Additive frequencies

[jmack]

Is it possible to have a gearbox with a 30Hz input and 35Hz output shaft speed cause a 65Hz vibration frequency response? We have a machine with repeat bearing failures which has a dominant frequency of vibration at 65Hz which lines up to nothing else except the addition of the input and output shaft speeds??

 

[FeX32]

what about the bearing failure freqs?


Fe

 

[GregLocock]

"Is it possible to have a gearbox with a 30Hz input and 35Hz output shaft speed cause a 65Hz vibration frequency response?" Not in a linear system. However gearboxes are full of non linearities. Gut feel is that second order of one or other shaft is a more likely contender.

Can you post a spectrum?


Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[electricpete]

Let's say the 30hz bull gear is eccentric. It puts 30-hz varying stress on 35-hz rotating pinion. That could create a 30hz varying bow on the 35-hz rotating shaft which might modulate 35hz unbalance or modulate 35hz misalignment forces resulting in 35 +/- 30.

Just a thought. One of many ways for modulation to occur.

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