Brochure

Mtd. Ball
Bearings
G-226
®
Mounted Ball Bearing Engineering Section
16667
1000
Question #2:
What is the adjusted bearing life (L10 hours) for an
NP-39 Sealmaster Ball Bearing with moderate shock
conditions and the same applications criteria from
above?
Solution:
1. From Table 2 on page G-221:
a
3
= 0.5 x 0.456
2. Re-Apply the life adjustment factors to the previ-
ously calculated L
10
life:
L
na
hours = L
10
x a
1
x a
2
x a
3
L
na
hours = 12,430 x 1 x 1 x (0.5 x 0.456)
L
na
hours = 2,830 hours
Example #2 - Combined Radial and Thrust Load
Question #1:
What is the adjusted bearing life (L
na
hours) for an NP-
39 Sealmaster Ball Bearing with no shock conditions
and the following application criteria?
Design Radial Load (F
r
) = 500 lbs.
Design Thrust Load (F
a
) = 1000 lbs.
Speed (n) = 1000 RPM
Shaft Size = 2 7/16 in.
Operating Temperature = 125°F
Solution:
1. Calculate F
a/
F
r
= 1000/500 = 2
2. Look up the insert of an NP-39 on page G-31. From
Table 4 on page G-228, ND
2
is 3.969 lbs and Basic
Dynamic Rating is 11,789 lbs.
3. Begin by calculating the Relative Axial Load (RAL):
RAL = = = 251 lbs.
4. From Table 3 on page G-222, interpolate RAL be-
tween 200.10 and 300.15 and “e” between 0.30 and
0.34 to obtain “e” value:
=
Therefore e = .32
5. From Table 3 on page G-222, determine the value
of “X” and “Y” through interpolation. Interpolate “e”
between 0.30 and 0.34 and “Y” between 1.45 and
1.31 because F
a/
F
r
> e
=
Therefore Y = 1.38 and X = .56
6. Determine the equivalent radial load (P)
P = (X F
r
) + (Y F
a
)
= (0.56 x 500) + (1.38 x 1000) = 1660 lbs.
L
10
= (C/P)
3
x
Look up the insert of an NP-39 on page G-31. From
Table 4 on page G-228, the Basic Dynamic Rating is
11,789 lbs.
L
na
= .456 x x = 2722 hours
11789
1660
(
3
(
F
a
ND
2
1000
3.9690
251 - 200.10
300.15 - 200.10
0.32 - 0.30
0.34 - 0.30
e - 0.30
0.34 - 0.30
Y - 1.45
1.31 - 1.45
16667
n
Load Ratings and Life Continued