Tail Pipe Vibration causes muffler Crack

[Darrel Starr]

Note: Later in the thread I point out that this muffler crack was a result of allowing the tail pipe to vibrate against the firewall. The failure in no way reflects on Leading Edge design or workmanship. The lesson is to make sure the muffler and pipes all have adequate clearance.


I changed oil today and was thinking about unplugging the heater box for the winter. But then I saw exhaust residue on the lower cowl and air box – a little investigation led to the conclusion that the Leading Edge muffler is cracked on the right side (carburetor heat and rear seat heater) and leaking into the jacket – 175 hrs on this supposedly bullet proof system – Bummer! Taking the exhaust apart is my most un-favorite task firewall forward. So a word of caution, as you get ready for the winter, make sure the exhaust system is sound before sealing up the cabin and taking a long ride.
I’ll post pictures of the crack(s) when I get it apart.
What are other Leading Edge customers experiencing?

 

[skywagon8a]

That stuff happens. I had a brand new Achorn exhaust on my 185. It cracked 7/8 of the way around on the very first flight. You're lucky, as you got 175 hours on yours. Get a GOOD local welder to fix it. Stresses build up around the weld, stainless is very susceptible to this. Have the welder purge the inside with argon while welding the crack.

 

[sj]

Been lots of this over the years, Darrell. Here is one of the old threads: http://www.supercub.org/forum/showt...t-muffler-cracks&highlight=leading+edge+crack

 

[Darrel Starr]

Thanks guys. I'll take it apart today. SJ, I remember that thread in 2005. My system was new and the plane was not yet assembled so I sent my new unused muffler back to Dane that year and they updated it at no charge. So my muffler already has the last known improvements. Once it is apart and I can photograph the problem, I'll give them a call. In the past, the Leading Edge folks have bent over backwards to help out.

 

[Darrel Starr]

Well I have the muffler out and the crack is 100% my fault -- Not a Leading Edge problem. For the first 100 hrs, the tail pipe was rubbing on a screw head on the firewall. I found this contact during an inspection and readjusted the exhaust system to provide clearance. But apparently the damage had already been done as a crack developed in the weld then recently progressed.

 

[mike mcs repair]

glad you caught it on the ground!

shouldn't you be able to see a LARGER than normal drop on run-up when checking carb heat, when its broken on the carb heat side of muffler like that, since instead of hot air, its feeding carb hot exhaust with no good air??? .... that's always what I had thought.....

 

[Darrel Starr]

I didn't notice anything changed even pulling carb heat before landing -- probably lucky the engine didn't quit at that point in the last flight but it motored along as usual. I think it was a minor crack for a while then really let go in the last few hours.
We have smelled an exhaust odor most of this season ( http://www.supercub.org/forum/showt...g-Edge-Exhaust-Exhaust-Odor-in-Cabin-on-Final ) but always just descnding during landing -- probably primarily when the carb heat was on. I thought it was the short tail pipe or possibly the junctions around the muffler which Leading Edge had some problems with. We had the cabin heater blocked off so we never got much smell. I should have been more suspicious. We were lucky.

 

[Dave Calkins]

Darrel, I'm glad you found this before it hurt you.

This is an alarming thread. Please consider how the title sounds. It would seem most fair to LEES if you were to edit your first post to make it clear from the beginning that this was not LEES fault. Maybe even edit the title of the thread.

 

[StewartB]

That stuff happens. I had a brand new Achorn exhaust on my 185. It cracked 7/8 of the way around on the very first flight. You're lucky, as you got 175 hours on yours. Get a GOOD local welder to fix it. Stresses build up around the weld, stainless is very susceptible to this. Have the welder purge the inside with argon while welding the crack.

I'm curious about the Acorn muffler crack. Please describe it. Thanks.

Darrell, You're acceptance of responsibility for your muffler failure was a stand up thing to do. Thanks for the rest of the story.

SB

 

[Darrel Starr]

Dave, good idea, I see that the title seems to malign the manufacturer -- not my intent. I can't figure out how to change the title -- maybe Steve can. However, I put a statement right at the beginning as you suggested to, at the outset, make sure people know that Leading Edge is clear. I'll contact Steve regarding the title. Does the statement look OK?

 

[skywagon8a]

I'm curious about the Acorn muffler crack. Please describe it. Thanks.

SB

I bought a complete new system from Achorn. It was not the muffler that cracked. The muffler is fine. It was at the base of the exhaust collector cluster where the elbow to the muffler is welded on. I called them and they told me to send it to an outfit in Minnesota (I think it was) to be repaired. After they got it and repaired it they wanted several hundred $$ for me to get it back. I was over a barrel. After it was reinstalled after about 3 hours it cracked again. Believe me there were a lot of unpleasant words. I had a local cracker jack welder repair it the second time, no more trouble. It was installed correctly with no abnormal stresses. I will never do any business with Achorn again. Had I known that they would not honor their stated warrantee I would have had my local welder fix it in the first place.

