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  #1  
Old 06-06-2020, 08:51 PM
Joe Joe is offline
 
Join Date: Oct 2005
Location: Independence, OR
Posts: 428
Default RV-8A Weld Crack at #4 Exhaust Flange

This is for an '8A, not an '8 or any of the other RVs.

Caught this on an oil change: my Vetterman exhaust developed a crack in the weld at the exhaust flange for the #4 cylinder. Naturally this is the "busiest" of the four cylinders' exhausts. :-(





I would like to remove the pipe to have it welded but can't seem to do it. Obviously, I installed the exhaust when I built the airplane but the exhaust was most likely installed before the other engine items (and maybe even before hanging the engine -- I can't remember).

I've removed the EGT probe, a heat muff, the exhaust hanger tubes, and the entire #3 tube where it connects to the crossover tube but I still cannot remove the #4 pipe. The crossover tube and exhaust tube go between between tubes in the engine mount and don't allow me the rotation I need. Any ideas other than a torch or pulling the engine?

IO360, 624 hours, standard Vetterman crossover exhaust purchased through Van's with my finish kit in 2012. Again, this is an RV-8A.
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Independence, OR

Last edited by Joe : 06-06-2020 at 10:01 PM.
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  #2  
Old 06-06-2020, 09:07 PM
azonic75 azonic75 is offline
 
Join Date: Dec 2010
Location: Salem, OR
Posts: 132
Default Annoying

At least you found it without being out on the road! Pays to look carefully at oil change time. You can absolutely take off the exhaust without pulling the engine. You may have to remove the other pipes though as it does go together like puzzle.

Kai
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  #3  
Old 06-06-2020, 09:17 PM
Joe Joe is offline
 
Join Date: Oct 2005
Location: Independence, OR
Posts: 428
Default

Quote:
Originally Posted by azonic75 View Post
... You can absolutely take off the exhaust without pulling the engine. You may have to remove the other pipes though as it does go together like puzzle.
Kai, nice to hear from you!

OK, that's encouraging. Tomorrow I'll look into taking off the #1/#2 crossover pipes too. And if you're flying around, please land here, taxi over, say "hi" and have a look at this sad situation. (Two airplanes in my hangar and neither is airworthy.)





Thanks,
Joe
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RV-8A
Independence, OR
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  #4  
Old 06-06-2020, 09:22 PM
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rvbuilder2002 rvbuilder2002 is offline
 
Join Date: Jul 2005
Location: Hubbard Oregon
Posts: 9,653
Default

There is likely a slip joint in the cross over tube that will allow it to be separated into two parts, but they often get frozen with time in service (which can have an impact on causing the crack).
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Hubbard, Oregon
Van's Aircraft Engineering Prototype Shop Manager
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RV-6A (aka "Junkyard Special ")
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  #5  
Old 06-06-2020, 10:00 PM
Joe Joe is offline
 
Join Date: Oct 2005
Location: Independence, OR
Posts: 428
Default Slip joint

Quote:
Originally Posted by rvbuilder2002 View Post
There is likely a slip joint in the cross over tube that will allow it to be separated into two parts, but they often get frozen with time in service (which can have an impact on causing the crack).
Thanks. I went out to the hangar and checked. Right you are -- on both counts. There is a slip joint (it's the thing I've been putting Mouse Milk on each time the cowl is off) and it is frozen. Maybe I can break it loose with more Mouse Milk, some heat, and a little cursing <g>.
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  #6  
Old 06-06-2020, 10:20 PM
walkergp walkergp is offline
 
Join Date: Sep 2007
Location: Fort Worth, Texas
Posts: 11
Default Me Too

Joe,
I had this very same thing happen to me on my 8A IO360 A1B about two weeks ago..Cracked in between flange and EGT sensor on #4. I was able to get off by removing #3 flange and working the slip joint loose on the crossover. I only have 50 hours on mine which might have made it easier to separate. I sent it to Clint at Vetterman and he turned around the repair in a little over a week.

Now for fessing up. Like a dummy I put a heat shield over the joint with a clamp and binding the joint. How many airplanes do you need to build before you stop doing dumb things???

A Falco builder near me said he uses copper anti seize on those joints every other condition inspection.
Greg Walker
RV-8A
KGDJ - Granbury, TX
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  #7  
Old 06-07-2020, 01:17 AM
DTARM1 DTARM1 is offline
 
Join Date: Feb 2016
Location: Planet Earth (and it's lonely here)
Posts: 53
Default

I don't think your exhaust is made of regular stainless steel, but Monel or Inconel - some kind of fancy stainless steel - something like that. I sent a cracked exhaust to Aerospace Welding Inc.. The aircraft owner told me to first get an estimate for the repair from AWI. The quote was so high the owner opted for a "junk-yard" pipe which was $2,200

If you go to a local guy, make sure he knows how to test for the correct material and knows what he's doing. AWI uses jigs, but wouldn't guarantee their work anyway. I mention this because if the pipe isn't welded in a fixture, it's just going to crack again. Exhaust pipes like yours isn't ductile at all.

Good Luck.
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  #8  
Old 06-07-2020, 12:51 PM
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skylor skylor is offline
 
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Location: Southern California
Posts: 1,021
Default

Quote:
Originally Posted by DTARM1 View Post
I don't think your exhaust is made of regular stainless steel, but Monel or Inconel - some kind of fancy stainless steel - something like that. I sent a cracked exhaust to Aerospace Welding Inc.. The aircraft owner told me to first get an estimate for the repair from AWI. The quote was so high the owner opted for a "junk-yard" pipe which was $2,200

If you go to a local guy, make sure he knows how to test for the correct material and knows what he's doing. AWI uses jigs, but wouldn't guarantee their work anyway. I mention this because if the pipe isn't welded in a fixture, it's just going to crack again. Exhaust pipes like yours isn't ductile at all.

Good Luck.
Vetterman states their exhaust are made from 321 stainless steel. Vetterman Exhausts will repair their exhaust systems if you send them your damaged section and folks seem to have good luck with their repairs.

Skylor
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  #9  
Old 06-07-2020, 03:43 PM
Joe Joe is offline
 
Join Date: Oct 2005
Location: Independence, OR
Posts: 428
Default Success!

Quote:
Originally Posted by Joe View Post
... There is a slip joint (it's the thing I've been putting Mouse Milk on each time the cowl is off) and it is frozen. Maybe I can break it loose with more Mouse Milk, some heat, and a little cursing <g>.
With a helper on the other side of the airplane holding the crossover pipe I was able to rotate the #4 pipe and work the slip joint apart. Soaking in Mouse Milk overnight didn't hurt and I didn't need the heat or cursing.

I'll be phoning Vetterman tomorrow to arrange for the repair.
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  #10  
Old 06-07-2020, 07:29 PM
mcgaughy mcgaughy is offline
 
Join Date: Mar 2009
Location: Fayetteville, NC
Posts: 59
Default

Would be a good idea to also have your prop dynamically balanced if you haven't already. And keep in mind a balance is not a "one and done" deal. If it's been years or if you have done engine work, might need to be done again.

Ellis
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