https://youtu.be/A9oe-pRLeGk I designed "A 3D Printed Balloon Powered "Jet" Car With Inflator" for our grandkids. The inspiration for this model was from a YouTube follower of mine who asked how I thought a version he had seen worked. Well I'm not sure how the model he saw worked, but this one certainly entertains the grandkids (a "driver" is in the works, I wonder who that could be?)! My design uses a 67mm ID silicone "hemisphere", that I carefully removed from a silicone baking mould, as a bellow and 3D printed TPU95A valves and gaskets to create a balloon inflator. As seen in the video, the car's nozzle plugs into the inflator, the car's balloon is inflated by repeated presses on the inflator red button, and the car is released by a single press of the inflator green button. As usual I probably forgot a file or two or who knows what else, so if you have any questions, please do not hesitate to comment as I do make plenty of mistakes. Designed using Autodesk Fusion 360, sliced using Ultimaker Cura 4.9.1, and 3D printed in Ultimaker PLA and Ultimaker TPU95A on an Ultimaker 3 Extended and Ultimaker S5s.