In belt drive, pulleys are made a slightly convex surface. This convex surface is called crown.
6) In belt drive, pulleys are made a slightly convex surface (rather than flat). This convex surface is called
crown
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They make too much noise
A timing belt is a non-slipping mechanical drive.
Balata
Balata belts are similar to rubber belts except that balata gum is used in place of rubber. Balata belts are acid proof and water proof and it is not effected by animal oils or alkalies. The balata belts should not be at temperatures above 40° C because at this temperature the balata begins to soften and becomes sticky. The strength of balata belts is 25 percent higher than rubber belts.
It causes excessive belt wear
it is required to start or stop driven shaft without disturbing the driving shaft
A fast and loose pulley, used on shafts enables machine to be started or stopped at will. A fast pulley is keyed to the machine shaft while the loose pulley runs freely. The belt runs over the fast pulley to transmit power by the machine and it is shifted to the loose pulley when the machine is not required to transmit power. By this way, stopping of one machine does not interfere with the other machines which run by the same line shaft.Paper Pulleys, Fast and Loose Pulleys.