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  #1  
Old 12-27-2016, 07:36 PM
Storch Storch is offline
 
Join Date: Dec 2016
Location: South
Posts: 10
Thumbs up Prop vibration solved.

We bought our 10 with 150 hours on it. IO-540D4A5, two bladed Hartzell HC-C2YR-1BFP/F8068D.
It has had that nagging slight vibration since completion.It follows the engine RPM,gets worse at lower RPM. We put an additional 350 hours on it in the last couple of years. We read all the posts, did all the usual magneto timing, chaffing inspection, prop balance twice, retorquing of everything, etc. Nothing worked.Fortunately we found Les Doud, ldoud@hartzellprop.com, and he suggested reclocking of the prop.
But as most of you know this engine-prop combination will not allow the prop to be moved at all (because of the physical location of the bushings-the prop will not receive them due to their differing lengths). Les sent us the Lycoming crank flange bushing guideline, with the stock location and the desired reclocked location of the bushings and their respective Lycoming part numbers. We ordered the bushings from AC Spruce, it took about a month to get them.
Now for the big news. You cannot remove and install the bushings without a special tool. We tried all the homemade remedies. There simply is not enough clearance between the backside of the crankshaft flange and the engine. I finally located the tool at Lycoming. Its a ST-115 (Special tool). They will not sale it or rent it to you but Van Bortel-Air Power will because they are an authorized Lycoming dealer. I called them, gave them the part number and it was at my place in a few days. Costs-they charged me $1354.00, but refunded it when I returned the tool. Rental cost-$100 per month plus shipping. The tool makes it a snap.We did have to use a long socket and an AN 6 bolt on one or two of the bushings to start them. Very obvious and simple. Entire project can be done in less than a day.
We reclocked the prop so that with #1 at TDC, the prop is horizontal. The prop only needed to be moved one hole. Previously it was at the traditional 11-5 position for hand propping.
Smooth as silk.
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  #2  
Old 12-27-2016, 07:55 PM
Steve Barnes Steve Barnes is offline
 
Join Date: Jul 2008
Location: Santa Rosa, CA
Posts: 516
Default Kudo's for Les Dowd

My story is identical to yours. And the path sounds identical including two dynamic balanceing's, and lots of research, then Les. My experience was about 10 years ago with a Super Six. I am surprised not more people have talked about reclocking their IO540.

Steve
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  #3  
Old 12-27-2016, 11:58 PM
climberrn climberrn is offline
 
Join Date: Oct 2008
Location: Carson City, NV
Posts: 276
Default

I had the exact same problem, although I have an IO-360 with a WW RV74 prop. Balanced twice, everything else you can think of. A friend suggested re-clocking the prop. Fixed instantly. Never been smoother.
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  #4  
Old 12-28-2016, 03:14 AM
supik supik is offline
 
Join Date: Mar 2014
Location: Bratislava, Slovakia
Posts: 60
Default

Thanks for sharing your experience! I am still far away, but does it mean this prop & engine combo should be installed this way by default?

Thanks,
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RV-10 in progress
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  #5  
Old 12-28-2016, 06:30 AM
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rleffler rleffler is offline
 
Join Date: Jun 2006
Location: Delaware, OH (KDLZ)
Posts: 3,697
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I understand that you had a positive result with your re-clocking. But I don't understand the physics on why this was a solution. I would have thought that a balanced prop wouldn't have made any difference. Can you elaborate more on the details on how you or Les came to this conclusion?

thanks,

bob
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  #6  
Old 12-28-2016, 08:43 AM
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airguy airguy is offline
 
Join Date: Oct 2006
Location: Garden City, Tx
Posts: 3,886
Default

The prop wash from the blades hitting the wing roots could cause enough "thump" (I'm guessing here) that if it was in resonance with an existing engine first-order vibration it becomes noticeable, but if it's out of phase it is not?
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Built an off-plan 9A with too much fuel and too much HP. Should drop dead any minute now.
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  #7  
Old 12-28-2016, 09:14 AM
Marc Bourget Marc Bourget is offline
 
Join Date: Apr 2009
Location: Stockton, California
Posts: 143
Default

I don't recall the conversation exactly, but I have a friend who was a member of the "core" engineering design group for several OEM engines.

We got to discussing crankshafts, including why/how you can get a crank failure by taxing into high grass.

Possibly related to the above is the several "orders" of crank vibrations (think bending) that exist. It may be the location of the mass in conjunction with what the crank is doing (because of firing impulses and shape of crank) that leads to this "Phenomena"

FWIW
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  #8  
Old 12-28-2016, 09:23 AM
Storch Storch is offline
 
Join Date: Dec 2016
Location: South
Posts: 10
Default Vibration resolved.

Quote:
Originally Posted by rleffler View Post
I understand that you had a positive result with your re-clocking. But I don't understand the physics on why this was a solution. I would have thought that a balanced prop wouldn't have made any difference. Can you elaborate more on the details on how you or Les came to this conclusion?

thanks,

bob
Bob,
The prop balance(s) did not work. I sent Les the spectrum plot data card from the balance and he deduced, correctly, that it was a 1/2 per revolution vibration. After balancing, the prop was at .01 IPS, nearly perfect. So there is nothing wrong with the prop. I had even sent the prop back to the shop for an internal inspection. More wasted money.
There are tons of smart guys who have very in depth engineering-physics backgrounds who have posted very complex explanations for why this phenomena exists. In 40 years of working on airplanes I had never experienced it. It simply does not seem to make sense.

But it does exists and the solution works. Thanks Les and the folks on this site who helped!
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  #9  
Old 12-28-2016, 09:32 AM
Storch Storch is offline
 
Join Date: Dec 2016
Location: South
Posts: 10
Default Vibration thump

Quote:
Originally Posted by airguy View Post
The prop wash from the blades hitting the wing roots could cause enough "thump" (I'm guessing here) that if it was in resonance with an existing engine first-order vibration it becomes noticeable, but if it's out of phase it is not?
During this grand adventure, I did discover a very pronounced "thump" type vibration. I have a basic interior with no side panels so it was easy to find. It is located on the side wall where the copilots right knee touches the side wall of the fuselage. Very noticeable in flight when you place your palm on this area. I affixed a sheet of ABS plastic with some heavy duty Velcro and it helped. Probably a 2024 doubler would be better.
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  #10  
Old 12-28-2016, 09:49 AM
cajunwings cajunwings is offline
 
Join Date: Jun 2007
Location: new iberia la
Posts: 489
Default Clocking

Can't offer a scientific reason for why this works but Mooney issued service bulliten M20-206 to reclock the prop 60 deg backwards. This was for the 201 models with counterweighted Lyc IO-360s. It states that it doesn't change the engine vibration level but does make it less noticeable in the cabin.

Don Broussard

RV9 Rebuild in Progress
57 Pacer
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