Aramid Hoist Belt Bending Fatigue Cycle Predictor

The formula

This is the expression the tool evaluates. Every term is named underneath, with the unit it must be supplied in.

How the result is derived

Step by step, from the values you type to the figure on screen.

1. The 8 inputs are read from the form on every keystroke: Belt Thickness, Sheave Diameter, Reference Bending Strain, Life at Reference Strain, Fatigue Exponent, Bends per Trip, Trips per Day and Target Life.
2. Each value is checked against the accepted range in the input table below. A value outside its range stops the calculation rather than producing a misleading figure — the results blank out and a message appears.
3. The validated values are substituted into the expression above, which resolves Bending Cycle Life together with every supporting figure in one pass — no value is carried over from a previous entry.
4. The supporting outputs — Bending Strain, Bends per Day, Days to Retirement, Years to Retirement and Sheave Diameter for Target Life — come from the same pass, so they always describe the same case as the headline figure.
5. Results are rounded for display only. The full-precision value is used throughout the chain, so reading a rounded intermediate figure back into the tool by hand can shift the last digit.

What each input means

Where to read each value on the floor, the unit it must be in, and the range the tool accepts.

What the tool returns

The headline figure and every supporting value it is built from.

Worked example

The tool loads with this case already solved — the Bending Cycle Life shown above is its answer. Change one value and the difference from this baseline is the sensitivity of the result to that variable.

How to use it

1. Work through the input groups in order — Belt & Sheave and Fatigue Data & Duty. The defaults are a realistic case, so you can change one value at a time and watch what moves.
2. There is no calculate button. Every figure recalculates as you type or drag, which is what makes this usable for a what-if sweep rather than a single answer.
3. Read Bending Cycle Life in the dark results panel — that is the headline figure, expressed in cycles.
4. Check the supporting rows underneath (Bending Strain, Bends per Day, Days to Retirement, Years to Retirement and Sheave Diameter for Target Life) before acting on the headline — they are where an implausible input usually shows itself first.
5. Reset to defaults returns every field to the reference case, which is the quickest way to check whether a surprising result came from the tool or from an input you had changed earlier.

Where this is used

• Process planning — establishing Bending Cycle Life before a trial is booked, so machine time and material in Ropeway, Cable & Webbing Dynamics are committed against a calculated figure rather than an estimate.
• Costing and quotation — Bending Cycle Life is an input to the cost sheet, and quoting from a worked number rather than a remembered one is what keeps a margin intact.
• Troubleshooting — when the floor result drifts from plan, entering the measured values (starting with Belt Thickness) shows how much of the gap in Bending Cycle Life each variable explains.
• Teaching and study — the accepted ranges bracket normal Ropeway, Cable & Webbing Dynamics practice, so moving one variable at a time shows the shape of the relationship rather than a single answer.

Assumptions and limits

• 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.
• Every input is bounded to the range normal practice occupies (Belt Thickness 0.5 to 25 mm, Sheave Diameter 20 to 1200 mm and Reference Bending Strain 0.2 to 10 %, and so on for the rest). Those bounds are guard rails against typing errors, not a claim that the formula fails one unit outside them.
• The calculation is deterministic: the same inputs always give the same result. It carries no allowance for machine condition, operator skill, ambient conditions or lot-to-lot material variation unless an input above explicitly represents one.
• Nothing is sent anywhere. The maths runs in your browser, so the numbers you type never leave the page.

Questions people ask