Page 15 - NSK_CAT_E1102m_A7-141

SELECTION OF BEARING SIZE

5.7 Examples of Bearing Calculations (Example3) The dynamic equivalent load P of spherical roller 50 Bearing II
bearings is given by: 40 10 HR30206J
(Example1) Obtain Cr / P or fatigue life factor fh when an axial Bearing I
when Fa / Fr≤e HR30305DJ
Obtain the fatigue life factor fh of single-row deep load Fa=1 000N, {102kgf} is added to the conditions of
(Example 1) P = XFr + YXa = Fr + Y3 Fa
groove ball bearing 6208 when it is used under
When the radial load Fr and axial load Fa are applied on when Fa / Fr>e 59.9 23.9
a radial load Fr=2 500 N, {255kgf} and speed single-row deep groove ball bearing 6208, the dynamic
P = XFr + YFa = 0.67 Fr + Y2 Fa
n =900 min–1. equivalent load P should be calculated in accordance
Fa / Fr = 8 000/45 000 = 0.18
with the following procedure. 2000N, {204kgf} 83.8
We can see in the bearing table that the value of e is
The basic load rating Cr of 6208 is 29 100N, {2 970kgf} Obtain the radial load factor X, axial load factor Y and 5500N
(Bearing Table, Page B10). Since only a radial load about 0.3 and that of Y3 is about 2.2 for bearings of
is applied, the equivalent load P may be obtained as constant e obtainable, depending on the magnitude series 231: {561kgf}
follows: of fo Fa /Cor, from the table above the single-row deep
Therefore, P = XFr + YFa = Fr + Y3 Fa Fig. 5.14 Loads on Tapered Roller Bearings
P = Fr = 2 500N, {255kgf} groove ball bearing table. = 45 000 + 2.2 × 8 000

Since the speed is n = 900 min–1, the speed factor fn The basic static load rating Cor of ball bearing 6208 is = 62 600N, {6 380kgf}
17 900N, {1 820kgf} (Page B10)
can be obtained from the equation in Table 5.2 (Page
A25) or Fig. 5.3(Page A26). fo Fa /Cor = 14.0 × 1 000/17 900 = 0.782 From the fatigue life factor fh, the basic load rating can To distribute the radial load Fr on bearings1and2, the
eH0.26 effective load centers must be located for tapered roller
fn = 0.333 be obtained as follows:
and Fa / Fr = 1 000/2 500 = 0.4>e bearings. Obtain the effective load center a for bearings
The fatigue life factor fh, under these conditions, can be 1and 2 from the bearing table, then obtain the relative
X = 0.56 position of the radial load Fr and effective load centers.
calculated as follows: The result will be as shown in Fig. 5.14. Consequently,
Y = 1.67 (the value of Y is obtained by linear
fh = fn Cr = 0.333 × 29 100 = 3.88 interpolation) fh = fn Cr = 0.444 × Cr ≥3.45 the radial load applied on bearings1 (HR30305DJ) and
P 2 500 P 62 600 2 (HR30206J) can be obtained from the following
Therefore, the dynamic equivalent load P is equations:
This value is suitable for industrial applications, air consequently, Cr≥490 000N, {50 000kgf}
Among spherical roller bearings of series 231 satisfying
conditioners being regularly used, etc., and according this value of Cr, the smallest is 23126CE4 Fr1 = 5 500 × 23.9
(Cr = 505 000N, {51 500kgf}) 83.8
to the equation in Table 5.2 or Fig. 5.4 (Page A26), it P = XFr + YFa Once the bearing is determined, substitude the value of = 1 569N, {160kgf}
Y3 in the equation and obtain the value of P.
corresponds approximately to 29 000 hours of service = 0.56 × 2 500 + 1.67 × 1 000
P = Fr + Y3 Fa = 45 000 + 2.4 × 8 000
life. Fr2 = 5 500 × 59.9 = 3 931N, {401kgf}
= 64 200N, {6 550kgf} 83.8
= 3 070N, {313kgf}

(Example 2) Cr = 29 100 = 9.48 From the data in the bearing table, the following values
Select a single-row deep groove ball bearing with a P 3 070 are obtained;
bore diameter of 50 mm and outside diameter under
100 mm that satisfies the following conditions: fh = fn Cr = 0.333 × 29 100 = 3.16 ( )Lh = 500 fn Cr 10 Basic dynamic Axial load Constant
P 3 070 P 3
Radial load Fr = 3 000N, {306kgf} load rating factor e
This value of fh corresponds approximately to 15 800 505 000 10 Bearings
Speed n =1 900 min–1 64 200 3 Cr Y1
hours for ball bearings. ( )= × (N) {kgf}
Basic rating life Lh≥10 000h 500 0.444

10

= 500 × 3.49 3 H32 000 h Bearing1(HR30305DJ) 38 000 {3 900} Y1= 0.73 0.83
Bearing2(HR30206J) 43 000 {4 400} Y2 = 1.60 0.38
The fatigue life factor fh of ball bearings with a rating (Example 4)
fatigue life longer than 10 000 hours is fh≥2.72. Select a spherical roller bearing of series 231 (Example 5) When radial loads are applied on tapered roller
Because fn = 0.26, P = Fr = 3 000N. {306kgf} satisfying the following conditions: Assume that tapered roller bearings HR30305DJ and bearings, an axial load component is produced, which
HR30206J are used in a back-to-back arrangement must be considered to obtain the dynamic equivalent
fh = fn Cr = 0.26 × Cr ≥2.72 Radial load Fr = 45 000N, {4 950kgf} as shown in Fig. 5.14, and the distance between the radial load (Refer to Paragraph 5.4.2, Page A31).
P 3 000 Axial load Fa = 8 000N, {816kgf} cup back faces is 50 mm.
Calculate the basic rating life of each bearing when
therefore, Cr≥2.72 × 3 000 = 31 380N, {3 200kgf} Speed n = 500min–1 beside the radial load Fr = 5 500N, {561kgf},
0.26 axial load Fae=2 000N,{204kgf} are applied to
Basic rating life Lh≥30 000h HR30305DJ as shown in Fig. 5.14. The speed is
Among the data listed in the bearing table on Page 600 min–1.
B12, 6210 should be selected as one that satisfies the The value of the fatigue life factor fh which makes
above conditions.
Lh≥30 000h is bigger than 3.45 from Fig. 5.4 (Page
A26).

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