Prop balance after overhaul

Ted DuPuis said:
N2 (core) vibes can be an issue on turbofans as well, which I'm sure you know. Not so much from a passenger comfort perspective, but they can impact bearings. Oh can they impact bearings...
Click to expand...

I said "most likely cause." There are other possibilities like core FOD, or a loose component/accessory.
 
GlennAB1 said:
I said "most likely cause." There are other possibilities like core FOD, or a loose component/accessory.
Click to expand...

Yep, lots of issues. And NSV... that's especially fun.
 
GlennAB1 said:
Tom, they are under the impression that starting and stopping the engine several/numerous times for vibe/balance runs will adversely affect break in.
Click to expand...
You may have a point in that respect. but how many time does the engine get stopped and started on the test cell?

I seriously doubt any damage to new error cylinders will occur if stopped and started 5-10 times during the first hour of their life. Remember you should be doing a pre-oil prior to start. (we hope)
 
GlennAB1 said:
I said "most likely cause." There are other possibilities like core FOD, or a loose component/accessory.
Click to expand...

If any thing like that occurs the QA guy should be looking for a new job.

Core FOD,, ??
 
Checkout_my_Six said:
yup....he hasta know this stuff. He's an IA right?:rolleyes:
Click to expand...

And owner operators should know how to maintain engines? or do they state their opinions as facts?
When you order a custom firewall forward it will be delivered with a newly overhauled prop tested and balanced on the test cell.

When you can't state a valid reason for any action, don't blame the folks who question your opinion.
 
Tom-D said:
Until WHAT is broken in ?

What in the engine will wear enough to effect the rotating group's balance
Click to expand...

Hmm. Yeah, if enough metal wears off during the break in to affect the balance there is a serious problem. I was wondering though, what affect does engine "tune" have on balance. If one cylinder isn't putting out as much as it should because of bad compression, bad injector, bad plug etc, does that weak power stroke throw the dynamic balance off very much?
 
luvflyin said:
Hmm. Yeah, if enough metal wears off during the break in to affect the balance there is a serious problem. I was wondering though, what affect does engine "tune" have on balance. If one cylinder isn't putting out as much as it should because of bad compression, bad injector, bad plug etc, does that weak power stroke throw the dynamic balance off very much?
Click to expand...

To a degree it will have an impact on balance as it will show up as vibration. IOW, if you show up with a sick engine, no amount of dynamic balancing will improve vibration.
 
My preferred prop balancer advised me to fly 100 hours on my new engine and then call him. I did so and at the 100 hour balancing my 3-blade Mac was dead nuts perfect. I'm not as big a fan of dynamic balancing as I once was. But I favor regular prop maintenance while most of you rationalize how you don't need it. Go figure.
 
Stewartb said:
My preferred prop balancer advised me to fly 100 hours on my new engine and then call him. I did so and at the 100 hour balancing my 3-blade Mac was dead nuts perfect. I'm not as big a fan of dynamic balancing as I once was. But I favor regular prop maintenance while most of you rationalize how you don't need it. Go figure.
Click to expand...

Regular prop maintenance is a good thing. A static balanced prop that is done correctly also helps.

The dynamic balance is more for the hardware (spinner, backplate, etc) once installed as these will cause the rotating mass to imbalance. Some spinners are way out of balance when delivered.

Another very important point to remember once you have a dynamic balance is to index the prop. The spinner, backplate and other hardware must be marked and if removed, replaced back at their correct position. Changing the spinner screws from the original to say one that's slightly longer will also affect balance.
 
Tom-D said:
If any thing like that occurs the QA guy should be looking for a new job.

Core FOD,, ??
Click to expand...

Tom, we got off subject with turbines for a second.... or do you just need **** explained every time? (Engine CORE, Foreign Object Damage) Why do A&P's blame QA for their mistakes? We don't get a premium for babysitting or holding your hand. By the way, welcome back!
 
Last edited:
Thinking back, a good guy who knows his balancer should be able to get you done in 3 starts.
 
GlennAB1 said:
Tom, we got off subject with turbines for a second.... or do you just need **** explained every time? (Engine CORE, Foreign Object Damage) Why do A&P's blame QA for their mistakes? We don't get a premium for babysitting or holding your hand. By the way, welcome back!
Click to expand...


Any QA that allows an engine to leave the assembly floor with a Piece of FOD in it need to find another job. I was QA at the engine build shop here at Whidbey, for 3 different shops. Our FOD program was absolute. anything less is a recipe for failure.
You and every one else still has not given a solid reason for not balancing a prop during the break in run.

If it were bad to stop and restart, any engine during break in there would be red flags all over the internet, plus many engine builders will have warnings not to do it every instruction they produce.
Not a single cylinder manufacturer will say it is not allowed or advised to stop the engine on the test stand or first run on the aircraft.
Yet posters like your self say not to WHY? Do you know some thing the manufacturers don't ?
 
James331 said:
Thinking back, a good guy who knows his balancer should be able to get you done in 3 starts.
Click to expand...

