Yes. There are three methods we inspected.

1. Equalize the "area momen"t so that the belt's crossectional neutral axis is at the pulley plane. Many have applied this approach, believing it to have merit where the steel cord or fabric stress in the outer cords/fibers are equal to the center cords/fibers. Although we have practiced this, we believe it now to be incorrect.

2. Split the neutral path at half the wing roll height. THis is an attempt to equalize the length of edge cord length with center cord path. This is closer to the truth. This also better maintains the material from spilling as it leaves the trough to transition to flat.

3. Apply Finite Element Analysis (FEA) to the trough rough to flat. Minimizing the outer cord stress must also consider the length of the path. Longer = lower stress. We apply a multiple of the belt width to determine a rational for the transition length. In order to obtain a meaningful value the end of the transition path must include a length beyond the last full trough configuration to establish a meaningful boundary condition. The value we found exceeds the 50% rule regardless of transition distance.

However, there are other compelling reasons to find the appropriate minimum stress path. The belt's rubber splice shear stress between outer cables must also be considered. Therefore a new criteria should be formulated that includes the idler trough angle, transition length together with belt safety factor, splice pattern, and splice endurance/fatigue performance as a % of ST rating. The endurance strength is achieved in destructive testing or approved FEA equivalent program. Unfortunately, not an easy formulation that can be rendered to textbook now. ■

The above notes should also include a note on pulley elevation above the idler trough center roll plane. When the pulley is raised it changes the ore trajectory leaving the pulley, depending on the belt tension and the transition geometry. ■