Planetary Gears
Planetary gear systems are somewhat more complex than standard gear pairs due to the fact that the planet gear centers rotate around the sun gear at a rate called the train frequency. The sun gear RPM, a planet gear RPM or the train frequency can modulate the tooth mesh frequency. This can produce complex sets of sidebands in the spectrum, and can be difficult to interpret.
Planetary gear set characteristic forcing frequencies may be calculated by the following formulas:
Where RPMP = Planet RPM,
RPMS = Sun RPM,
RPMC = Carrier RPM
N = number of teeth
GMF = Gear mesh frequency
Defects in the Ring Gear will show up at number of Planets time Carrier RPM
Defects in the Sun gear wills show up at number of planets times Sun RPM minus Carrier RPM
Defects in a planet gear will show up at:
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