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  #11  
Old 03-01-2019, 04:18 PM
pilotyoung pilotyoung is offline
 
Join Date: Jan 2018
Location: Birmingham, AL
Posts: 102
Default Vibration Problem

My engine was produced in 2012. When I was talking to Morris Smith, Ronnie's son, about the possibility of the gear box gears and dogs being bad, he told he he would know when he took it apart and saw the parts if it was the problem. In my case, it was obvious that there was abnormal wear.

If it had looked normal, I think we would have put it back together and not replaced the gears. But that is speculation.

The spring washers also had abnormal wear on them. They were wearing unevenly.

I ask Ronnie if he could tell if the cause was abuse or what. He said no way to know. He did allude to some defective parts along the way. He also said they have taken the dogs out of the gear box on the 912is engine.
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John D. Young, RV-12 Owner
Serial Number 120022, N6812Y
Bought it as a flying airplane in Feb. 2018
Just passed 140 hours flight time in RV-12, and 10,000 hours mostly in corporate jets. I am a CFI; CFII; MEI; and a advancd Ground Instructor, CFIG; and hoping to be able to help new RV-12 owners by doing some transition training for new builders and owners in RV-12's.
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  #12  
Old 03-10-2019, 11:22 PM
pilotyoung pilotyoung is offline
 
Join Date: Jan 2018
Location: Birmingham, AL
Posts: 102
Default vibration

Scott, when you say "Being casual about maintaining a proper carb. sync is a sure way to cause gear box wear.", can you explain what you mean. Do you mean checking and ressetting it every 100 hours? More often than 100 hours? Other inspections besides just syncing the carbs?

I would like some guideance on going forward so I will know I have maintained it properly.

Thanks.

John
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John D. Young, RV-12 Owner
Serial Number 120022, N6812Y
Bought it as a flying airplane in Feb. 2018
Just passed 140 hours flight time in RV-12, and 10,000 hours mostly in corporate jets. I am a CFI; CFII; MEI; and a advancd Ground Instructor, CFIG; and hoping to be able to help new RV-12 owners by doing some transition training for new builders and owners in RV-12's.
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  #13  
Old 03-11-2019, 09:29 AM
rvbuilder2002 rvbuilder2002 is offline
 
Join Date: Jul 2005
Location: Hubbard Oregon
Posts: 8,115
Default

Quote:
Originally Posted by pilotyoung View Post
Scott, when you say "Being casual about maintaining a proper carb. sync is a sure way to cause gear box wear.", can you explain what you mean. Do you mean checking and ressetting it every 100 hours? More often than 100 hours? Other inspections besides just syncing the carbs?

I would like some guideance on going forward so I will know I have maintained it properly.

Thanks.

John
Yes
Checking and adjusting it every 100 hrs.

My "being casual" comment was based on the large # of comments I see that mention initially running the engine without doing a synch (don't have gauges yet), "it felt pretty smooth but I sure could tell the difference after we got it synched properly, etc.

Assuring that the carb's are and remain well synched at idle and low throttle settings is crucial to gear box longevity. If at any time between the 100 hr inspections the engine seems to not be as smooth as it has in the past, it should be checked and the problem resolved ASAP.
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Scott McDaniels
Hubbard, Oregon
RV-6A (aka "Junkyard Special ")
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  #14  
Old 03-11-2019, 01:41 PM
NinerBikes NinerBikes is offline
 
Join Date: Dec 2018
Location: Granada Hills
Posts: 129
Default

Quote:
Originally Posted by rvbuilder2002 View Post
Yes
Checking and adjusting it every 100 hrs.

My "being casual" comment was based on the large # of comments I see that mention initially running the engine without doing a synch (don't have gauges yet), "it felt pretty smooth but I sure could tell the difference after we got it synched properly, etc.

Assuring that the carb's are and remain well synched at idle and low throttle settings is crucial to gear box longevity. If at any time between the 100 hr inspections the engine seems to not be as smooth as it has in the past, it should be checked and the problem resolved ASAP.
So, with the 912 iS package motor on the 2018 and later RV-12iS builds, if the idle speed is kept above 1800 rpm, the gearbox causing vibrations should be a non issue anymore, due to lack of synching the carburetors? Any other considerations to be aware of to prevent gearbox wear?
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  #15  
Old 03-11-2019, 02:29 PM
rvbuilder2002 rvbuilder2002 is offline
 
Join Date: Jul 2005
Location: Hubbard Oregon
Posts: 8,115
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Quote:
Originally Posted by NinerBikes View Post
So, with the 912 iS package motor on the 2018 and later RV-12iS builds, if the idle speed is kept above 1800 rpm, the gearbox causing vibrations should be a non issue anymore, due to lack of synching the carburetors? Any other considerations to be aware of to prevent gearbox wear?
Blade track (blades at the same pitch angle)
Propeller balance.
Excessively worn spark plugs
Etc.

Anything that could have an influence on smooth engine operation
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Any opinions expressed in this message are my own and not necessarily those of my employer.

Scott McDaniels
Hubbard, Oregon
RV-6A (aka "Junkyard Special ")
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  #16  
Old 03-15-2019, 07:49 PM
Jolly Jolly is offline
 
Join Date: Nov 2016
Location: San Francisco, CA
Posts: 51
Default

Common vibration causes and fixes.

https://www.rotax-owner.com/en/rotax...vibration-help
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  #17  
Old 03-16-2019, 10:47 PM
pilotyoung pilotyoung is offline
 
Join Date: Jan 2018
Location: Birmingham, AL
Posts: 102
Default Vibration Problems

Jolly,

Thanks for your list of possible causes. I worked through most of them in an effort to properly diagnose my vibrations. I finally concluded it was the gear box, and disassembly confirmed my conclusion. The dogs were worn as well as he spring washers. They were all replaced, the greabox is reinstalled and I will fly it as soon as the annual condition inspection is over, hopefully Wednesday.

