Not automotive but trebuchets ROCK!
Our son built one for his 6th grade science project. His was a tennis ball trebuchet, about 3.5 feet tall. His experiment was to see the average distance that dry tennis balls, wet tennis balls and tennis balls soaked in kerosene AND LIT ON FIRE would go!
Ahh, yes... We were the hit of the neighborhood that night. You're not having fun until you are launching flaming tennis balls down the (very quiet) street at night! They are really, really cool looking. Especially when they bounce and live little droplets of flame behind.
Very, very cool! We took a bunch of pictures and Ryan got an A for his project, plus we didn't catch anything on fire that didnt' belong to us.
angela