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Prop Balance

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Roger Lee

Joined: 10 Jan 2006
Posts: 1464
Location: Tucson, Az.

Posted: Fri Mar 30, 2007 5:21 pm Post subject: Prop Balance

Hi All,     



Just had my Warp Drive prop balanced today. It was out .30" which is significant. I had a post once before about balancing your props and I still highly recommend it for the health and longevity of your tranny/engine. You blades may be weighed to with in a few grams, but the few grams coupled with out of round spinners, nuts, bolts washers any, the prop hub. Everything will add up and will put you drive system out of balance. Cost was $200 and it took about 2 hrs.

You may not feel any vibration in a Kolb because of its control system unless it is really bad, but it is still there.

Any prop that is just bolted on to an engine is most likely out of balance due to all the mounting hardware. Even Rotax says your supposed to do a dynamic balance of your prop. If you spent all that time building and all that time in the air then this one item is worth the money.

_________________
Roger Lee
Tucson, Az.
Rotax Instructor & Rotax IRC
Light Sport Repairman
Home 520-574-1080 TRY HOME FIRST
Cell 520-349-7056

John Hauck

Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

Posted: Fri Mar 30, 2007 5:30 pm Post subject: Prop Balance

Cost was $200 and it took about 2 hrs.

 |

| --------

| Roger Lee

Roger:



Could you tell any difference in the engine and prop between before 

and after balance?



john h

mkIII

_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama

Roger Lee

Joined: 10 Jan 2006
Posts: 1464
Location: Tucson, Az.

Posted: Fri Mar 30, 2007 7:32 pm Post subject: Re: Prop Balance

Hi John,



 Not really in my stick, but my tranny could. I balanced it at 4800 rpm.

 Typically you do a balance at the lower rpm cruise. I had to add two large washers (1 1/8")  on two different bolts on one side. Warp Drive or any prop MFG. can match the weight of each blade, but they can't make it balanced on an engine.

Out of balance can cause bearing and seal leaks and faster wear on gears. You and I have flown helicopters. When I did a balance on my main rotors what a difference. Because of the large heavier rotor blades it was felt much more because it produced a larger frequncey vibration. Our system is very small in comparison and it produces a smaller frequency vibration which is harder to feel unless it is really out of balance, but non the less there.

Out of balance is kind of like smoking cigeretts. It won't get you today, but it will some day.

_________________
Roger Lee
Tucson, Az.
Rotax Instructor & Rotax IRC
Light Sport Repairman
Home 520-574-1080 TRY HOME FIRST
Cell 520-349-7056

Paul Petty

Joined: 11 Jan 2006
Posts: 226
Location: Mississippi

Posted: Sat Mar 31, 2007 12:51 am Post subject: Re: Prop Balance

Roger,

Didn't someone design a harmonic balencer for airplane props? I know i saw it somewhere. It used tiny ball bearings in a hub that allways found the out of balance point. I tried to google it but came up with snake eyes.



did find this tho  http://www.dssmicro.com/faqs/fqprpbl.htm interesting!



do not archive

_________________
Paul Petty
Kolbra #12
Ms Dixie
912 UL 70" warp

Paul Petty

Joined: 11 Jan 2006
Posts: 226
Location: Mississippi

Posted: Sat Mar 31, 2007 1:15 am Post subject: Re: Prop Balance

I think this may be what i found once.



 http://www.balancemasters.com/ultralights.html

_________________
Paul Petty
Kolbra #12
Ms Dixie
912 UL 70" warp

rowedenny(at)windstream.n
Guest

Posted: Sat Mar 31, 2007 3:32 am Post subject: Prop Balance

Paul,

I use one of these on my Mk-3, 690L-70 with a 68 inch three blade Powerfin F 

model prop.  I took it off once to see if it made a differance and decided 

to put it back on after taxiing a short distance.

It definitly reduces vibration.



Denny



 	  Quote: 	
		   I think this may be what i found once.



 http://www.balancemasters.com/ultralights.html



 --------

 Paul Petty

 Kolbra #12

 Ms Dixie

 Final assembly!

d-m-hague(at)comcast.net
Guest

Posted: Sat Mar 31, 2007 3:50 am Post subject: Prop Balance

At 11:32 PM 3/30/2007, Roger Lee wrote:

 	  Quote: 	
		  ...Our system is very small in comparison and it produces a smaller 

frequency vibration which is harder to feel unless it is really out of 

balance, but non the less there.

Out of balance is kind of like smoking cigeretts. It won't get you today, 

but it will some day...


	


I also fly PPG, and when the engine is strapped to your back, you sure feel 

the vibration!  On a PPG, out of balance props tend to lead to cracked 

exhaust components.  Depending on the result, you may never have to worry 

about balancing THAT particular prop again...



