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Propeller Balancing and Vibration Spectrum

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12 Mar 2023 15:40 #1 by John Earl
Replied by John Earl on topic Propeller Balancing and Vibration Spectrum
Tracking is good. I do not think a bent propeller can be balanced. In this case, I was able to balance the propeller to 0.1 Inches Per Second Velocity, which is considered good for an airplane engine propeller.

The lower frequency vibrations could indicate other problems, such as a weak cylinder or something on the airframe loose. I am hoping someone might be familiar with the typical vibration spectrum for this engine and propeller combination.

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12 Mar 2023 15:35 #2 by John Earl
Replied by John Earl on topic Propeller Balancing and Vibration Spectrum
The prop is freshly rebuilt and is indexed per the Coupe Capers article. Previously it was not properly indexed and it really shook on climbout. That article was very helpful.

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12 Mar 2023 14:57 #3 by Ronald Raty
Replied by Ronald Raty on topic Propeller Balancing and Vibration Spectrum
I was complaining to my A&P about vibration. It wasn't extreme, but it was irritating. He checked the tracking on my McCauley, it was off by 1/4" He said that was it. The prop shop fixed the tracking, and noted it was already in balance. Weather has kept me from seeing if there is a difference. Tracking is something you can check yourself.

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12 Mar 2023 14:49 #4 by Larry Snyder
Replied by Larry Snyder on topic Propeller Balancing and Vibration Spectrum
Is the prop correctly indexed? There was an article in the Coupe Capers a few years ago describing how prop indexing can cause vibration. Is your prop at 10-4 at TDC on #1?

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12 Mar 2023 14:40 #5 by John Earl
I am looking for guidance to interpret the vibration spectrum on my C8512F with a McCauley 7146 propeller.  The assembly balanced okay but I see a lot of low frequency vibration on the spectrum.  Is anyone familiar with this?
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