Introdução aos rolamentos, tipos, aplicações e cuidados.

1. Bearings
• Types of bearings:
• Rolling contact or anti-friction bearing
• Journal or sleeve bearings(sliding contact
bearing)
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Bearings are used for carrying loads while allowing
relative motion(rotation) with minimum friction

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Bearings
Rolling Contact Bearings – load is transferred through
rolling elements such as balls, straight and tapered cylinders
and spherical rollers.

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Journal (sleeve) Bearings – load is transferred through
a thin film of lubricant (oil).

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Bearings
Journal (Sleeve) Bearings
Load is transferred through a lubricant in sliding contact

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Design Considerations
• Bearing life and reliability
• Bearing speed (rpm)
• Space limitation
• Accuracy
• Bearing load – radial, thrust (axial) or both
Radial load
Radial load
Thrust load
Bearings are selected from catalogs, before referring to
catalogs you should know the followings:

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Rolling Contact Bearings
• Deep groove ball bearing
• Angular contact bearings (AC)
• Self alignment ball bearing
1. Ball bearings
3. Thrust bearings
• Cylindrical bearings(straight roller
bearing)
• Needle bearings
• Tapered bearings
• Spherical bearings
2. Roller bearings
In general, ball bearings
are capable of higher
speeds and roller
bearings can carry greater
loads

7. Comparison of rolling contact and
journal bearings
• Rolling contact bearings have low starting friction and are
used for applications with high starting loads(coefficient of
friction between 0.001 and 0.002)
• Journal bearings with hydrodynamic lubrication are suited
for high rotating speeds with impact loads(the higher the
rotating speed, the more effective the hydrodynamic
pumping action
• Rolling contact bearings take up more radial space around
the shaft, but journal bearings usually require greater axial
space
• Rolling contact bearings produce more noise
• Journal bearings are less expensive than ball or roller
bearing for simple applications
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8. Types of Ball bearings
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Ball Bearings
Deep groove (Conrad) bearing
• Primarily designed to support radial loads, the thrust
capacity is about 70% of radial load capacity
• Load capacity is limited by the number of balls

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Ball Bearings
Angular contact bearings (AC)
The centerline of contact between the balls and the raceway is
at an angle to the plane perpendicular to the axis of rotation.
• Used for high radial and thrust load applications
Extra support
in the back
Direction
of thrust

11. Self alignment bearing
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Roller Bearings
Roller bearings have higher load capacity than ball bearings, load is
transmitted through line contact instead of point contact.

13. Cylindrical bearing
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14. Needle bearing
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Roller Bearings
Tapered bearings
Designed to withstand high radial loads, high thrust loads, and
combined loads at moderate to high speeds. They can also withstand
repeated shock loads.

16. Car wheel bearings
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Tapered Bearings
Indirect and Direct mounting
Indirect mounting
Direct mounting
Indirect mounting
provides greater rigidity
when pair of bearings is
closely spaced: front
wheel of a car, drums,
sheaves,..
Direct mounting
provides greater rigidity
when pair of bearings is
not closely spaced:
transmission, speed
reducers, rollers,..
aa = effective bearing spread
Measure of the rigidity
of the bearing mounting

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Roller Bearings
Bearing design uses barrel shaped rollers. Spherical roller bearings
combine very high radial load capacity with modest thrust load capacity
and excellent tolerance to misalignment.

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Roller Thrust Bearings
Spherical Thrust Bearings
Cylindrical
Thrust
Bearings
Tapered Thrust
Bearings

20. Ball thrust bearing
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Mounting Bearings
Pillow Block Flange
Common mounting, inner ring
held in position by nuts threaded
onto the shaft.
Alternative method, inner ring is
press fitted onto the shaft.
Two-bearing mounting