5. • Rolling Bearing is a machine element used to reduce
friction of rotating or movable parts.
• It transmit motion through roller element by:
1- Point contact 2- Line contact
9. Parameters control Bearing Manufacturing and Selection
1- Load 2- Velocity 3- Temperature
• Loads: Bearing designed to receive:
1- Pure radial load: ( i.e. Ball Roller Bearing )
2- Pure axial load: ( i.e. Ball Roller Thrust Bearing )
3- Combined load: ( i.e. Tapered Roller Bearing ) 1 2 3
10. Parameters Control Bearing Selection
1- Load 2- Velocity 3- Temperature
• Velocity: Bearing roller type selected according to:
1- Velocity with light loads: ( i.e. Needle Roller Bearing)
2- Velocity with heavy loads: ( i.e. Spherical Roller Bearing )
• To Calculate shaft speed: V (m/s) = ω (rad/s) r(m) = 2 π r (m) n (rpm) / 60
1
2
11. Parameters Control Bearing Selection
1- Load 2- Velocity 3- Temperature
• Temperature: Is a one of criteria control the material selection of
bearing material and its geometrical clearance in design, where in
high temperature working area lubricant life will be short, also
material will be expanded so bearing must have facilities to face
this so some special bearing material is produced for furnace
conveyors.
• Temperature defined in part number by letter “C0” or “CN” it take numbers from C1 to C5
which constrain the type of lubricant and working temperature.
17. Bearing Basic Loads & Rating Life
1- Basic Static Load: (C0)
The Bearing Static Capacity Co, is the radial load which a non-rotating ball bearing will support without damage, and will
continue to provide satisfactory performance and life.
The static radial load rating is dependent on the maximum contact stress between the balls and either of the two raceways.
2- Basic Dynamic Load: (C10)
Defined as the calculated, constant radial load that a group of apparently identical bearings will theoretically endure for a
rating life of one million revolutions. A bearing should only be subject to a maximum operating load equal to half its Bearing
dynamic capacity. The load that will give a life of 106 revolutions of the inner race.
3- Basic Rating Life): (L10)
“Rating life” is the bearing life calculated for 90% reliability. This is the amount of time that a group of apparently identical
bearings will complete or exceed before the formation of a fatigue spall.
18. •Rating Life Formula:
C10 (LR nR 60)1/a
= FD (LD nD 60)1/a
Note: C10 x L10 = FD x LD , where L = (L x n x 60)
where L represent cycles or rev/sec and L10 = 106 cycles according to Standard of Roller bearing fatigue test.
666
a = 3 for ball bearings
a = 10/3 for roller bearings
LD = desired life ( hours )
nD = desired speed ( rpm )
FD = desired load ( kN )66
LR = rating life ( hours )
nR = rating speed ( rpm )
C10 = Catalog rating ( kN )
19. Consider SKF, which rates its bearings for 1 million revolutions. If you desire a life of 5000 h at 1725
rev/min with a load of 1780 N with a reliability of 90 percent, for which catalog rating would you
search in SKF catalog?
Example1
Solutions:
𝐶10 (LR nR 60)1/a
= FD (LD nD 60)1/a
G i v e n :
LD = 5000 hour
nD = 1725 rpm
FD = 1.78 kN
L10 = 106
cycles
C10 = ?
Take a = 3 ,when type of
bearing not mentioned
consider it ball bearing.
𝐶10 (106)1/3 = 1.78 (5000 x 1725 x 60)1/3
𝐶10 = 1.78 x ( 517500000 / 106 )1/3
𝐶10 = 14.3 kN
