At 09:12 AM 2/12/99 -0700, you wrote: >Roger Carson wrote: > >> Recently changed C-85 engines which now has approx 80 hours. Always >getting >> a vibration on the recently installed engine between 1800-2200 RPM only as >> well as some vibration on take-off climb out. At or above 2200 runs >smooth >> and below 1800 runs without vibration. Anyone have any ideas. > >Received alot of ideas and alot recommended that we move the prop one hole >and try, etc. Since alot said this we thought this would be the first thing >to try. Worked like a charm....Still have some roughness between 1900-2100 >but can live with that. I can atleast now view my GPS without holding it >because of the vibration. >Many thanks to all who replied.
Had an interesting thing happen today. A friend who recently had his prop overhauled complained that he was experiencing more vibration than before the overhaul. He had sent it back and was told that it checked out. I finally talked him to checking it out. The first thing we found is one blade is 1/8th of an inch shorter. Next I placed an inclinometer on the prop to measure the amount of pitch at 5 set points (these were not the established "stations") along the blade. One blade was off from 3 degrees at one point to only 2 at the other points. Tracking was also off 1/4. I have no idea if these differences are significant or not. He plans to contact Sensenich next week to ask them about it. The big question he posed is, will they give him the truth or not. If they say it makes no difference is it because that is about as close a tolerance as can be achieved or not and if they say no is it to hopefully either sell a new prop, have that one sent to them for an overhaul, or to recommend it be scrapped. Like the old saying goes "just because you're paranoid doesn't mean they're not out to get you". If you have ever seen how props are pitched it is somewhat amazing they even get them that close, so I suspect it is probably within tolerance and that opinion is based only on a SWAG (scientific wild ass guess). Guess I'll have to do mine now just for reference. This is merely an observation and not meant to establish what is acceptable or not, so please don't everybody get their panties in a wad over this.
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