windshafts

A windshaft is a horizontal beam in a windmill that transmits the rotational power generated by the sails to the machinery within the mill. It is a crucial component of most traditional windmill designs, particularly tower mills and post mills. The windshaft is typically a large, sturdy wooden beam, though in some modern designs metal can be used. It is connected to the sail-bearing arms at one end and extends inwards to a brake wheel or a gear system at the other.

The rotation of the sails, driven by the wind, causes the windshaft to turn. This rotation is then transferred to other parts of the mill's mechanism, such as the millstones or pumps. The windshaft is supported by a bearing, often a greased collar or a more complex arrangement, which allows it to rotate smoothly. The design and strength of the windshaft are critical for the efficient and safe operation of the windmill, as it must withstand significant forces generated by the wind and the machinery. In post mills, the entire body of the mill pivots on a central post, and the windshaft extends from this rotating body. In tower mills, the windshaft is housed within the fixed tower and rotates within a cap that can be turned to face the wind.