Muffler Crack...

[Piper J3]

I'm doing Annual Condition Inspection now and found a crack in the muffler where the exit exhaust tube is welded on. Looks like vibration induced metal fatigue from long cantilever exhaust tube. TT=750. Muffler is in back of car and headed for local TIG welding shop...
-

[RFSchaller]

Jim,

Thanks for posting. I’m in annual now and will take a close look tomorrow. I’ll post my results (about 1250 hrs total).

Rich

[Walt]

In the certified world, some exhaust system manufacturers double their warranty if you have the prop balanced, vibration causes cracking.

[RFSchaller]

Checked mine today. No crack! Maybe the Thunder gods are displeased with you, Jim!

[Tony_T]

Started my annual today. After reading Jim's posts, the muffler was high on my list. Found a pretty nasty crack, almost 180 degrees around the exhaust tube the exits the muffler and also extends into the muffler body just like Jim's. An experienced welder here thinks it will be an easy fix. If that doesn't work out, I guess I will be looking at the new EX-00044 exhaust system. Airplane has 690 hours, my prop has been dynamically balanced from early on.

[seagull]

Jim, Tony, have either of you had to replace muffler springs, if so how often?

I wonder if the vibrations that are getting to the muffler to cause the cracks are the same that cause spring breakage / wear. I remember reading on here someone had the bell sockets on the muffler wear, another sign things are moving around.

[Tony_T]

Walt
I have never had a broken muffler spring. I did replace all the springs about 300 hours ago, just because.

[seagull]

I am at 930 hrs and inspected my muffler because of the cracks you and Jim found. Mine isn’t cracked, yet. I have never broken a spring but 4 were worn 1/2 way through on the spring, the muffler hooks were fine. I replaced all 8 with the stainless ones from Spruce.

[jrtens]

Originally Posted by seagull

I am at 930 hrs and inspected my muffler because of the cracks you and Jim found. Mine isn’t cracked, yet. I have never broken a spring but 4 were worn 1/2 way through on the spring, the muffler hooks were fine. I replaced all 8 with the stainless ones from Spruce.

Since you would rather replace springs than muffler hooks, perhaps stainless steel is not the way to go?

[seagull]

Originally Posted by jrtens

Since you would rather replace springs than muffler hooks, perhaps stainless steel is not the way to go?

That very thought came to mind, I am not sure which would wear faster. Sometimes the softer material takes on surface grit and wears the harder material. I believe the original springs were high temper steel. They should have been harder than the hooks especially after annealing from the welding. I will watch these to see which side is wearing.