Pneumatic logic gates

Make pneumatic AND and OR gates and more complex logic assemblies together with [thing:3142024](https://www.thingiverse.com/thing:3142024). It allows mounting various valves and sockets on a base plate, interacting with each other in different ways.

Each base plate has four ports (two on top, two on bottom), allowing to mount up to four sockets on it. Each socket can have a non-return valve to block flow in a specific direction, allowing to directly create OR gates. By placing a special pin inside the base plate, two non-return valves can be made mutually exclusive to create a two-port AND gate. Unused ports can be permanently shut off with blinders.

A bridge rectifier can be created with four base plates, four non-return valves, four sockets and four blinders. This is useful for e.g. creating an air compressor.

Update Nov 3, 2018: Modified DualBase to 23 mm spacing to avoid issues with small brims around valves etc.