Theory of Machine
In railway axle boxes, the bearing used is

Deep groove ball bearing
Cylindrical roller bearing
Double row self aligning ball bearing
Double row spherical roller bearing

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Theory of Machine
The frictional torque transmitted in a flat collar bearing, considering uniform wear, is (where r₁ and r₂ = External and internal radii of collar respectively)

(1/2) μ W (r₁ + r₂)
(1/2) μ W [(r₁³ - r₂³)/(r₁² - r₂²)]
(2/3) μ W [(r₁³ - r₂³)/(r₁² - r₂²)]
(2/3) μ W (r₁ + r₂)

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