Practical Solutions to Machinery and Maintenance Vibration Problems
Chapter 10, Gear Vibration
Section 4, Gear Vibration Frequency of 2 x rpm
Gear vibration frequency of 2 x rpm of the "offending" gear has been extremely rare in the writer's experience. However, it has occurred and, in the rare cases experienced, there was a resonant part that magnified the vibration at that frequency. This again was on an old papermachine with a pinion gear driving the dryer roll system. The pinion was at the end of a long cantilevered shaft. As the cantilevered shaft was bent, one side of the gear was applying most of the load toward the mating gear, and one half revolution later the other side of the gear was applying the load. This resulted in two impulses per revolution. The answer was to straighten the cantilevered shaft so that the pinion would not "wobble."
In this case, the first resonant frequency of a span of paper sheet (between two rolls) matched the 2 x rpm vibration coming from the pinion. It was easier to straighten the shaft than change the resonant frequency of the sheet. It is doubtful if this 2 x rpm vibration would have been a problem if there had not been a resonant length of sheet to magnify it.
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