What is Bearing ? Type of bearing and Classification of Bearing

BEARING

What is Bearing ?

A Bearing is a machine element that constrains relative motion to only the desired motion and reduces friction between moving part. 

   

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 force that bear on the moving part

Type of bearing 

There are at least 6 common type of bearing 

1.   Plain Bearing. 
2.   Jewel Bearing.
   
3.   Rolling -Element Bearing. 
     a) Ball Bearing.  
   
     b) Roller Bearing.
4.   Fluid Bearing.
5.   Magnetic Bearing.
6.   Flexure Bearing.

1. Plain Bearing

Plain bearing are the simplest type of bearing and are composed of just the bearing surface with no rolling elements. They have a high load - carrying capacity, are generally the least expensive and, depending on the materials, have much longer lives then other type.

 2. Jewel Bearing

Jewel bearing are plain bearing with a metal spindle that turns in a jewel-lined pivot hole. They carry loads by rolling the axle slightly off-center and are usually used in mechanical watches or clocks. 

 3. Rolling -Element Bearing 

Rolling-element bearing in which rolling element placed between the turning and stationary races prevent sliding friction. There are two main types Ball bearing and roller bearing.

 

a. Ball Bearing 

                   

The ball bearing is the most common type of bearing. It consists of small metal balls that are located between two metal rings which are known as Races. Balls are also kept in position using an assembly called Cage. Since sliding friction is very high compare to rolling friction ball bearing provides less energy loss. The inner Races and balls are free to rotate and the outer races is stationary. The shaft is fitted inside the inner races and the outer races is fixed to a motor.

b. Roller Bearing 

Roller bearing are designed to carry heavy loads-the primary roller is a cylinder, which means the load is distributed over a larger area, enabling the bearing to handle larger amounts of weight.

 4. Fluid Bearing

Fluid bearing support their load using a thin layer of gas or liquid and can be classified into two types:-

Fluid-dynamic bearing use rotation to form the liquid into a lubricating wedge against the inner surface. In hydrostatic bearing, the fluids usually oil, water, or air - rely on an external pump. Fluid bearing are used in high load, high speed or high precision applications.    

5. Magnetic Bearing 

Magnetic bearing support moving parts without physical contact, instead relying on magnetic fields to carry the loads. They require continuous power input to keep the load stable, thus requiring a back-up bearing in the case of power or control system failure.

 

6. Flexure Bearing

A typical flexure bearing is one part joining two others, like a hinge, in which motion is supported by a load element that bends. These bearing required repeated bearing.

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