Hi Gordon, At one time Ercoupes with McCauley Met-L Props had a recommended RPM range to avoid. McCauley has since rescinded it.
That said, it is certainly possible that an individual engine-airframe may demonstrate more "instrument vibration" at certain rpms. I would first replace engine mount rubber bushings and play with upper and lower torque applied. I might then get my prop balanced. My "point" is that operational vibrations should be reduced to an absolute minimum before taking common-sense steps to note and avoid extended operation at those rpms where those vibration are most perceptible. JMHO, WRB -- On Jun 6, 2010, at 17:01, Gordon Smith wrote: > > > It is my understanding that operation at certain RPM s can set up a > harmonic vibration that could cause this plate to crack. I have been > told to watch for vibrations in the instruments > for this vibration range and make note of it not to operate at that > RPM. > > My Stinson had a plaque on the dash, not to operate at 2250 RPM. > > Socialism will eventually run out of other peoples money.
