watermill

by Saghar Nazari 

A watermill is a structure that uses hydropower. It uses a water wheel or water turbine to drive a mechanical process such as milling. Such processes are needed in the production of many material goods like flour.

Before World War II most of the corn ground to produce the flour for bread, was processed by watermills and More than 300 watermills were at work in Iran till 1960 Now only a few are still working.

water-mill types in Iran

Two types of water-mill survive in Iran: the Vitruvian mill, the type common throughout the Western world with its water-wheel set vertically on a horizontal axis; and the little-known Greek mill with its water-wheel set horizontally-the fore-runner of the turbine. Persians, with their long tradition of efficient use of water, favour the Greek mill which is powered by a small quantity of water directed at high velocity to turn the horizontal water-wheel. The water-mill system in ancient Iran consists of the following parts. It is necessary to bring out this point that, the location of water mills selected somehow to have 5 to 6 meters head between up streams and down streams.Apparently higher pressure caused problem for turbine’s wheel and wouldn’t let it work properly.

watermill 1

  • Water Resources: The resources, which were generally used to operating the mills, were rivers, springs and qanats.
  • Water Tower: This tower was similar to an incomplete cone, and the cross-section decreased as it went down.This tower led to a narrow channel with a wooden weir, which could be moved from inside the mill in order to open and close.
  • Grain Storage and Wooden Hopper: Grain was stored in a small room just above the millstone. And from the bottom of the room there was a wooden hopper, which led the grain to the sole in the middle of the upper stone of the mill. When the mill was under operation, caused vibration, its vibration reflected.
  • Downstream Canal: When water passed through turbine, entered downstream canal and led to the river.

watermill 2

  • Upstream Canal: This canal directly related to water resources. Besides the main channel, there was a diversion one or a wooden weir before water entered the tower. This diversion channel was connected to downstream channel and it diverted water while the mill was at rest
  • Wooden Turbine: It consisted of a wooden axle with a diameter, which gradually increased as it went down. The two ends of this axle are generally made of iron. The lower end of the axle was fixed to a stone, which was the support of the turbine. The upper end tightened to the upper millstone, rotated when the turbine was under operation. The lower end of the axle had some grooves with blades, made of wood and their free ends were connected to each other
  • Millstones: The diameter of stones depended on water quantity and water head.The lower millstone was very strong and unmovable, but the upper one, which was tightened to the axle of turbine, could rotate and it was generally lighter than the lower one. In the middle of upper stone, around the axle there was a hole, which led the grain to the space between two stones. The two stones were not completely horizontal; in fact they had a moderate slope. This simple technique caused flour jumped out from the highest point according to centrifugal force and collected in a shallow hole. Then the miller collected the flour in bags and delivered to the owners.

 

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