https://en.wikipedia.org/wiki/Wax_motor https://en.wikipedia.org/wiki/Wax_motor If you've flown, you put your life in a wax motor's waxy hands: "Wax motors are

https://en.wikipedia.org/wiki/Wax_motor https://en.wikipedia.org/wiki/Wax_motor If you've flown, you put your life in a wax motor's waxy hands: "Wax motors are used...to control fuel, hydraulic, and other oils critical to safe flight today in modern airplanes."