Prop balance after overhaul

timwinters

timwinters

Ejection Handle Pulled
Joined
Feb 23, 2008
Messages
13,733
Location
Conway, MO
Display Name
Display name:
LTD
Is there a minimum amount of time one should wait before doing so?

Ted?
 
I'd wait till the engine is broken in. No real biggie to wait.... other than the few half dozen starts and stops measuring imbalance won't be good for break in.
 
Last edited:
Checkout_my_Six said:
I'd wait till it's broken in. No real biggie other than the few half dozen starts and stops measuring imbalance won't be good for break in.
Click to expand...

Until WHAT is broken in ?

What in the engine will wear enough to effect the rotating group's balance
 
The problem with doing a dynamic balance on a new engine is it isn't very good with the starts and shutdowns that need to be done repeatedly while finding a solution.

Break in the engine, then do the balance.
 
How about if you have the option to leave the sensors attached during the break in flights? Hook them up, fly your couple of hours at high power, and then adjust the weights between long flights?
 
I'd fly it to the first oil change and get it done at that time.
 
Checkout_my_Six said:
I'd wait till the engine is broken in. No real biggie to wait.... other than the few half dozen starts and stops measuring imbalance won't be good for break in.
Click to expand...

That's kinda what I thought but wanted to make sure there weren't other considerations. Thanks!

James331 said:
I'd fly it to the first oil change and get it done at that time.
Click to expand...

After one hour might be a tad soon. :)
 
RotorAndWing said:
The problem with doing a dynamic balance on a new engine is it isn't very good with the starts and shutdowns that need to be done repeatedly while finding a solution.

Break in the engine, then do the balance.
Click to expand...
How many starts and stops do you need to find a solution.
 
I would go with 3-4 hours. The most important part is the first flight you take with the airplane. Being winter, I would pre-heat the engine as much as possible. Start it up, have a plan to do the necessary checks so you don't waste time, make sure any minimum temp requirements are met, and take off asap.
 
Last edited:
Wait until the cylinders are fully broken in. That's the only part to really be concerned about. As was mentioned already, but starts/stops and runs on the ground with power aren't great on a fresh engine.

When I had the 310's engines overhauled, we ended up waiting about 75 hours just because that's when it was convenient to do.
 
GlennAB1 said:
The manual doesn't specify when the dynamic balance is to be accomplished?
Click to expand...

Most manufacturers only concern themselves with the static balance. And the majority of GA planes never do a dynamic balance.

Get into the turbo props and dynamic balance is used more.
 
GlennAB1 said:
I would think an overhauled prop would come balanced. ;)
Click to expand...

"Prop balancing" is a misnomer. You're actually balancing the entire drive train, or at least doing the best you can to do so. If you were only balancing the prop then there wouldn't be a vibration sensor mounted on the ass end of the engine during the process.

Sure, the weights are placed on the spinner but all vibration is measured, not just the prop.

Besides, my prop wasn't overhauled, only IRAN'ed. It's my engine that was overhauled.
 
Been doing vibration surveys and fan balancing on turbofans for almost 30 years. The prop, or fan in my case, is the most likely cause of vibration due to its large rotational mass. Thanks for clearing up which was overhauled.
 
Last edited:
timwinters said:
"Prop balancing" is a misnomer. You're actually balancing the entire drive train, or at least doing the best you can to do so. If you were only balancing the prop then there wouldn't be a vibration sensor mounted on the ass end of the engine during the process.

Sure, the weights are placed on the spinner but all vibration is measured, not just the prop.

Besides, my prop wasn't overhauled, only IRAN'ed. It's my engine that was overhauled.
Click to expand...

I used an Aces 2020 ProBalancer when I did dynamic balancing. We never put an transducer on the back of the engine, it was mounted on the nose of the engine at either a 180 degree mount or a 270/90 degree mount. Then the electric eye was mounted with a piece of reflective tape on the back of a blade.

The 2020 was capable of doing spectrum analysis of vibration as well, but rarely used it. The majority of it's work was helicopter track and balance.
 
Last edited:
Vibration monitoring is very interesting, transducers are sometimes wire coil, or piezoelectric. My shop took care of the T-38 wing vibration monitoring system, back in the 70's.
 
RotorAndWing said:
I used an Aces 2020 ProBalancer when I did dynamic balancing. We never put an transducer on the back of the engine, it was mounted on the nose of the engine at either a 180 degree mount or a 270/90 degree mount.
Click to expand...

