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  #1  
Old 07-11-2018, 03:29 PM
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Paul Eastham Paul Eastham is offline
 
Join Date: Oct 2005
Posts: 503
Default Prop RE-balancing

Hi, has anyone had their prop dynamically balanced a second time and found any significant changes?

I had mine balanced about 10 years ago, before first flight. Over the years I feel like my floorboards are vibrating more and more...or maybe I'm just becoming more sensitive. Have tried the usual things of checking for stuff rubbing on cowl, wheel spin, fairings, etc. And all this despite a few layers of foam, carpet, and thin plywood on the floor.

Thanks for any data points!
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  #2  
Old 07-11-2018, 05:41 PM
Ralph Inkster Ralph Inkster is offline
 
Join Date: Feb 2008
Location: Calgary, Alberta
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Prop wise, if it is in itís same condition as before (no rock chip repairs etc), it should be the same. Engine wise, balancing not only considers the rotating mass, but also takes into account the power pulses, numerous misc small internal parts movements, looseness of exhaust and other bolted on accessories, etc. So in the 10 years wear & tear the whole assembly is probably creating more or different vibrations than what that tight new assembly had originally. Even that(common snag) fiberglass repair to the air filter housing would change the overall mass.
So, dynamic balancing probably isnít a one time ever event.
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  #3  
Old 07-12-2018, 03:50 PM
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ChiefPilot ChiefPilot is offline
 
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Location: Twin Cities, MN
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I balance mine yearly during the condition inspection, and there are usually minor changes. I attribute this to wear, as mentioned, and also small balance changes due to dressing the aluminum prop blades when needed.
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  #4  
Old 07-12-2018, 06:07 PM
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Jesse Jesse is offline
 
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Location: X35 - Ocala, FL
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Removing and reinstalling the spinner can be enough to change the balance.
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RV Hotel (hangar, room, car) at X35 in north FL

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Dynamic Prop Balancing, Prebuy Inspections, Condition Inspections, Repairs and Mods, Injector Tuning, Airframe, Engine, Panel Upgrades, Ferrying, etc.
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  #5  
Old 07-12-2018, 08:47 PM
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Walt Walt is offline
 
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Location: Dallas/Ft Worth, TX
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Quote:
Originally Posted by Ralph Inkster View Post
Prop wise, if it is in itís same condition as before (no rock chip repairs etc), it should be the same. Engine wise, balancing not only considers the rotating mass, but also takes into account the power pulses, numerous misc small internal parts movements, looseness of exhaust and other bolted on accessories, etc. So in the 10 years wear & tear the whole assembly is probably creating more or different vibrations than what that tight new assembly had originally. Even that(common snag) fiberglass repair to the air filter housing would change the overall mass.
So, dynamic balancing probably isnít a one time ever event.
Dynamic balancing can only correct the rotating mass imbalance of the propeller assy, which would include the flywheel, spinner and spinner bulkhead, and associated components. It cannot correct anything else. It can only change if something mechanical changed that would alter the balance.

I've rebalanced my own prop a number of times over the years just to "check" it but have never seen a significant change in vibration levels.

After 10 years I would be much more suspect of the engine mounts, especially if they were the Van's mounts. Engine mounts wear out and will transmit more and more vibration to the airframe.
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Walt Aronow, Dallas, TX (52F) RV7A, IO360, C/S, 1500+hrs

EXP Aircraft Services LLC
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Dynamic Prop Balancing, Pitot-Static Altmeter/Transponder Certification
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  #6  
Old 08-08-2018, 10:22 PM
TurnsWrenches TurnsWrenches is offline
 
Join Date: Aug 2018
Location: Winnipeg
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Quote:
Originally Posted by Walt View Post
I've rebalanced my own prop a number of times over the years just to "check" it but have never seen a significant change in vibration levels.

After 10 years I would be much more suspect of the engine mounts, especially if they were the Van's mounts. Engine mounts wear out and will transmit more and more vibration to the airframe.
^This!

Check your mounts for eccentricity and drift first. If they are sagged out, they will cause headaches.

Periodic Dynamic rebalancing is a good idea, especially if you can carry out the work yourself. Just make sure you do it properly, in cruise.
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  #7  
Old 08-09-2018, 06:23 AM
mcgaughy mcgaughy is offline
 
Join Date: Mar 2009
Location: Fayetteville, NC
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Companies such as Powerflow exhaust recommend rebalance every two years or so. I dynamically balance props and absolutely see changes over time. While I’m not certain, I believe things such as cylinder wear, spark timing / strength, etc can contribute to a dynamic balance. Bottom line real world experience tells me that having a dynamic balance done ever 2-3 years is wise....or whenever major maintenance is done like reclocking props, cylinder work, overhaul, etc.

Ellis
Final Approach Aviation LLC
A&P / IA
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  #8  
Old 08-09-2018, 08:48 AM
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FasGlas FasGlas is offline
 
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Location: Prescott, AZ
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Tip: Before balancing a constant speed prop make sure you fill the grease ports (as per manufactures procedures). The weight of the grease can effect the balance and it changes as the grease slowly leaks out. A full prop is always your reference point.
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  #9  
Old 08-09-2018, 09:06 PM
Tankerpilot75 Tankerpilot75 is offline
 
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Location: Oklahoma City, OK
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Donít want to steal this thread but typically what does it cost to have a C/S prop balanced?
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  #10  
Old 08-10-2018, 04:51 AM
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Walt Walt is offline
 
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Location: Dallas/Ft Worth, TX
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I charge $250 for experimental, owner RR's the top cowl.
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Walt Aronow, Dallas, TX (52F) RV7A, IO360, C/S, 1500+hrs

EXP Aircraft Services LLC
Specializing in RV Condition Inspections, Maintenance, Avionics Upgrades
Dynamic Prop Balancing, Pitot-Static Altmeter/Transponder Certification
FAA Certified Repair Station, AP/IA/FCC GROL, EAA Technical Counselor
Authorized Garmin G3X Dealer/Installer
RV7A built 2004, 1700+ hrs
Website: ExpAircraft.com, Email: walt@expaircraft.com, Cell: 972-746-5154
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