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A ball bearing is a type of rolling-element bearing that uses balls to maintain the separation between the bearing races. The purpose of a ball bearing is to reduce rotational friction and support radial and axial loads. It achieves this by using at least two races to contain the balls and transmit the loads through the balls. In most applications, one race is stationary and the other is attached to the rotating assembly (e.g., a hub or shaft). As one of the bearing races rotates it causes the balls to rotate as well. Because the balls are rolling they have a much lower coefficient of friction than if two flat surfaces were sliding against each other. Ball bearings tend to have lower load capacity for their size than other kinds of rolling-element bearings due to the smaller contact area between the balls and races. However, they can tolerate some misalignment of the inner and outer races. ==History== Although roller bearings had been developed since ancient times, the first modern recorded patent on ball bearings was awarded to Philip Vaughan, a Welsh inventor and ironmaster who created the first design for a ball bearing in Carmarthen in 1794. His was the first modern ball-bearing design, with the ball running along a groove in the axle assembly. Jules Suriray, a Parisian bicycle mechanic, designed the first radial style ball bearing in 1869,〔See: * Suriray, ("Perfectionnements dans les vélocipèdes" ) (Improvements in bicycles), French patent no. 86,680, issued: August 2, 1869 , ''Bulletin des lois de la République française'' (1873), series 12, vol. 6, page 647. * Louis Baudry de Saunier, ''Histoire générale de la vélocipédie'' (history of cycling ) (Paris, France: Paul Ollendorff, 1891), (pages 62-63 ).〕 which was then fitted to the winning bicycle ridden by James Moore in the world's first bicycle road race, Paris-Rouen, in November 1869.〔(Bicycle History, Chronology of the Growth of Bicycling and the Development of Bicycle Technology by David Mozer ). Ibike.org. Retrieved on 2012-09-01.〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「ball bearing」の詳細全文を読む スポンサード リンク
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