I was inspired by an old film of a Western Pacific SW9 switcher where you could see the front radiator fan turning through the nose grille. Using the smallest stepper motor I could find, which is used in cameras for focus drive, I needed to drive it directly from an Arduino without a commonly used driver circuit because of the limited space I had to work with. I had to experiment with the software to keep the motor current down because it could easily damage the Arduino. The speed ramps up and down and can be turned off using the AUX1 function output of the LokSound 4 decoder. Video by Bruce Kingsley.