Rotax 582 Muffler

[NorthIdahoAvidflyer 374]

When I bought my plane the muffler was in sad looking shape. I was talked into coating it with some high temp powder coating product. Needless to say it started to come off immediately. I was skeptical about any product holding up to 1200 degrees that is applied and cured at 450 degrees. 

I cleaned it off the other day and found a couple of pin holes in the main muffler body. The plan is to get the mig welder out and fix them to get me through the next flying season. 

My question is has anyone else welded up holes in the muffler with any success and is there other options for replacing a muffler on a 582 besides the standard stuff sold by Aircraft Spruce or Leading edge?

[Matthewtanner 44]

Following

[akflyer 1427]

I have welded them up.. once they are rotten don't expect them to last long.  They will crack out in short order.  At least, that is my experience on sleds and on my Avid.

 

[TJay 1041]

Ha I have done that too on sleds its a bitch because you are welding on very thin rust.

[Cloud Dancer 69]

It will stink until it's been run awhile but you can paint it with flat black paint designed for wood burner stoves. I've got an old wood burner from the  early 70's that's green enamel but that type of coating is  basically glass and won't hold up to vibration.

I should point out that when I say enamel I am not referring to house or car paint but to the powdered glass you see on kitchen sinks and metal bath tubs. Also used on ovens, washers and dryers from the past.

Link here to enamel description: https://en.wikipedia.org/wiki/Vitreous_enamel  My father was a watchmaker and a jeweler and in the jewelry trade many of the colored pieces are referred to as enamelware.

Edited 14 Jan 2019 by Cloud Dancer
clarification of enamel

[akflyer 1427]

If you do weld it up, I would also take a torch to it after welding and "stress relieve" the welded area then let it slowly cool.  you need an accurate way of tracking the temp and don't go over 1100 degrees with it.  Best if you have some kaowool or other type of high temp insulation to wrap it with after you heat it.  You can have them ceramic coated and they will look better and last longer, but I would not bother doing that to a rotten exhaust system.  When you do buy new I would spend the $ to get it ceramic coated.

 

[Cloud Dancer 69]

If you do weld it up, I would also take a torch to it after welding and "stress relieve" the welded area then let it slowly cool.  you need an accurate way of tracking the temp and don't go over 1100 degrees with it.  Best if you have some kaowool or other type of high temp insulation to wrap it with after you heat it.  You can have them ceramic coated and they will look better and last longer, but I would not bother doing that to a rotten exhaust system.  When you do buy new I would spend the $ to get it ceramic coated.

 

Since the ceramic is a glass it has two properties that prevent it from being an ideal candidate for muffler use. Glass is a great insulator and it does not flex well. When you bond it to metal on a muffler your asking two different materials to expand and contract at the same rate. Then throw in the hammer effect these mufflers get from vibration and the glass may not fair so well. I've got some very expensive high temperature paint covering the  exhaust manifold on my Austin Healey car. It's basically powered glass added to a binder to get it to stick. It looks nice but i have no idea how long it will hold up. The metal on the cars exhaust manifold is much thicker than my Rotax exhaust so the expansion rate will be slower. And the car engine does not vibrate like my Rotax exhaust. I've had my share of broken mufflers, broken muffler springs and broken muffler ball joints. Almost always they seem to be vibration/heat related. How many old antique pots and pans have you seen with chips out of the ceramic coating? Most are probably from rough handling which again brings me back to the vibration of a Rotax exhaust. The Kaowool you suggested is a far more flexible substrate than a brittle enamel coating painted on.

If you apply Kaowool to the exhaust manifold and the muffler it will work great for keeping the heat away from items around the exhaust. I question if this heat being retained by the exhaust components is a good thing? With exhaust gas temperatures above your recommended 1100 degrees to stress relieve the muffler and insulation to insure this heat stays within the exhaust components, it seems the muffler would stress relieve itself just from being run to temperature and allowed to cool down after flight. I'm in agreement that stress relief is a good thing, I'm not so sure that constant stress relief is a good thing  as metal at high temperature is not as strong as metal at a cooler temperature. Until Rotax either supplies insulating muffler tape or at least endorses it I'll remain on the sidelines and see how the game unfolds.

[akflyer 1427]

If you do weld it up, I would also take a torch to it after welding and "stress relieve" the welded area then let it slowly cool.  you need an accurate way of tracking the temp and don't go over 1100 degrees with it.  Best if you have some kaowool or other type of high temp insulation to wrap it with after you heat it.  You can have them ceramic coated and they will look better and last longer, but I would not bother doing that to a rotten exhaust system.  When you do buy new I would spend the $ to get it ceramic coated.

 

Since the ceramic is a glass it has two properties that prevent it from being an ideal candidate for muffler use. Glass is a great insulator and it does not flex well. When you bond it to metal on a muffler your asking two different materials to expand and contract at the same rate. Then throw in the hammer effect these mufflers get from vibration and the glass may not fair so well. I've got some very expensive high temperature paint covering the  exhaust manifold on my Austin Healey car. It's basically powered glass added to a binder to get it to stick. It looks nice but i have no idea how long it will hold up. The metal on the cars exhaust manifold is much thicker than my Rotax exhaust so the expansion rate will be slower. And the car engine does not vibrate like my Rotax exhaust. I've had my share of broken mufflers, broken muffler springs and broken muffler ball joints. Almost always they seem to be vibration/heat related. How many old antique pots and pans have you seen with chips out of the ceramic coating? Most are probably from rough handling which again brings me back to the vibration of a Rotax exhaust. The Kaowool you suggested is a far more flexible substrate than a brittle enamel coating painted on.

If you apply Kaowool to the exhaust manifold and the muffler it will work great for keeping the heat away from items around the exhaust. I question if this heat being retained by the exhaust components is a good thing? With exhaust gas temperatures above your recommended 1100 degrees to stress relieve the muffler and insulation to insure this heat stays within the exhaust components, it seems the muffler would stress relieve itself just from being run to temperature and allowed to cool down after flight. I'm in agreement that stress relief is a good thing, I'm not so sure that constant stress relief is a good thing  as metal at high temperature is not as strong as metal at a cooler temperature. Until Rotax either supplies insulating muffler tape or at least endorses it I'll remain on the sidelines and see how the game unfolds.

2 stroke exhausts are ceramic coated in the sleds all the time.  No ill effects.  I know of sled exhausts that were coated and have in excess of 14k miles on them and they still look damn near new. 

 

Wrapping with kaowool was ONLY for the stress relief after welding until it had cooled slowly to room temp not for continued use in flight.

 

 

 

[Cloud Dancer 69]

2 stroke exhausts are ceramic coated in the sleds all the time.  No ill effects.  I know of sled exhausts that were coated and have in excess of 14k miles on them and they still look damn near new. 

 

Wrapping with kaowool was ONLY for the stress relief after welding until it had cooled slowly to room temp not for continued use in flight.

I didn't know that. I have not kept up with the sleds since I got rid of my Yamaha Phazer years ago. I've welded up plenty of regular sled exhausts but never a ceramic coated one. Do they repair as easy with a glass coating? How far back do you grind the glass to weld up a crack?

 

 

[akflyer 1427]

I have never had to repair a new one that was ceramic coated but I would say to sand it back just enough to make a good weld.  If it cooks off while welding so be it.