This fascinating model has three rotating arms each of which is a four bar linkage that moves the paddles through a given angular orientation. In the four bar drag linkage, rotary motion of one link drives the opposite link into rotary motion. [See one of the inversions in model C01, click on movie.] This mechanism is similar to that used for steam driven paddle boats or other water wheel applications. A modern application with a different mechanism is used to orient helicopter blades as they turn. Sometimes this is called a feathering mechanism.

Francis Moon 2004-10-25