                                 -Dana



do not archive



--

--

The citizens of the United States are getting the government they deserve. 

The problem is that I'm also getting the government they deserve.

Thom Riddle

Joined: 10 Jan 2006
Posts: 1597
Location: Buffalo, NY, USA (9G0)

Posted: Sat Mar 31, 2007 5:32 am Post subject: Prop Balance

Roger,



How does one dynamically balance a prop attached to an engine? I know 

how to statically balance one and also know how to calculate the moment 

of inertia. Details are needed. Or did you take it to someone with 

special machinery to do that?



Thom in Buffalo

_________________
Thom Riddle
Buffalo, NY (9G0)

Don't worry about old age... it doesn't last very long.
- Anonymous

John Hauck

Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

Posted: Sat Mar 31, 2007 5:45 am Post subject: Prop Balance

| I also fly PPG, and when the engine is strapped to your back, you 

sure feel

| the vibration!   |

|                                 -Dana

Dana:



 Wouldn't it be more comfortable to have the engine bolted to a 4130 

airframe, like we do in our Kolb airplanes?



john h

mkIII

_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama

d-m-hague(at)comcast.net
Guest

Posted: Sat Mar 31, 2007 10:06 am Post subject: Prop Balance

At 09:45 AM 3/31/2007, John Hauck wrote:



 	  Quote: 	
		    Wouldn't it be more comfortable to have the engine bolted to a 4130

airframe, like we do in our Kolb airplanes?


	


Well, some PPG's are 4130... 



Actually the PPG seat is pretty comfortable once you're airborne.  PPG and 

planes are equally fun in different ways... a PPG is very weather limited 

and only goes 20-25 mph (which is both and advantage and a disadvantage) 

but a Kolb can't take off and land in 10', either.



                                 -Dana



do not archive

--

--

The citizens of the United States are getting the government they deserve. 

The problem is that I'm also getting the government they deserve.

Roger Lee

Joined: 10 Jan 2006
Posts: 1464
Location: Tucson, Az.

Posted: Sat Mar 31, 2007 10:47 am Post subject: Re: Prop Balance

Hi All,



The prop vibration can cause exhaust to break, seals to go bad, bearings to go bad, parts to crack. The funny thing is you won't even know it. Mine was out .30" and by adding the proper weight I am now down to .03". Anything .06" and under is good. Of course .00 would be great. Anything can cause the out of balance. It may be hardware, something out of round, large nicks in a prop, spinners. All the components from the tranny hub back must be put into sync or balance, not just the blades of the prop.



Things to know. 

First make sure your prop blades are all equal(i.e. 68 degrees of pitch) and not to have one out by .5 degree. This is really easy if anyone wants me to explain later.

If you have a relatively new prop it should be statically balanced off the plane to make sure one spot or area is not out of a static balance.

Just for a dynamic balance, you call someone and have them hook up a small computer box to your plane. You will have one sensor, sometimes two, placed on your gear box. You will have a photo-eye mounted to aim at a piece of reflective tape on your prop to check rpm. You then run you engine at about low cruise rpm i.e. 4800rpm or so and the computer takes measurements. It will then tell the operator where in degrees relative to the tape on the prop where and how much weight should be added. Depending how far out you are depends on the amount of weight and location of the weight. Sometimes it my suggest two weighted areas. You would be supprised at how much weight and you didn't even feel it in the stick. Then you run it again and double check the vibration on the computer box. It may be ok or it may suggest you move a weight or add more, just depends. You may run your engine 2-3 times or 8-10, but your tranny and engine parts that aren't vibrating anymore will love you.



Two strokes are more vunerable than 4 strokes and need to be balanced, also.



I have tried, in the earlier days, those add on balance devices with different things in them. They really only help if you are shaking bad, but you are still way out of balance, you just can't feel it as much anymore. If you need proof put the balance device on and then get the dynamic balance done and it will enlighten you right away.

If one other person here on the forum would get a balance and see how far out they most likely are then I think there will be believers.



I'm only trying to help everyone have a fun, with less long term maint. issues.

_________________
Roger Lee
Tucson, Az.
Rotax Instructor & Rotax IRC
Light Sport Repairman
Home 520-574-1080 TRY HOME FIRST
Cell 520-349-7056

jbhart(at)onlyinternet.ne
Guest

Posted: Sat Mar 31, 2007 2:51 pm Post subject: Prop Balance

At 11:47 AM 3/31/07 -0700, you wrote:

 	  Quote: 	
		  

Two strokes are more vunerable than 4 strokes and need to be balanced, also.




	


Roger,



I am curious, why this is so?



Jack B. Hart FF004

Winchester, IN

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