Powder Coated Exhaust System

[Chuck Irby]

Has anyone had their exhaust system powder coated?

If so, is it holding up okay?

My powder coater told me that his process generally gets the metal up to 1200 degrees. Therefore, it seems to me that the paint should hold up to the exhaust temp.

[Harry_S.]

My p/c guy told me that p/c will eventually burn off if subjected to continuous temps above 600 degrees. That's why I had my exhaust porcelinized.



Dirty Harry

[Chuck Irby]

Harry,

Thanks a lot. Based on that, maybe I should just paint them with high temp paint.

[gyropilot]

Chuck,

I've tried high-heat header spray paint on my Rotax exhaust system, and while it looks good at first, inevitably surface rust would creep back.

A couple of years ago an UL pilot friend told me about Jet Hot coatings. I did some research and then had their "Sterling" coating applied to the exhaust system. Cost was $159.00 which included return shipping. I had to ship my exhaust down to one of their facilities in Colorado... or maybe it was Arizona... I don't remember now. It took about 2-1/2 weeks total round trip (including coating) by UPS ground.

The coating is darn near indestructible and withstands 1300 degrees F continuous. After two winters and one flying season the coating looks as good as good as the day it came back from Jet Hot. You can have the coating applied in a smooth semi-gloss silver finish (most popular) or a matte black finish. For the matt black finish, they first coat the exhaust with a couple of layers of the silver finish, and then one coat of matt black. I went with matt black to more closely match the original Rotax look.

You can read all about the process here:

http://www.jet-hot.com/pages/headercoatings.html

If you decide to have this done, be sure to send everything from the exhaust system... muffler, manifold, elbows, and even the springs!

Oh... one other nice thing about the Jet Hot process (unlike some ceramic coatings) is they don't care if the exhaust system is used. You don't even have to clean the parts first... they take care of all that for you.

Best regards,

John L.

[Chuck Irby]

John,

Thanx a lot for this info. That definitely sounds like the way to go. However, I can't do without the exhaust system for that long at this time. I will keep this info until I can though.

I think for now, I'll sandblast everything and go ahead and try the powder coat for the interim.

Do you know of a good source for new springs. Mine are a little worn in places and will eventually break. I have even considered welding the three pieces together, but figure that might be a mistake. Maybe they need to to be able to flex at the joints. It's still tempting though, especially since Greensky and the others I have seen show a price of $2.22 each

Thanx again, Chuck

[gyropilot]

Chuck,

For this flying season I'd simply spray paint your exhaust system using high-heat header paint available at any auto supply store. It'll look good enough for now and then next winter you could go ahead and ship it to Jet Hot for coating. That's what I did.

Also, I'm not so sure what'll happen when that powder coated paint starts to burn off. Might make a mess... then again maybe not.

As far as springs go, I buy most of my Rotax parts from California Power Systems (CPS) at:

http://www.800-airwolf.com/

You'll probably need either Rotax exhaust spring part number 938-790 (which is 2-5/8" long - $2.95 each), or 938-795 (which is 2-1/4" long - $2.40 each). They should be replaced periodically when you see wear. It's a small price to pay to avoid buying a new prop if one breaks and comes free! When you get into the CPS online store, look under "Rotax Engines & Parts" and then "Rotax Exhaust Parts."

In no case do you ever want to weld the exhaust section together. The separate sections Rotax has provided allow the exhaust system to absorb vibrations, thus preventing unwanted cracks to develop elsewhere. In effect, the exhaust system is "pre-cracked" with those flexible joints.

An alternative to the standard Rotax exhaust springs is an "exhaust ball joint conversion kit." In the CPS online store, look under "Rotax Engines & Parts" and then "Rotax Options."

Good luck,

John L.

[Chuck Irby]

Thanx again John. Re the welding, that was my thinking as well. I'm just too much like Ron Awad in that it bothers me to pay 3 bucks for a 2 bit spring just because it is for a Rotax.

[GyroRon]

I use the spray paint on my Rotax exhaust and it works fine. One good sanding and a couple coats of header paint or even cheaper BBQ grill paint and it will look great for a month or two. After then like John said rust will re appear and so what I do is before the rust gets a chance to really start going I just use a piece of cardboard to shield the engine and rest of the area from overspray and then I spray a new coat on the exhaust again. I must do this once a month or so, BUT I only use one can of paint every few months and the paint is only a few bucks.....

