Weather vain

Weather vain is a tool which is used to envisage the direction of wind. It is a movable device which is attached to any elevated object mostly roof. They are balanced in such a way that half of its weight is on either side of its axis and the areas exposed to air on both sides are unequal. It minimizes the force of wind and cause vane to rotate. It is also known as weather vane, weather vain etc.

A weather vain is a vertical plate which is mounted on a vertical pivot or axle. So a small force at a lengthy distance can conquer a larger force at a small distance. Now the tail of a weather vain could consequently actually have a smaller area than the head but still rotate the vane if it is placed sufficiently far from the pivot.

Portion of weather vain with greater surface area gives more resistance to wind which causes the vane to take position in such a way that the forward part points in direction of wind. By the help of compass rose we can determine the direction of wind. There are various shapes of weather vain. Most popular shapes are arrows and cocks.

Weather vain must be mounted at least twice the height of nearest obstacle like another building, tree, and any other object so that they can not interfere the true wind direction. For that reason it is mounted on big poles and on the roof of the tall buildings. Orientation of the vane may be communicated to a remote calibrated dial.