Designing and manufacturing of exhaust pipes

[Grumph]

Your English is pretty good. Your work is too.
I like the furnace used for annealing/softening prior to hydroforming. I used an LPG torch which is slower to get the job done.

Layout can be quite simple. I did a straight centerline drawing full size of what i wanted. Marked off every 20mm with measured diameters. Calculated 1/2 Pi.D
and wrote it alongside. Then a full size drawing with the curved centerline i wanted,lines drawn every 20mm square to the centerline. Mark off the points on those lines representing the calculated outside shape and join the dots. Fair the shape to taste.

[Tunisti]

Thanks!

That hand drawing way of your´s is exactly the same that I used to do (though those 20mm steps may be bit large, when doing tight corners/having rapidly expanding sections). But if something can be done with CAD softwares, it has to be done! Not only is it cool, but you can also do lots of parameters in the models, which make the needed modifications fast and easy.

Oxy-acetylene torch would be great to have, since it´d be easy to anneal those MAG welds into soft state. Somehow my propane torch isn´t powerful enough to give the sufficient amount of heat for annealing the pipe. Even though it is rated at 6kg/hr propane consumption... The annealing of the welds only would also let the sheet metal itself to stay into bit more durable state. The cracking of pipe happens at much lower pressure when the whole pipe has been annealed. But, it´s a compromise bethween the absence of wrinkles and pipe´s tendency to crack... With TIG welds there were no problems with wrinkles nor pipe cracking, and the welding itself was a pleasure as well.

Though I´m newbie, I thought whether this topic should be renamed as "Designing and manufacturing of exhaust pipes" etc.?

[Grumph]

Thanks!

That hand drawing way of your´s is exactly the same that I used to do (though those 20mm steps may be bit large, when doing tight corners/having rapidly expanding sections). But if something can be done with CAD softwares, it has to be done! Not only is it cool, but you can also do lots of parameters in the models, which make the needed modifications fast and easy.

Oxy-acetylene torch would be great to have, since it´d be easy to anneal those MAG welds into soft state. Somehow my propane torch isn´t powerful enough to give the sufficient amount of heat for annealing the pipe. Even though it is rated at 6kg/hr propane consumption... The annealing of the welds only would also let the sheet metal itself to stay into bit more durable state. The cracking of pipe happens at much lower pressure when the whole pipe has been annealed. But, it´s a compromise bethween the absence of wrinkles and pipe´s tendency to crack... With TIG welds there were no problems with wrinkles nor pipe cracking, and the welding itself was a pleasure as well.

Though I´m newbie, I thought whether this topic should be renamed as "Designing and manufacturing of exhaust pipes" etc.?

Yes, I'm disappointed in Sketchy too - it's not just for 2 strokes, as you've seen elsewhere i've just done a set of four curved megaphones for a CB350/4.

Despite the more sophisticated computer based methods available for sheet metal layout, some of us (read, a poor pensioner...) don't even have good internet, let alone anything as sophisticated as a modern phone...
However, once i'd done a full size drawing of what I wanted i was happy to turn it over to a company here - ProMetal Industries in ChCh - who scanned it.
Initially as it was too big for their scanner it was 2 piece but some juggling on their part saw it one piece and in form for laser cutting. As I wanted multiples cut it was much easier and cheaper to do it that way. Bradley in The GP Motorcycle Vol 2 recommends getting multiples cut to practise on. I'd endorse this fully as it will be several attempts before you get something usable....

Pipe cracking. What sort of pressures are you seeing ? Do you have a pressure gauge on your pump ? Oxy acetylene is Ok for annealing but like your Argon price, takes a lot of expensive gas....

[Sketchy_Racer]

Yes, I'm disappointed in Sketchy too - it's not just for 2 strokes......

You mean to tell me that there is anything other than 2 strokes ??

More than happy to change the title, I'm not sure I can do it so i'll PM a mod if I cant.

[Grumph]

You mean to tell me that there is anything other than 2 strokes ??

More than happy to change the title, I'm not sure I can do it so i'll PM a mod if I cant.

Much obliged....
What sort of pump arrangement are you looking to use ?

[Sketchy_Racer]

What sort of pump arrangement are you looking to use ?

At this stage I think I will start with using my little Karcher water blaster and make a push lock fitting like Tunisti has. I also have access to a big bastard water blaster if the Karcher doesn't have the power.

I'm chomping at the bit to give this hydroforming a go now that i've done a bit of research. Certainly seems that once the technique is sorted that it will be a lot less time and effort than making cone style chambers.

The hard part for me now is refining the design of the pipe itself. For the first one I am going to just use Frits formula but one day it would be great to make a pipe that has been designed specifically for the motor using engmod2t or the like

[Sketchy_Racer]

Thanks!

That hand drawing way of your´s is exactly the same that I used to do (though those 20mm steps may be bit large, when doing tight corners/having rapidly expanding sections). But if something can be done with CAD softwares, it has to be done! Not only is it cool, but you can also do lots of parameters in the models, which make the needed modifications fast and easy.

