The familiar cup-anemometer, is the best-known and most generally used wind speed indicator, It consists of three to four hemispherical cups, mounted one on each end of radiating arms, A vertical axis round which the cups turn passes through the center. The cups are placed symmetrically on the end of the arms, so it is easy to see that the wind always has the hollow of one cup presented to it; the back of the cup on the radii also faces the wind, but the pressure on them is naturally less, and hence a continual rotation is produced; each cup in turn as it comes round providing the necessary force.

Designed to easily fit 3/4"  posts, the rotating copper windcups mounted on a brass bearing system will indicate the speed of the wind with just a glance and is a great way to increase the function and fun of a weathervane.