Tolerances on belts and pulleys lead to a nonuniform tension distribution among the belts in a multiple belt drive. Material imperfections lead to a service life distribution. Both phenomena contributes to the life of the drive i.e. the shortest life of any of the belts. To compensate for life reduction a belt number factor is introduced. The combined effect of tension and life distributions is simulated and compared with analyses. It appears that life distribution is the major contributor. Practical values of the belt number factor are presented.
