More Science
The device has a variety of names, probably because it was popularized independently in many places. Some of the names in English are gee-haw whammy diddle, wammy doodle, beano stick, and idiot stick. Despite its simplicity, physical principles governing the motion of the stick and the propeller are rather complicated and interesting.
When the normal stick is pulled over the notches of another stick, the propeller starts to rotate. The vibration it generates translates into rotation of the propeller.
There have been many research papers written about how a hooey stick works but they all do not agree with each other. One possible explanation is, rubbing the stick over the notches creates both vertical and horizontal vibrations- and leads to an elliptical motion of the nail in the centre of a propeller, which begins to rotate due to friction with the nail.
The crucial feature is that the propellor must not be pinned at its CM – which can be avoided by making the hole in the propellor at least twice the diameter of the pin. The larger the distance of the CM from the pin, the larger the amplitude of vibrations of the pin needed to rotate the propeller.
Extra Bit:
There is a secret trick you can enjoy a lot, when rubbing the sticks you don’t just rub over the notches(rubber bands). The trick is that when you rub, press against the propeller-stick from one side with your index finger or the other side from your thumb. In that way you can control the direction of rotation of the propeller
