Theory of Machine
Crowning on pulleys helps

In increasing velocity ratio
For automatic adjustment of belt position so that belt runs centrally
In decreasing the slip of the belt
Increase belt and pulley life

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Theory of Machine
Two pulleys of radii r₁ and r₂ and at distance x apart are connected by means of a cross belt drive. The length of the belt is

π (r₁ + r₂) + [(r₁ + r₂)²/x] + 2x
π (r₁ - r₂) + [(r₁ + r₂)²/x] + 2x
π (r₁ + r₂) + [(r₁ - r₂)²/x] + 2x
π (r₁ - r₂) + [(r₁ - r₂)²/x] + 2x

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Theory of Machine
Higher pairs are those which have

Point or line contact between the two elements when in motion
Elements of pairs not held together mechanically
Two elements that permit relative motion
Surface contact between the two elements when in motion

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