I have been watching a gearbox that the spectrum changed suddenly and hasn’t gotten any worse. The peak near 100 HZ is BPIR There are no harmonics of that peak. If I move the cursor low by output speed to BPIR-Output speed the harmonics line up in the middle of the burst of peaks down the spectrum. Which would be (BPIR-Output) with sidebands of +- output speed. I think the Inner race may be cracked, the time wave reveals nothing on this. Regardless of what the problem the gearbox has to come out soon. It’s just odd that the peaks line up where a sum and difference frequency WOULD be with sidebands of speed. I really like it when I have the primary with harmonics lol. Any other ideas or comments are welcome.

Mike,

From a signal processing perspective, when fundamental center frequency is low amplitude compared to the sidebands, it indicates that the modulating signal's amplitude is high. This assumes that the signal (BPIR) is amplitude modulated by the 1xSS from unbalance or misalignment force. I made a simulation of this effect using DasyLab. When I raised the modulation signal amplitude (say 1xSS), then the sideband amplitudes increased, and the center frequency (say BPIR) amplitude decreased. You could also measure a demodualted spectrum or ultrasound to get confirming data. Anyway, it looks like there may be a bearing fault that needs attention.

Walt

If you are running CSI, I would suggest collecting a peakvue spectrum. A good place to start is a 1000 f max w/ a 1000 High pass filter and 500 f max w/ a 500 filter. If you need some screen shots for set up, just shout.

I have ENTEK Odyssey. I did do ESP with several different filters. There was still not a primary just the sum and difference.

Did you do a spike energy?

Dave

The overall Spike energy was around 2g's. Very low to have a bearing problem.

Mike,

I assume you have calculated all gear tooth-mesh frequencies and still suspect that it is a bearing fault. Gears typically produce more vibrations than bearings, so you have to identify them first.

Walt