Balloon Powered Car

A simple design for the classic balloon powered car engineering competition. I couldn't resist desgining my own when one of my kids had a competition at school. After trying several iterations with various approaches, I landed on this minimal frame. I used 4mm brass rod for the axles (anything smooth that you can cut to 85mm - 100mm lengths would be fine) The weight is so low, that I had to reduce the nozzle diameter to get a longer thrust curve and even so the car would spinout at higher speeds so I changed the wheels to be a bit thicker with a TPU tire wrapped around. That gives them enough grip to keep it straight most of the time.