Prop balancing questions?

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Alexb2000

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Alexb2000
I have just under 500 hours on a new McCauley 3 blade prop. The prop was statically balanced at the factory and other than beating a lot of paint off of it in the rain it hasn't been touched.

I noticed on the last couple of annuals I was having some minor repairs that were most likely due to vibration. Cracked fittings, broken bolts, etc. Over the last two years these added up to $500ish in expense.

Most people that flew with me felt the aircraft was very smooth, although I could feel a slight resonance in the airframe. I always run at 2400 in cruise so there wasn't anything different about my operation.

I decided to have the prop dynamically balanced, my shop uses a specialist who only does this kind of work. Anyway the results are:

Before: .3 IPS
After: .02 IPS repeatable on three attempts.

Do these numbers represent something that might have created vibration related repairs? Is this a good result? Did I waste my money? Thoughts?
 
Alexb2000 said:
I have just under 500 hours on a new McCauley 3 blade prop. The prop was statically balanced at the factory and other than beating a lot of paint off of it in the rain it hasn't been touched.

I noticed on the last couple of annuals I was having some minor repairs that were most likely due to vibration. Cracked fittings, broken bolts, etc. Over the last two years these added up to $500ish in expense.

Most people that flew with me felt the aircraft was very smooth, although I could feel a slight resonance in the airframe. I always run at 2400 in cruise so there wasn't anything different about my operation.

I decided to have the prop dynamically balanced, my shop uses a specialist who only does this kind of work. Anyway the results are:

Before: .3 IPS
After: .02 IPS repeatable on three attempts.

Do these numbers represent something that might have created vibration related repairs? Is this a good result? Did I waste my money? Thoughts?
Click to expand...


Can you tell the difference? If yes, it was justified but at what expense?
 
bnt83 said:
Can you tell the difference? If yes, it was justified but at what expense?
Click to expand...

It is very smooth, but before it wasn't terrible just a slight resonance as I said. I don't have the final bill yet, I expect about $400-500.
 
Alexb2000 said:
I have just under 500 hours on a new McCauley 3 blade prop. The prop was statically balanced at the factory and other than beating a lot of paint off of it in the rain it hasn't been touched.

I noticed on the last couple of annuals I was having some minor repairs that were most likely due to vibration. Cracked fittings, broken bolts, etc. Over the last two years these added up to $500ish in expense.

Most people that flew with me felt the aircraft was very smooth, although I could feel a slight resonance in the airframe. I always run at 2400 in cruise so there wasn't anything different about my operation.

I decided to have the prop dynamically balanced, my shop uses a specialist who only does this kind of work. Anyway the results are:

Before: .3 IPS
After: .02 IPS repeatable on three attempts.

Do these numbers represent something that might have created vibration related repairs? Is this a good result? Did I waste my money? Thoughts?
Click to expand...


.3 to .02 is HUGE.....:yes::yes:.

Going price for a dynamic prop balance out here is 175-200 dollars/
 
That was definitely money well spent if you can feel a difference. Now, will you see a reduction in vibration-induced repairs? Hard to say conclusively, but you can look at your future maintenance bills for a best guess.

Another consideration is the long-term impacts on the engine, which you may not feel. One of my friends ended up having his Mooney start making metal at 1700 hours, and he said that he'd always felt a slight vibration in the propeller. It wouldn't surprise me if, as the engine aged, there was some impact there. Like many things, it's hard to say with any certainty.

For what it's worth, we are planning on taking the 310 to get the props dynamically balanced now that the new engines are sufficiently broken in.
 
I think you did alright. Let us know the final d$amages.
 
N801BH said:
.3 to .02 is HUGE.....:yes::yes:.

Going price for a dynamic prop balance out here is 175-200 dollars/
Click to expand...

I do mine for free, I have my own balancer. I balance 3-6 planes a year.

Here is one companies opinion on IPS ( Inches (of vibration) Per Second)

Over 1.25 IPS Danger! Statically balance prop first, then dynamically balance.
1.00 - .25 IPS ROUGH
0.25 - .15 IPS Fair
0.14 - .07 IPS Good
0.04 -.02 IPS Excellent
0.00 Perfect ( very tough to do)

Any vibration in an airplane is bad. Eliminating the most you can is good. Every airplane should be dynamically balanced. It is the best money you can spend on preventive maintenance.

All other possibilities for vibration must be addresses before dynamically balancing.
 
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Alexb2000 said:
Before: .3 IPS
After: .02 IPS repeatable on three attempts.

