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A balance wheel, or balance, is the timekeeping device used in mechanical watches and small clocks, analogous to the pendulum in a pendulum clock.It is a weighted wheel that rotates back and forth, being returned toward its center position by a spiral torsion spring, known as the balance spring or hairspring.
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Center or second wheel which turns once per hour. Its pinion is turned by the teeth on the mainspring barrel in watches and spring driven clocks, and by the weight pulley in weight driven clocks. Its arbor projects through a hole in the face and drives, via a friction coupling, the cannon pinion , which carries the minute hand .
In modern mechanical watch designs, production of a highly accurate watch does not require a tourbillon. There is even debate among horologists as to whether tourbillons ever improved the accuracy of mechanical watches, even when first introduced, or whether the watches of the day were inherently inaccurate due to design and manufacturing ...
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The invention of the escapement was an important step in the history of technology, as it made the all-mechanical clock possible. [1]: p.514-515 [2] [3] The first all-mechanical escapement, the verge escapement, was invented in 13th-century Europe.
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In watches, the "drive" wheel is the one that winds up the spring, and the Geneva wheel with four or five spokes and one closed slot prevents overwinding (and also complete unwinding) of the spring. This so-called Geneva stop or "Geneva stop work" was the invention of 17th or 18th century watchmakers.