Maximum Quiet.....

[Deleted member 12676]

To quiet it down just plug the stinger with JBWeld and then drill a hole in it to reduce the stinger size. Don't go any smaller than 11/32"

 

[Fabian]

Now that's my kind of muffler, but your bike might have even more stage presence if fitted with twin mufflers and exhaust flappers.

Maybe you could paint your bike yellow and throw some Caterpillar decals on it !!!

 

[bigoilbob]

Now that this thread has the attention of some of the more clever forum members, I'm going to exploit it to ask my old question again. What is a practical way to further quiet a stock GX35? Might be more help than you realize, as your method might be more generally applicable to other small 4 strokes. GX35's are good for what they are, but my build is a tandem, and I would like for the stoker to have a pleasant ride.

 

[geebt48cc]

AWESOME!~ It's even aerodynamic also!!!!!!!!!~ You've got to send this to Jeff Foxworthy................

 

[HeadSmess]

two things with good muffler design... attenuation and flow

we all know about blowing across the top of a bottle. its called a cavity resonator.

so get a pipe, say the stinger.

you drill one hole in it. you encase it in a larger diameter pipe, so you end up with a chamber around the stinger pipe, which the exhaust doesnt flow through (unlike most peoples concept of mufflers). instead, it resonates at a specific frequency determined by the chamber dimensions, hole size, number of holes, etc.

so, ive made noise? how does that work? the sound waves are hopefully matched in frequency with the sound waves coming down the exhaust. matched in frequency, but opposed in PHASE.

two opposing signals CANCELS. so, you attenuate that frequency. it gets cut out of the sound spectrum.


so, by combining several of these chambers down the pipe, you can attenuate a fairly large range of frequencies.


then, a take more commonly used in large auto mufflers, that are getting extremely effective these days, is to split the flow into two paths. one is slightly longer than the other.

when the sound waves emerge, they match in frequency, but, depending on temperature and frequency and length, should be out of phase.

once again cancelling.


baffles do work, theyre the standard method, but they arent as effective as using sound itself as your friend

 

[bigoilbob]

Thanks HeadSmess;

Your idea has potential, but I'm not a welder. My ideal solution would be a bolt on replacement for the little GX35 muffler.

 

[Deleted member 12676]

You can make an excellent silencer by following the plans on my site. But the cheapest easiest to make silencer is by using two food cans of different sizes. Drill small holes in the sides of the smaller can. Clamp it onto the exhaust pipe. Drill small holes in the end of the larger can. Put metal scouring pad into it and clamp it over the smaller can. I used this setup on my Husqvarna CR125 which I rode on trails adjoining my neighborhood to keep the neighbors from calling the cops on me. works good.

About sound waves "cancelling" each other;
1. when waves meet their two amplitudes momentarily combine, not subtract.
2. opposing waves just go thru each other like two ghosts. they don't cancel each other out.
Silencers work by spreading out the exhaust pulse over time.

 

[HeadSmess]

sorry jag, but physics agrees with me...


http://www.uaudio.com/blog/understanding-audio-phase/


you really need to play with a microphone in front of a speaker... or a guitar... or look into negative versus positive feedback in amplifier design...

it really is amazing with two speakers what types of sounds you can get, just by moving the mic around. and how some spots dont do anything at all.



http://recordingdope.typepad.com/my_weblog/phase-and-phase-cancellation/


in fact a common guitar effect is a "phaser"...


cooinciding peaks and troughs accentuate or boost.

opposing peaks and troughs cancel.


http://www.mediacollege.com/audio/01/wave-interaction.html


strangely, light behaves much the same way, or else lasers wouldnt work... at the same time light just plays silly buggers


https://en.wikipedia.org/wiki/Double-slit_experiment



ever been around a radio that gets all staticy when someone moves to a certain point? or how you gotta move the aerial only half an inch and the signal vanishes? wave effects, cancelling and accenting... a web of nodes, all over the place. the locations can be figured out with mathematics... waves do follow simple laws after all. just like finding the epicentres of earthquakes. just like two speakers and a microphone.


oh. and play with a ripple tank. watch water flowing...etc

see how it all fits together like music? music of the spheres had the frequencies for that somewhere once...

 

[HeadSmess]

completely off topic, but the most interesting use of interference patterns in waves is holographic photography.

http://www.imagesco.com/articles/holography/HowToShootHolograms01.html



i will agree with the fact that the main intention of a silencer is to spread the pulse out. the more steady the exhaust stream, the less vibration. noise is vibration.

 

[bigoilbob]

Thanks Jaguar, I'll find your site and look at it. Biggest challenge for me would be making the appropriate connections, mounting properly, and keeping my forced air cooling capacity.

But FYI, you are correct on (1), not so much on (2). (2) is how sound cancelling (as opposed to muffling) devices work - the opposing waves do, in fact, cancel each other out. Tuning HeadSmess's device might be a challenge, but HeadSmess is theoretically right.