Topic: Machine Design
In a ball bearing, if the number of balls is reduced to half and diameter of the ball is increased to 4 times, then static load capacity of the ball bearing is
- A. reduced 4 times
- B. reduced 8 times
- C. increased 4 times
- D. increased 8 times
Answer: D. increased 8 times
Explanation: According to Stribeck's equation, the static load capacity of a bearing is $C = \frac{k d² Z}{5}$, indicating $C \propto d² Z$. With the new configuration, the number of balls is $Z_2 = Z_1 / 2$ and the ball diameter is $d_2 = 4d_1$. The ratio of the new capacity to the old is $C_2/C_1 = (d_2/d_1)^2 (Z_2/Z_1) = (4)^2 \times (1/2) = 16/2 = 8$. Therefore, $C_2 = 8C_1$.