Run by just blowing air into it. Demonstration: https://www.youtube.com/watch?v=_FDZzKAFSz4 Exploded view in 3d viewer: https://skfb.ly/6LQBR There's a LEGO compatible version of the motor: https://www.youmagine.com/designs/air-balloon-motor-for-lego If you like how it works, you can support me by purchasing the Pneumobile chassis: https://cults3d.com/en/3d-model/game/pneumobile-pneumatic-toy-car (3d Viewer: https://skfb.ly/6LV6D) Extra parts needed: - M3x8 Bolts (x15) - M3 Nuts (x15) - Thin Nitrile Gloves (thumbs from M sized gloves worked the best) or Silicon (worse) or PET (not tested) ones Optional parts: - M3x12 or longer bolts (2x)(for the gears) - M3 Nuts (x2)(for the gears) - 6x4mm Silicon Pipe (can be found in aquarium shops) - M5x10mm Washers (x2) (instead of printed ones) - 105ZZ Bearings (x2) (noticed no difference in performance) Parts with "X_" in their names are optional. Assembly: - Use 3d diagram as a guide: https://skfb.ly/6LQBR - Cut off a glove finger tip (thumbs from M sized glove worked well) - Pull it onto a Cylinder_Ring (Use Helper_Finger to leave enough height) - Connect a Piston to it with two Washers - Clamp the Cylinder_Ring between Cylinder_Plate and and Cylinder_Lid - Clip them with Helper_Clamp so they won't fall apart at once - Bolt them together to Plate_Top - Repeat for the other 2 cylinders - Insert th Crank with 2 Washers - Fix it in place with Frame_Bottom - Bolt all the parts together - Put the Valve_Inner in place - Bolt the Valve_Lid into place - The engine should be running! Troubleshooting: 1. Rotated freely by hand, but struggling when working - the inner valve may have too much friction against the frame (sanding the valve and the frame may help for a while). 2. Jams on a certain cylinder - this glove finger may need a bit more slack. 3. Isn't rotated freely by hand - gears bolted too tightly to frame (should have a bit of play), some gear teeth didn't print very well, or the whole gear printed with "elephant foot" and runs too tight with another gear.