Two flexible rotors (65 lbs. and 130 lbs.) having critical speeds of about 1300 rpm were run in six journal bearings to study instability characteristics. Bearing clearance ratios were two and four mils. Bearing diameters were two inches. Length to diameter ratios were one half, three quarters and one. Unit bearing loads were between 8 psi and 32 psi. With few exceptions, whirl impending speeds were very near twice critical and a slight decrease in whirl impending speed was noticed with decreasing viscosity. No stable range was observed above the speed at which whirl set in.n A method for determining the running position of a journal bearing by photographic means is described and several determinations of running speed position are presented. The ratio of the maximum stable speed to the critical speed is plotted as a function of inlet oil viscosity.n Some interesting trends of whirl impending speed with L/D ratio, clearance and temperature are presented.
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