An Explanation for the Asymmetry of the Modulation Sidebands about the Tooth Meshing Frequency in Epicyclic Gear Vibration

The vibration spectra of epicyclic gears commonly exhibit considerable asymmetry of the modulation sidebands and even complete suppression of the component at the tooth meshing frequency. A model is proposed which explains these observations in terms of the relationship between the vibrations generated by each of the planet gears as they move relative to the transducer location. Comparisons of the predictions of the model with measured vibration spectra for several epicyclic gearboxes show good agreement.