I just thought a post on here would be good to find out where people are getting there mufflers or how they make them. A muffler is one part of doing a conversion that can stop some one from doing a conversion and go out and pay big money for a engine. I have some good ides but have not tried them yet. In the passed I pick up my mufflers from a place that is no longer around. Witch sucks. So lets here what you do for a muffler on your conversions.

Paul

You can try Carr Precision and/or www.lambertsrc.com. I don't know of any others at the moment that are making mufflers/parts for conversion engines. Actually due to a health problem, I don't think Lambert's is making them anymore, though he might have one already in stock for you so it is worth checking.

I usually just cut the stock muffler apart and gut it. If it is large, I cut it down to size, weld a piece of thin steel over the opening, and weld outlet tube(s) into that. They seem to be lighter actually than purpose made aluminum mufflers.

I had a bad computer crash and haven't re-loaded all my pics yet, so sorry I don't have some good ones to post. Here though, is one of the muffler I made for my big Fokker Dr1. This one was more involved as I needed it to be narrow. I took a piece of automotive muffler tubing, squashed it flatter, welded endplates on it, (one of them with two outlet tubes), welded in anti squash tubes in the mounting holes, and cut an opening for the exhaust port. Admittedly this was pretty involved; most of the ones I make are pretty simple to do. Just don't try to use regular solder nor even the Sta-Brite Silver Solder they sell at hardware stores. It will melt instantly. You need to use either real silver solder or braze, (very expensive), steel, or bronze braze.

AV8TOR

That looks good. What about the opening? How big must the exit hold be? I cut one down but made the exit hole to small. I was only getting about 6000 rpms out of the engine. I pick up and b&b and just used that on a 25cc engine. I have some aluminum square tubing that I was going to try to make some out of. and I was going to try alumoweld and see how that will work. but not sure on how hot the muffler gets.
Paul

Well, the exhaust gases run around 1200 degrees Farenheit on a properly tuned engine. The muffler itself won't reach that, but close on a long, high throttle run especially at low airspeeds.

I use two outlets of at least 1/2" i.d. on 25/30 cc engines. Bigger is louder but better for power. On larger engines I use correspondingly larger tubing. Around 3/4" for 50+ cc engines.

AV8TOR

Another option is to go to the Mac Products website. They have the mounting hole dimensions for all their tuned pipe headers, and what engines they fit. Then you can see if a relatively inexpensive muffler for a DLE, RCGF, or one of the other "alphabet" engines from China will fit.

AV8TOR

Do you think the muffler gets over 715F?

I cant seem to find a Mac Products website

Yes, I would have to say at least parts of the muffler consistently get over 750 degrees when the engine is run at full throttle.

That Mac Products page can be hard to find for some reason. Here it is: www.macspro.com/

AV8TOR

I was going to try weling up a muffler with Alumioweld. It has a melting point of 715F. That was the idea I had. I am going to try to test it and see if it will work just for fun. I mite put cooling fens on it to see if it will keep it below that.
Should be fun to try..

I tried some of those low temp aluminum brazing / soldering materials without success. Had trouble fixturing the muffler during assembly as aluminum conducts heat so well it was easy to disassemble previous welds doing the next weld. Once assembled, welds quickly failed. When I work with aluminum these days, I just have it TIG welded by a pro and the cost is still less than a commercial product. Maybe you will have better luck than I did.

Steel is much easier to work with and is easily welded with an oxy / acetyl torch using steel filler rod. When I can find it, I'll post a photo of one muffler I made for a scale Zero.

Man I would love to have a Tig welder!! Just can't begin to justify the cost for how little I would actually use it.

AV8TOR

Me too

I have had success with the alumaweld by making the muffler fit together mechanically. I will use overlap joints and screws to secure them. I typically use thin wall rectangular aluminum and only have to secure the ends. Make sure you use crush tubes for the fastener holes. The problem with the muffler coming apart is not the with the braze, but with the vibration. Good luck, red

How about the heat? Does the Alumiweld hold up with the heat? If so I am going to play :-)

I use a product called HTS2000. Google this and all your questions will be answered. As the video shows, cleaning and tinning is the most important step in the procedure. I also only use MAPP gas. Good luck, red

I am going through the same process of deciding on a muffler configuration for a converted Poulan 46.

I am planning on just brazing the old hole shut (hoping to be-able to braze just with a mapp swirling torch), and then adding in a few pipes. Should I go with anything specific for these pipes (i.e. copper plumbing, electrical conduit etc.)?

I plan on doing this soon any will update with news.