Springs....... I have rarely had to replace them and I think how I install them helps. First I run safety wire through the inside of the spring all the way through the welded loops the springs clip onto and go over the outside of the spring as well. This is done with a little slack in the wire to allow movement of the parts. I do this so if the spring breaks the muffler won't fall apart and the spring even if broke in half won't go anywhere. Then I take red silicone RTV gasket goo and squeeze out a thick bead and run that bead from one end of the spring clear over to the other end. The Silicone is like a dampener and keeps the spring from vibrating excessively which is the main reason they fail - second to rust - I believe if you keep them painted and rust free and use the silicone you would only have to replace them once in a Blue moon.....

just my two cents.

[Chuck Irby]

Makes sense to me. Good idea Mr. Awad.

[gyroblackwell]

I use those ball joint kits that were mentioned, and I think they are the way to go! the plates and springs don't wear. the AN bolts take all the wear, and are easy AND CHEAP to replace. I have been using them on my 503 for two seasons, and have only replaced the bolts this year.

check them out! You can also get them from lockwood aviation supply in Sebring FL.

just my 2 cents worth!

Tim

[CLS447]

I got tired of repainting my 447's exhaust with "Fireplace Black". When I was having my cowlings powdercoated, the guys at the shop said they would try the exhaust for free.

They thought that their flat black would hold up best. Within minutes it started smoking & peeling off!

Then I sent it to JETHOT. Looks great & havn't touched it since! I highly recommend their service. Quick turnaround & free decals! At the time they had 3 colors: black, silver & blue. I opted for black.

[ToddP]

I've been looking at the same issue recently. I tried duplicolor "high heat" paint. That took about 15 minutes to peel off. I'm in the same boat as Chuck, don't want to be out of commission for 2 weeks or more. I also saw this advertised on Leading Edge Airfoils Site:

Exhaust System Aluminizing Service
Includes aluminizing your Rotax exhaust manifold, elbow and muffler. For other types of exhaust systems and/or components please call for a quote. $75.00

You can check it out here:

http://www.leadingedge-airfoils.com/services.htm

Has anyone had this done? How is it compared to the Jet Hot Ceramic type coatings?

[ToddP]

I also saw a product listed in the California Power Systems Catalog for coating exhaust. It sounds like a Do It yourself ceramic coating product. There is silver and black. They both cost $30 for a 6 oz. Bottle. You have to sand and prep your exhaust, then "airbrush" the stuff on. The black stuff will cure itself on your hot exhaust. The silver stuff has to be baked in your oven then buffed and polished out. Might do the trick without sending it off.

[Chuck Irby]

Decisions, decisions . . . . Thanks a lot Todd for adding these options. :-

[daveeisler]

I saw several job's done by Jet Hot and it is the best way to go, do it only one time and it will last.

[Chuck Irby]

Dave, thanx for your input. Have you, by chance seen an aluminized exhaust?

[Screw]

Hey Chuck,

I had mine "Ceramicoated." Don't think I spelled it right. It is holding up ok so far. They coat it in and out and it helps hold the heat.

John-

[Harry_S.]

Chuck; before I had my exhaust porcelainized, I used a can of John Deere' black exhaust paint. Not cheap but it held up till I decided to add some "beauty" to my exhaust. Any John Deere store will have it.

[daveeisler]

I am not familiar with the alluminium process, but I spent some time with maxie W. and he showed me his exh. done by jet hot and it was impressive.

[Chuck Irby]

John, Harry and Dave,

Thank you all for your input. I had decided, based on the replies I got yesterday, to call my powder coater and tell him not to paint it. I got to him too late. It was already powder coated. So now I'll just have to burn it off before I can do anything else. It sure looks good now though. I sandblasted it before I took it to him.

BTW, I found some springs that work at least as well as the Rotax springs at my local hardware/building supply store for just over a buck each.

[daveeisler]

Be sure and let us know how well it holds up. best of luck with it and all your flying. Dave

[Chuck Irby]

Dave,
I am planning to put about an hour on it tomorrow afternoon. So that will be a pretty good initial test. I suppose some powder coats could hold up better than others. I know little about the process. However, my powder coater said that his oven gets the metal up to 1200 degrees during the process.
Thanx again,
Chuck

[gyroblackwell]

Be sure and safty-wire those "hardware store" springs ! I had put some of those on my 503 about 3 yrs. ago, and about 15 hrs. later, I had to replace my IVO prop due to the springs letting loose during flight.

