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Author Topic: Mufflers for engines with 360 degree exhaust porting  (Read 642 times)

Offline frank mccune

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Mufflers for engines with 360 degree exhaust porting
« on: April 02, 2022, 04:42:19 PM »
     How does one add a muffler to these types of engines?  In some cases, the engine mfg. may offer a muffler for that type of engine.  The engine in question is a Webra Mark II.  Perhaps a small worm gear type hose clamp would suffice.  Remember some Cox .049 engines used such  device.  I do not need much if any noise reduction, but rules are rules. Lol. A .15 Diesel is very quiet sans a muffer.

    Suggestions/comments

   Tia

   Frank

Offline Dave Hull

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Re: Mufflers for engines with 360 degree exhaust porting
« Reply #1 on: April 03, 2022, 02:03:04 AM »
Frank,

In general, you don't. But you could, which will take a bit of fabrication. It depends on what you have the tools to accomplish.

One of the Cox-type mufflers used a steel "washer" and a machined aluminum "bowl." If your Webra has a small shoulder between the finned cylinder and the aluminum case (I think the Mark II does) you could register a close-fit steel "washer" there. A section of tubing could form the outer diameter. A press-fit aluminum slug could close out the tube. Drill a hole for the sleeve to poke out....  Etc.

To avoid taking apart the engine every time you want to install/remove the muffler, you could make it like a clamshell--in two halves. Then your hose clamp idea could be used.

Another way to deal with this is to put it into a cowling, not on a profile. Then put a collector groove in the cowling and line it with an thin aluminum, probably J.B. Welded. A diesel exhaust is hot enough to char epoxy coated wood, so you need some kind of metal lining wherever you direct the exhaust.

Just "hiding" the exhaust helps. Imagine on a full fuselage plane that the cylinder is enclosed left and right and there is no direct path outwards towards either wingtip. Put a top (bottom) on it so only the tommy bar sticks thru. Can still be a wide-open channel front to back but it will knock down some of the bark.

A .15 sport diesel may not be too loud. A .15 racing diesel makes a lot of noise. And noise level is always in the ear of the beholder....

Dave

Offline Dan McEntee

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Re: Mufflers for engines with 360 degree exhaust porting
« Reply #2 on: April 03, 2022, 08:00:53 AM »
    I don't know how to begin going about searching for it, but I recall someone coming up with a muffler for Cox engines and it involved using bicycle inner tube section and some other easy fabrication. It sounded quite ingenious, but I never tried to make one. It was either on Stunhanger or Stuka Stunt, and that's about all I can remember.
  Type at you later,
   Dan McEntee
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Offline Dan McEntee

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Re: Mufflers for engines with 360 degree exhaust porting
« Reply #3 on: April 03, 2022, 07:51:17 PM »
   OK, Thanks to 944_Jim of this forum he succeeded where my brain cells failed. Check out this thread:

     https://www.coxengineforum.com/t5505-a-cheap-sport-muffler?highlight=DIY+muffler

  It's not pretty but should be very effective for  what you need. It has a pretty large volume and may take some experimenting with the exhaust tubes but I think this concept would be very adaptable to any engine of this type. With some work and imagination, I think it could be made to look better also.

   Type at you later,
   Dan McEntee
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Offline Dave Hull

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Re: Mufflers for engines with 360 degree exhaust porting
« Reply #4 on: April 04, 2022, 12:05:51 AM »
Interesting.....

Offline Dan McEntee

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Re: Mufflers for engines with 360 degree exhaust porting
« Reply #5 on: April 04, 2022, 08:07:17 AM »
Interesting.....

  Isn't it though?? I think it has some real possibilities for any Cox engine, and for any engine like Frank is describing. I think gluing the rubber discs with some kind of vulcanizing glue like is used for tire and tube repair instead of staples is in order, but leave one or two "exits for exhaust to find it's way out. I wonder how a series of holes around the metal collar , and then just open slits in the rubber would work?. Just kind of let exhaust pressure build up and then just "fart" it's way out!!! Depending on the size of the collar, that's a lot of volume in there and shouldn't restrict the engine much, if any at all. Warmer weather is coming around and time to find some cheap bicycle tubes and do some 'sperimentin'!! I think there is lots that can be done with this.
   Type at you later,
   Dan McEntee
AMA 28784
EAA  1038824
AMA 480405 (American Motorcyclist Association)

Offline Dave Hull

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Re: Mufflers for engines with 360 degree exhaust porting
« Reply #6 on: April 04, 2022, 11:45:32 PM »
Don't forget that with any kind of muffler on an engine with sub-piston induction, you are diluting the new fuel charge. So in addition to a power reduction due to increased backpressure, you are losing a secondary source of air. On the other hand, the little engines may stand the reduced cooling effects pretty well.


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