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  #51  
Old 12-05-2019, 07:09 AM
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So just out of curiosity I contacted Les Dowd at Hartzell which is my go-to guy for propeller technical stuff. Les reviewed this thread and had the following comments. Copied and pasted with his permission:

"I read the thread and want to point out a few things.* 1.* The propeller that was out of static balance is shown in the photos with the spinner aft bulkhead and forward bulkhead installed.* When we do the static balance at the factory, there is no spinner components installed…* 2.* I tend to agree with your comment about balancing equipment and the person using it…* I’ve run into many techs that have minimal amount of understanding of what they’re doing during the dynamic balance.* I’ve done troubleshooting on vibration problems only to discover a tech installed the dynamic balance weights 180 degrees from where they should be…* 3.* Mass can shift slightly with blade angle and after break-in.* A dynamic balance solution at 2400 on the ground at zero airspeed can shift when inflight at 150 kts (mass shifts with blade angle increase).* This can be especially true with composite blades because the “vertical balance” of the blade can be dramatically different at low blade angle vs. high blade angle.

In general, yes, a dynamic balance should account for discrepancies in static balance.* The static balance is done to get you close to the solution.* The dynamic then corrects for the engine-propeller-spinner assembly as a unit and during operation.* The problem with relying on the dynamic balance only is, the solution may require a very large amount of weight, so much so that you would have to “punt” and be forced to do a static balance to get in the ballpark.* In theory, the dynamic is done after all the big components are statically balance already and you are “fine tuning” the solution.

When troubleshooting vibration, I really think you are guessing what the problem is without a spectrum analysis.* When people complain about cabin vibration, I firmly believe the only way to find the source is to have the sensor mounted in the cabin when getting that spectrum

I also wanted to point out that re-indexing a prop is not officially approved, endorsed or encouraged by Hartzell Propeller Inc. *It is one solution to a 1/2 order vibration problem that I’ve found works if all other attempts don’t work. Those that do it are moving into the Experimental category on their own.*"
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Walt Aronow, DFW, TX (52F)

EXP Aircraft Services LLC
Specializing in RV Condition Inspections, Maintenance, Avionics Upgrades
Dynamic Prop Balancing, Pitot-Static Altmeter/Transponder Certification
FAA Certified Repair Station, AP/IA/FCC GROL, EAA Technical Counselor
Authorized Garmin G3X Dealer/Installer
RV7A built 2004, 1700+ hrs, New Titan IO-370, Bendix Mags
Website: ExpAircraft.com, Email: walt@expaircraft.com, Cell: 972-746-5154

Last edited by Walt : 12-05-2019 at 07:22 AM.
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  #52  
Old 12-05-2019, 09:44 PM
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donaziza donaziza is offline
 
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Here's my non builder, non mechanic solution that happened to me about 10 years ago. My first RV 8 had an Lycoming O-320/hartzell prop. Had a vibration. Prop balancing didn't do any good. My mechanic was scratching his head, and if memory serves, found the word experimental on the back of the flywheel. (might have been a different word, I can't remember anymore.) Anyway, he temporarily put someone else's flywheel on mine, and said go try it out. "That" was the problem. New flywheel installed.

Last edited by donaziza : 12-05-2019 at 09:49 PM.
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  #53  
Old 12-06-2019, 07:41 AM
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majuro15 majuro15 is offline
 
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I understand his comment about not re-indexing the prop meaning pressing out or changing the bushing locations. But my prop and seems like others don't come with instructions on how to index it to begin with. For example, my prop can be bolted on two ways, each 180* from the other. Nothing says put blade 1 at TDC, etc. So I can't see how it could be wrong to turn it on the flange 180* if you don't know which way it's supposed to go anyway!

I reclocked mine last night and have it retorqued. I'll do another dynamic balance Saturday before flying.

This is experimental aviation!
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  #54  
Old 12-06-2019, 08:03 AM
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D Weisgerber D Weisgerber is offline
 
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Quote:
Originally Posted by majuro15 View Post
I understand his comment about not re-indexing the prop meaning pressing out or changing the bushing locations. But my prop and seems like others don't come with instructions on how to index it to begin with. For example, my prop can be bolted on two ways, each 180* from the other. Nothing says put blade 1 at TDC, etc. So I can't see how it could be wrong to turn it on the flange 180* if you don't know which way it's supposed to go anyway!

I reclocked mine last night and have it retorqued. I'll do another dynamic balance Saturday before flying.

This is experimental aviation!
I agree about indexing the prop, a friend of mine is a IA, he said it didn't matter which way I put the prop on, if I had a vibration I shouldn't get rid of I would also recheck mine 180. When you do a dynamic balance is it done at 2700 rpm? I've heard of people doing them at 2500 rpm.
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  #55  
Old 12-06-2019, 01:37 PM
rdrcrmatt rdrcrmatt is offline
 
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Quote:
Originally Posted by majuro15 View Post
I understand his comment about not re-indexing the prop meaning pressing out or changing the bushing locations. But my prop and seems like others don't come with instructions on how to index it to begin with. For example, my prop can be bolted on two ways, each 180* from the other. Nothing says put blade 1 at TDC, etc. So I can't see how it could be wrong to turn it on the flange 180* if you don't know which way it's supposed to go anyway!

I reclocked mine last night and have it retorqued. I'll do another dynamic balance Saturday before flying.

