Hi Bob, Interesting experience! We will be removing the prop next week (along with additional investigation) when my AP has time to work on my Coupe.
Thanks, David N95CV --- In [email protected], "BobD KSVE" <bevbob...@...> wrote: > > David, > When I bought my coupe N3047H, it had a bad vibration. After doing what you > are doing, motor mounts, clearances, engine stuff, dynamic balancing, we > removed the prop and took it to a prop shop. They promptly red tagged it!! > (someone had drilled a couple of extra holes in the back of the hub) > > A new prop and dynamic balance and empty wallet later and I could finally > make out the writing on the gauge faces while flying. > Bob D. > 1946 415E N3047 "Honey" > Susanville, CA > > > --- In [email protected], "drdlhammond" <drdlhammond@> wrote: > > > > Hi John, > > > > How can I/we tell if the rubber motor mounts are bad??? The AP thought > > they looked normal (i.e. compared to others he had replaced). His torque > > wrench was "validated" about 1-2 months prior to my job (he questioned both > > the 60 inch pounds - too tight - and his wrench but a second, older wrench > > was almost identical). Should we further tighten the mounting bolts? > > > > Both magnetos checked good during the March annual and both have been > > acting "normally" since (i.e. no difference has been noted during engine > > run up prior to take off). Yes, the right exhaust pipe vibrates enough to > > touch the cowling at its exit hole (has since I bought the plane a little > > over 2 years ago). Otherwise, we have not found anything that touches the > > cowling. I will pass along the suggestion to check for valve spring and > > lifter malfunctions. > > > > The engine vibration reminds me of the old K&B 0.35 nitro/methane/castor > > oil model airplane engines we used in the late '60s and early '70s. These > > engines were mass produced and inexpensive. Regardless of how well the > > prop was balanced, they vibrated! At the time, older modelers told me > > these engines were not internally "balanced" and thus their vibration. How > > much engine vibration is "normal" for a 43 year old 4 cylinder 4 stroke > > engine??? > > > > Thanks for your input! > > > > David > > N95CV > > > > --- In [email protected], John Cooper <john@> wrote: > > > > > > On 8/14/2010 10:32 AM, drdlhammond wrote: > > > > We could NOT tighten the mounting bolts to the prescribed 60 inch > > > > pounds (we had metal to metal contact between the engine and the > > > > mount). At 45 inch pounds there was very little clearance so we > > > > settled on 40 inch pounds. > > > > > > OK, there's something wrong there. Bad rubbers, bad torque wrench??? > > > > > > Once that's corrected, there are many possible causes of vibration. > > > How's your mag check? Any baffles, exhaust or intake parts touching the > > > cowl? Broken valve springs? Bad lifters?.... > > > > > > -- > > > John Cooper > > > Skyport East > > > www.skyportservices.net > > > > > >
