Lifting Systems
Life falls as the fifth power of bending strain. A sheave 20% smaller costs about two thirds of the belt.
— cycles
Cycles to retirement at the resulting bending strain
Bending strain alone drives this model, and tension is not in it — real belt life depends on tension and bending together, with reverse bends over back-guide sheaves substantially worse than same-direction bends of the same magnitude. Rope and belt fatigue exponents are also fitted over a limited strain range, so extrapolating far outside it, in either direction, is not supported by the data behind the constant. Traction belts additionally wear at the sheave interface and can fail there long before the fibre fatigues. **This is a decision-support estimate only.** Elevator and hoist components are life-safety equipment with mandatory inspection regimes and manufacturer-specified retirement criteria that govern instead of any calculation.
Aramid Hoist Belt Bending Fatigue Cycle Predictor — free, with the formula and a worked example, at Textile School.