![]() ![]() The earliest recovered example of a rolling element bearing is a wooden ball bearing supporting a rotating table from the remains of the Roman Nemi ships in Lake Nemi, Italy. Wheeled vehicles using plain bearings emerged between about 5000 BC and 3000 BC. There are also Egyptian drawings of plain bearings used with hand drills. The Egyptians' own drawings in the tomb of Djehutihotep show the process of moving massive stone blocks on sledges as using liquid-lubricated runners which would constitute plain bearings. Though it is often claimed that the Egyptians used roller bearings in the form of tree trunks under sleds, this is modern speculation. It may predate the invention of a wheel rotating on a plain bearing. The invention of the rolling bearing, in the form of wooden rollers supporting or bearing, an object being moved is of great antiquity. History Tapered roller bearing Drawing of Leonardo da Vinci (1452–1519) Study of a ball bearing A wide variety of bearing designs exists to allow the demands of the application to be correctly met for maximum efficiency, reliability, durability, and performance. In the ball bearing and roller bearing, to reduce sliding friction, rolling elements such as rollers or balls with a circular cross-section are located between the races or journals of the bearing assembly. The choice of lubricant depends on the specific application and factors such as temperature, load, and speed. Lubricants come in different forms, including liquids, solids, and gases. The simplest form of bearing, the plain bearing, consists of a shaft rotating in a hole. Rotary bearings hold rotating components such as shafts or axles within mechanical systems and transfer axial and radial loads from the source of the load to the structure supporting it. The most sophisticated bearings for the most demanding applications are very precise components their manufacture requires some of the highest standards of current technology. Other bearings are separate devices installed into a machine or machine part. The simplest bearings are bearing surfaces, cut or formed into a part, with varying degrees of control over the form, size, roughness, and location of the surface. The term "bearing" is derived from the verb " to bear" a bearing being a machine element that allows one part to bear (i.e., to support) another. Bearings are classified broadly according to the type of operation, the motions allowed, or the directions of the loads (forces) applied to the parts. Most bearings facilitate the desired motion by minimizing friction. 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. ( June 2023)Ī bearing is a machine element that constrains relative motion to only the desired motion and reduces friction between moving parts. ![]() Please consider expanding the lead to provide an accessible overview of all important aspects of the article. This article's lead section may be too short to adequately summarize the key points. ![]()
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