 

[StewartB]

Are you referring to Acorn Welding in Edmonton? I installed a complete system of theirs a couple of years ago. My experience was fantastic both for product quality and customer service.The Acorn I used has a unique outlet pipe reinforcement and a very unique shroud that exposes the outlet pipe for easy inspection. That's why I was curious about the crack. I'll take a peek at my collectors.

SB

 

[Steve Pierce]

So a screw rubbed on the tail pipe and caused it to crack? Are there support rods attached to the LEE eshaust like on a stock SC system? I have worked on one in a long long time.

 

[Darrel Starr]

Actually, I was wrong, no screw head, but the pipe was just touching the lower edge of the firewall. Yes there is a brace triangulating up to one of the pipes from the cylinder - picture. The lever arm though of a vibrating force several inches out on the pipe seems to have fatigued the weld. We are sketching variations on a doubler plate thinking about how to spread out the load path back to the muffler shell. I was able to readjust the exhaust system once I saw the rubbing and get the pipe to clear the firewall but the crack seems to have already started 75 hrs ago. I put a dab of silicone on the firewall at that time so I could more easily see if it was still hitting after the adjustment -- apparently it did clear after the 100 hr mark.

 

[skywagon8a]

Are you referring to Acorn Welding in Edmonton? I installed a complete system of theirs a couple of years ago. My experience was fantastic both for product quality and customer service.The Acorn I used has a unique outlet pipe reinforcement and a very unique shroud that exposes the outlet pipe for easy inspection. That's why I was curious about the crack. I'll take a peek at my collectors.

SB

Yes, that is the same outfit. They are the same folks who weld up the Seaplanes West engine mount which I also acquired at the same time.

 

[StewartB]

Your story sure is different than mine. Acorn impressed me from the first phone contact to the last email. Unknown to me at the time a local parts house stocks Aerospace Welding exhaust systems but I went to market and selected Acorn based on web pireps. My mechanic was familiar with AWI but was very impressed with fit and finish of my Acorn system. I guess any supplier has successes and failures. I'm pleased to be a satisfied Acorn customer. Odd that a fabricator/manufacturer would have you send a failed part to a competitor for repair. That part has me puzzled.

For what its worth everyone I know who uses Leading Edge components has given rave reviews. If I was Darrel I'd give LEE the first opportunuty to repair the problem.

SB

 

[Darrel Starr]

I'll talk to LE but they are closed this week according to their email automatic response.

 

[StewartB]

Hunting season in Alaska. My own shop's been on half staff and will remain that way through closing day on Sunday!

SB

 

[jk]

D.S.,

I hear your plight, but I don't see why you would have to think about re-designing the installation?
The instructions that come with the LEE's is very descriptive and complete. As you know I have the extended overboard pipe on my ship (talk about a moment arm!!) and have no problems what so ever. I have adequate clearance all arournd the system to avoid the start-up or shut down vibrations.

It's a very good thing you caught this when you did as the results of prolonged use, well we don't have to go there.

I would re-read the installation instructions to make sure you complied with all points.

Good luck and get flying. The LEE system rocks!!

JK

 

[AkPA/18]

Hey JK---you have quite a bit more clearance than Darrel with the TL installed. You should even be able to still swing the engine without hitting the boot cowl on the left side?

Mark

 

[skywagon8a]

Your story sure is different than mine. Acorn impressed me from the first phone contact to the last email.
SB

I too was impressed until that first flight when it all went to ****. Unfortunately Edmonton is a long $$$ way from here.

 

[jk]

Hey Mark, how goes it?

Yes, I do have more clearance but buy looking at Darrel's pic of his overboard pipe support strut It appears to be lower than whats called for in the install instructions. I could be mistaken, it's been years since I read it, and I don't have the paperwork in front of me, but I think that the O pipe strut clamp is supposed to be within 2 or 3 inches of the pinned clamp. I'm sure Darrel has his paper work out and maybe he could check that option, just a thought?

JK

 

[Darrel Starr]

Yes, I do have the paperwork. I'll review it all going back together. While apart, I am having AWI make up a 2 inch longer tail pipe with a square cut end -- trying to get the exhaust further away from the cabin. It seems like a doubler to relieve the weld stress will be cheap insurance.

 

[Darrel Starr]

JK -- "The instructions that come with the LEE's is very descriptive and complete. As you know I have the extended overboard pipe on my ship (talk about a moment arm!!) and have no problems what so ever. I have adequate clearance all arournd the system to avoid the start-up or shut down vibrations."

I just looked over the Leading Edge Instructions. It says to adjust the clamp on the tailpipe so the brace will clear the engine mount -- not very descriptive and/or complete.

 

[jk]

Darrel,

Well your latest post got me thinking, so I broke out my instuctions.
My instructions (report number: LEESPA-18EXH-INST-1, revision G, Dated 11/02/05) are 20 pages long. Your situation is covered on pages 10, 11, 12, 13, 14, 15 (2.3 #4 should be of interest) and page 16.

This is a little more than your post text.

Hope you find resolution.

JK

 

[Darrel Starr]

I don't have that document but Dane is going to call me back today. I'll ask him for a copy. My system dates back to 2003 so I must not have the latest paperwork.
Thanks, Darrel