[Walt]

Thought this was interesting as Stephen "Christo" was in the neighborhood to get some work done at "Glo Custom" paint and asked me if I had time to check his prop balance. Steve seemed convinced it was really smooth and probably wouldn't need anything but wanted to check it just the same... just to be positive. I told him that if it didn't need any balance adjustment I would run the check and vib survey for half price so that pushed him over the edge and he said ok lets do it. He seemed a little reluctant to want to spend the money (don't know why, his next stop was Vegas so he was going to lose it anyway ) but his curiosity to see where it was was just to compelliing.

Well as you can see below it was over twice the limit (.403 IPS) when we checked it

A couple of runs later we had him running nice and smooth at .021 IPS

Below is the Vibration survey, engine was built well (Lyc Thunderbolt) and the counter balanced crank is obvious by the low 2.5 and 3.5 harmonics.

I might add that Steve's machine is a sweet ride with great workmanship, (and I was drooling over the IO-390).

 

[jartlip]

Does anybody do prop balancing in South Florida?

 

[AX-O]

Walt,
I hear the same thing every time I do a balance job too. ?Feel pretty smooth to me?, ?I am not going to be able to tell a difference?, ?is it really worth it?

Most people call me on the radio as soon as they lift off and start their journey home. Telling me how the bottom of the panel is not shaking or they can read their GPS without holding it, the plane sounds different etc, etc. It is definitely worth it.

By the way, nice equipment.

 

[Brantel]

Walt,

I had mine checked back this time last year and I was told it was so low that there was nothing that could be done.

My engine is a FP and at 2500+ rpm it is smooth as butter but around 2400 I have a pretty good vibration.

Of course during balancing, I could only get about 2200 static.

Is this typical of what I can expect or is there a better balance out there for me to find?

 

[Walt]

Walt,

I had mine checked back this time last year and I was told it was so low that there was nothing that could be done.

My engine is a FP and at 2500+ rpm it is smooth as butter but around 2400 I have a pretty good vibration.

Of course during balancing, I could only get about 2200 static.

Is this typical of what I can expect or is there a better balance out there for me to find?

Well this is a tough question to answer. Do you know what the vibs were when they checked it? The upper "limit" is generally considered to be .2 IPS before balance and .1 IPS after balance (McCauley recommends .07 as the upper limit after balance). Some folks who balance (like some prop shops I know) will tell you it's as good as it can be if it's below .2 IPS which we all know isn't true

I have generally seen very little difference above 2200 rpm and in fact it "usually" improves up higher. So I balance most FP props at 21-2200 and constant speeds around 23-2400 (only because they can get there and most folks cruise in that range).

The nice thing about the MicroVib is the spectrum analysis fuction which looks at the 150-15000 cpm vibrations. For example I can easily see a cylinder thats not doing its job by looking at the crankshaft half order (.5) vibration. Pistons and rods that are mismatched will typically exhibit high 2.5 and 3.5 vibrations.

Have I answered your question.... probably not, but my point is without good numbers and good equipment to measure the vibration it it's impossible to say what the problem is.

 

[Brantel]

Walt,

The final was 0.08 ips after the balance and only slightly worse before. The tool used did not seem to be as sophisticated as yours.

 

[Walt]

Vibration Troubleshooting...

Here is some troubleshooting info from the McCauley manual on tracking down vibrations.. some things for you to look at (obviously some of these things do not apply to an RV but the theory is still the same):

VIBRATION TROUBLESHOOTING
Troubleshooting vibration problems can be very challenging and time consuming. Most digital dynamic equipment can also be used to track down vibration problems. The digital dynamic balancing equipment can display the amplitude and frequency of the vibration, which will help determine the vibration source. While vibration problems are occasionally caused by the propeller, they are usually caused by other things. Below is a list of other possible sources of vibration:
1. Engine
2. Worn, old, cracked or loose engine mounts
3. Cracked or loose engine mount structure
4. Cracked or broken spinner bulkheads
5. Loose or improperly mounted engine cowlings
6. Loose cowl flaps
7. Loose landing gear doors
8. Out of balance elevators
9. Loose control yokes
10. Exhaust stack touching engine cowling
11. Component in engine compartment that is touching engine cowling

I would also add check the prop and spinner are tracking true and is properly torqued.

 

[Walt]

Walt,

The final was 0.08 ips after the balance and only slightly worse before. The tool used did not seem to be as sophisticated as yours.

