BEARING

BEARING :

A bearing is a machine element that constrains relative motion and reduces friction between moving parts to only the desired motion. The design of the bearing may, for example, provide for free linear movement of the moving part or for free rotation around a fixed axis; or, it may prevent a motion by controlling the vectors of normal forces that bear on the moving parts. Many bearings also facilitate the desired motion as much as possible, such as by minimizing friction. Bearings are classified broadly according to the type of operation, the motions allowed, or to the directions of the loads (forces) applied to the parts



Ball bearing 


A ball bearing is a type of rolling-element bearing that uses balls to maintain the separation between the bearing races

The largest ball bearings in the world:-

Having a diameter about 17.5 feet, these ball bearings are in the San Francisco Bay area of the USA, within the Benicia-Martinez Bridge, three parallel spans that carry 100,000 vehicles a day across Carquinez Strait west of Suisun Bay. As part of California Interstate Highway 680, these bridges link the town of Benicia at the northern end to the town of Martinez at the southern end. This segmented concrete structure was originally built in 1962 as a replacement for the car ferry services across the strait; the newest span was constructed alongside the original by the T. Y. Lin International construction firm, and was opened to the public on August 25, 2007.