The Bucket Foundry

[WilDun]

Hes putting the stinger outlet in the pipe mid section. rather than the end of the baffle cone.

AHA! - this brain fade thing does have it's advantages too you know, life becomes more exciting all the time - I get to learn new concepts every day!!..... (sort of W.T.F. is this? what have they done with megaphones anyway?).

Seriously however, I haven't heard of this before, (may have seen pictures which I didn't really check out) - I guess it does a lot towards shortening the system at least. - still bulky compared to say, a straight pipe, but a step in the right direction!
Husa thanks for the clarification!

........ end will be plugged with exhaust gas being drawn off the center section.......

BTW, After checking, I found why I didn't understand what you meant - I misinterperated that statement as "the end will be plugged with exhaust gas" instead of "the end will be plugged....with exhaust gas being drawn..... etc "

Another question, - does that stinger coming out of the mid section extend into the tail section? or does it come directly from the mid section?

[WilDun]

........ end will be plugged with exhaust gas being drawn off the center section.......

After checking, I found why I didn't understand what you meant - I misinterperated that statement as "the end being plugged with exhaust gas" instead of "the end being plugged, with exhaust gas being drawn..... etc "

[Flettner]

directly off the mid section. very important to flare the outlet pipe (bell mouth) from the main pipe into the tail pipe. In a normal system this is done by the taper cone leading into the tail pipe.
This is important because there is a restriction (in my system, swapable) in the outlet pipe and you don't want a restriction further up the pipe doing the job instead. You will see.

[Frits Overmars]

AHA! - this brain fade thing does have it's advantages too you know, life becomes more exciting all the time

Ah yes, the three advantages of Alzheimer: you meet new people every day, you can hide your own easter eggs, and you meet new people every day .

[WilDun]

Ah yes, the three advantages of Alzheimer: you meet new people every day, you can hide your own easter eggs, and you meet new people every day .

Frits that's right, I'd forgotten what else there was .........

Neil, has anyone else tried this layout in Motocross etc. or is it all brand new?

[ken seeber]

Frits that's right, I'd forgotten what else there was .........

Neil, has anyone else tried this layout in Motocross etc. or is it all brand new?

Will,

The following is an extract from the Two Stroke Tuners Handbook by the late Gordon Jennings:

"These several difficulties should convince anyone that a different approach to the problem of effectively silencing the expansion chamber is required. Lacking a more effective solution to the problem, we may eventually be forced to revert to a straightforward muffler in place of the expansion chamber and live with the loss of power and performance that entails. I do not believe that will be necessary, as I stumbled upon a phenomenon a few years ago that meant very little at the time but now assumes major importance: The then-existing general racing regulations required that a motorcycle's exhaust system terminate at some point forward of the rearmost edge of the back tire, and I was planning to race a bike with its cylinders reversed to provide rear-facing exhaust ports (for reasons that were important, but not pertinent here). The only major flaw in this scheme was that even with the motorcycle built on a longish wheelbase and with its engine located well forward, there was not quite enough room for the exhaust pipes within the length allowed by the rules. The expansion chambers themselves would fit, but there was some 12-inches of outlet pipe left hanging back behind the rear tire, and not enough room to curl these outlet pipes back within the limit. While groping for a solution, I hit upon the idea of simply sliding them forward, inside the baffle cones. There, they would still function as pressure-bleed resisters, and further contemplation led me to the conclusion that the expansion chambers might even work better with their outlet pipes positioned inside. With the forward end of the outlet pipe located at the chamber's maximum diameter, ahead of the baffle-cone, there should be a somewhat stronger reflection from the baffle, and that might very well give the engine a somewhat better boost. Or so I thought.

Anyway, I gave the scheme a try, and while certain other modifications prevented drawing any absolute conclusions from the experiment, the bike did prove to be very fast, and it seemed certain that while my inside stingers might not offer any real power advantage, they probably were at least as effective as those attached in the more conventional manner. But that is not to say that I did not notice a difference - and the difference was in sound. With those inside outlet pipes, the typical expansion chamber crackle was very noticeably subdued. That made sense, as the chambers' outlet to atmosphere was taken from a point where the pulse was at its lowest amplitude - rather than from the high-pressure area at the tip of the baffle-cone.

More recently, I have been able to perform a series of tests using a dynamometer, to see if my inside-stinger idea (which, I had learned, was an idea also advanced by an obscure German researcher some several years earlier) had any real merit. An expansion chamber was constructed with its baffle-cone terminating in a clamp, to allow rapid changes in outlet pipes. and we tried pipes of different diameters and lengths, and moved them back and forth in the clamp to find the change in output as the outlet's forward end was advanced up the baffle-cone. The results were most interesting: There was absolutely no difference in power output with the outlet pipe in full-forward and full-back positions, but we did find a quite noticeable drop in power with the pipe's forward end pushed up to the approximately-halfway point in the baffle-cone. We also found that the same outlet pipe diameter produced optimum results no matter what the location, but that the system was rather less sensitive to outlet pipe length when the pipe's forward end was located an inch or so ahead of the baffle-cone's forward end. Finally, we found that the noise output with the forward-located outlet pipe was very much reduced: to about the same level as a conventional expansion chamber fitted with a bolt-on, fiberglass-packed muffler. I was, of course, a bit disappointed that my inside-stinger pipe did not show a big advantage in power over the conventional variety (there may be a slight broadening of the power curve, but the differences observed were too small to offer conclusive proof). Still, by that time, the sound-damping properties of the inside-stinger arrangement had become extremely important, as they could be used in conjunction with a low-resistance muffler, located farther downstream, to meet the AMA's new noise-limit rule without any loss of performance. For that reason, this idea - the creature, indirectly, of the AMA competition rules book - did prove to be a success, even if not in precisely the form I had anticipated."

