Ball bearing in machine element nati fakkaata cargo skirting tay isa China fimiti

1. Bearing
Sliding bearings
Rolling element bearing
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2. Sliding Bearing
Boundary lubrication
Full film lubrication
Mixed film lubrication
P
N
Parameter
Bearing
.


 = viscosity of lubricant (pa.s)
N = speed (r.p.m)
P = load capacity
 
D
L
W
.
W = applied load (N)
L = bearing length (m)
D = journal diameter (m)
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3. Design of Boundary Lubricated Bearing
surface speed is less than approximately (1.5 m/s)
length to diameter ratio between (0.5 and 1.5)
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4. Design of Full Film Hydrodynamic Bearings
Criteria for optimization
Minimizing of the frictional loss
Minimizing the lubricant temperature rise
Minimizing the lubricant supply
Maximizing the load capability
Minimizing production costs
the radial clearance, 'c', to be in the
range (0.001*D >2c >0.002*D)
P
N
c
r
S s
.
.
2








The 'Sommerfield' number ' S '
Ns = is the journal speed (r.p.s) =N/60
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5. ' e ' the eccentricity
e
c
ho 

The ratio of the eccentricity 'e' to
the radial clearance 'c' is called
the eccentricity ratio
c
e




1
c
ho
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6. The temperature used for
determined viscosity can
be taken as the average of
the inlet and exit lubricant
temperatures
 
2
2
1
1
2
1
.
T
T
T
T
T
Tav






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7. Design Procedure of Full Film Bearing
Length bearing from 5
.
1
5
.
0 

D
L
Journal radial clearance
The lubricant type and its supply temperature, (figure (VII-8))
Calculate the load capacity  
D
L
W
P .
 'P' should typically
be between
(0.34 MN/m2)  for light machine
(13.4 MN/m2)  for heavy machinery
Estimate a value for the temperature rise 'T' across the bearing. The value taken for the initial
estimate is relatively unimportant. As a guide, a value of (T=100 C) is generally a good starting
guess. This value can be increased for high-speed bearing and for low bearing clearances
Determine the average lubricant temperature, (Tav.=T1+T/2) and find the corresponding value for
the viscosity for the chosen lubricant
Calculate the 'Sommerfield number'
P
N
c
r
S s
.
.
2








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8. determine values for the coefficient of friction
variable Use the charts, figures (VII-9)
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9. determine values for total lubricant
flow variable, use figure (VII-10).
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10. determine values for the ratio of the
side flow to the total lubricant flow ,
use figure (VII-11).
Calculate the temperature rise of the
lubricant through the bearing
 
 





















L
N
c
r
Q
f
c
r
Q
Q
P
T
s
s
.
.
.
.
*
.
1
*
10
*
3
.
8
2
1
6
If this calculated value dose not match
the estimated value for 'T' to within say
(0.50 C), repeat the procedure from
Determine the average lubricant
temperature, (Tav.=T1+T/2) and find the
corresponding value for the viscosity
The torque required to overcome friction in the bearing r
W
f
Torque .
.

The power lost in the bearing Torque
N
Torque
N
Torque
Power s.
.
.
2
*
60
.
.
2
* 

 


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