Do these numbers represent something that might have created vibration related repairs? Is this a good result? Did I waste my money? Thoughts?
Click to expand...

Yes! .3 was borderline rough. Avionics, gages, airframe, engine, engine seals, engine mounts, wheel pants, the whole plane, and your passengers thanks you. :lol:

Yes, .02 is very good, tip your balancer dude. Very professional of him to run 3 repeat tests, IMHO. Very thorough. :yes:

The hardest thing to recognize is the money you won't spend now for repairs. Pretty tough to put a number on that, hence why so few owners think it is necessary. Make sure you log in the engine log.

Theoretically , you will save fuel, increase speed, and get better mileage also. Not sure I totally agree with that claim, but that is what some balancing companies claim. :dunno:
 
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Geico266 said:
The hardest thing to recognize is the money you won't spend now for repairs. Pretty tough to put a number on that, hence why so few owners think it is necessary. Make sure you log in the engine log.
Click to expand...

I think this comes down to a similar classification as maintaining proper CHTs, pre-heating, and using good oil/oil additives/filters. The differences won't be immediately obvious and you'll never be able to quantify the benefits exactly due to a lack of scientific comparison. However, logically speaking the less you shake something, the better corrosion protection, the less cold start damage, etc the more likely you are to get good service life with minimal repairs.
 
Geico266 said:
Theoretically , you will save fuel, increase speed, and get better mileage also. :dunno:
Click to expand...

I think the amount of horsepower change you'll get will be undetectable in this regard.
 
Ted DuPuis said:
I think this comes down to a similar classification as maintaining proper CHTs, pre-heating, and using good oil/oil additives/filters. The differences won't be immediately obvious and you'll never be able to quantify the benefits exactly due to a lack of scientific comparison. However, logically speaking the less you shake something, the better corrosion protection, the less cold start damage, etc the more likely you are to get good service life with minimal repairs.
Click to expand...

I agree.

Put a radio on a paint shaker for an hour and see what you have. While not as violent vibration in a plane does the same thing over time. Getting the vibration as low as you can is going to result in fewer repairs. Dynamically balancing a engine & prop makes good $cents. :D
 
Geico266 said:
I do mine for free, I have my own balancer. I balance 3-6 planes a year.

Here is one companies opinion on IPS ( Inches (of vibration) Per Second)

Over 1.25 IPS Danger! Statically balance prop first, then dynamically balance.
1.00 - .25 IPS ROUGH
0.25 - .15 IPS Fair
0.14 - .07 IPS Good
0.04 -.02 IPS Excellent
0.00 Perfect ( very tough to do)

Any vibration in an airplane is bad. Eliminating the most you can is good. Every airplane should be dynamically balanced. It is the best money you can spend on preventive maintenance.

All other possibilities for vibration must be addresses before dynamically balancing.
Click to expand...

I agree with everything you said.. ( us experimental guys have to stuck together);););)....

I usually balance my prop 2-3 times a year, and I get it done free cause the head mechanic uses it to train the other mechanics and stay current on their balancing ability... Altho they really want to just sit in the plane and listen to the V-8 sing..:yes::D

Another reason I do will lead us off topic but................... I run the Carbon Fiber / Composite Ivo 3 blade and for some strange reason it will get out of balance every 50 hours or so.....

I have had several REAL smart guys debate the reason and so far no quantifiable answer.... Does it slip just slightly in its hub, making the blades clock differently :dunno:. Is it because the blades are so flexible they track differently :dunno:. Do the molecules move around and cause the out of balance :dunno:....
 
N801BH said:
I agree with everything you said.. ( us experimental guys have to stuck together);););)....

I usually balance my prop 2-3 times a year, and I get it done free cause the head mechanic uses it to train the other mechanics and stay current on their balancing ability... Altho they really want to just sit in the plane and listen to the V-8 sing..:yes::D QUOTE]


The V-8 gotta be SMOOOOOOOOTH, like a GL1800 Golwing.
Click to expand...
 
I would suspect that even if the radial motion at the balance sensing transducer is reduced to near-zero, the three prop blades won't always thrust exactly the same amount resulting in a nutating/rocking motion of the engine.

On the other hand, a combination of this rocking and radial out-of-balance will result in motion cancellation at some point such that if the balance sensing is done in only one plane, there could still be a residual imbalance.

I assume transducers were attached to both the front and the rear of the engine? .03 inches/sec = only .00025" double amplitude at 2400 rpm. Very smooth!
 