My only experience is with Kent Felkins in the TUL area. He has balanced two engines for me. I believe he uses microvibe equipment. Whatever he used had sensors both front and rear.
 
Last edited:
Buy yourself a Dynavibe and balance your prop whenever you want.

http://www.rpxtech.com/DynavibeClassicPropBalancer.html

At $1500 it's an essential hangar tool. Keeping your engine smooth pays off in the long run with reduced wear on everything, control hinges, instruments, passenger and pilot comfort, etc. Why pay somebody $250 or whatever they're charging when you can do it yourself, whenever you want? Go halves with a hangar neighbor - now you're talking $750. Go thirds with two hangar neighbors. Now you're talking $500, not far off from what it can cost to have it done once . . . by someone who may or may not do a good job. Did they even consider whether the wind was calm or not when they did it?

Things change over time. Just because you balanced your prop two years ago doesn't mean everything is still balanced. It's surely changed over time. And did whoever balanced it even do that good of a job when you had it done? Okay, it was better after the balance than it was before . . . or was it? Did you see the numbers? Or did it just feel smoother because you shelled out some money?

Get your own tools.

I consider mine to be indispensable. I bought it when it first came out, 2007 I think it was. I've done dozens of planes since then, some of whom thought their engines/props were "just fine". "Airplanes are supposed to vibrate!", said the old timer as he wandered off smoking a cigarette.

This balancer has held up fine with lots of use. Works just as well as it did when I first got it and has never needed any maintenance. Everybody appreciates a prop balance so you can do some nice favors for your friends. Really . . . get one.

***********

Edit:

Previous comments weren't directed necessarily at OP . . . was just some general comments about having your own prop balancer.

I think a couple of the other companies like Microvibe and probably ACES have their own low-cost balancers these days. They had to do something to compete with the Dynavibe so now there's one or two other balancers in the same price range as the Dynavibe. They're probably just as good, dunno. I do know the guys who run Dynavibe are really great with communication and support if needed. I had lots of dumb questions when I bought mine and they put up with me without any problem.
 
Last edited:
How do you get access to the rear of the engine to do dynamic balancing? or is it only single plane static balancing with weights on the spinner?
 
Tom-D said:
Tell me what difference does it make?

What will change/wear enough to alter the balance of the rotating group?
Click to expand...
the rings need to seat first....else they'll glaze the cylinder walls. All that starting and stopping and idling isn't good till the rings wear in.....
 
Ted DuPuis said:
Wait until the cylinders are fully broken in. That's the only part to really be concerned about. As was mentioned already, but starts/stops and runs on the ground with power aren't great on a fresh engine.

When I had the 310's engines overhauled, we ended up waiting about 75 hours just because that's when it was convenient to do.
Click to expand...

How is wear on a stationary object going to effect the balance of the rotating group.
 
Checkout_my_Six said:
the rings need to seat first....else they'll glaze the cylinder walls. All that starting and stopping and idling isn't good till the rings wear in.....
Click to expand...

What wears? the cylinder wall or the rings. Do you believe hard chrome rings will wear enough to off set the other rings on all the other pistons?
 
Checkout_my_Six said:
Tom......what is your point?:rolleyes:...it doesn't have to have anything to do with balance.
Click to expand...
If it is going to effect the balance of the rotating group, it certainly must.

My point is, there is no valid reason to wait.

If there is, show me.
 
The only real reason to wait, is the fact of knowing the engine will continue to operate correctly, and not require a second tear down, as some do.

I've balanced a good many props right on the test cell. as many aircraft restores do.
 
Tom...there is a reason to wait....and do certain maintenance actions in proper order.

for the same reasons....I'd not be monkeying with the carb settings either.
 
The reason to wait has nothing to do with balance, it has to do with ensuring the rings seat and the cylinders are properly broken in.
 
GlennAB1 said:
Been doing vibration surveys and fan balancing on turbofans for almost 30 years. The prop, or fan in my case, is the most likely cause of vibration due to its large rotational mass. Thanks for clearing up which was overhauled.
Click to expand...

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...
 
Ted DuPuis said:
The reason to wait has nothing to do with balance, it has to do with ensuring the rings seat and the cylinders are properly broken in.
Click to expand...

This is true,

Why will waiting until the rings seat. or the proper break in of the cylinder require waiting for the prop to be balanced.
 
You must log in or register to reply here.
Back
Top