VectoraLab Lab

Gearbox Vibration Fundamentals Key Frequencies: • Input shaft: f_in = RPM_in / 60 • Output shaft: f_out = f_in × (teeth_pinion / teeth_wheel) • Gear Mesh: GMF = f_shaft × #teeth • Sidebands around GMF: GMF ± n×f_shaft Healthy Gearbox Spectrum: • GMF present at moderate, stable level • Shaft frequencies (1X) at predictable amplitudes • No unexpected sidebands Fault Signatures: • Gear wear: elevated GMF + harmonics • Tooth breakage: strong sidebands + impacting in time domain • Gear eccentricity: amplitude modulation at shaft frequency • Bearing in gearbox: envelope analysis needed Time Synchronous Averaging (TSA): TSA filters out asynchronous components, leaving only gear mesh related content. Powerful for early fault detection. Oil Analysis: Combine vibration with oil analysis (debris particles) for higher confidence diagnosis. Measurement: • Measure on gearbox housing near each bearing • Accelerometers preferred (not velocity at high GMF) • High sample rate required: >10× GMF as Nyquist Important: Gearbox spectra are complex with many expected peaks. Building a "healthy baseline" spectrum is essential for comparison.