Tangential mufflers vs. tuned headers and flow-through

[plncraze]

It does work! Thanks. The reason I was curious about this is the homemade fiberglass packing mufflers have sometimes come apart and blocked exhaust gasses on engines and this design might be a little better. Thanks for sharing

 

[rv7charlie]

With rotaries, not sometimes. *Always.* But please tread cautiously if you build this design. As I said, the prototype quickly spun all its discs into a tight stack. If care isn't taken with structural issues, there's a big risk of completely blocking the exhaust. The Mistral blocked muffler incident wasn't packing (a rotary would shred that, quickly); it was the baffle material coming loose inside the muffler.

 

[plncraze]

I was thinking of having spacers to hold the spacing

 

[rv7charlie]

I should have included Ed's notes about his process. Here you go:

"Here are all the drawings I could find. Unfortunately, the old CAD program I used back then was discontinued and it had a proprietary drawing format. So these are just Jpg images I happened to make at one time.

The only thing is in some of the drawings I show an inner tube with holes its entire length, never incorporated that instead a long screw rod ran down the center and I used nuts to hold the discs in place – that didn’t work, so Tracy welded the nuts to the shaft which kept them in place, but did not keep some of them from spinning – ergo the Turbine sound.

I later decided the discs and outer tube were sufficint to suppress the noise yet permit good performance. Just never took the time to drill holes at the blade tips so they could be welded to the tube, thereby elminating/reducing their flexing under the shock wave and ultimately breaking.

I sometimes wish I had stuck with it, but life’s other projects were calling."

 

[plncraze]

I am thinking about using this in a recip rather than a rotary. I thought rotaries were known for high temps that would cook a normal exhaust. With tubing spacers separating the discs maybe this could be made to work. There is an old letter to Sport Aviation from Peter Garrison detailing his experience with a homemade muffler which had its gut come apart and almost killed the engine. He used fiberglass or stainless steel wool.

 

[rv7charlie]

If you're talking about a 2 stroke, it might work, at the expense of 2 stroke expansion chamber tuning. But I doubt it will do you much good on a 4 stroke. The whole point of Ed's design is stripping off those nasty high frequency harmonics generated by the 'snapping open' of the exhaust port, similar to a piston ported 2 stroke. Since 4 strokes have a very gradual (comparatively speaking) exhaust port opening, those harmonics aren't there.

 

[Sockmonkey]

Maybe one of these things? I don't know what it's called.

It sort of works like an exhaust header in reverse. Splitting the single pipe into three of different lengths that rejoin so the blast comes out in three staggered pops rather than one big BLAM.

 

[deskpilot]

Maybe one of these things? I don't know what it's called.

It sort of works like an exhaust header in reverse. Splitting the single pipe into three of different lengths that rejoin so the blast comes out in three staggered pops rather than one big BLAM.

Never heard of this but I like it. Fine in theory, but............

 

[Sockmonkey]

Never heard of this but I like it. Fine in theory, but............

Yeah I have no idea how well it would work, but it's easy enough for someone to test if they have a welder and some scrap tube laying around.
This is one of those things I'm sure must exist because it's too simple an idea for someone not to have thought of it before.

 

[poormansairforce]

Yeah I have no idea how well it would work, but it's easy enough for someone to test if they have a welder and some scrap tube laying around.
This is one of those things I'm sure must exist because it's too simple an idea for someone not to have thought of it before.

http://www.homebuiltairplanes.com/forums/showthread.php?t=29841&highlight=

 

[Sockmonkey]

http://www.homebuiltairplanes.com/forums/showthread.php?t=29841&highlight=

Well I guess great minds think alike. I hadn't thought about making the three pipes different diameters to account for the variation in impedance needed until after I'd posted it. Oopsy.

I'm remembering something that came up in my reading on pulsejets. It said that the pulsating flow travels like a sound wave which is why it can maintain speed around complex bends. You can make a Lockwood pulsejet in the shape of a pretzel and have it work fine, and the rat's nest of pipes that form exhaust headers don't slow things down significantly.

There's a lot of cross-pollination of ideas that could be done between mufflers, pulsejets, and silencers since they're all about trying to manage a blast in a desirable way.

This is giving me a lot of ideas. Gotta ponder...

Edit:
Having pondered a bit, assuming that it doesn't create significant back-pressure, I think a multi-tube like this might improve turbocharger performance since many smaller surges are much kinder to a turbine than a few big ones.