A great love of mine, is to build Lego pneumatic engines. If you check YouTube you’ll see that tons of other people also enjoy building them. It’s like building a real engine but running it off of compressed air. When I was little I used to go to Steam Rallies and Steam has always interested me.
So after playing around I managed to build a working pneumatic beam engine.
This is one of my favourite mocs, I can watch it for ages. It can be a bit temperamental, though.