Whilst Neil's tailpipe starts at the surface of the mid-section chamber, G Jennings had the tailpipe cantilevered or (sort of) freely suspended within the volume of the chamber.

What a great book it is.

[husaberg]

Will,



What a great book it is.

http://www.amrca.com/tech/tuners.pdf

[speedpro]

In buckets there has been a few bikes with the exhaust exiting the side of the pipe midsection. Neil is friends with one builder who did it. I've also built at least one pipe with the stinger supported in the centre of the exhaust cone and extended to where it meets the mid-section. As stated above, no obvious performance change but the noise was gone. In my case I was looking to make it more crash proof by getting the exhaust fully tucked under the bike and not extending around the swingarm to a muffler.

[WilDun]

Will,

The following is an extract from the Two Stroke Tuners Handbook by the late Gordon Jennings:
........What a great book it is.

Yes Ken, I remember reading that a long time ago - If that guy had lived in Britain instead of America, he would have been Sir Gordon Jennings! - I think he had a great way of getting the message across to the average two stroke tuner - without all the computer development coming from a department at Queens University run by Dr. Gordon Blair. Then there was the work of Walter Kaaden at MZ. who inadvertantly launched the Japanese into Orbit! when (apparently) his work was stolen by Ernst Degner and sold to Suzuki when he defected. - Not forgetting "our" Jan Thiel of course!

In buckets there has been a few bikes with the exhaust exiting the side of the pipe midsection. Neil is friends with one builder who did it. I've also built at least one pipe with the stinger supported in the centre of the exhaust cone and extended to where it meets the mid-section. As stated above, no obvious performance change but the noise was gone. In my case I was looking to make it more crash proof by getting the exhaust fully tucked under the bike and not extending around the swingarm to a muffler.

How the hell did I miss all this stuff? but then I completely lost all my enthusiasm and almost forgot about bikes for about 25 years or so after health problems and I'm glad to see something like this come up!

[WilDun]

In buckets there has been a few bikes with the exhaust exiting the side of the pipe midsection. Neil is friends with one builder who did it. I've also built at least one pipe with the stinger supported in the centre of the exhaust cone and extended to where it meets the mid-section. As stated above, no obvious performance change but the noise was gone. In my case I was looking to make it more crash proof by getting the exhaust fully tucked under the bike and not extending around the swingarm to a muffler.

How the hell did I miss all this stuff? but then I completely lost all my enthusiasm and almost forgot about bikes for about 25 years or so after health problems and I'm glad to see something like this come up!

[husaberg]

I have often wondered if the noise effect was real (as in measurable DB) or just a result of a different less objectionable frequency.
Or if it’s really a measurable and is actually the result of attenuation much like white noise is?
I always thought Roe and co were on to something with their original annular discharge silencers.
It’s a real shame there isn't a Dutch physicist with an interest in two strokes lurking about.

[husaberg]

I have often wondered if the noise effect was real (as in measurable DB) or just a result of a different less objectionable frequency.
Or if it’s really a measurable and is actually the result of attenuation much like white noise is?
I always thought Roe and co were on to something with their original annular discharge silencers.
http://yorkshireferret.blogspot.co.n...-silencer.html
It’s a real shame there isn't a Dutch physicist with an interest in two strokes lurking about.

[ken seeber]

It’s a real shame there isn't a Dutch physicist with an interest in two strokes lurking about.

Yeah Hooser, I am pretty sure you are referring to someone in particular. And fair enough, it's 1.00 pm in the land of tulips, wind turbines, bikes and dykes so surely he is awake by now...

[husaberg]

Yeah Hooser, I am pretty sure you are referring to someone in particular. And fair enough, it's 1.00 pm in the land of tulips, wind turbines, bikes and dykes so surely he is awake by now...

I know right, Gosh it was hard to find a pic with all four. Five if those two are more than just friends

[Frits Overmars]

I always thought Roe and co were on to something with their original annular discharge silencers.
http://yorkshireferret.blogspot.co.n...-silencer.html
It’s a real shame there isn't a Dutch physicist with an interest in two strokes lurking about.

Yeah Hooser, I am pretty sure you are referring to someone in particular. And fair enough, it's 1.00 pm in the land of tulips, wind turbines, bikes and dykes so surely he is awake by now...

On the presumptuous presumption that you're talking about me, no worries: I usually hit the sack after midnight: too much interesting things to read on internet forums, but I'm done sleeping at 6. In fact, the older I get, the less sleep I seem to need.
And on the subject of silencers: I did try some Roe annular discharge silencers but I wasn't impressed with the results.
I also tried Flettner's plan of an exit at the pipe belly (which I used to call a stoma when there was no-one around).
Back then I rode a Kawa H2 (for you youngsters: a 750 cc two-stroke triple) with a couple of mods, like three 38 mm Mikunis and a homebrewn exhaust system, consisting of three conventional expansion chambers, but without the tailpipes. Instead they had exits at their bellies that came together in a big empty pot,
120 mm Ø x 350 mm length, under the engine, in front of the rear tire.
My mates still made me ride at the rear of the group on our sunday tours, but its tin-can sound was a little quieter than three stingers with absorbtion dampers.