Hi Dennis, What kind of balance was done? I do a "static" balance on my mower blades every time I sharpen them before reinstallation. The "gold standard" is the Helmuth-Chadwick process practitioners. It should be done with a NEW spinner backplate by someone with experience KNOWN to achieve good results.
Did your prop pick up any nicks in the past year that were "dressed out"? That would affect balance. Factory balance specifications for the little Continentals are much less stringent than any competent mechanic would accept on his own bird (presuming, of course, that he/she takes pride in doing the best possible job on things mechanical). I'm talking of matching piston and rod weights, etc. before assembling an engine. Racers do this to "gain an edge" in power, efficiency, reliability, and (relative) longevity. Those are worthwhile goals for any private owner, too. I can't get my mind around how the hardness or torque of the rubber cones in the motor mount could have such significant effect on a spinner backplate held by significant torqued bolts directly to the engine crankshaft...and yet I wonder... Regards, WRB -- On Jun 5, 2010, at 13:18, Dennis wrote: > I have a 1946 415C with 85hp Continental engine and metal prop. About > one year ago I had the prop back plate replaced. The old plate had a > jagged break almost all the way around about 1-2" from the outside. > We now notice that the new back plate is broken almost all the way > around very similar to the break on the old plate. Just prior to > replacing the last plate I had the prop re-pitched and balanced. > > Other than replacing the back plate again, does anyone have a > suggestion on what I should do or what is causing the plates to break? > > Thanks, Dennis Hatfield N2738H
