Allied & ICAR Exam Bank • ALLIED_1069 NAT • 2 Marks

Section 2: Farm Machinery

Machine Design

Subtopic: Rolling Contact Bearings

Question Statement:

A deep groove ball bearing in a thresher shaft carries a radial load of 4 kN. If the dynamic load rating $C$ of the bearing is 20 kN, the rated bearing life in millions of revolutions ($L_{10}$) is:

Answer Key:

125

Step-by-Step Solution & Explanation

For ball bearings, rating life $L_{10} = \left(\frac{C}{P}\right)^p$, where $p = 3$. Here $C = 20\text{ kN}$ and $P = 4\text{ kN}$. $L_{10} = \left(\frac{20}{4}\right)^3 = 5^3 = 125\text{ million revolutions}$.
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