Algodoo

Purely mechanical AND gate as designed in the science paper: "Mechanical Computing Systems Using Only Links and Rotary Joints"

Controls:
1 - toggle the 1st bit
2 - toggle the 2nd bit
c - toggle the clock signal

!!The clock must be toggled AFTER the bits!!

How it works:

The system uses dual rail logic - two linkages for every bit. They represent either 0 or 1 depending on which linkage is toggled. If neither linkage moves forward it doesn't represent either value. In this simulation the input bits have been connected, so that they will always have defined value, however this would not be so in an actual circuit.

The gate is made up of 8 'locks'. These are made up of two 4-bar linkages in such a way that either one can move forward, but not both at the same time. If either half is in any position except the center it prevents the other half from leaving the center position - 'locks' it.

Thanks to the dual rails, the output can be easily modified to get any logic gate. Furthermore additional locks can be added to create logic circuits with any number of inputs.

The whole system is guided by a clock, which must be toggled after the input bits. Large downside of this system is that all gates must be toggled in succession - significantly slowing down larger circuits.

If you'd like to read the full paper you can find a pdf at https://arxiv.org/pdf/1801.03534.pdf