The temper in those springs does not hold up well to heat, and the hardness just kind of disolved. I had safety wired them to the hooks, but did not run the wire thru the middle of the spring also. (MY BAD !)

Just keep a close eye on them for the first 10 hrs.

Only my opinion of course !

[scottessex]

just an FYI, What we used to do on car headers was Strip down to bare metal and paint with VHT High heat paint. THEN, you start tthe engine up and run just until the paint starts to smoke, Then shut off and let cool. REPEAT,REPEAT, until they don't smoke, Seemed to bake the paint on and lasted a good long while.
Just firing the engine up and going will usually burn off any type of high heat paint.

[Chuck Irby]

Tim,

Your opinion is most appreciated. In fact, I appreciate almost all opinions. In my opinion, that's the main advantage to having a forum such as this.

I reinstalled the exhaust system yesterday afternoon and immediately safty wired all six springs, loosely, all the way through.

Thanx Tim

[Chuck Irby]

Hey Scott,
Somehow I missed your post. That sounds like it would work well. Maybe that's the way I need to go with the powder coat. I haven't even fired it up yet. So I will try that, hopefully today. I'll let you know what happens.
Thanx a bunch.

[daveeisler]

Springs , Be very carefull . There are brake caliper springs that are very good but they still are not the kind to use it is safer getting the one's designed for the exh. I tried the thing that you see in some of the catalogs that replace spring's and sort of lock the 2 parts together, I felt they were not good at all and got rid of them. Dave

[gyroblackwell]

Thats odd dave, I have been using them (clamp style) for a couple of years without a lick of trouble. :o

[Chuck Irby]

Thanx for that info Dave. I didn't particularly like the looks of that system either. Per Tim, I'm sure it works well. I just didn't like it's looks.

[daveeisler]

I did something most of you will not like , but after a carefull study of my machine I did it, I welded with a tig weld and made sure that I had a strong rubber mount on the motor support. The idea for this came from the factory, and yes it was a suprise to me that they would weld, but so far Iam very happy with this.I am not worried about cracking at all.

[Harry_S.]

Just a recollection. Years and years ago, when I was messing with Bensens', whenever I tore down the Mac after a seizure, I would clean and repaint the case. I was using a high-temp paint formulated for furnaces. It was brushed on and looked terrible but when it dried, it was smooth as glass and had a semi-gloss to it. Comes in colors too.

[Chuck Irby]

Dave,

More info please. I am very interested in the possibility of welding the three pieces together.

A few questions please:

1. What did the factory say?
2. What tig wire did you use?
3. Did the factory recommend the wire to use?
4. How many running hours since you did this?
5. What engine is it on?
6. Did you make the weld continuous all the way around each of the four joints? (I realize that you tacked them in at least three places before welding to prevent movement)

Thanks for this input Dave

Chuck

[daveeisler]

It was Doug Smith at Aircommand who first told me to weld then I was on the phone with a Rotax Rep. who also said it was o.k. to weld they both agreed on the tig, I do not know any more about what tig is you should call Doug, I do know that it does go all around the seam.My engine is a 582, it has 16 hrs. since . It is important to have a good thick rubber mount. to absorb the vibration. Dave

[gyropilot]

Dave,

I hate to be a nay sayer and I certainly hope I'm wrong, but with that solidly welded exhaust system attached to your 582, I think you'll be looking at some cracks sooner or later. Hopefully you'll catch the cracks early before something bad happens. The 16 hours of run time so far is not long enough to evaluate whether these solid welds were a good idea. Please update us at 100, 200, and 300 hours of flight time.

The fact that you have part of the exhaust system supported somewhere with thick rubber bushings (which is itself the proper way to support the system) doesn't solve a potential cracking problem. You still have a huge mass of thin metal *solidly* attached to the engine (via the exhaust manifold), and those engine vibrations will be trying to shake everything apart. By welding the exhaust sections together, you've effectively concentrated the vibrations somewhere in the system (probably the exhaust manifold) and failure is inevitable. I believe there was an article about this very subject in Kitplanes recently.

Think about this: Why would Rotax go through all of the trouble to design and specify all those flexible joints, hooks, and springs, when it would be a lot more simple and convenient for everyone to simply weld everything together? Oh wait... I know... it's so they can sell more parts (springs)... right? :)

Good luck to ya buddy!

John L.

