When a belt happens to start slipping

Question

Question

This question was previously asked in

BPSC AE Paper 6 (Mechanical) 2019 Official Paper

It can no longer transmit any power as kinetic friction is less than static friction
It will still continue to transmit power with some slipping
Power transmission efficiency will increase
Flat belts do not slip

Answer 1

Explanation:

A firm frictional grip between belt and pulley or shaft is essential. But sometimes it becomes insufficient.

This may cause some forward motion of the belt without carrying the driven pulley with it, is called Slip of the belt.

Static friction is always greater than kinetic friction irrespective of slipping or non-slipping.
Power transmission (P) is a function of torque (T) and speed (N), i.e. \(P=\frac{2\pi NT}{60}\)
Slipping reduces speed and torque
Slippage of the belt is less in the V-type belt with the respective pulley.
When the belt just starts slipping it will still continue to transmit power with some slip.

Additional Information

In pulley rotation certain portion of the belt will pass through the area where it will change from tight side to slack side, then the length of that specific portion of the belt will expand and contract subsequently and a relative motion will happen between the belt and pulley surface. This phenomenon is called creep of the belt.

Difference between slip and creep.

Creep is due to the elastic property of the belt whereas, the conventional slip is due to insufficient frictional grip between the belt and pulley.
However, the effect of the creep, as well as slip, is to reduce the speed ratio, and hence power transmission.