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Propeller Balancing

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jeffrey-j-paris(at)excite
Guest

Posted: Tue Feb 07, 2006 10:00 am Post subject: Propeller Balancing

Guru's of the Zenith List,



I've Googled without much luck, but does anyone have an inexpensive way, directions, instructions to balance ones' wooden propeller?  I'm curious to see what has to be said?



Thank you for your time and consideration.



Jeff Paris

N196ZP CH601XL Jabiru 3300

45 hours in the air and loving every minute of it!!!!

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Kevin Bonds

Joined: 09 Jan 2006
Posts: 171
Location: Nashville, Tn

Posted: Tue Feb 07, 2006 2:18 pm Post subject: Propeller Balancing

Statically or dynamically? A friend of mine dynamically balanced his prop

recently. He paid a guy about $150 to hook it up to a machine; run it up to

cruise speed; and balance it there. Man does it fly smoother now! I watched

the whole process and asked questions. Very cool. I do not often here anyone

talk about dynamically balancing a prop. Seems like one of those things that

people regard as voodoo or snake-oil or something. Also talk of indexing

ones prop to the piston closest to it, so that the weight of the blades

doesn't coincide with the force of the combustion event (I am not completely

clear on this myself, just seen some valid arguments for doing so) is not

often mentioned. I will be giving these things more thought as I get closer.

Seems like a good idea to index then dyn. Balance. FWIW



Kevin Bonds



Nashville TN



601XL Corvair powered; Plans building.



Empennage done; working on wings and engine.



http://home.comcast.net/~kevinbonds



 



do not archive DO NOT ARCHIVE 



 

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_________________
KevinBonds
Nashville, TN
Plans-building Zenith CH601XL w/Corvair Power
http://home.comcast.net/~kevinbonds

frank.hinde(at)hp.com
Guest

Posted: Tue Feb 07, 2006 2:44 pm Post subject: Propeller Balancing

Indexing the prop I simply don't buy...If the prop is balanced it is

already balanced relative to istelf. It should make no difference how it

is indexed.



Dynamically balancing does make make a HUGE difference that I can vouch

for personally.



Frank



Do not archive



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doug kandle

Joined: 09 Jan 2006
Posts: 33
Location: Boise ID

Posted: Tue Feb 07, 2006 3:45 pm Post subject: Propeller Balancing

I too have had very good results from dynamic balancing.  Even after 

a new 72", balanced at the factory, three blade prop had been 

installed on an IO-520, the dynamic balancing still made quite a difference.



As for indexing. A few years ago I had a long talk with one of the 

engineers at Macauley.  I wanted to know why a particular prop could 

be used on another aircraft but not on mine even though the two used 

the same engine.  What I came away with from that discussion was a 

much better appreciation of how much complex engineering goes into 

propeller design.  The entire engine, prop, and engine mounting 

structure must be considered.  It is a dynamic system and resonances 

are an important component.  The prop flexes, the engine mounts move, 

and the forces on the system are impulsive.  This all leads to a very 

complicated system.  This is one area that it is best not to do much 

experimenting and just go with the propeller manufacturers 

recommendations.  I have been told that on some prop-engine-mounting 

combinations that the orientation of the propeller relative to the 

crank shaft is critical to avoid resonance problems.



  At 03:41 PM 2/7/2006, you wrote:

[quote]

<frank.hinde(at)hp.com>



Indexing the prop I simply don't buy...If the prop is balanced it is

already balanced relative to istelf. It should make no difference how it

is indexed.



Dynamically balancing does make make a HUGE difference that I can vouch

for personally.



Frank



Do not archive



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frank.hinde(at)hp.com
Guest

Posted: Wed Feb 08, 2006 7:03 am Post subject: Propeller Balancing

Indeed, But that is resonance which is not the same as assuming that it

is a good thing to have the prop blade going the other way to the

nearest piston. Its (as you say) a much more complex system than that.



In fact, that is why the reduction drive manufacturers use an "odd

ratio" 2.1:1 in the case of the Stratus...This means the prop is

constantly moving relative to the engine to avoid getting a standing

resoanant wave. There is a resonant point somewhere along the travel

though, that is why we get the classic "rum rum" sound and feel from the

engine.



I agree props are complex animals, wish I had time to study the physics

more.., Maybe after I finish the RV.



Frank



Do not archive



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zodie(at)adelphia.net
Guest

Posted: Wed Feb 08, 2006 7:49 am Post subject: Propeller Balancing

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japhillipsga(at)aol.com
Guest

Posted: Wed Feb 08, 2006 10:57 am Post subject: Propeller Balancing

Jeff, Spruce has (had) an inexpensive plug, line level, string device for sale to balance props. Saw it, but have not used it. Seem similar devices in other DIY plane building books, Bill 

 

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