I have determined that there is some minute induced oscillation at 2500 to 2550 rpm.
-------------------- While it may not necessarily be damaging, what you have found is a resonate frequency between the flex plate and the engine RPM. It is possible that it could eventually cause cracking of the flex plate. Whether that would take 10 hours or 10,000,000 hours to crack is beyond the scope of any advice I could give. Since the "flexplate" is designed to flex and it would be quite rare to run a flying 'vair at 2500 RPM for an extended period of time, the resonating of the flexplate will probably not cause any problems. If it's of concern to you, almost any modification you do to the flex plate will change the resonate frequency. Usually stiffening it raises the frequency and reducing the stiffness lowers it, just like tuning a guitar string. If it was mine, I would take a look at it periodically during the test flying, then add it onto my inspection list for the annual inspections. The Stinsons with a McCauley metal prop had a placard advising not run between something like 2100 - 2300 RPM. That was due to a resonant freqency between the engine and the prop that would eventually cause crankshaft cracking, usually in the keyway for the flywheel on the back end of the engine. The vibration from the McCauley prop was noticeable at those RPMs. Since you have a wood prop, that failure mode would be most unusual as wood props typically have such a low resonance that they almost never cause a harmonic vibration. Jeff Scott ________________________________________________________________ The best thing to hit the Internet in years - Juno SpeedBand! Surf the Web up to FIVE TIMES FASTER! Only $14.95/ month - visit www.juno.com to sign up today!
