Hui machine
A Hui machine , also known as Hui-Hui machine , Hui-Rad , Hui-Hui-Rad , Hui-wheel , Hui-Hui-wheel , Magic windmill , magic screwdriver or magic propeller , is a simple wooden toy, which consists of two wooden rods consists: one is notched several times and typically provided with a nail at one end on which a propeller-like piece of wood can loosely rotate; the other wooden stick is rubbed over the notches by the player. This allows a player who knows the trick of the Hui machine to set the "propeller" in a controlled direction in a right or left direction.
trick
When simply rubbing the wooden sticks, the propeller of the Hui machine usually does not start to turn at all. This is because it is necessary to additionally guide a finger or thumb along the notched wooden stick when rubbing and to exert pressure on it either at an angle from above or from below. Since this is not recognizable for the ignorant viewer, changing the direction of rotation can be accompanied by the exclamation “Hui”, which supposedly works as a magic formula.
physics
In fact, the function of the Hui machine is based on the fact that the vertical vibration of the notched wooden stick generated by the rubbing is converted into an elliptical vibration by the pressure of the thumb. The nail transmits the elliptical oscillation to the propeller and sets it in a rotating motion.
literature
- H. Joachim Schlichting, Udo Backhaus: On the physics of the Hui machine (PDF; 48 kB). Physics and Didactics 16/3, 238 (1988)
