Bearing Materials
1. Babbit 4. Bronze
2. Aluminum 5. Porous Metal
3. Plastics
Classification of Bearing According to Type of friction
1. Sliding Bearing
2. Rolling Bearing
Classification of Rolling-Element Bearing
1. Ball Bearing
2. Roller Bearing
3. Needle Bearing
Classification of Bearing According to Load Application
1. Radial Bearing
2. Thrust Bearing
3. Guide Bearing
THE PURPOSE OF BEARING LUBRICATIONS
1. To provide a low-friction film between the rolling elements and the races of the bearing and at point of contact with cages, guiding surfaces, retainers and so on.
2. To protect the bearing component from corrosion.
3. To help dissipate heat from the bearing unit.
4. To carry heat away from the bearing unit.
5. To help dispel contaminants and moisture from the bearing.
FORMULAS
1. Maximum Contact Stress for Balls
Ssmax = 0.31 Smax
Where:
Ssmax = maximum contact stress, psi
Smax = maximum Herzian Contact stress, psi
2. Maximum Contact Stress for Cylinder
Ssmax = 0.31 Smax
Where:
Ssmax = maximum contact stress, psi
Smax = maximum Herzian Contact stress, psi
3. Bearing Pressure
P= F/A or F/LD
Where:
P= maximum bearing pressure, Mpa, Psi
F= load, N, or lb
A= across section area, mm2, in2
L= length, mm or in.
D= diameter, mm or in.
4. Frictional Torque
Tf= Ff (D/2)
Where:
f= coefficient of friction
N= rotative speed, rpm or rps
W= weight or load, N or lbs
V= velocity, m/s or ft/s
Tf= frictional torque, N-m or lb-in
5. Frictional Power
Pf= 2ΠTN = fwv
Where:
f= coefficient of friction
N= rotative speed, rpm or rps
W= weight or load, N or lbs
V= velocity, m/s or ft/s
Tf= frictional torque, N-m or lb-in
P= frictional power, KW or Hp
6. Life in Millions of Revolutions
a. For Ball Bearing
L3 = (C/P)3
b. For Roller Bearing
L10 =(C/P)10/3
Where:
C=specific dynamic capacity, lb
P= equivalent load, lb
L3 and L10 = life of bearing
7. Life in Hours
a. For Ball Bearing
L3 = 16667 (C/P)3
Rpm
B. For Roller Bearing
L3 = 16667 (C/P)10/3
Rpm
Where:
C=specific dynamic capacity, lb
P= equivalent load, lb
L3 and L10 = life of bearing
Rpm= revolution per minute
8. Compressive Breaking Load
Fc = _k_ (D2)
FS
Where:
K= 100, 000 for carbon steel balls
= 125,000 for hardened alloy steel balls
FS = factor of safety
D = ball diameter, in
Fc = compressive breaking load, lb
9. Maximum load
Fmax = 4.37 (F)
N
Where:
n= no of ball
F= total radial load, lb
Fmax= maximum load, lb
10. Diameter Clearance
Cd = D-d
Where:
d= journal diameter, mm or in.
D= bearing diameter, mm or in.
Cd= diameter clearance, mm or in.
The main advantages of antifriction bearings are low friction, less wear and tear, moderate dimensions, easy to replace and high reliability. babbit bearings
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