The shop uses this brand... http://www.acessystems.com/

It has just one accelorometer that mounts on engine centerline and is position sensitive. ie, has to point fore and aft, not side to side.... Also has a photo eye that picks up a reflector that is taped to the backside of one prop blade... On a calm day with absolutely no wind we can get it down to .01 IPS consistantly. Any breeze at all will disturb the unit...IMHO.
 
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Chadwick-Helmuth, makers of vibration analyzers, say that 0.2 IPS is what one should accept as a minimum. Lots of airplanes are much rougher than that. This exhaustive document, here:

http://www.acessystems.com/index.php?option=com_edocman&task=document.viewdoc&id=635&Itemid=142

...says that 0.15 should be the minimum acceptable. It also says that .07 is undetectable by the pilot or passengers. The OP's 0.2 is smooth indeed.


A propeller out of track can cause vibration not readily picked up by the sensors. They only look for vertical movement.

Dan
 
Is 0.00 IPS even possible? When I talked to the mechanics they said you can get that but it won't be repeatable. One teeny tiny bug splat can throw it off.

What kind of numbers do you guys have?
 
Geico266 said:
I agree.

Put a radio on a paint shaker for an hour and see what you have. While not as violent vibration in a plane does the same thing over time. Getting the vibration as low as you can is going to result in fewer repairs. Dynamically balancing a engine & prop makes good $cents. :D
Click to expand...

And that is why a 6 cylinder engine is better than a 4 .
 
Alexb2000 said:
Is 0.00 IPS even possible? When I talked to the mechanics they said you can get that but it won't be repeatable. One teeny tiny bug splat can throw it off.

What kind of numbers do you guys have?
Click to expand...

We can get 0.00 but it will not repeat.... Closest reliable number is .002. IMHO.
 
N801BH said:
I agree with everything you said.. ( us experimental guys have to stuck together);););)....

I usually balance my prop 2-3 times a year, and I get it done free cause the head mechanic uses it to train the other mechanics and stay current on their balancing ability... Altho they really want to just sit in the plane and listen to the V-8 sing..:yes::D

Another reason I do will lead us off topic but................... I run the Carbon Fiber / Composite Ivo 3 blade and for some strange reason it will get out of balance every 50 hours or so.....

I have had several REAL smart guys debate the reason and so far no quantifiable answer.... Does it slip just slightly in its hub, making the blades clock differently :dunno:. Is it because the blades are so flexible they track differently :dunno:. Do the molecules move around and cause the out of balance :dunno:....
Click to expand...

I use to do prop balancing also when I had my helicopter business. I used the Aces 2020 Probalancer.

Blade track has everything to do with a balance, same as in a helicopter. One blade slightly out of track will set up a vibration. I'm not sure what prop you are using but that would be my starting point.
 
N801BH said:
And a 8 cylinder is smoother then a 6..;):yes:
Click to expand...


I've done lots of airplane prop balancing. One thing that is true is 2 blade props work better on 4 cylinder engines, 3 blades work better on 6 cylinder engines.

One of the worst combinations to try to balance is a 3 bladed prop on a 4 cylinder engine. Getting the correct phase and clock angle is a bit of voodoo to get a smooth running prop. Sometimes it requires removing the prop and setting over a bolt hole or setting back a bolt hole. Most mechanics won't take the time when installing one to get it right.
 
Alexb2000 said:
Is 0.00 IPS even possible? When I talked to the mechanics they said you can get that but it won't be repeatable. One teeny tiny bug splat can throw it off.

What kind of numbers do you guys have?
Click to expand...

Very difficult to get 0.0.

Also after each balance the prop and spinner need to be "indexed", or marked so that is removed they are placed back in the right place, otherwise the balance is no good.
 
RotorAndWing said:
I use to do prop balancing also when I had my helicopter business. I used the Aces 2020 Probalancer.

Blade track has everything to do with a balance, same as in a helicopter. One blade slightly out of track will set up a vibration. I'm not sure what prop you are using but that would be my starting point.
Click to expand...

