Belt Tension Frequency Calculator

This estimates belt tension from the vibration frequency of a plucked belt span. It runs locally in your browser; audio is not uploaded anywhere.

Current preset

Speed Queen / Alliance 804985 washer belt test

Preset values: 54 lbf target tension, 13.5 in measured free span, 2.47 oz belt weight, 56.5 in whole belt loop length. Expected target frequency should be about 102 Hz.

Read the Q&A blog post about replacing the washer motor and belt.

Inputs

Target tension, lbf

Free span length, inches

Whole belt weight, oz

Whole belt loop length, inches

Measured frequency, Hz

Optional known belt weight, lb/ft

Microphone frequency finder

Current frequency: -- Hz

Tap Start, allow microphone access, hold the phone near the 13.5 inch belt span, then pluck the belt.

Results

Belt weight per length: -- lb/ft

Target frequency: -- Hz

Calculated tension from measured Hz: -- lbf

Enter or capture a measured frequency to compare.

Formula used

T = 4 W L² f² / g

T = belt tension in lbf, W = belt weight per length in lb/ft, L = free span in ft, f = frequency in Hz, g = 32.174 ft/s².

To get W from a whole belt: W = (belt weight oz / 16) / (belt length inches / 12).