Examples of logic gates using non-standard models These are the only ones I have been able to find online:


Pulley Logic Gates
Marble adding machine
MARBLE COMPUTER LOGICAL AND GATE


I would like to find some more discrete models like these (as opposed to say, water logic gates or things like that). Not sure if there is a library of different techniques to build logic gates outside of electronics, or if not, what some other good examples are like these above, that perhaps demonstrate further their functionality.
Picture hanging can realize any monotonone boolean function. 

I.e., you can hang a picture using two pins so that it falls IFF both pins are removed. This is trivial to achieve, and realizes an AND gate.

However, you can also hang it so that it falls IFF either pin is removed. Implementing this OR gate is not so trivial at first.

See the linked paper for nice pictures.