R&W.. All your posts here are right on track. Instead of me quoting each one I will answer all in this post as I have NO idea how you guys take multiple quotes and add them to a single post....:no:

Blade tracking.................. I run the Ivo composite blades and they are VERY flexible.. I can literally bend the tip a couple of inches back and forth so that might be my having to rebalance issue.:dunno:

My set up is even more difficult as I have an 8 cylinder motor, swinging a 3 blade prop and it goes through a 1.43 -1 redrive.... :eek::yikes:... But it is smooth as silk when the prop is balanced to .02 or so..:)
 
N801BH said:
R&W.. All your posts here are right on track. Instead of me quoting each one I will answer all in this post as I have NO idea how you guys take multiple quotes and add them to a single post....:no:

Blade tracking.................. I run the Ivo composite blades and they are VERY flexible.. I can literally bend the tip a couple of inches back and forth so that might be my having to rebalance issue.:dunno:

My set up is even more difficult as I have an 8 cylinder motor, swinging a 3 blade prop and it goes through a 1.43 -1 redrive.... :eek::yikes:... But it is smooth as silk when the prop is balanced to .02 or so..:)
Click to expand...

If given the chance I would try a 2 blade or a 4 blade prop with that engine.

Another idea is re indexing the prop a bolt hole or two and see how that works.

With lots of flexibility the blades will go in and out of track. The key is when one goes out of track will it return to the original track. With the bending maybe it flexes and stays slightly out.
 
N801BH said:
R&W.. All your posts here are right on track. Instead of me quoting each one I will answer all in this post as I have NO idea how you guys take multiple quotes and add them to a single post....:no:

Blade tracking.................. I run the Ivo composite blades and they are VERY flexible.. I can literally bend the tip a couple of inches back and forth so that might be my having to rebalance issue.:dunno:

My set up is even more difficult as I have an 8 cylinder motor, swinging a 3 blade prop and it goes through a 1.43 -1 redrive.... :eek::yikes:... But it is smooth as silk when the prop is balanced to .02 or so..:)
Click to expand...

What kind of year box do you have?
 
N801BH said:
R&W.. All your posts here are right on track. Instead of me quoting each one I will answer all in this post as I have NO idea how you guys take multiple quotes and add them to a single post....:no:
Click to expand...
Click on the icon to the right of the one you usually click on for the first post you want to quote.

Pete and repeat as necessary

click on the usual "quote" icon for the last one.

RotorAndWing said:
Another idea is re indexing the prop a bolt hole or two and see how that works.
Click to expand...
The prop re-indexes itself 43% every time it goes around due to his gear reduction.
 
IMHO Prop balancing is the best bang for the buck in maintenance. Vibration is hard on everything. Around here it's about $200, less than an oil change.....
 
RotorAndWing said:
If given the chance I would try a 2 blade or a 4 blade prop with that engine.

Another idea is re indexing the prop a bolt hole or two and see how that works.

With lots of flexibility the blades will go in and out of track. The key is when one goes out of track will it return to the original track. With the bending maybe it flexes and stays slightly out.
Click to expand...

I can switch from 3 blades to 2 blades in about 15 minutes... That is one of the blessings of the Ivo prop. In the first 50 hours of test flights I did try to 2 blade set up.... it was NEVER as smooth as the three blade though.

I run both of these set ups..

http://www.ivoprop.com/magnumodel.htm

http://www.ivoprop.com/paddlemodel.htm
 
Capt. Geoffrey Thorpe said:
The prop re-indexes itself 43% every time it goes around due to his gear reduction.
Click to expand...

The re indexing is for the slight (if any) out of round crank flange/ propeller flange. If the prop flange and crank flange have a small amount out (.002 to .005) it will create a greater out of track at the prop tip. Re indexing sometimes brings this in closer.
 
N801BH said:
....

Does it slip just slightly in its hub, making the blades clock differently?
Click to expand...

We had an Ivo on a Glastar, and that's what it did. The blades were shifting just enough to throw the whole thing off balance chordwise. The aluminum bushings in the blades have holes a bit bigger than the bolt shanks, so there's some room for movement, and no matter how carefully we torqued the bolts we still had some shifting. Fretting was visible between the bushing ends and hub plates. We finally put a Warp Drive on it.

This was on a Subaru conversion.


Dan
 
Geico266 said:
....Theoretically , you will save fuel, increase speed, and get better mileage also. Not sure I totally agree with that claim, but that is what some balancing companies claim. :dunno:
Click to expand...

Well, lets look at it this way; the engine doesn't need to work as hard to support the vibration, and still make power. So It would burn less fuel to do the same job with less vibration. :confused:
 
RotorAndWing said:
The re indexing is for the slight (if any) out of round crank flange/ propeller flange. If the prop flange and crank flange have a small amount out (.002 to .005) it will create a greater out of track at the prop tip. Re indexing sometimes brings this in closer.
Click to expand...

How do you "RE-index" a prop when the Maintenance manual tells you what position it must be installed?
 
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