Review and summary

REVIEW AND SUMMARY

• Based on the shape of cross-section of the belts, belts are classified as flat belts, V- belts and ropes (i.e., circular belts).

• Velocity ratio of belt drive:

where N1 and N2 = Speeds of the driver and driven pulleys respectively,

d1 and d2 = Diameters of the driver and driven pulleys respectively,

t = Thickness of the belt,

s = Total percentage slip,

E = Young's modulus of the belt material, and

σ1 and σ2 = Stresses in the belt on tight and slack sides respectively.

Velocity ratio of a compound belt drive:

• Length of an open belt:

• Length of the cross belt:

where d1 and d2  = Diameters of the larger and smaller pulleys respectively, and 

x = Distance between the centres of two pulleys.

• Determination of angle of contact:

For open belt drive:

For cross belt drive:

• Tension ratio for flat belt drive:

• Power transmitted by a belt;

P = (T1 - T2) v

where P = Power transmitted by a belt in watts,

T1 and T2 = Tensions in the tight and slack sides of the belt in newtons respectively, and

v = Linear velocity of the belt in m/s.

• Centrifugal tension: TC = m v2

where m = Mass per unit length of belt

• To find the width of the belt, use the formula, Tmax = σ • b • t

where

σ = Maximum safe stress,

b = Width of belt, and

t = Thickness of belt

• Conditions for the transmission of maximum power are:

• Initial tension (T0) of the belt:

• Tension ratio for V-belts and rope drives:

• Number of V-belts (or ropes) =