That is certainly not an excessive number and at face value I would not suspect that would be the cause of the vibration you're feeling. I'd love to work on it with you next time you get down to TX

 

[Bavafa]

Walt,
Being on the subject of prop balancing and my recent experience helping a friend balancing his prop on a Subi with not so great luck...

What is the typical way of balancing a prop, just front or front and rear? To be more specific, I had mine done little over 2 years ago and the guy that did it had a two probe type balancer, front and back. He ran a few test to get a good average between the two as oppose to just getting the front side smooth.

I am still trying to understand his numbers as the hand written report says, 0 IPS front and .06IPS in the back but the computer printed report is slightly different.

Also how often do we really need to balance them?

 

[Geico266]

Thanks Walt for reminding everyone the importance of dynamic balancing. The results are stunning.

 

[Walt]

Walt,
Being on the subject of prop balancing and my recent experience helping a friend balancing his prop on a Subi with not so great luck...

What is the typical way of balancing a prop, just front or front and rear? To be more specific, I had mine done little over 2 years ago and the guy that did it had a two probe type balancer, front and back. He ran a few test to get a good average between the two as oppose to just getting the front side smooth.

I am still trying to understand his numbers as the hand written report says, 0 IPS front and .06IPS in the back but the computer printed report is slightly different.

Also how often do we really need to balance them?

The mass imbalance is located at the front of the engine (the prop, spinner etc) and so that is the standard place to measure vibration. Excessive vibration at an aft engine location would likely be a from a bent crankshaft or other internal engine problem. Being that we can't do anything to balance internal engine problems monitoring this location is not of much value.

I've never seen a "0" IPS, I don't care how good you are or how much time you take you'll never get there. What you are doing is reaching the limit of your equipment to measure it. My balancer goes out to 3 places while many the older balancers only went to 2 places and were not as sensitive as todays balancers.

If nothing is changed that would effect mass balance then I would suggest about every 500 hrs would be a good time to recheck things.

 

[Webb]

Not balancing

Not balancing a prop is the equivalent of buying new tires for your car and not getting them balanced.

Enough said........

 

[Walt]

Walt,

My engine is a FP and at 2500+ rpm it is smooth as butter but around 2400 I have a pretty good vibration.

Is this typical of what I can expect or is there a better balance out there for me to find?

Aerodynamic Imbalance:Something to consider, I have seen this before on FP props (never on a CS)when balancing. The symtoms while balancing is any change in RPM results in a differnent vibration solution so I end up chasing my tail trying to get it balanced. You can see from the above balance I did on Steves airplane in 3 runs it went from .4 to .02, very stable runs each time and a linear response to adjustments. On a prop with an aerodynamic imbalance I end up doing 5 or 6 runs and each time the weight calculation calls for something different, and you never get there to that magic number and end up settling for the best you can get. I currenty don't have the equipment to do dynamic blade tracking.

CORRECTING AN AERODYNAMIC IMBALANCE;
You may have performed a dynamic propeller balance and achieved a vibration level of 0.05 IPS, which is well below the 0.07 IPS target, yet you or the owner of the aircraft still complains of a vibration in the airframe or instrument panel. In this instance, the problem could be that there is an aerodynamic imbalance in the propeller. In some cases you will find that you chase your tail on a propeller with this problem. You may be able to lower vibration levels to a certain IPS level but then it seems no further type of adjustment will give satisfactory results. The way to detect this type of imbalance is to install reflective tape on each of the propeller blades in a manner that will distinguish one blade from the other. Then, operate the aircraft at balancing RPM while you stand to the side of the propeller during operation. Use a light source to observe the propeller tip path. If a difference in tracking of the blades is seen, then an aerodynamic imbalance is present. In a variable-pitch propeller the problem may be corrected by verifying the blade angles. In a fixed-pitch propeller, the only alternative may be to replace the propeller.

 

[Bavafa]

I've never seen a "0" IPS, I don't care how good you are or how much time you take you'll never get there. What you are doing is reaching the limit of your equipment to measure it. My balancer goes out to 3 places while many the older balancers only went to 2 places and were not as sensitive as todays balancers.

If nothing is changed that would effect mass balance then I would suggest about every 500 hrs would be a good time to recheck things.

Thanks for the info. I also doubt seriously the 0 IPS which is hand written in the report but the computer generated report says 0.04 IPS for the front but I am not positive if it is before the added wight or after.

