Frequencies of vibrations in gears

ByCarlos Aroeira

Here are presented the frequency of vibrations in gears, generated by its operation.

Types of vibrations in gears

Even though, on one vibration analyzer, the frequency spectrum of vibrations produced by a gear often appears to be very complicated, It can usually be decomposed in the combination of the following effects:

  • Gear frequency and harmonics

          Represent the average deviation from the ideal profile meshing tooth profile, that is, the perfect tooth profile.

  • side bands

Components usually originated in the modulation of meshing, caused either by slow variations (by eccentricity) or sudden changes caused by occasional irregularities (bites, slots, etc.). In addition to the modulation of engagement, the sidebands can also arise modulate a Natural Frequency. In this case indicate the shock repetition rate which excites the Natural Frequency.

  • Rotation speed and harmonics
  • phantom components

Appears to be a gearing frequency, but with a different number of teeth that the gear has. Generally they can be related to the number of teeth of the indexing gear cutter which carried out the machining, and are due to errors in this gear.

  • assembly frequency

Component created a pair of gears used when it changed its relative position.

  • Teeth repetition frequency

Component created when a pair of faulty teeth mesh.

  • natural frequencies

Components that arise when a damaged gear begins to cause shock.

Frequencies of vibrations in gears – normal gears (non planetary)

Being that:

  • Pinion Fp RPM
  • Crown Fc RPM
  • Np Number of pinion teeth
  • Nc Number of crown teeth
  • MDC Greatest common divisor of number of gear teeth

Frequencies of vibrations in gears – Fixed Crown planetary gears

Frequencies of vibrations in gears 7

Frequencies of vibrations in gears 5

Being that:

  • F1 e F2 – rotation speeds
  • Nc – Number of crown teeth
  • For example, – Number of teeth on the planet
  • MDC.- greatest common factor of the number of teeth 2 gears

Rotation Frequency of the Planets =

Moving Crown planetary gears

Frequencies of vibrations in gears 6
Frequencies of vibrations in gears 7

Being that:

  • F1 e F2 – rotation speeds
  • Nc – Number of crown teeth
  • For example, – Number of teeth on the planet
  • Ns – sun teeth numbers
  • MDC.- greatest common factor of the number of teeth of 2 gears

Rotation Frequency of the Planets =

Planetary gears with Fixed Solar

Frequencies of vibrations in gears 14

Being that:

  • F1 e F2 – rotation speeds
  • Nc – Number of crown teeth
  • For example, – Number of teeth on the planet
  • Ns – sun teeth numbers
  • MDC.- greatest common factor of the number of teeth 2 gears

Rotation Frequency of the Planets =

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