Modular compressed air engine (Working)

Singe cylinder: https://www.youtube.com/watch?v=CXvYDukyVZk
Flat twin: https://www.youtube.com/watch?v=BERMDl2_mkg
Inline 5: https://www.youtube.com/watch?v=2sBuIyi753A

After the radial (https://www.thingiverse.com/thing:3224004) I wanted a couple of improvements,
- modular design (inline and/or flat twin)
- different crank
- more efficiënt, the goal is to make it run on lung power ;)
- mostly parametric design

This design can be built as a single, a flat twin, or any multiple of those. You just need to print the cylinder 21mm apart so it's fused in your slicer. You should be able to make any inline or flat design. My goal is to make an inline 5, that's why the crank has a 72 degree offset.There is also a 90 degree offset crank for a twin/four.

Tips and requests are welcome ;)

WARNING, although I can run them at rediculous high pressures for something made of the cheapest PLA available, it IS dangerous. If your's doesn't explode it will propably make lots of torque l