Theory of Machine
The relation l = (2/3).(j + 2) apply only to kinematic chains in which lower pairs are used. This may be used to kinematic chains in which higher pairs are used, but each higher pair may be taken as equivalent to

Two lower pairs and two additional links
Two lower pairs and one additional link
Any one of these
One lower pair and two additional links

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Theory of Machine
Crowning on pulleys helps

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

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Theory of Machine
Higher pairs are those which have

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

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