The one item on his list that I would never have thought of was the wheels being out of balance. So as I get mine airplane back together, I will be eager to see the results. If it is not smooth, I will have the prop balanced, then the tires balanced. I can do the remainder of the items on the list.

But I do appreciate your providing a comprehensive list for us to use to trouble shoot.
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John D. Young, RV-12 Owner
Serial Number 120022, N6812Y
Bought it as a flying airplane in Feb. 2018
Just passed 140 hours flight time in RV-12, and 10,000 hours mostly in corporate jets. I am a CFI; CFII; MEI; and a advancd Ground Instructor, CFIG; and hoping to be able to help new RV-12 owners by doing some transition training for new builders and owners in RV-12's.
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  #18  
Old 03-17-2019, 05:14 AM
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TomVal TomVal is offline
 
Join Date: Dec 2007
Location: SC & CA
Posts: 824
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Quote:
Originally Posted by pilotyoung View Post
Jolly,

Thanks for your list of possible causes. I worked through most of them in an effort to properly diagnose my vibrations. I finally concluded it was the gear box, and disassembly confirmed my conclusion. The dogs were worn as well as he spring washers. They were all replaced, the greabox is reinstalled and I will fly it as soon as the annual condition inspection is over, hopefully Wednesday.

The one item on his list that I would never have thought of was the wheels being out of balance. So as I get mine airplane back together, I will be eager to see the results. If it is not smooth, I will have the prop balanced, then the tires balanced. I can do the remainder of the items on the list.

But I do appreciate your providing a comprehensive list for us to use to trouble shoot.
John,

Hopefully the gearbox was the culprit. Another item for the comprehensive list is to consider re-clocking the prop one prop flange bolt hole forward or back from present position.
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Tom Valenzia
RV8 (Sold)
RV12 Jabiru 2200 Powered
Dues contributor since 2007

Learn from the mistakes of others. You won't live long enough to make all of them yourself...Anonymous
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  #19  
Old 03-17-2019, 06:26 AM
Piper J3's Avatar
Piper J3 Piper J3 is offline
 
Join Date: Nov 2014
Location: Hinckley, Ohio
Posts: 1,321
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Quote:
Originally Posted by TomVal View Post
John,

Hopefully the gearbox was the culprit. Another item for the comprehensive list is to consider re-clocking the prop one prop flange bolt hole forward or back from present position.
I don't know if re-clocking the prop will have any effect. The gearbox ratio is 2.43:1 which means it is a "hunting tooth frequency" to distribute wear. The odd gearbox ratio constantly changes prop/crankshaft relationship.
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Jim Stricker
Hinckley, Ohio (1OA2)
EAA #499867
PPL/ASEL 1970 - Sport Pilot since 2007
80 hrs Flying Aeronca Chief 11AC N86203
1130 hrs Flying 46 Piper J-3 Cub N6841H
RV-12 E-LSA #120058 AWC July 2012 N633CM
RV-12 Bought Flying Oct 2015 with 48TT - Hobbs now 421

LSRM-A Certificate 2016
Special Thanks... EJ Trucks - Crew Chief A-4 Skyhawks
and MJ Stricker (my flight instructor) - 1st Lt./Captain B-17H WWII
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  #20  
Old 03-25-2019, 06:37 PM
Piper J3's Avatar
Piper J3 Piper J3 is offline
 
Join Date: Nov 2014
Location: Hinckley, Ohio
Posts: 1,321
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Quote:
Originally Posted by pilotyoung View Post
I have been having vibration problems with my RV-12. It ran smoothly at cruise, but when I reduced the power from about 4600 to 3000 there would be a vibration. I tried several possible solutions: 1, did the friction test on the gear box; 2, weighed the floats to see of they were too heavy; 3, sycnhed the carburetors; 4, replaced the soft engine isolators; and 5, replaced all the muffler springs. Since those didn't fix the problem I then decided it was the Gear Box. Ronnie and Morris Smith of South Mississippi Light Aircraft agreed with my thoughts.

Today I took the gear box to them for repair. The dogs were worn and the disks were worn. All were replaced and Ronnie says my vibrations will be gone. I will be out of town next week so I won't get the gear box back on to know for sure for a week or two. But if any one is interested, here are some pictures of the worn gears and dogs.

The aircraft has 450 hours on it. I ask Ronnie is this was from abuse, bad parts, etc. He said there was no way to tell. I have flown it 120 hours and I have not let it idle at slow speeds.

I am posting these pictures in the hope it will help others understand the problem if they experience vibrations like this.







Is there resolution on your vibration problem?
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-
Jim Stricker
Hinckley, Ohio (1OA2)
EAA #499867
PPL/ASEL 1970 - Sport Pilot since 2007
80 hrs Flying Aeronca Chief 11AC N86203
1130 hrs Flying 46 Piper J-3 Cub N6841H
RV-12 E-LSA #120058 AWC July 2012 N633CM
RV-12 Bought Flying Oct 2015 with 48TT - Hobbs now 421

LSRM-A Certificate 2016
Special Thanks... EJ Trucks - Crew Chief A-4 Skyhawks
and MJ Stricker (my flight instructor) - 1st Lt./Captain B-17H WWII
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