This RPM restriction was due to a service bulletin published by McCauley when the prop first came out. It was because of a suspected resonance between the prop and the crankshaft. Apparently, further testing indicated that there was no problem, and the bulletin was recinded. I had the exact bulletin number and text, but can't lay my hands on it right now. It was SB 11 and 12 or 12 and 13, I think. In any case, the recinding bulliten said to remove the placard referencing the restriction.
John > Much is being said about engine vibrations at certain rpm. All my Ercoupe > manuals say to "Avoid Continuous operation between 1850 and 2020 rpm with > McCauley 1A-90 propeller. The reason for this is: that rpm range causes a > natural critical frequency of vibration that can cause severe damage if it > is maintained. > I remember years ago I bought a new McCauley "Clip Tip" prop for my > Aeronca Champ which had a Continental A-65 engine. When the prop was > installed we had to put a placard on the instrument panel saying to avoid > this rpm range (because of bad vibrations). > Of course some of you may experience vibrations for other reasons but if > they occur in this rpm range I would suspect that this might be the reason > and then try to avoid extended operation in these ranges. > --------------------------------- to unsubscribe send mailto:[EMAIL PROTECTED] _________________________________________________________ Enlighten your in-box. http://www.topica.com/t/15
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