Welding Muffler

[Peteohms]

Almost lost my tailpipe. (kitfox 3, 912) The side of the muffler around the tailpipe is cracked and the pipe is barely hanging on. I tried to weld it but guess its stainless. Any ideas where to take it to be welded?

[Geowitz]

You can still weld stainless with regular 70s-6 wire through a mig. I did it for my exhaust and just painted the welds with high temp paint. You can see the black paint on my exhaust joints in the pic near the firewall.

[Peteohms]

Thanks for the reply, but I'm looking more for where to take it to be welded. How to find someone local who can weld this thin stainless. I can just barely weld with oxy/acet.

[Steves142]

Pete, I just repaired one twice for a 912. The first time I tig welded the tail pipe back on the end of the muffler, welded up the cracks and added a support bracket. That lasted about 5 hours. The second time I cut the end of the muffler off, made a new one, welded a tube extension with holes in it on to the inboard side of the tail pipe so it would sit inside a socket on the opposite side of the muffler and tig welded it all back together. So far so good. I guess the tail pipe needs to be supported on both sides of the muffler.

[Peteohms]

Thanks Steve, Could you dive me more detail on what kind of wire you used etc. so I can pass the info along to whom ever does the weld.

[tucsonchris]

I currently have a similar issue with a cracked muffler. Search for "cracked muffler" on the Matronics forums and you will get lots of advice. The consensus is it should best be done by some skilled in Tig and stainless welding. I'm going to start with calling some race/offroad fabrication shops locally.

[n85ae]

I had my IO-240B exhaust rewelded to re-route a pipe that was hitting the
cowl inside. These folks did a super job, and the price and turnaround was
very good.

http://www.awi-ami.com/

Jeff Hays

[SkyPirate]

when welding stainless,..if you have an extra tank of argon,..or a "T" in line from tank to tig head,..you should purge the interior of the pipe being welded or it will crack again,..stuff a wrag around the hose going into the pipe and reduce the outlet with another piece of tubing and another wrag,..it will look like you tig'ed it on the inside as well if done properly,..if you don't do this you get perocity on the interior of the pipe where the heat is ,..the perocity heats up quicker,..making the external weld weaker..

Chase

[mr bill]

An excellent exhaust welding vendor is Dawley Aviation (dawleyaviation.com)in Burlington, Wi. I have used them many times over the years and their work is excellent. The last job I gave them was to weld .012 thick stainless steel. While I was there, they showed me work they had done on someone else's project, where they welded .015 thick aluminum. First rate people and workmanship.

[Steves142]

I think the important thing is supporting the tail pipe on both sides of the muffler. There is a socket welded on the inside, opposite the tail pipe. They used to weld a perforated stainless tube over the tail pipe on the inside. This would extend into the socket on the opposite side giving the pipe support on both ends of the muffler. According to Kitfox they don't use perforated pipe any more they just extend the tail pipe and drill holes in it.

[Dave F]

Skypirate is correct.

Your have to back purge with argon to get rid of the oxegen. Porosity nad cracking with happen otherwise especially on used SS material.

Best advice is take to a knowledgable Tig Welder and if he does not think back purging is important then he either does not know or wants to to come back for more money when it cracks again.

[Dave F]

You can still weld stainless with regular 70s-6 wire through a mig. I did it for my exhaust and just painted the welds with high temp paint. You can see the black paint on my exhaust joints in the pic near the firewall.


70s wire is the wrong wire to use on SS

with SS alloys 304L- 316L your enemies is carbon and Manganese.
You will definalety be more prone to cracking with higher manganese levels in your wire. Mig can work with ss wire like 308 but on thin wall SS you will have alot less control

70s is as mild steel wire and great for carbon steel..


Hope this helps to rectify.

[Geowitz]

I think we all know(or could find out pretty easily) 70s6 is a mild steel wire... Yes, for the "know it alls" it isn't correct, but it does work and is an option. My intention was to explain that if he needed a quick fix on the cheap was that he could do it with mild steel wire as it sounded like he was trying to do it himself and gave up. It's done all the time and whether you get cracking can really go either way and has more to do with mounting and vibration than dissimilar metals. I did it with my exhaust and it's working fine. Just letting him know it's an option.

Hope this helps to rectify.

[Dave F]

Quick fix yes - but will not last.

Cheaper to do it correctly the first time than have to clean off the failed weld area again and remove the mild steel wire.

I have been welding for over 40 years and work in the steel business now and work with over 300 alloys for repair and re-manufacture as well as casting.

We do not weld $500 or $100,000.00 castings with the wrong materials or procedures as failure is not an option.

This should help rectify any confusion that any might have.

[Geowitz]

Never mind. Not worth it.

Pete - Sounds like whatever you do you may still have problems because of the design. Maybe investigate bracing your tailpipe or addressing vibration sources like Steves142 mentioned.

[Peteohms]

The muffler lasted 20 years. Not bad. I'll be taking it to a well respected welder
who was just recommended by an A&P friend.

I appreciate all the comments.

[turboturner]

Am not a weld expert but the chap who repaired mine the last time added a 3rd support brace from the edge of the muffler to the exhaust pipe. That was 2 years ago - no cracks since (50 hrs). As someone else mentioned in this thread, additional, all-round support is the answer, IMO.