Synchronous averaging is difficult to use with epicyclic gear systems because the dominant frequencies are slightly skewed and asymmetrical. This Tech Brief uses Fourier series analysis to add new insight to this phenomenon. The results are illustrated on vibration data recorded from a Cobra AH-1S helicopter gearbox.

Issue Section:
Technical Briefs
Keywords:
Fourier series, helicopters, vibrations
Topics:
Fourier series, Mechanical drives, Vibration
1.
Dousis, Dimitri A., 1992, “A Vibration Monitoring Acquisition and Diagnostic System for Helicopter Drive Train Bench Tests,” 48th Annual Forum Proceedings of the American Helicopter Society, Vol. 1, pp. 355–369.
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Ma
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C. J.
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Gear Defect Detection Through Model-Based Wideband Demodulation of Vibrations
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McFadden
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P. D.
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Smith
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J. D.
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An Explanation for the Asymmetry of the Modulation Sidebands About the Tooth Meshing Frequency in Epicyclic Gear Vibration
,”
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Copyright © 2002
 by ASME
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