I thought you might like the pneumatic engine i built : r/legotechnic
Lego Pneumatic Engines Are Available For Sale - autoevolution
Nico71 - Lego Switchless Pneumatic engine mk2. With stacked 4 valves instead of side by side, one cylinder and two speeds gearbox. Expected to me mounted soon in a two wheels creation
LEGO MOC 1 Cylinder Lego Pneumatic Engine - Modified (High RPM) by Green Gecko | Rebrickable - Build with LEGO