Which pulley diameter should be entered?

Use pitch diameter for synchronous belts. For V-belts use the applicable datum/effective diameter and matching datum/effective belt length from the selected manufacturer system; do not substitute outside diameter.

What does belt-loop frequency mean?

It is the rate at which one marked point on the belt completes a full circuit, equal to pitch-line speed divided by pitch/datum belt length.

Does the calculator include slip?

No. Shaft ratio and loop frequency use ideal no-slip kinematics. A V-belt drive with slip requires measured speeds or a validated slip model.

Do 2× and 3× prove two defects or severe wear?

No. They are only mathematical harmonics of loop frequency. Diagnosis requires spectra, phase, operating condition and inspection.

Can shaft speeds define a belt-flutter frequency range?

No universal range is derived from shaft speeds alone. Span natural frequencies depend on tension, span length, mass per length and boundary conditions.

Free Engineering Tool

Belt Loop and Shaft Frequency Calculator

Calculate ideal no-slip belt-loop frequency, pitch-line speed and shaft frequencies from matching pitch/datum dimensions.

Pitch/Datum GeometryNo-Slip KinematicsReference, Not Diagnosis

Kinematic Results

Belt-loop frequency

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Pitch-line speed

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Driver shaft frequency

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Driven shaft frequency / speed

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Speed ratio n₂/n₁ = d₁/d₂

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Mathematical loop-frequency harmonics

Multiple	Hz	cycles/min

Harmonic presence alone does not identify a unique fault or severity.

Ideal no-slip kinematics

v = π d₁ n₁ / 60,000 [m/s]

f_loop = v / (L/1000) = π d₁ n₁ / (60 L)

n₂ = n₁ d₁/d₂; f₁=n₁/60; f₂=n₂/60

All length inputs must describe the same pitch/datum system. Gates distinguishes pitch diameter from outside diameter for synchronous sprockets; Optibelt likewise distinguishes timing-belt pitch diameter and V-belt datum diameter/length.

Sources: Gates Light Power and Precision Manual, Gates timing-belt design manual, and Optibelt V-belt manual.

Diagnostic boundary: a localized belt feature can repeat at loop frequency, but harmonics are not one-to-one fault labels. Belt-span natural frequency requires tension, free span, mass per length and boundary conditions; it is not bounded universally by the two shaft frequencies.