Bearings | Types Of Bearings | Bearings Online

BEARINGS

A bearing is a machine element that constrains relative motion between moving parts to only give the desired motion. The design of bearing may be provide for free linear movement of the moving parts or free rotation around a fixed axis or it may prevent motion by controlling the vectors of normal forces that bear on the moving parts .They are mainly used to minimize the friction between moving parts.

The invention of the rolling bearing, within the sort of wood rollers supporting, or bearing, associate object being affected is of nice antiquity, and may predate the invention of the wheel. The ball bearing was originally described by GALILEO in the 17th century.

01-bearings-sealed ball bearings-high temperature bearings

Bearings played a significant role in technological revolution allowing the new industrial machinery to work with efficiency. There are various types of bearings. The most common bearing is plain bearing which uses lubricant between the rubbing surfaces.

Types of bearings:

  • Plain Bearing
  • Journal bearing
  • Sleeve bearing
  • Rolling element Bearing
  • Jewel Bearing
  • Fluid Bearing
  • Magnetic Bearing
  • Flexure Bearing
  • Common motions permitted by bearing are as follows

    • Axial Rotation
    • Linear Motion
    • Spherical Rotation
    • Hinge Motion

    Bearings are designed on the basis of the following subjects

    • Friction
    • Speeds
    • Loads
    • Purpose
    • Stiffness
    • Life

    Maintenance and Lubrication of a Bearing is very important. The external factors that effect a bearing are electrical signals, temperature,exposure to environment. To prevent bearing from these external factors they should be frequently lubricated and maintained properly.

    Plain Bearing:

    They have rubbing surfaces with lubricants between them .Friction factor depends on the material and construction. Stiffness is good. Life depends on application and also depends on lubrication

    01-plain_bearing-linear_bearing-sleeve_bearing

    Roller Bearing:

    Ball or rollers are used between rotating surfaces. This prevent and minimize the friction. Life is moderate and speed changes according to requirements. These kind of bearings are widely used now a days.

    01-roller bearing-thrust roller bearing-roller ball bearing

    Jewel bearing:

    Jewel bearing has an off centre bearing rolls in seating. Friction of this bearings is very low.  Speed and life are low.

    01-jewel bearings-plastic bearings

    Fluid Bearing:

    In these bearings fluid is forced between two faces and held in by edge seal. Friction is zero at zero speed. Stiffness is very high. Can be used for high speed applications. Life is infinite in some applications.

    01-fluid bearings-fluid circulative bearings-liquid bearings

    Magnetic Bearing:

    The two faces of bearing are kept separate by magnets. Zero friction at zero speed but eddy currents are often induced. Stiffness is low and there is no practical limit for speed and life.

    01-magnetic bearing-magnetic levitation bearings

    fag active magnetic bearing, magnetlager

    Flexure Bearing:

    These bearings are provided with material flexes to give any constrain movement. Friction is very low. Stiffness is low, and speed can be very high with high life.

    01-flexure bearing-air bearing-frictionless bearing

    Reducing friction in bearings is commonly important for efficiency. It helps to cutback the wear and tear and to facilitate extended use at high speeds and to avoid heating and premature failure of the bearing. Friction of a control depends on its form, material, and fluid used between two surfaces applied on bearings. Completely different bearing operative have different operational speed limits. Plain bearings generally handle only lower speeds. However the gap between the components that are separated by the bearing varies with load. Forces working on the bearing may be radial, axial or bending moments perpendicular to the most axis.

    Engine Speed Governors | Speed Control Governor | Speed Limiters

    Speed Governor

    The governor is a device which is used to controlling the speed of an engine based on the load requirements. Basic governors sense speed and sometimes load of a prime mover and adjust the energy source to maintain the desired level. So it’s simply mentioned as a device giving automatic control (either pressure or temperature) or limitation of speed.

    01-speed governor

    The governors are control mechanisms and they work on the principle of feedback control. Their basic function is to control the speed within limits when load on the prime mover changes. They have no control over the change in speed (flywheel determines change in speed i.e. speed control) within the cycle.

    Take an example:

    Assume a driver running a car in hill station, at that time engine load increases, and automatically vehicle speed decreases. Now the actual speed is less than desired speed. So driver increases the fuel to achieve the desired speed. So here, the driver is a governor for this system.

    So governor is a system to minimise fluctuations within the mean speed which can occur as a result of load variation. The governor has no influence over cyclic speed fluctuations however it controls the mean speed over an extended period throughout that load on the engine might vary. When there’s modification in load, variation in speed additionally takes place then governor operates a regulatory control and adjusts the fuel provide to keep up the mean speed nearly constant. Therefore the governor mechanically regulates through linkages, the energy provided to the engines as demanded by variation of load, so the engine speed is maintained nearly constant.

    01-engine_speed_governor_four_stroke_diesel

    Types of Governor:

    The governor can be classified into the following types. These are given below,

    1. Centrifugal governor

    a) Pendulum type watt governor

    b) Loaded type governor

    i) Gravity controlled type

    Ø Porter governor

    Ø Proell governor

    Ø Watt governor

    ii) Spring controlled type

    Ø Hartnell governor

    Ø Hartung governor

    2. Inertia and fly-wheel governor

    3. Pickering Governor

    Purpose of governor:

    1. To automatically maintain the uniform speed of the engine within the specified limits, whenever there is a variation of the load.

    2. To regulate the fuel supply to the engine as per load requirements.

    3. To regulate the mean speed of the engines.

    4. It works intermittently i.e., only there’s modification within the load

    5. Mathematically, it can express as ΔN.

    01-speed limiter-speed control governor

    Terminology used in the governor:

    1. Height of the governor (h):

    Height of the governor is defined as the vertical distance between the centre of the governor ball and the point of the intersection between the upper arm on the axis of the spindle. The height of the governor is denoted by ‘h’.

    2. Radius of rotation (r):

    Radius of rotation is defined as the centre of the governor balls and the axis of rotation in the spindle. The radius of rotation is denoted by ‘r’.

    3. Sleeve lift (X):

    The sleeve lift of the governor is defined as the vertical distance travelled by the sleeve on spindle due to change in equilibrium in speed. The sleeve lift of the governor is denoted by ‘X’.

    4. Equilibrium speed:

    The equilibrium speed means, the sped at which the governor balls, arms, sleeve, etc, are in complete equilibrium and there is no upward or downward movement of the sleeve on the spindle, is called as equilibrium speed.

    5. Mean Equilibrium speed:

    The mean equilibrium speed is defined as the speed at the mean position of the balls or the sleeve is called as mean equilibrium speed.

    6. Maximum speed:

    The Maximum speed is nothing but the speeds at the maximum radius of rotation of the balls without tending to move either way is called as maximum speed.

    01-simplified_representation_diagram_of_engine_speed_governor_limiter

    7. Minimum speed:

    The Minimum speed is nothing but the speeds at the minimum radius of rotation of the balls without tending to move either way is called as minimum speed.

    8. Governor effort:

    The mean force working on the sleeve for a given change of speed is termed as the governor effort.

    9. Power of the governor:

    The power of the governor is state that the product of mean effort and lift of the sleeve is called as power of the governor.

    10. Controlling force:

    The controlling force is nothing but an equal and opposite force to the centrifugal force, acting radially (i.e., centripetal force) is termed as controlling force of a governor. In other words, the force acting radially upon the rotating balls to counteract its centrifugal force is called the controlling force.