[gyropilot]

Dave,

In 1987, Rotax released Service Bulletin 11 UL 87/E: "Exhaust Systems for Rotax 2-Stroke Engines. In it they explained how they went from a *single* ball joint to *two* separate ball joints in the exhaust system to reduce breakage problems. Makes you wonder how good *no* ball joint would be???

From the Service Bulletin:

Problem:
--------
- The weight of the muffler itself and the acceleration forces impose load on the exhaust manifold and inlet cone.

- Depending on engine installation, engine vibrations are transmitted to the exhaust muffler.

Tests with a double ball joint showed that this solution means a sensible improvement interrupting transfer of engine vibrations to the muffler.

The lifetime of the exhaust systems herewith is noticeably increased.

Also, in Service Bulletin SI 9 UL 91-E, which covered 2-stroke engine installation, Rotax stated:

The exhaust system is to be mounted on vibration-damping elements and secured against loss.

Take care that the ball joints are not under tension.

All ball joints should be lubricated regularly with heat-resisting grease (e.g. LOCI’ITE Anti- Seize, Rotax part no. 297 431) to allow them to move freely and thus avoid breakage of the muffler system.

That pretty much says it all I think.

John L.

[Doug Riley]

I'm with John L. on this one. Cracking at some point along the megaphone pipe is fairly common. Poke around a flyin and you'll see welds at various spots on this pipe that became necessary because of cracks.

[Chuck Irby]

Okay Dirty Harry and John Landry, I know you told me so, and I thought you were correct. Well, you were.

Before I flew today, I ran the engine and let it cool off three times before I flew. Each time I got it hot enough so that the paint started smoking.

I flew it for 45 minutes. Look at it now.

[Chuck Irby]

Pic 2

[Chuck Irby]

Pic 3: My Sweet Little Baby

[daveeisler]

I am still concerned about crack's in the exh. and I look for them before and after each flight , I know I listened to the pros. but I still have my concerns and I will keep all of you posted as to when ( in hours ) a crack happens. I hope it is in the muffler and not on the engine as I hear is possible.

[GyroRon]

Chuck you need to wash that gyro! I will tell you my secret formula if you email me in private

[Caribean_gyro]

I suggest ceramic coatting. We did it in a hirth engine and it still shinning. Ceramic will withhstand 2000 degrees. The guy we use had only chrome look alike or black.

Chuck P.

[Chuck Irby]

Hello Caribean Gyro,

Welcome to the forum and thanks for the advice about the ceramic coating.

Do us a favor and go back to your profile page and show your full name, your age and place of residence. It is a requirement of the forum that you do this. Besides, we all would like to know more about you.

Thanks again,

Chuck

[Chuck Irby]

Ron, How can you tell it's dirty from the picture?

[GyroRon]

Chuck I can just tell. If I had it for a few hours It would look new again, especially the engine!

[Chuck Irby]

Ron, a ultralight guy at the airport yesterday told me that he had read on his forum that I would get more power from the Rotax if I did away with the silencer. True, or False?

[GyroRon]

The muffler??? Oh you must be talking about the intake silencer............

Yes he is right.

But it wouldn't be much of a power gain. Maybe one to two horses. You already got a lot more power than most Single place Dominators.

Most of the engine noise on a Rotax comes from the prop and then the intake. I would leave the silencer on there.

[Chuck Irby]

No, the intake.

[Chuck Irby]

Okay, we're back on the same page now. In a way, I would like to get rid of the silencer though. It would make the carburators much easier to get to.

[GyroRon]

If you take it off I want it! and very important, you will have to re jet the carbs if you take that off. DO NOT FLY with it off without rejetting first or you will burn up your engine, it will be too lean

[Chuck Irby]

Gotcha, Thanx Ron.

[robertstodaro]

here's one more.

ceramic coated silver by" American Coatings"

in Humble Tx.

these guys normally coat Exaust headers for high performance engines.

this stuff does not burn off but you can take it off with a scotch brite pad.

the manifold and muff were rusted and pited when I gave it to them and it came out beautifull

[Chuck Irby]

Robert,
Thanx for that info. I will file it with the other info. Then when I can't fly for a couple of weeks, due to weather, I'll send it off to someone for coating.

[robertstodaro]

Other side, not bad for a $2000.oo machine, huh?

[Chuck Irby]

Robert, post a pic of the entire machine.

[robertstodaro]

sold!

[Chuck Irby]

That's very nice Robert. Would you care to get your money back?