To obtain the best performance from V-Belts, it is necessary to design the drive correctly. The procedure for the same is as follows.

STEP 1    Calculate Speed Ratio (SR)

           Speed Ratio (S R ) = r.p.m of Faster Shaft (R)

r.p.m of Slower Shaft (r)

STEP 2    Select Service Factor (K)

Service factor is obtained from table Service Factor

STEP 3    Calculate Design Power (Pd)

Design Power (P d ) = Power (P) x Service factor (K)

STEP 4    Select Belt Cross Section

Belt cross section is obtained from the Belt Cross Section Selection Chart. When the point of intersection falls on or near the dividing line, feasibility of both cross sections should be checked.

STEP 5    Select Pulley Pitch Diameters

Refer to  Recommended Pulley Diameters for selecting pulley pitch diameters. Try to avoid use of non-standard pulleys but in some cases, it is necessary if the exact ratios are not covered by standard pulleys.

STEP 6    Calculate Belt Pitch Length (Lp) and Center Distance (C)

           Belt Pitch Length (Lp) =  2C + 1.57  (D + d) + (D-d)^2

Where, D & d are pitch diameters of larger & smaller pulleys respectively.

Choose the nearest available belt length from V-Belts Production Range If there is a space  constraint or center distance limitation, use the same calculated length. If so, exact centre distance calculation is not required again.

Calculate the exact center distance by the formula

C=A+ v A 2 -B

STEP 7    Determine Power Rating (P)

Refer to Power Rating Tables from for different belt sections.

Power rating per belt (P) = rated power + Additional power for speed ratio

STEP 8    Find Arc of Contact Correction Factor (Fc) & Belt Pitch Length Correction

Factor (Fd)

Refer  for Arc of Contact Correction factor & Belt Pitch Length Correction factor respectively.

STEP 9    Find Number of Belts (N)

            Number of Belts (N) = Pd
P x Fc x Fd

If the number of belts comes in a fraction, use next whole number.


 i) Smaller & larger pulley pitch diameters & number of grooves obtained.

ii) Number of belts along with size & section obtained.