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. 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 2005-00-00