Propeller Balancing Issues

[Mooney_Allegro]

I’ve decided to have my prop balanced by a leading prop shop in Gainesville, GA since I’ve never had it done.  I’m not experiencing any unusual vibrations.  The tech has been doing this for 15 years and has done 100’s of planes.  He’s very experienced.   He spent four hours and 10 run-ups and each time, his computer was telling him conflicting information that didn’t make any sense with moving weights all over the place and sometimes doubling weights from the previous run in completely different positions.   

He concluded that he couldn’t balance my prop and never charged me.   He thinks it could be either his equipment or my engine.

  Has anyone experienced a Prop Balance where the readings were all over the place and it was impossible to balance the prop?

[carusoam]

That sounds like a terrible experience for all involved...

See if @Cody Stallings is around for some insight... Cody is MS’ prop guy...

Best regards,

-a-

[jaylw314]

1 hour ago, Mooney_Allegro said:

I’ve decided to have my prop balanced by a leading prop shop in Gainesville, GA since I’ve never had it done.  I’m not experiencing any unusual vibrations.  The tech has been doing this for 15 years and has done 100’s of planes.  He’s very experienced.   He spent four hours and 10 run-ups and each time, his computer was telling him conflicting information that didn’t make any sense with moving weights all over the place and sometimes doubling weights from the previous run in completely different positions.   

He concluded that he couldn’t balance my prop and never charged me.   He thinks it could be either his equipment or my engine.

  Has anyone experienced a Prop Balance where the readings were all over the place and it was impossible to balance the prop?

The guy who did mine said a crosswind can be a game-stopper, but I don't know if that was an issue

[Cody Stallings]

It’s strange we are talking about this.

i just attempted to balance a Fellow MS drivers Mooney yesterday, an had something happen that had never happened to be before in 14yrs an several 100 Propellers.

Balance started at .83 ips an balanced down to .07 ips in 4 runs an a verify run.

Bring the spectrum down that much I would expect the Driver to be able to tell a real HUGE difference..... WRONG!!! 

Said it is shaking more(or different) now.

Should Be Hearing Back From Chadwick-Helmuth Tomorrow on this situation.

 

Now to the OP question:

When you have issues that having you moving weights all over, basically working around the entire arch of the Propeller, it’s been my experience the propeller needs to be Re-Static Balanced, Or the Hub has been over services with grease(Hartzell), Or the Red-Oil Level inside the hub is Low(McCauley). Any of the 3 will create a Balance issue. Without a good a Static Balance, it won’t ever Dynamic Balance.

When a Balance machine starts giving a Tech conflicted information, it’s time to stop. You have to understand where the machine gets it’s info from. Comes from the accelerometer on top of the engine, an if there is no repeatability then something is changing with every start.

Edited May 9, 2019 by Cody Stallings
Spelling

[BDPetersen]

Spark plugs? Injector?

[Davidv]

I posed this in the other prop balance thread but just properly turning the baffling in the right direction made a big difference in the vibration I was feeling.  I thought my prop was out of balance but then we checked it and it was reading .03-05 depending on rpm.  When we initially uncowled the engine the left baffling was turned down rather than up.  Even though we didn't touch the prop I noticed a huge difference on flight home.

[JimB]

Do you know what IPS reading he was getting? I know you said he was very experienced but when you are balancing props, once you get it balanced and the reading very low it will move around a bit. It could be that your prop is already very well balanced, or as suggested, he was trying to balance it with a gusty wind or the equipment is faulty. 

[johncuyle]

This behavior is consistent with mine before they discovered the prop wasn't bolted securely to the engine and was chucking around a bit.  Essentially made it impossible to balance.  I had come in for a static balance and they discovered the issue while removing the propeller.  As noted by others, could be a bunch of causes, wind, ignition, fuel, busted motor mount (though I'd think they could find that fast.)

[Mooney_Allegro]

On 5/8/2019 at 8:58 PM, jaylw314 said:

The guy who did mine said a crosswind can be a game-stopper, but I don't know if that was an issue

It was VERY gusty that day and a quartering crosswind.  You would think that this experienced tech would know not to attempt a balance in such conditions.  I spoke to a MSC that does prop balancing a few days ago, and he told me they never do prop balances in high wind, that they strive for calm conditions.  I bet this is why my prop couldn't be balanced.

[Mooney_Allegro]

On 5/9/2019 at 5:02 AM, JimB said:

Do you know what IPS reading he was getting? I know you said he was very experienced but when you are balancing props, once you get it balanced and the reading very low it will move around a bit. It could be that your prop is already very well balanced, or as suggested, he was trying to balance it with a gusty wind or the equipment is faulty. 

Yes, I took a photo copy of the tech's notes.  Here they are.   He said the numbers were all over the place and he couldn't make any sense out of it.  His boss finally told him to stop after 4 hours of grinding away at the starter on and off.   All were very hot starts plus all the turbo cool downs.   

IPS

.28 @ 208

.31 @ 180  24.3 @ 249'/260

.35@ 324 18.7 @ 304

.22 @ 210  37.9 @ 303

.24 @ 7  22.3  320

.48 @ 17

.48 @201

[jaylw314]

56 minutes ago, Mooney_Allegro said:

It was VERY gusty that day and a quartering crosswind.  You would think that this experienced tech would know not to attempt a balance in such conditions.  I spoke to a MSC that does prop balancing a few days ago, and he told me they never do prop balances in high wind, that they strive for calm conditions.  I bet this is why my prop couldn't be balanced.

Ooops