Muffler Cracks

[AirFox]

325 hours of fun in the past year and half. My plane has been awesome. Yesterday while changing my oil I discovered two cracks in my exhaust. Looks like the cracks started front the spring tab welds. I'm having the exhaust welded now. Hope the fix works. Just thought I'd share my experience so you could keep an eye on yours.
9381
above is the crack. When I remove the exhaust I discovered another one of the tabs was developing a crack. I'll share the results when I get back in the air.
Scott

[AirFox]

9382
Here is a side view.

[jamesmil]

Mine cracked 3 times around the number 1&2 stack at the muffler as yours has.welded it up three time, seems like third time is the charm.don,t forget to purg the inside with an inert gas before you start welding to get a good weld inside and out.

[AirFox]

Thanks for the tip.

[jiott]

Thanks for the heads-up Scott. You can bet I will be keeping close watch on mine-250 hours now.

[Dick B in KY]

Looks almost like mine at 60 hours. Mine was non repairable, so a new muffler was purchased. Hope this one last a lot longer.

Dick B

[Av8r3400]

Wow. That's odd. I just rebuilt my muffler due to a crack, too. About 500 hours TT.

Mine failed at the blast tube inside the muffler which caused the stinger end cap to crack. I made my own blast tube from perforated 304 stainless I bought from Amazon.

I started this new thread about the muffler cracking for future reference.

[rosslr]

Interesting reports. I am not flying yet, however, took these pics of the muffler on my 912is - the muffler came fitted with the engine. The obvious differences are the use of 2 springs and the different weld pattern. I have no idea if there are other differences such as the type of materials used or thicknesses used. I don't know if others have this design with hours on it? It will be interesting to see if this arrangement avoids the cracking issues reported here.

cheers

ross

[jiott]

Ross, I see you safety wired the springs differently than most of us. Your method could still allow broken spring pieces to not be contained by the wire. I would recommend running the wire from welded loop to loop thru the center of the spring. Don't twist it tight so the spring has room to stretch and do its thing. Also don't forget the bead of hi temp silicone along the spring for vibration damping. Someone probably has a nice photo of what I am saying.

[Dorsal]

+1 on the silicone, broke 4 spring in my first 100 hrs, added the silicone and none since (now at 430 hrs).

[rosslr]

HI Jim and Dorsal (for whom I thank for making me super conscious every time I duck under the flappers!),

Thanks for the tips. The Muffler came fitted and springs wired from he Rotax supplier so I never questioned it - I will now though!

And have ordered the High temp silicon!

cheers

ross

[Paul Z]

+1 on the silicone, broke 4 spring in my first 100 hrs, added the silicone and none since (now at 430 hrs).

When I purchased my plane, all of the springs had Silicon, no safety wire. When I was working on the hoses, I noticed one sprin on the right rear cylinder was gone I hope no one was hit when it exited the cowling. It was there for my annual in February, but gone in June. I put on all new springs, Sylicon, & safety wire.