It’s interesting to consider the possibility of making a siphon based computer that is operated by turning a handle which rotates a circuit through successive steps of operation. A 3D printer could be used to print the device all in one piece.

Perhaps a 1D cellular automaton would be a good demonstration. The geometry of the circuit could be perhaps arranged so that a light shining through the circuit would project the CA pattern onto the wall once during each turn of the handle.

One potential problem that might need to be overcome is making sure that the volumes of liquid don’t become unbalanced. The splitters at the outputs of each siphon might not split volumes perfectly in half after each operation. Any imbalance might accumulate over successive operations.

I’m unlikely to have time to fully explore all of this, so if you are interested in doing this please go ahead, I would love to see the results. I would be happy to offer advice to anybody attempting this.

Alternatively, the siphon logic circuit could remain in a fixed position and a cylinder surrounding it could rotate and supply the inputs at the right times, and collect the outputs and bring them back up to the top of the circuit. This is probably easier to make than a one-piece circuit where the entire circuit rotatates.

The power source that turns the cylinder could be a person or a motor, but to remain in keeping with the rest of the project it should probably be a water wheel. Ignoring losses, if the circuit is 1 metre high with 100 inputs, each of which requires a volume of say 10ml of water, then 1Kg must be lifted through 1 metre on each revolution. Since each revolution will probably take at least 10 seconds, the power requirement is less than 1 Watt, and a 100 litre tub of water with a head of 1 metre could run the circuit for 100 revolutions over the course of 15-20 minutes.