David, 11 and 5 viewed from the cockpit is not correct and will cause vibration. Viewed from the cockpit is should be more like 2 and 8.
Kevin1 --- In [email protected], "drdlhammond" <drdlhamm...@...> wrote: > > Hi Kevin, > > We had the prop off during the March 2010 annual and it was re-mounted in the > same spot on the hub. Engine vibration following the annual was no different > than prior to the annual. The increase vibration was noted following > replacement of the rubber motor mounts. > > After re-indexing the magnetos during the annual (to obtain proper impulse > coupling for hand propping the engine), the prop stops at the 11 and 5 > position as viewed from the cockpit. Again, the engine vibration post-annual > was not different that pre-annual. > > Thanks, > David > N95CV > > --- In [email protected], "Kevin" <kgassert@> wrote: > > > > And make sure the prop is mounted in the proper spot on the hub. When your > > engine stops does it usually stop with the blades at about 10 and 4 looking > > at the front of the aircraft from outside? > > > > Kevin1 > > > > > > > > --- In [email protected], "BobD KSVE" <bevbobdtn@> 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 > > > > > > > > > > > > > > >
