Dynamic balancing

Dynamic balancing

I have a newly overhauled 0-320 e2d.The prop has about 100 hrs since overhaul. I"ve been feeling a vibration that is not real bad , but bugs me. I just had the prop dynamic balanced. The prop guy said it's not off by much , but lets dial it in. He ran it at 2000 rpm then added weights to the starter ring gear. On the third run it was about as perfect as could be. Well I flew it home and of course it's worse. How could this be ? Any ideas ?

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Re: Dynamic balancing

Joe,
were you running the engine during the balancing and if so did it feel better?  meaning the vibration is gone.  you state that he only checked it at 2000 rpm.  have you reduced power to that value to see if it goes away inflight?
does the vibration only seem to happen at certian rpm settings or does it vary with airspeed?  it could be an airframe thing.

in any case I recommend taking it back and explaining the problem.  offer to take him up for a demo.  if the prop/engine is truly balanced it will be balanced on the ground and in the air.  I have had airplanes come in for prop balance only to realize when running the engine that its not a prop balance issue but an ignition issue.  a faulty / weak spark plug and bad wires will cause a vibration as well as a mag or mag timing issue.
mark

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Re: Dynamic balancing

I was the one at the controls when he did the balance and I didn't notice a vibration on the ground. 2000 RPM was the magic setting I guess when he took the measurement and also to confirm the change he made worked.Flew the plane again today & tried cruising at 2000 rpm and the vibration is still there. Maybe I'm just to unreasonable thinking I can get it as smooth as a jet engine. After all it is a prop.
Looked for any signs of cowling rubbing, but nothing obvious. When I installed the new engine we used all new mounts and hardware.

Thanks for any imput
Joe

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Re: Dynamic balancing

Joe
I just went through prop vibration pain Dynamic balanced it yet but the source was from three separate sources and all would show there own unique vibration at different power settings . First I sent the prop in to be checked it was according to manufactures specs , After being reassembled the prop was dialed and deturmend to be slightly out , and was corrected by replacing the Spacer. This was a great improvement but did not completely eliminate the problem ,Next the spinner was turned 180,again an improvement but still some vibration at high power settings, lastly the forward Bulk Head was looked at and replaced that managed to get it all of it.
Now I'm going to have it Dynamic balancing.

Good Luck
Dave

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Re: Dynamic balancing

I am having the some problem on a complete engine rebuild, I also had the prop rebuilt. I am wondering if the problem could be in a bad motor mount, or crack in the frame or ??
What do you guys think??

Allen Bingham
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Re: Dynamic balancing

How much vibration is consided normal? Is it possible to have no vibration ? I have not flown another airplane in two years since I bought mine so how do you compare ?
I have flown rentals years ago that were like flying wash machines.

Joe La Russa
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Re: Dynamic balancing

Recently changed engine to reman IO520 from TCM. Now have vibration that worsens as I reduce from 2500 rpm. 2400 is worse and 2300 is worse yet. Only have about 35 hours on new engine and am using Hartzell prop about 5 years old that was smooth on old engine. Is it likely that rotating hub 180 degrees will help? Any ideas?

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Re: Dynamic balancing

I read an article in one of the aviation mags about a brand new prop causing a vibration that couldn't be tracked down.The author found it to be that it was just a different set of vibrations than the old prop.Not worse,just different.The prop's manufacturer,Hartzell,even had the owner come to their facility for a dynamic balance with no change.They flew the airplane,and after landing,asked the owner if he had ever flown behind a new propeller.No he hadn't.This turned out to be the answer.The power pulses from the engine were being transfered to the airframe more efficiently than before,hence the new vibration.

Oh well,it made sense to me anyways.

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