The guy who does mine gets it done just that way.

Installs the tape, and transducer, runs the engine, shuts down, makes the calculations, places the weight. runs the engine to be certain he got it. then he's done.

Chadwick is a great tool, but it is only as good as the operator.
 
Checkout_my_Six said:
welcome back Tom.....:yikes::hairraise::yikes:....:goofy::rofl:
Click to expand...

Ya gotta remember with me you only get an opinion, the rest of you wonderful on line trouble shooter's words must be taken as fact. Even though you never done the job, had the training, or the certificates.

If any one should disagree, or ask questions that the perfect folks can't answer, they'll be shunned, made fun of, or suffer the snide remarks of the favored ones.

But if the thread stays on topic more than 5 posts that would be a change for the great ol Blue page .
 
Tom-D said:
Any QA that allows an engine to leave the assembly floor with a Piece of FOD in it need to find another job. I was QA at the engine build shop here at Whidbey, for 3 different shops. Our FOD program was absolute. anything less is a recipe for failure.
You and every one else still has not given a solid reason for not balancing a prop during the break in run.

If it were bad to stop and restart, any engine during break in there would be red flags all over the internet, plus many engine builders will have warnings not to do it every instruction they produce.
Not a single cylinder manufacturer will say it is not allowed or advised to stop the engine on the test stand or first run on the aircraft.
Yet posters like your self say not to WHY? Do you know some thing the manufacturers don't ?
Click to expand...

Tom, Tom, Tom, FOD refers to the foreign object, as well as damage, caused by foreign objects. The reference pertains to an engine imbalance due to damage that could be caused anytime in operation.
 
We had a epic saga on the balance of my most recent work plane, but the guys never balanced a fixed wing before, never used that balancer before, I'll stick with a good guy who knows his balancer shouldn't take much more than 3 starts.
 
Tom-D said:
Ya gotta remember with me you only get an opinion, the rest of you wonderful on line trouble shooter's words must be taken as fact. Even though you never done the job, had the training, or the certificates.

If any one should disagree, or ask questions that the perfect folks can't answer, they'll be shunned, made fun of, or suffer the snide remarks of the favored ones.

But if the thread stays on topic more than 5 posts that would be a change for the great ol Blue page .
Click to expand...
ya but.....it's the questions that are entertaining....almost as good as Henning. :yes::D
 
James331 said:
We had a epic saga on the balance of my most recent work plane, but the guys never balanced a fixed wing before, never used that balancer before, I'll stick with a good guy who knows his balancer shouldn't take much more than 3 starts.
Click to expand...

James, it's not "knowing the balancer" that makes the difference. There are many factors in dynamic balance. Worn engine mounts will effect the balance as will engine mounts that were not installed correctly. Worn spark plugs will effect the balance, weak plug wires, old magnetos, etc, etc.

Start up and do the first run, get an ips of .60, plot the solution, add the test weight and run again. Now the clock angle changes and the vibration stays up at .50 to .60ips. Plot another solution and run again only to find the clock angle moves again.

Now you have to start troubleshooting, which will result in another run, another solution and another run.

I've had to remove props and move them left or right by a bolt hole to get the ips down to acceptable levels. Three bladed props on 4 cylinder engines can be a bear to balance, again, due to prop location in relation to the crankshaft.

And I've found spinners so bad out of whack that the balance weights to bring it back to a low ips was simply too great.

So sometimes you get lucky and get it done quickly, and sometimes you don't.
 
RotorAndWing said:
James, it's not "knowing the balancer" that makes the difference. There are many factors in dynamic balance. Worn engine mounts will effect the balance as will engine mounts that were not installed correctly. Worn spark plugs will effect the balance, weak plug wires, old magnetos, etc, etc.

Start up and do the first run, get an ips of .60, plot the solution, add the test weight and run again. Now the clock angle changes and the vibration stays up at .50 to .60ips. Plot another solution and run again only to find the clock angle moves again.

Now you have to start troubleshooting, which will result in another run, another solution and another run.

I've had to remove props and move them left or right by a bolt hole to get the ips down to acceptable levels. Three bladed props on 4 cylinder engines can be a bear to balance, again, due to prop location in relation to the crankshaft.

And I've found spinners so bad out of whack that the balance weights to bring it back to a low ips was simply too great.

So sometimes you get lucky and get it done quickly, and sometimes you don't.
Click to expand...

If the plane is a basket case, yeah.

But with the example I'm talking about, a 2000tt PC12, with the dudes calling the balancer company, it's just a issue of familiarity. But yeah if the plane is jacked up, I could see that causing issues.
 
> "Another very important point to remember once you have a dynamic balance is to index the prop. The spinner, backplate and other hardware must be marked and if removed, replaced back at their correct position. Changing the spinner screws from the original to say one that's slightly longer will also affect balance."

All true. If we're talking about an engine that's hand propable it's especially important to get one blade at about the 30° position to make it easier to pull it through.

