Windmills are known worldwide as an iconic symbol of Dutch culture. Some 1,200 historic windmills survive, most of which are gristmills or polder mills. Many remain fully functional, and their upkeep and operation is promoted by a number of civic organizations, including De Hollandsche Molen, Gilde van Vrijwillige Molenaars and Stichting De Fryske Mole. Several Dutch villages are known for their concentration of windmills, including Kinderdijk, Zaanse Schans, and Schiedam, home to the tallest windmill in the world. Tjaskers, a kind of windmill native to Friesland, were also used for water management.
A windmill is a structure that converts wind power into rotational energy by means of vanes called sails or blades, specifically to mill grain (gristmills), but the term is also extended to windpumps, wind turbines and other applications. Windmills were used throughout the high medieval and early modern periods; the horizontal or panemone windmill first appeared in Greater Iran during the 9th century, the vertical windmill in northwestern Europe in the 12th century.
Gears inside a windmill convey power from the rotary motion of the sails to a mechanical device. The sails are carried on the horizontal windshaft. Windshafts can be wholly made of wood, or wood with a cast iron poll end (where the sails are mounted) or entirely of cast iron. The brake wheel is fitted onto the windshaft between the front and rear bearing. It has the brake around the outside of the rim and teeth in the side of the rim which drive the horizontal gearwheel called wallower on the top end of the vertical upright shaft. In grist mills, the great spur wheel, lower down the upright shaft, drives one or more stone nuts on the shafts driving each millstone. Post mills sometimes have a head and/or tail wheel driving the stone nuts directly, instead of the spur gear arrangement. Additional gear wheels drive a sack hoist or other machinery. The machinery differs if the windmill is used for other applications than milling grain. A drainage mill uses another set of gear wheels on the bottom end of the upright shaft to drive a scoop wheel or Archimedes’ screw. Sawmills use a crankshaft to provide a reciprocating motion to the saws. Windmills have been used to power many other industrial processes, including papermills, threshing mills, and to process oil seeds, wool, paints and stone products.
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