In time, I may try to make something else. I am thinking of going with thin gauge steel(aluminum seems difficult to stick together and not much lighter if light steel is used) and making something simple and efficient. The part I am having the hardest time conceptualizing is how to make the header work out. Solid steel stock as a header flange seems like it would work simply but would perhaps be too heavy. Any ideas on making a nice little header for a simple expansion chamber steel muffler?

AV8TOR,
"I usually just cut the stock muffler apart and gut it. If it is large, I cut it down to size, weld a piece of thin steel over the opening, and weld outlet tube(s) into that."

Why do you cut down the stock muffler expansion chamber? I was under the impression that larger expansion chamber = more power while maintaining silencing capabilities. I know from your posts that you don't mind noise but wouldn't a larger chamber still help with power?

I was under the impression that that was the whole reason not to use the stock saw silencer (other than the small opening) because they are smaller in volume than is ideal. (what is it, something like at least 10 times the cylinder bore is better?). I actually considered using an old muffler from a larger chainsaw, but perhaps that is not the way to go... maybe should go the automotive muffler tubing route. (although I do like the idea of something even lighter like a mousse can or similar, if i can find a way to easily braze/ hard solder it with just a mapp torch.

I don't worry too much about the volume as long as the exits are large enough. But then again as you mentioned noise is not an issue for me. I often convert leaf blower engines, and they tend to have huge mufflers that are 6" or more long and very heavy as well. These are the ones I cut down, gut, and then cap and add exit tubes. I generally use 1/2" or 3/4" copper tubing. It brazes well. In the past I have used thin wall K & S brass tubing, but it is really thin and tough to braze. It really should be silver soldered or silver brazed, but that's expensive!

AV8TOR

It has to fit on an airplane and be light, both of which are problems with the OEM mufflers.


That would be 10 times the cylinder displacement. That is a recommended rule of thumb minimum for a quiet muffler, which isn't really what a large majority of model aircraft mufflers are. Along with volume you need to be tuning tube lengths and using baffles if you want to really quiet an engine down and not hurt power output too much.


Mark

Here are the photos I promised awhile back. This muffler, made in 2007 and still in service today is all steel construction and was assembled from cut steel flat stock. The area where it bolts to the engine is 1/8" thick and the balance of the muffler is relatively thin stock though I no longer remember the thickness. The exhaust pipe is a cut off table leg. Note there is a support strap to bolt to a motor mount bolt. The notch is there to clear another mounting bolt .... I think. The whole thing was oxy / acetylene stick welded and the black was BBQ grill or header paint, again I no longer remember for sure. This is used on a 3mm 53 in a Yellow Aircraft Zero and it really wasn't as heavy as I expected it to be. Not a problem on a short nosed Zero as I still had to add nose weight.

I would go with steel again unless I needed a super light muffler then if I couldn't fabricate one, I would have a company such as Jtec build a custom muffler which I have done several times.

Sorry no it does not. It will melt. Consiter using steel and brazing it with a map gas torch. If you use thin steel, like food cans and electrical conduit it will work. Also look at beach furniture tubing. Also look at making adapters for replacement mufflers for lawn mowers.

Could a MIG welder work for the steel mufflers? Lots of people have these at home to beg, borrow or steal or whatever, for a beer even. They are much cheaper than TIG and are ok for thin steel, I did some body work with mine on an old van. I made a couple of mufflers for glow, which runs cooler. Everything was a .001" press fit out of aluminum.

If you're fairly good with a Mig welder you can weld the thin steel that is good for a muffler, but it's not easy. Gas welding or brazing is better, as mentioned.

AV8TOR

You can MIG weld thin aluminum but it would be a real chore .... pain in the arse would be a better description. I certainly wouldn't expect attractive welds unless you have a lot of experience. If I was making an aluminum muffler and I didn't have the proper equipment and knowledge to use it, I would pay someone to TIG weld up a muffler before doing it myself. I wouldn't even MIG weld thin steel as it is so easy to oxy-acetylene weld thin steel using a bit of filler rod. Note I say weld and not braze as it is a much simpler process than brazing along with being lighter and stronger. Any filler rod used goes 100% to the weld joint where with a braze, the filler material flows in a rather uncontrolled manner, unless lap or similar joints can be provided. The welds are also good looking with minimal to no cleanup required. Every corner on the muffler shown in post 20 is a butt weld and other than brushing off a bit of oxidation before paint, there was almost no other cleanup.

Gas welding with steel filler rod is how I make all my mufflers. And I have a good Miller Mig welder.....

AV8TOR