This is experimental aviation!
Quote:
Originally Posted by D Weisgerber View Post
I agree about indexing the prop, a friend of mine is a IA, he said it didn't matter which way I put the prop on, if I had a vibration I shouldn't get rid of I would also recheck mine 180. When you do a dynamic balance is it done at 2700 rpm? I've heard of people doing them at 2500 rpm.


Both of you guys are missing a detail here.

The discussion is around moving the prop one set of bolt holes, not 180. In order to re-clock the prop one set of holes, the bushings need to be pressed out and moved on the crank flange.
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  #56  
Old 12-06-2019, 05:09 PM
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Bill Boyd Bill Boyd is online now
 
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Which I just did - and I'll let you know next year how it works! Decided to get out ahead of the reported vibration issues and move the lugs while building. Wasn't easy using C-clamp but got it accomplished.

I figure if SacSkyRanch has no issues with it, neither do I. A prop is always going to be in line with the crank throws on a pair of cylinders on the 540, it's just a question of which pair, right?
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  #57  
Old 12-07-2019, 08:09 AM
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rvanstory rvanstory is offline
 
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Quote:
Originally Posted by Bill Boyd View Post
Decided to get out ahead of the reported vibration issues and move the lugs while building.
Though the question was asked several times, I didn't see a definitive answer... should a builder reclock the prop while building like Bill did? I'll be installing mine after 1st of the year and would like to know if re-clocking by one hole up front has the potential to induce a problem as well. Should one wait on fixing a problem ONLY if the problem exists, or is being proactive and doing this during the build advisable since so many people have had the same experience?
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  #58  
Old 12-08-2019, 09:24 AM
rdrcrmatt rdrcrmatt is offline
 
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Quote:
Originally Posted by rvanstory View Post
Though the question was asked several times, I didn't see a definitive answer... should a builder reclock the prop while building like Bill did? I'll be installing mine after 1st of the year and would like to know if re-clocking by one hole up front has the potential to induce a problem as well. Should one wait on fixing a problem ONLY if the problem exists, or is being proactive and doing this during the build advisable since so many people have had the same experience?

If I had the option, I would have gotten ahead of it. I'm going to do it next time I pull the prop.


My only question is.. how? On an installed engine. Who rents the tool to press the bushings out and back in? I remember hearing there was a specialized tool. Do I need to replace the bushings? If so, where do I order them from?
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Last edited by rdrcrmatt : 12-08-2019 at 09:28 AM.
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  #59  
Old 12-08-2019, 10:28 AM
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Walt Walt is offline
 
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Quote:
Originally Posted by Bill Boyd View Post
Which I just did - and I'll let you know next year how it works! Decided to get out ahead of the reported vibration issues and move the lugs while building. Wasn't easy using C-clamp but got it accomplished.

I figure if SacSkyRanch has no issues with it, neither do I. A prop is always going to be in line with the crank throws on a pair of cylinders on the 540, it's just a question of which pair, right?
Quote:
Originally Posted by rvanstory View Post
Though the question was asked several times, I didn't see a definitive answer... should a builder reclock the prop while building like Bill did? I'll be installing mine after 1st of the year and would like to know if re-clocking by one hole up front has the potential to induce a problem as well. Should one wait on fixing a problem ONLY if the problem exists, or is being proactive and doing this during the build advisable since so many people have had the same experience?
Quote:
Originally Posted by rdrcrmatt View Post
If I had the option, I would have gotten ahead of it. I'm going to do it next time I pull the prop.

I don't get it, why would you try to 'fix' something that isn't broke?

I'm pretty sure Sacskyranch hasn't done any real vibration or harmonic testing and there opinion is based on theory, so I would not consider them an authority on propellers.

Hartzell which is likely the most knowledgeable source of information when it comes to prop testing in the world, made the following statement, you can choose to ignore it if you wish, but be aware that ignoring proven test results and instead going with suggestions you heard on the internet has risks.

" I also wanted to point out that re-indexing a prop is not officially approved, endorsed or encouraged by Hartzell Propeller Inc. *It is one solution to a 1/2 order vibration problem that I’ve found works if all other attempts don’t work. Those that do it are moving into the Experimental category on their own.*"
__________________
Walt Aronow, DFW, TX (52F)

EXP Aircraft Services LLC
Specializing in RV Condition Inspections, Maintenance, Avionics Upgrades
Dynamic Prop Balancing, Pitot-Static Altmeter/Transponder Certification
FAA Certified Repair Station, AP/IA/FCC GROL, EAA Technical Counselor
Authorized Garmin G3X Dealer/Installer
RV7A built 2004, 1700+ hrs, New Titan IO-370, Bendix Mags
Website: ExpAircraft.com, Email: walt@expaircraft.com, Cell: 972-746-5154

Last edited by Walt : 12-18-2019 at 05:35 PM.
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  #60  
Old 12-18-2019, 11:19 AM
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majuro15 majuro15 is offline
 
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Update on my prop, I clocked it 180* and re-balanced it to .03 IPS at 2450 RPM again. Starting off the balancing, I was at .2 IPS instead of .6. It only took 17 grams vs over 60 for it to balance out. It's at .01 at idle RPMs now. Flying it has made a noticeable difference. While I still feel a bit of a rumble in the seat, the air frame itself is much smoother and more stable. The tips don't bounce anymore! Oddly, the biggest difference has been the noise level. There was a huge drop in resonance noise in the cabin and it's very welcomed!

I'd definitely recommend clocking as allowed if folks are having issues that a dynamic balance doesn't solve.
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