Theory of Machine
Crowning on pulleys helps

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

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Theory of Machine
In a steam engine, the earlier cut-off with a simple slide valve may be obtained by increasing the steam lap and the angle of advance of the eccentric but keeping constant the travel and lead of the valve, this method will

Reduce length of effective stroke of piston
All of the listed here
Reduce maximum opening of port to steam
Cause withdrawing or throttling of steam

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