Topics

• Introduction to bearings• Types of bearings• Plain bearings• Antifriction bearings• Axial and Radial Loads• Questions

Chapter 9 BearingsMECH 1200

IntroductionPurpose of bearings:- Support loads- Reduce friction

The PV factor:- PV factor refers to the Pressure and Velocity

ratings of the bearing. - Pressure is the load on the bearing in pounds

divided by the projected area in square inches.- Velocity is the surface velocity of the shaft.

MECH 1200

Some types of Bearings

Plain (Journal) Bearings

Solid

Split

Antifriction (rolling) Bearings

Deep Groove Ball Bearing

Angular Contact Ball Bearings

Self Aligning Ball Bearing

Pure Thrust Ball Bearing

Cylindrical Roller Bearing

Spherical Roller Bearing

Tapered Roller Bearing

Needle Roller Bearing

MECH 1200

Plain Bearings• Other names: journal, friction, or sleeve bearings• They work by sliding action in contrast to rolling action of the

antifriction bearings. • Types: Solid and split types• Advantages:

– Can handle high loads– Quite operation: because no rolling elements exist.– Require less space than antifriction bearings.– Low cost

• Disadvantages:– Limited to low speed applications – Require precise alignment – Lubrication is essential for their performance.

MECH 1200

Antifriction Bearings• Parts: inner ring, outer ring, rolling element,

and retainer. • They work by rolling action.• Advantages:

– Higher efficiency than plain bearings– Can handle high speeds– Can tolerate misalignment better than journal

bearings

• Bearing Types by rolling elements:– Ball bearings – Cylindrical Roller Bearings – Taper Roller Bearings– Spherical Roller Bearings

• Point contact vs line contact:Ball bearings make a point contact with the race, but cylindrical bearings make line contact, therefore ball bearings are more efficient, but cylindrical roller bearings can handle higher loads.

BallCylindrical roller

Taper roller

Spherical roller

MECH 1200

Axial and Radial Loads

Radial load

Axial (thrust) load

Some bearings are designed to handle only radial loads, others are designed to handle axial loads, others are designed to handle a combination of both.

Axial load

Radial load

MECH 1200

Ball Bearings

Deep groove ball bearing Self-aligning double row ball bearing

Light radial load

Light axial (thrust)

load

Moderate radial load

Light axial load

Moderate radial load

High axial load

Angular contact ball bearing

High axial load

Single acting thrust ball bearing

Light radial load

MECH 1200

Other Antifriction BearingsLow axial load High radial load

Moderate axial load

High radial load

Cylindrical roller bearing

Spherical roller bearing

Needle roller bearing

Tapered roller bearing

High axial load

High radial load

MECH 1200

Questions1) What other names are plain bearings called?

Other names are journal, friction, or sleeve bearing

2) Why cylindrical roller bearings can handle more radial load than ball bearings can?

Because the cylindrical roller element makes a line contact with the rings, but the ball bearing makes a point contact, therefore a higher pressure is exerted on the ball element from the load.

3) Which of the two bearings mentioned above is more efficient?

Ball bearings because of the less contact area, and less friction.

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4) What type of bearing is shown in the figure below?

a) Journal bearing

b) Double row deep groove ball bearing

c) Spherical roller bearing

d) Self aligning double row ball bearing

e) Tapered roller bearing

5) The bearing is designed to carry:a) High radial loads

b) High axial loads

c) Moderate radial but high axial loads

d) High radial and axial loads

e) It only can carry light loads

MECH 1200

6) Determine if each of the following bearings is loaded correctly or not:

7) These bearings shown above are:a) Friction bearings

b) Journal bearings

c) Plain bearings

d) Antifriction bearings

correct Incorrect Incorrect correct Incorrect

MECH 1200

Homework

1. Do the student exercise on page 235 of the text.

2. Answer questions 1,2,34,8,10, and 14 on page 236.

MECH 1200