This is a small steam engine I made, mainly from bits of junk around my garage, playing a Sex Pistols punk LP. The engine speed is controlled by a throttle being driven from a servo controlled by an Arduino. The RPMs are measured by a coil detecting the passing of six magnets in the edge of the platter and the approximate revs are displayed on an analogue meter. I am using the PID controller library to do the work out how to control the servo based on the input speed. The safety valve is making the whistling noise at the start as steam pressure is built up. A small flick of the platter will start the engine and then the Arduino takes over trying to maintain 33 1/3 RPM. At the end the meths burner runs out of fuel so the steam pressure, and therefore the speed, drops. You can see the Arduino trying to throttle up to maintain the speed right at the end.