True tunned pipe length

[HeadSmess]

oooh, thats a thought, innit? paper and compressed air even! behaves a little bit differently to steel but...hmmm...

i tried brazing once too... dont butt braze! it lasts all of...ten minutes. i meant to cut tags and do proper lap joins but yeah...work. effort. yuk.

the smoother the bends the better for flow. the pressure waves dont care, but the gas flowing DOES.

 

[FurryOnTheInside]

oooh, thats a thought, innit? paper and compressed air even! behaves a little bit differently to steel but...hmmm...

i tried brazing once too... dont butt braze! it lasts all of...ten minutes. i meant to cut tags and do proper lap joins but yeah...work. effort. yuk.

the smoother the bends the better for flow. the pressure waves dont care, but the gas flowing DOES.

Plastic bags and sellotape? Inflate with a bicycle pump?

So you just bend the edges a bit so the sides are separated, file them flat and TIG weld right along the outside edges? What gauge of mild steel sheet do you need to use, and how to connect to the pressure washer?

 

[Arty]

I'm in talks currently to have an actual exhaust company make a run of pipe's for our bike's for the go fast guys and street performers LOL.anyway this will be engineired and designed by a friend and manufactured by his company if I can do a small run,So i'm doing the market survey currently and curious how many folks on here would be interested in a Quality bolt on pipe that will actually work?

I'm interested!!

 

[HeadSmess]

you do need something reasonably stiff, ie, non elastic( no plastic bags!) or its gunna be pointless. you could probably lay a pipe out using conical sections like i do with paper(180GSM...use heavy stuff! as heavy as your printer can take!), then just squash it flat? (why dont i ever think of these things at the time?)

yep, the edges need to be rolled if you want the pipe to pop out "round". laying them side to side stretches the weld out which breaks. thats why i gave up. having to reweld the seam every ten seconds. pre-bending them means the weld is in pure tension, not being cracked open from the inside. transitions between tapers and parallel sections also need to be smoothed out, or you get bad kinks there.

most sheet metal workers should have a little doodad for rolling the edges neatly...

um. the thinnner, the better! then you get that "ball bearing in a tin" sound! and its lighter. easy to cut out with tinsnips rather than the nibbler or bandsaw... less pressure to inflate...

theres meant to be a specific steel intended for pressing/deep drawing, but is it worth the extra expense?

i made all my pipes out of whatever i could lay my hands on... anything less than 0.8mm is impossible to weld with a cheap chinese TIG welder. that set my limit. and 1.2mm wall pipe etc for the header section (make it a slip joint with springs like a real bike pipe, or it will quickly rattle itself to pieces at the flange. the whole pipe needs to be supported on springs/rubber mounts.)

the welding, and the attaching to the pressure washer are the challenges you have to sort out yourself . i made a little threaded brass thingy so i just push the pressure washer hose into that instead of the handpiece...


if someone pulls it off properly, i wanna see!

oh yeah. they dont get that hot either, when theyre running.

everyone always asked if i burnt myself on this... no. i could hold my hand on it during a good WOT thrash.

i preferred the older twostroke wizard v3 over v5... the pipes just looked... pipey-er?

and jamming the stinger right up inside the reversion cone makes them quiet. it HAS to be past the halfway mark. though adding a muffler helps

 

[Deleted member 12676]

I've been looking over what was thought to be the correct rules for pipe design back in the early 70's. Just out of curiosity sake, like to get a historical perspective.
It's obvious that in 1972 Gordon Jennings was stepping off of Blairs 1970 pipe design recommendations.
He varied greatly.
One example is that Blair said that bellys up to 4.5 times the diameter of the header had been successfully used.
Jennings said 2.5x was the maximum.
I think the graph I have about 45% down this page tells the truth of diminishing returns as the belly gets larger: http://www.dragonfly75.com/motorbike/ECtheory.html
So I generally recommend not going over 3x.
Blair said the tuned length is to the end of the baffle and Jennings said it was to halfway down the baffle if the baffle extended to a point.
Here's my write-up opinion of Jennings recommendations: http://www.dragonfly75.com/motorbike/Jennings.html
and access to my spreadsheet using his formulas. The data in the spreadsheet was from the DT250 he used as an example in his 1972 magazine article about designing expansion chambers. You can see the ridiculous length of 16" for the belly. wow!

 

[Street Ryderz]

You need to look at what design's are working today NOT in 1972,We use Blair's and Jennings formulas to see what it's all based on and figure out how they play into today's pipe design's then see how they can be tweeked yet.Alot of folks right now ARE using large belly,steep baffle angle,short header into long covergent of course the big belly and small dia stinger with great results 70+ mph under 11 grand and lasting.Then there are even more people using the MZ 65 pipe as pictured below on a basicly stock kit and 36t gear doing 50+ 55 if they clean it up.This pipe is also a large belly pipe but with equal diverging and converging angles a bit larger stinger and a longer header.The next pipe is what I am currently running and it's a great pipe it's in between the above two.

This is the MZ pipe

Then My current pipe,How I made the header and fitted is on this site.

 

[FurryOnTheInside]

Alot of folks right now ARE using large belly,steep baffle angle

That's how my Aprilia RS50 pipe is shaped. It has about 4" OD belly (I can only measure the outside) and a 1" ID header. The baffle cone is steep, and with the wide belly this pipe's looks are not stealthy, so I think it will work best for my upcoming shifter (trail bike) build rather than my stealthy single speed (street bike) first build.

I would love to have a 3" belly and long/multiple stage baffle for the single speed but I don't have a lot of metalworking tools and materials, and I want to keep things simple so I don't have to pay too much for welding.
I value the stealth of a narrow pipe so I don't mind seeing what improvement over stock I can get using a narrower pipe perhaps only as wide as the stock muffler (2") and with just a single stage long/shallow baffle cone.
Whatever pipe gives the best boost in power it still has to (physically fit on and) suit the bike.