Purpose:Illustrate a combination of simultaneous orthogonal oscillations.
Description:Stroke the notches with the V-shaped section on the stroker stick. The end pin will execute circular or elliptical motion, causing the propeller to rotate. Rubbing either your thumb or your forefinger on the stick (by sliding your hand slightly back and forth) reverses the phase of the horizontal oscillation with respect to the vertical oscillation of the pin, causing the rotation of the pin and the propeller to reverse.
If you call this thing the HOOEY stick, you can actually get it to reverse rotation by shouting "HOOEY" at it! Freaks out the little kids and confuses the older ones.