Oxy-acetylene torch would be great to have, since it´d be easy to anneal those MAG welds into soft state. Somehow my propane torch isn´t powerful enough to give the sufficient amount of heat for annealing the pipe. Even though it is rated at 6kg/hr propane consumption... The annealing of the welds only would also let the sheet metal itself to stay into bit more durable state. The cracking of pipe happens at much lower pressure when the whole pipe has been annealed. But, it´s a compromise bethween the absence of wrinkles and pipe´s tendency to crack... With TIG welds there were no problems with wrinkles nor pipe cracking, and the welding itself was a pleasure as well.

Though I´m newbie, I thought whether this topic should be renamed as "Designing and manufacturing of exhaust pipes" etc.?

Hi Tunisti,

Thanks for your post, very informative!

I really love your tool for making the curved edge on the metal, I will try make my own ones of those too.

I am really fortunate to work in a place where I have access to all welding forms so I think I am going to try gas welding first. Do you think it would still be a good idea to anneal the weld after or with gas welding is this not necessary?

[Grumph]

At this stage I think I will start with using my little Karcher water blaster and make a push lock fitting like Tunisti has. I also have access to a big bastard water blaster if the Karcher doesn't have the power.

I'm chomping at the bit to give this hydroforming a go now that i've done a bit of research. Certainly seems that once the technique is sorted that it will be a lot less time and effort than making cone style chambers.

The hard part for me now is refining the design of the pipe itself. For the first one I am going to just use Frits formula but one day it would be great to make a pipe that has been designed specifically for the motor using engmod2t or the like

If you can find a copy of Bradleys book, Vol 2, he goes into quite a bit of detail on how to set up a waterblaster incl a buffer chamber to avoid a too sudden pressure rise. Hand pump suits me very well. Very controllable.

[Lightbulb]

AutoDesk Cad 360 is free for individual home use and a business earning less than 100K US a year.
I am sure it can have a spread sheet driven drawing parameters in it. I know it can be done with Inventor and Autocad.
Neil

[AllanB]

Excellent thread and very impressive work. I am surprise a home water blaster can get up enough pressure.

[mr bucketracer]

Excellent thread and very impressive work. I am surprise a home water blaster can get up enough pressure.

i used to split the chambers with a water blaster , you watch for the last stretch of the sheat and try catch it in time lol , used a modified bottel jack in the end

[mr bucketracer]

here is the tool i made years ago works like a hammer, can run around a chamber in 2 or so mins , will clean it up and show later , here are 2 rs250 chambers that over blew up years ago , rusty but maybe a good start for my 300

[Tunisti]

Grumph:
I wouldn´t say that you need fast internet nor a fancy phone to have a decent (and free) CAD software. DesignSpark and DraftSight are free, at least that´s what I remember. I´ve been using quite a few: Solid Edge, AutoCAD, Inventor, SolidWorks and Catia. Ofcourse those all are student licenses for students in mechanical engineering. I´d say that the streching of the metal makes it really hard to use the Add-On for SolidWorks, mentioned in the opening post. I prefer Catia, but for a beginner I would suggest the DraftSight. But, I must say that I´m not really talented with any CAD software.

Pipe cracking & pressures: I think my Einhell pressure washer is rated at 160 bar, BUT it is old and I am certain that it won´t produce anything near that. I think something like 100-120 bar would be the maximum. Sometimes pipes won´t crack, even though the pressure is at "full rating". It is rather easy to regulate the pressure by carefully snapping the trigger. With good welds (=soft welds) and easy shapes there is no need to use the maximum pressure. Some make successful hydroformings with only 50-60 bar pressures.

You are right with that gas price thing, maybe propane+oxygen would be somewhat affordable compromise.

Sketchy_Racer: I think your Karcher will do just fine. I also think that there is no need at all to anneal weldings made with gas welder. If you are going to copy those pliers I´d suggest you to concentrate on the ergonomy and need of finger pressure. Those pliers of mine need a bit too much force and the handles get bit too close to each other while pressing. Try to make the tip in such a way, that instead of sharp edge it forms more like a smoot rounding. The lower tip is made of M6 bolt and the upper tip is modified with long M8 nut cutted in half. Don´t get too greedy with the widht of the tip, you´ll only get big problems when handling the corners.

[Grumph]

i used to split the chambers with a water blaster , you watch for the last stretch of the sheat and try catch it in time lol , used a modified bottel jack in the end

The tendency seems to be to use something with a lot of pump capacity - and then watch as it splits. As i said, the hand pumps are more controllable.

Edit - Sketchy, I'm mid 60's with a heart condition...Just went out and checked the pump, the telltale is sitting on 33bar which is from the last use.
Formed annealed 20g quite well at that. And i survived.......

[Sketchy_Racer]

Hand pumps sounds like hard work, i'm allergic to hard work.

I have an idea that might work, I was thinking that I could put an adjustable pressure relief valve on the fitting using a spring loaded plunger. I don't think I would bother with a pressure gauge for now.

With the pressure relief it would hopefully allow me to sneak up on the desired pressure without having to worry about splitting the seams uncontrollably