system on.
Now if you can simplify operations like DNA... you may have a chance, but it's still quite difficult.
The great thing about transistors is their localized non-liniarity (gain)... which was used to create simplified digital systems from analog circuits. This allowed fan-out and noise tolerance... which allowed more complex abstractions, processors and OSes to be built on top them.
It was the inspiration for Terry Pratchett's Making Money, just without the magic ability to control the economy. :)
He worked as a crocodile hunter and cinema manager in ANZAC and later moved to China during the Sino-Japanese War, but had to escape via the Soviet Union during the height of the Stalinist purges. Yet immediately after that he ended up joining the RAF and being posted in Singapore, which was then invaded by the Japanese, and he ended up being sent to a POW camp after being caught after trying to escape via Indonesia. During his time in the POW camp, he learnt Chinese, jerryrigged a secret water boiler for tea, and built a secret radio. Following WW2 he was then made an OBE due to his exploits in SEA.
As if that wasn’t enough, he went back to school to study maths and Econ at LSE and ended up developing the epynomeous Phillips Curve that is the backbone of macroeconomics (and his coauthor won a Nobel for it since Phillip died before the recognition).
In the end he found it too difficult ("It would have necessitated a 60 foot high water tower to provide the necessary pressure, and a far greater budget.")
Instead he built one using ball bearings:
Located at Trinity Buoy Wharf, London E14 0JW
I think his or gate is overthinking the issue. The only thing needed is a bunch of one way valves on each of the inputs, thus creating a sort of "wired OR": any input can create pressure on the output but that pressure can't disspate back to the unpressurized inputs.
By passing this "valve OR" through a single amplifier element set up as an inverter you get NOR gates which can have a large number of inputs and can be futurer used to synthesise any circuit.
The approach I took in my course, which seemed to work, was bottom up:
* Bits: answers to yes/no questions
* Binary Numbers and Arithmetic
* Logic and gates: AND/OR/NOT
* Combinatorial logic: XOR, Half-adder, Full-adder, 4-bit adder
* Sequential Logic: RS-Latch, Master-Slave Register, 4-bit register
* A counter (=register+adder)
* Mux/Demux, Encoder/Decoder
* Memory (=registers+decoder+mux)
* Arithmetic Logic Unit (=functions+mux)
* Program Counter, Instruction Register
* Fetch/Decode/Execute cycle
* A complete computer using gates
* Machine Code (write and run a program on our gate level computer)
* Assembly Code
The entire course was run using SimcirJS .
I think hierarchy is key, as each level of the hierarchy can be presented as a relatively small and simple to understand circuit. For example, the bulk of the gates in the final computer are in the memory, but the memory is presented as a single schematic symbol with the complexity hidden. The child understands what is inside the memory symbol but doesn't have to think about it while comprehending the computer as a whole.
It worked to present the entire computer in symbolic form (in SimcirJS), then demonstrate how we could use different easily understandable technologies to build a simple gate: electricity, mechanics, hydraulics, ... The students were able to see that once we had a basic gate in a technology of choice, we could just "turn the handle" to produce a complete computer by mirroring the easy to understand symbolic form and that there was no "magic" involved.
It might be easier to solve with small 3-D printed digital parts (AND, NAND, etc) that could be fitted together with rigid PVC off a plumbing manifold.
This might allow you to make smaller parts also.
I think you’d also need some sort of hydraulic expansion tank that would act like capacitors - necessary for storing memory and improving signaling.