Hi, my first post. So brief presentation, I'm an undergraduate mechanical engineer student. I hope this doesn't actually fall in homework, but it's a project that I have this semester: a steam engine car (small). I've made a bit of research and I ended up discovering the following "engine": http://www.youtube.com/watch?v=brf0Ga0wnRc Like in this video, I am provided with a soda can that acts as the boiler which has a nozzle attached to it and also pressure tested. As for the rest of the car and system, i am suppose to design it. But this steam engine is very inspiring. Anyone can explain me how this system is actually made? What I can't figure out is how the steam actually drives the piston inside. Also, is the valve necessary? Thanks in advance =).