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At 04:38 PM 1/5/2005, William R. Bayne wrote: > ...If this was my McCauley prop, first I would check the plane's > paperwork and see if there is a 377 or one-time STC for this prop to be > on this airframe and see if acceptable static rpm limits are given. If > so, I would get a Helmuth-Chadwick balance done (with proper spinner > mounted) and worry no further, presuming present static rpm is within the > stated range.... The issue is not balance. It's harmonics based on the power pulses and the resonance of the casting, combined with the same characteristics of the rotating mass, especially the crank. The crank and prop together have a resonance that must be considered. That said, I retract my original "cry wolf' statement. There are some interesting boundary conditions wrt rpm limits and the O200 crankshaft when combined with the C85 prop, but that's not important right now... The McCauley 1A/B90 prop is certified for use on the C85 for lengths from 70" - 78" and RPMs up to 2600. As long as you respect those limits and don't have an O200 crank, you're likely safe, albeit not legal... John Cooper Skyport Services PO Box 249 4996 Delaware Tnpk Rensselaerville, NY 12147 518 797-3064 ========================================================================== ==== To leave this forum go to: http://ercoupers.com/lists.htm Search the archives on http://escribe.com/aviation/coupers-tech/
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