Balloon Powered Single Cylinder Air Engine Open Chassis is an open chassis version of Balloon Powered Single Cylinder Air Engine Toy Train (https://www.youmagine.com/designs/balloon-powered-single-cylinder-air-engine-toy-train). Having the same drive train as, and weighing less than, the train version, this vehicle has traveled over 70 feet on smooth surfaces, and over 55 feet outdoors on concrete into a slight headwind, all on balloon power. We race these vehicles for longest distance. Some of the race strategy is to inflate the balloon as much as you dare, wearing safety goggles just in case. As a "professional" balloon powered single cylinder air engine racer, my hint to all up and coming racers is..., use a new balloon, but please don't tell anyone. A distance test video follows: https://www.youtube.com/watch?v=wkyOi47r9Io You will need to purchase 4 "AS568" #219 o-rings (1 5/16" I.D., 1 9/16" O.D, 1/8" section) for the tires and at least 1 "punch balloon" (I found mine at a local party supply store, but they also are available on line). I probably forgot a file or two or something, so if you have any questions, please feel free to ask. Designed using Autodesk Fusion 360, sliced using Cura 2.3.1, and printed in PLA on an Ultimaker 2+ Extended and an Ultimaker 3 Extended.