https://youtu.be/UFPNWZeeXQw
Lego Pneumatic Engine.
What is it?
How to make it?
The first it needs to finish Lego fake cylinder like in this video https://youtu.be/HcHneyewATE or https://youtu.be/0aZvWva41Ek.
The second - to add o-ring to Lego piston like in this video https://youtu.be/wZu-l32Dajw or
.