We had a little Philmont training recently and one of the activities included a No Rules Pinewood Derby. The only rule was no fire. So Mike thought a compressed air propulsion system would be pretty good. It took a couple weeks to build and figure out. A 20 oz. soda pop bottle provided the pressure vessel, a 1/8-inch ball valve, a schrader valve, and some mouse trap parts did the job. The release mechanism was the trickiest part. The ball valve was spring loaded to flip to the open position and held with a mouse trap latch that was tied to the front bumper, which was spring loaded with ball point pen springs. As soon as the gate dropped, the mouse trap lever sprung open and the bottle released air at 120 to 150 psi in about 2 seconds.
There was only one real contender, an ordinary car that got fired from the gate with a heavy duty spring. It had a faster initial velocity, but the air rocket car had continuous thrust and passed it just before the finish line. Mike had a lot of fun making the car and was pleasantly surprised that he won. Picture and video provided for your viewing pleasure.