I have now 300+ hours on the engine and still runs smooth but if you were nearby, I would go for another balancing.

Thanks again

 

[[email protected]]

good vibrations...

Thanks Walt, hard to quantify in flight but I think that it feels smoother ... kind of like after a fresh oil change or 'tune up' in the car

Using my fingernail as a vibration sensor there is about zero vibration most places; no more than very light vibration anywhere... definitely some reduction.

Great to get together and glad that I did.

See you at Oshkosh!

Stephen

vibration and tach sensors on the engine

ready for testing, with wires taped and the beast chocked up and tied off to a truck for safety

walt the prop wizard at the ready

 

[N42AH]

Sensenich - Gainsville

In 09 I had my FP Sensenich balanced by Sensenich in Gainsville, GA. The final outcome was a .04 and cost $210.00.

In the eyes of those who balance props, is this a good level or should I have it redone to lower the ips"s?

 

[Geico266]

In 09 I had my FP Sensenich balanced by Sensenich in Gainsville, GA. The final outcome was a .04 and cost $210.00.

In the eyes of those who balance props, is this a good level or should I have it redone to lower the ips"s?

Good enough in my book. You could play with it some more, but technically you are good to go.

 

[Peterk]

In 09 I had my FP Sensenich balanced by Sensenich in Gainsville, GA. The final outcome was a .04 and cost $210.00.

In the eyes of those who balance props, is this a good level or should I have it redone to lower the ips"s?

Yeah...Walt got mine from .63 to .03 and the difference was very noticable...not to mention how happy my airframe and engine and brain must be. I think the standard that Hartzell is happy with is .30 so I'd say you're in great shape!

Pete

 

[RV7Guy]

Got a Zero

I've never seen a "0" IPS, I don't care how good you are or how much time you take you'll never get there. What you are doing is reaching the limit of your equipment to measure it. My balancer goes out to 3 places while many the older balancers only went to 2 places and were not as sensitive as todays balancers.

Hey Walt, Great information. I'm running an ECI IO 360 with Whirlwind 200RV prop. Andy Elliot did my balance and got it to "0." Before he started it was .05 and was pretty good. He messed with it and got the 0. We checked it and it was accurate. He had previously never got one before.

The WW was already smooth but the "0" was real smooth!!

The other reason to balance is to comply with manual. WW wants the prop balanced within 10 hours. Very smart money in my book.

 

[RV10inOz]

Feels like a Turbine now........I still do not believe we snagged it this good.

But it is possible. And yes this was the real deal.

 

[Walt]

Balancing...

In 09 I had my FP Sensenich balanced by Sensenich in Gainsville, GA. The final outcome was a .04 and cost $210.00.

In the eyes of those who balance props, is this a good level or should I have it redone to lower the ips"s?

Your final result of 0.04 IPS is excellent, my goal is to get all of them to this same number or less but I am very happy at 0.04 IPS.

Keep in mind that 0.2 IPS is still considered the upper limit. Most prop manufacturers consider 0.1 IPS to be an acceptable after balance number and only one prop manufacturer (McCauley) recommends 0.07 IPS as the upper limit after balancing.

In reality going from 0.07 to 0.03 or trying to go from .04 to .02 IPS are very small changes and would not be noticable by the average pilot. I would estimate at least 90% of the props I balance are over the 0.2 IPS limit and will benefit significantly from the balance.

Just for reference: adding just one 1/4" thin washer to the flywheel of a lycoming will change the balance by approx 0.02 IPS. So you can see that sometimes hardware selection alone can make it impractical to get to these ultra low numbers.

I just did an RV4 this past week that was at 0.65 IPS to start and .031 IPS when finished, it was immediately noticable by the pilot how much smoother it was both on the ground and in the air. Below was a note he sent me after he flew it: (I loved this guy, he was 81 yrs old still flying an RV4 and had lots of stories!)

"Flew it this morning and it was great. Just in the traffic pattern for three touch and goes. Run up at 2000 for mag check was rock solid. Thanks for the super work! I wish I had had it done five years ago. Hit 400 touch and goes and 101 hours this morning! A/C since new and Engine since Major Overhaul!
Hope your flight home was a-ok! Very best regards, Bruce Bell RV-4 N23BB"

 

[flynwest]

Prop Balance in Nor Cal

Anybody know a place in Sacramento Area to get a prop balance? Thanks in advance. Nordo