Some engine/prop combinations actually require the prop be indexed to TDC on #1 cylinder for resonance issues. Other variations of this exist. It'll be in the documentation.

Using a longer spinner screw when fine tuning is an elegant way to make a minor adjustment.

**********

Reading through the thread I'm a little bit curious why anyone would spend 20-30K or more on an overhaul and not spend the relatively piddley amount of money to buy their own prop balancer? If you ever pick up a nick that needs dressing how nice it is to do your own re-balance. The slightest change, including engine wear and tear over time, will compromise the balance. Sure, it'll still be running relatively smoothly but if you have your own tools you can keep it perfect and not have to worry about scheduling it with somebody else nor have to worry about how good a job they do, or not do. Nobody will do as nice a job as you will when using your own equipment on your own plane. And of course at some point the money saved in doing it yourself will have paid for the equipment. This goes double for twins.

************

Somebody mentioned leaving the sensors mounted permanently. If there's room under the cowling to do it, no reason why one couldn't do that. I have a friend who leaves his sensors permanently mounted so he can watch the vibration levels when doing aerobatic maneuvers, so that's a completely practical idea. It would concern me that it might cause premature wear with the accelerometer, but they're replaceable. I doubt the optical sensor would wear, just the accelerometer . . . and maybe not even that.

Some turbine installations have balance sensors permanently installed for the purpose of giving early warning in case something is getting out of whack.
 
MikeS said:
Some engine/prop combinations actually require the prop be indexed to TDC on #1 cylinder for resonance issues. Other variations of this exist. It'll be in the documentation.
Click to expand...

Most do, but we have those won't read the MM. Then try to correct it with the prop balance.
 
Tom-D said:
when you are trouble shooting engine problems with a Chadwick, you probably don't know what a Chadwick does.
Click to expand...

I wasn't talking about a shade tree C150
 
FYI, I associate the term "accelerometer" with inertial navigation and autopilot systems, and "transducer" with vibration monitoring and NDT.
 
Last edited:
Tom-D said:
Ya gotta remember with me you only get an opinion, the rest of you wonderful on line trouble shooter's words must be taken as fact. Even though you never done the job, had the training, or the certificates.

If any one should disagree, or ask questions that the perfect folks can't answer, they'll be shunned, made fun of, or suffer the snide remarks of the favored ones.

But if the thread stays on topic more than 5 posts that would be a change for the great ol Blue page .
Click to expand...

I have to admit, this group has a lot of intelligent individuals with varying experiences. Not just pilots, they have worked in all sorts of industries. They have enlightened me, and I appreciate it. Straying off topic can be interesting too.
 
MikeS said:
> Some engine/prop combinations actually require the prop be indexed to TDC on #1 cylinder for resonance issues.
Click to expand...
I'd sure like to find out why this is so on many 4 cyl engines. And what's more, it shows up as fundamental to crankshaft revolution. I could understand it being a second harmonic due to short L/R of the conrods but why does it show as a fundamental?

Might it be caused by crankshaft bending as it restrains the rotation plane of a metal two bladed prop in the face of second harmonic 4 cyl engine yawing? For that matter, does it also happen with a light weight wood prop? or a 3 blade prop on a 4 cyl engine?
 
Last edited:
On a Cub you index the prop so it stops at 10:00-4:00 as viewed from the front. That allows easy hand starting. My C401 3-blade Mac is required to be indexed specifically per the installation manual. In either case I wouldn't know what the consequences are for being out of index because it's so darned simple to install them correctly.
 
MikeS said:
Reading through the thread I'm a little bit curious why anyone would spend 20-30K or more on an overhaul and not spend the relatively piddley amount of money to buy their own prop balancer?
Click to expand...

Mmm...

Likely because I can have a prop balanced 6 times (by someone who knows what they're doing) for the same cost as buying my own balancer.

My prop was balanced three times during the last engine run and 12 year period. That's every 400 to 500 hours.

A 24 year payback? Nah, I'll pass
 
Last edited:
Which brings up another topic/question. How often should a prop be balanced? (Assuming no large nicks have been picked up)
 
timwinters said:
Mmm...

Likely because I can have a prop balanced 6 times (by someone who knows what they're doing) for the same cost as buying my own balancer.

My prop was balanced three times during the last engine run and 12 year period. That's every 400 to 500 hours.

A 24 year payback? Nah, I'll pass
Click to expand...

timwinters said:
Which brings up another topic/question. How often should a prop be balanced? (Assuming no large nicks have been picked up)
Click to expand...

Seems like what you have been doing is working well.
 
Only balance a prop when the engine vibrates excessively. Its possible to balance a prop with paint, BTW. At least to some extent.
 
RotorAndWing said:
You would have to use a lot, and I mean A LOT of paint on a propeller to get it out of balance.
Click to expand...

Many of the little 2 blade props are final static balanced with the final coat of paint. Specially the light weight wooden from Sensenich.
 
You must log in or register to reply here.
Back
Top