# Numerical - Basic dynamic capacity, given equivalent dynamic load & speed

Q.  The expected rating life of roller bearings rotating at 1000 r.p.m. is 30000 hours and equivalent dynamic load of 4000 N acts on it. What is the basic dynamic capacity of the bearing?
- Published on 23 Sep 15

a. 26000.12 N
b. 30000.23 N
c. 37900.22 N
d. 48657.61 N

#### Discussion

• Sravanthi   -Posted on 01 Oct 15
Given: Roller bearings, equivalent dynamic load = 4000 N, speed = 1000 r.p.m, Lh10 = 30000 hours

L10 is the rating life of a group defined as number of revolutions completed by 90 % of group of bearings before the first evidence of fatigue failure appears.

Formula: 1) L10 = (Lh10 x 60 x n) / 106
2) L10 = (Basic dynamic capacity of bearing / Equivalent dynamic load on bearing)a

For roller bearings constant (a) = 10/3
For ball bearings constant (a) = 3

Therefore substituting the given values we get,
L10 = (Lh10 x 60 x n) / 106
= ( 30000 x 60 x 1000) / 106
= 1800 million revolutions

L10 = (Basic dynamic capacity of bearing / Equivalent dynamic load on bearing)a
1800 = ( Basic dynamic capacity of bearing / 4000)3

Basic dynamic capacity of the bearing = 37900.22 N

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