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  #1  
Old 07-12-2016, 06:36 AM
rv8apilotpab rv8apilotpab is offline
 
Join Date: Dec 2013
Location: southwesern Ontario Canada
Posts: 2
Default Exhaust stack failure problem RV-8A

Fellow RVators

I have 750 Hrs on my 8a. It is certified and used for IFR flight and I need reliability.

I have Vetterman stainless exhaust and Vetterman pipe support bracket system. I have a Lycoming IO 360 angle valve. I have just had my 4th exhaust stack failure in the 750 hous I have flown on this airplane. Each time the stack breaks at the weld of the pipe to the exhaust manifold flange. 2 times on no 2 cylinder and 2 times on no 3 cylinder. 3 breaks have been on new stacks and one on a reweld by a local shop, not Larry V. One of the broken stacks was rewelded and fortified by Larry who uses a jig. It has not rebroken.

One of these failures occurred at night in winter over Lake Eirie. With typical British understatement, (she is British, I am Canadian) my wife who was with me on 2 of thes failures, stated, "I don't like it when that happens."

So, can you help me please with ideas about how to prevent a re-
occurrence.

Yours pab
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  #2  
Old 07-12-2016, 07:30 AM
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N941WR N941WR is offline
 
Join Date: Jan 2005
Location: SC
Posts: 12,884
Default

How are you securing the ends of the exhaust and are you using Mouse Milk to lubricate the slip joints whenever you have the cowl off?
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  #3  
Old 07-12-2016, 09:19 AM
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RVG8tor RVG8tor is offline
 
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Location: McKinney, TX
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Default 500hrs still okay

I have an 8A and so far not issues with cracks. I am always readjusting to keep the pipes off the weld mounts. Mine always just touch the low part.

I also add mouse milk to each joint every time I have the cowl off which seems to be 6 or so times a year. Along with this is an inspection of each pipe.

Cheers
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  #4  
Old 07-12-2016, 12:25 PM
Marc Bourget Marc Bourget is offline
 
Join Date: Apr 2009
Location: Stockton, California
Posts: 352
Default

Cross over arrangement? If so, which cylinders are you pairing?

If what I'm seeing from the Vetterman site is what you have, it appears that the cylinders "before" the exhaust tube are experiencing the problem.

I'll also assume you've been using mouse milk each repair (if not more often)

I'm guessing you could investigate doing something to better support the exhaust pipe closer to the ball joint???

FWIW
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  #5  
Old 07-12-2016, 03:23 PM
scsmith scsmith is offline
 
Join Date: Jan 2008
Location: Ashland, OR
Posts: 3,059
Default Where are the clamps anchored.

Where the clamps/supports that support the tail pipes are anchored makes all the difference. If you have them anchored to the engine mount, I think you are going to get cracks.

If you anchor the clamps to the cylinder block, I doubt you will get cracks. This allows the whole engine and exhaust system to move as a unit on the dynafocal mounts without putting any stress on the pipes.

I have 400 hrs on mine, clamped to the engine block. I do not use any mouse milk. No issues.
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  #6  
Old 07-12-2016, 03:49 PM
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Kevin Horton Kevin Horton is offline
 
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Location: Green Bay, WI, USA
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I had problems with exhaust pipe cracks on a Vetterman crossover system on an RV-8 with IO-360-A1B6. I had the #3 pipe break completely off at the flange on the way back from OSH in 2011, with about 250 hours on the system. The exhaust went back to Vetterman for repair. A year later, I found a significant crack at a Y joint, also repaired by Vetterman. In July 2013 I found a crack at the #3 flange - there wasn't enough time before OSH to get it to SD and back, so I had it repaired locally.

I discussed my issues with Larry Vetterman, and he said that the crossover system on angle valve engines on RV-8s had the worst failure rate for cracks of all the RV model/engine model/exhaust configuration combinations. He suggested that I replace it with a four pipe system, as that was the most durable configuration (with the four-into-one a close second). I had Vetterman make me up a four pipe system with thicker than normal tube for the first few inches on each cylinder. That system went on in December 2013. So far it has been trouble free (I've probably cursed myself for saying that in public though). I'm a few thousand miles from the logbook, so I'm not sure how many hours I've put on it, but it isn't a huge number yet.
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  #7  
Old 07-12-2016, 09:07 PM
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Arvey Fleur Arvey Fleur is offline
 
Join Date: Mar 2015
Location: Sacramento, CA
Posts: 51
Default What does that sound like?

A pipe breaking off in flight?! I am curious what that sounds like as well as other in-flight indications when the event happens? Seems like a frightening event, considering 1200+ deg exhaust leaking into the cowled area? Perhaps only a smallish gap appears, still funneling most of the exhaust thru the pipe?? More details appreciated.
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  #8  
Old 07-12-2016, 09:31 PM
eaglen92ce eaglen92ce is offline
 
Join Date: Oct 2009
Location: Chandler, AZ
Posts: 203
Default

Well it can sound pretty bad! I had a pipe on my #1 cylinder break very near the cylinder flange. This happened on initial climb out, probably 350 feet AGL or so.

I thought I had a major engine failure. Reduced power to idle, pitched for best glide. I then made a 180 back to the airport after I confirmed that I was still able to make power. I landed on the same runway I took off on (opposite direction). I pulled the mixture as soon as I touched down and coasted onto the taxiway. The local FBO came and towed me to the ramp.

I was very relieved when I removed the cowl and saw the #1 pipe completely broken off. It was a PITA, but the engine was all good so I was happy!

My exhaust was also Vetterman cross-over on an angle valve motor. Clint got me fixed up, but I also experienced a couple other more minor cracks in the system. I now have the four pipe system with a couple hundred hours on it and no problems. I think that not tying the cylinders together will make it more reliable. Very pleased with the four pipe!
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  #9  
Old 07-12-2016, 10:05 PM
Marc Bourget Marc Bourget is offline
 
Join Date: Apr 2009
Location: Stockton, California
Posts: 352
Default

Wonder if some head girdles, like those produced by Skydynamics would help
solve the cracking problem on the angle valve motors ??

I'm considering turning something similar out on my cnc mill for my parallel valve O-360.
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  #10  
Old 07-12-2016, 10:08 PM
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hydroguy2 hydroguy2 is offline
 
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Location: Townsend, Montana
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Default

Quote:
Originally Posted by Arvey Fleur View Post
A pipe breaking off in flight?! ...... More details appreciated.
During GNAR III, I sheared off #2 pipe at the flange while at full power race speed and <200agl. Scared the **** out of me, I didn't know what when wrong at first. The power pulses were loud and was torquing the engine over enough I could see the engine hitting the cowl. Almost thought I lost a piece of the prop or something, maybe a piston and cylinder had come apart. pulled power and pulled up to best glide, called ABORT on the race channel. Seemed smoother at 1800 but popping loudly.
As I turned inward on the course(towards the finish airport 20miles away, Bob B was behind me and said don't go across there, its no mans land all lava rock and scrub brush. I was looking for a landing place certain that my engine was not going to be running much longer. 15seconds in the engine is still running, still have oil pressure but EGT was under 100 and CHT was falling fast. I was holding 1400agl and 100kts paralleling a highway. Bob flew under me looking for smoke or oil streaming...nothing. 14nm to Waterville took for ever.
yeah it gets your attention and was so happy it was only a failed exhaust. Got a local welder to tack it together then we removed it and took it to his shop where they welded it up nicely. Flew it home later that evening 300+miles.
To be fair I had been experimenting with a different exhaust hanger arrangement to minimize drag in the cowl outlet.
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