Center Distance and Belt Length

The relationship between center distance and belt pitch length is given by the following formula:

a mathematical formula

Lp = pitch length of belt, inches
C = center distance, inches
D = pitch diameter of large pulley, inches
d = pitch diameter of small pulley, inches
ø = sin–1 (D-d/2C), degrees

The approximate center distance can be found by this formula:

another mathematical formula

where: K = 4L – 6.28 (D+d)

The exact center distance can then be determined by trial, using the belt pitch length formula, or use center distance tables available from belt manufacturers.

Design software such as York Industries free DriveWorks program, can also be used to easily provide exact center distances and belt lengths.

The pitch length increment of a synchronous belt is equal to some multiple of the pitch of the belt. For example, the belt length increment of XL section (0.200 pitch) must be 0.200, 0.400, 0.600, etc.

Belt drive drawing with table below

a table with horsepower ratings

another horsepower table with ratings