Slip of Belt:- Ans:- When driver pulley rotates firm grip between its surface and the belt. This firm grip between pulley and belt is because of friction and known as frictional grip. If this frictional grip becomes insufficient to transmit the motion of pulley to belt. Then there will be. 1) Forward motion of driver pulley without carrying belt called as slip on driving side.
4 Power transmission (17412)
Law of Gearing :
Generally, the lower side is kept “Tight side” and upper side is kept as “Slack side” with the belt drives having small driving pulley and big driven pulley. Why ?
Power transmission in belt drive depends on angle of lap and frictional grip between belt and pulley. As slack side is at upper side angle of lap and grip increases.
Flat belt speed = V = 600 m/min = 600/60 m/sec = 10 m/sec;
Power transmitted = P = 4 kW ;
Coefficient of friction =µ = 0.3;
Angle of lap = θ =1600
Belt tension ratio = T1/ T2 = eµθ = e 0.3(160x π/180) = 2.31; T1/ T2 = 2.31;
T1= T2 x 2.311--------------------------------(1)
P = ( T1 - T2) x V ; --------------------------------(2)
P = ( T2 x 2.31- T2)x 10; Putting value of power
P = 4 kW 4 x1000 = ( T2 x 2.31 - T2)x 10;
T2 = 305.34 N
T1 = 705.34N
Effect of centrifugal tension on power transmission:
As the belt passes over the pulley with high velocity, centrifugal force is produced on the belt, which tends to act on the belt. This force tries to move the belt away from the pulley.
This force is given by,
TC = m x V2
There is no effect of centrifugal tension on power transmitted.
Advantages of chain drive over belt drive
a) No slip takes place in chain drive as in belt drive there is slip.
b) Occupy less space as compare to belt drive.
c) High transmission efficiency.
d) More power transmission than belts drive.
e) Operated at adverse temperature and atmospheric conditions.
f) Higher velocity ratio. g) Used for both long as well as short distances