4 x bevel set frequency only
4 x bevel set frequency only
(OP)
I have a 2 stage gearbox and a vibration consulatnt has measured a 4x bevel set frequency (first or high speed stage of the gearbox)in the vertical direction only. All other frequencies 1x, 2x and 3x are all very low. The 4x has a a RMS velocity of 11.23 mm/s.
Any idea as to what this could be.
Greg.
Any idea as to what this could be.
Greg.





RE: 4 x bevel set frequency only
C. Hugh (www.Hatch.ca)
RE: 4 x bevel set frequency only
Typical resonant frequencies for the body of an automotive alternator are 1400 Hz, so the frequency you estimate seems high, but not ridiculous.
On the other hand if you assume an 11 tooth pinion and 1800 rpm motor then 4th harmonic is 1320 Hz. ;)
Cheers
Greg Locock
RE: 4 x bevel set frequency only
Some additional information:
Input speed = 1480 rpm
Bevell pinion has 14 teeth
Bevel Pinion frequency (measured)= 349 Hz
4x (measured) = 1396 Hz
If this is a resonance frequency it will obviously not result in any damage in the long term?
Greg
RE: 4 x bevel set frequency only
On the other hand 10g's on the gearbox casing indicates a very noisy gearbox and if the casing is in resonance I would expect to see cracking at some point.
You should establish if the 4X component is steady or changes with speed. Shut down the driver and monitor the 4X freq. If it shifts, you don't have a resonance.
A frequency of 1390 Hertz could be related to the bearings. Calculate all the bearing fault frequencies and compare them. Bearing faults will be related to the operating speed.
C. Hugh (www.Hatch.ca)
RE: 4 x bevel set frequency only