Designing and manufacturing of exhaust pipes

[Sketchy_Racer]

After reading some of the content in the ESE thread, I've become really inspired to take a closer look at hydroforming chambers. In particular for our NSR300s which we are currently using the Tyga chambers but are having lots of reliability issues with them and also I am sure that there are gains to be made.

So I had a good look at the link to the Pitlane thread that Husa put in ESE See Here For Link to Pitlane (http://www.pit-lane.biz/t3107-gp-125-250-why-hydroforming-is-not-as-good-as-welded-cones)

There are some gems of information there as well as a few photos which I've attached here. From what I have read so far there is a large importance placed on the smoothness of any of the transitions in the pipe. And sharp changes in angles will cause wrinkles when pumping it up. Second important detail is to roll the edge of the two halves of the pipe so that you can butt weld them. If you don't do this it will cause the pipe to try tear the weld apart when pumping it up. It seems that the general consensus is that gas welding the two halves gives the best results, probably something to do with the spread heat of gas welding that will help anneal the metal as you weld as opposed to tig welding which has a very intense but small area of heat which can cause the creation of a brittle martensitic structure in the steel if there is enough carbon content.

I have my sheet of steel turning up on Monday so will get straight into it. I am going to start with my first pipe using Frits Overmars guideline for the pipe design. I am very limited on time for this project (work and study is a killer!) so any input on the actual design would be much appreciated

For getting the flat pattern I am going to give a new feature in solidworks a try. In the 2015 version I have the ability to model the whole chamber as a surface then flatten that surface. This tool was developed for the textile industry where users need to flatten complex curves into 2d paters (think shoe manufactures getting leather cut as flat) So I am hoping that the same principle will apply for the flattening of the chambers.

[Bert]

Nice

We have been playing around with this concept again. Scottie use to have some amazing hydro formed pipes back when we first started buckets last century... He has built a cool tool to make the physical process a lot easier.
Anyway I was directed to
Ezin Hobeki - pipe designer software
Outside of doing some magic two stroke calcs - you can load in your own specs. It has a good hydroforming construction tool allowing you to generate what ever you like (DXF file output).
316304
cone designer
316305
A9 cad consuming the DXF output.
316306
After contacting Ezin he added in a little more flexibility so I could design four stroke megaphone (using the pipedesigner software and outputting to DXF files to tweak in A9Cad freeware).
Either send the DXF file to the water cutter or print out on paper and cut away....

[Drew]

Subscribing.

[190mech]

Glad to see this thread!I did a hydroformed tapered headpipe for a quite pipe design that needed extra length for lower RPM torque.I found that the bends form tighter than the pattern and must be adjusted because of this;
http://i639.photobucket.com/albums/uu112/190mech/Hydro1.jpg (http://s639.photobucket.com/user/190mech/media/Hydro1.jpg.html)

http://i639.photobucket.com/albums/uu112/190mech/Hydro2.jpg (http://s639.photobucket.com/user/190mech/media/Hydro2.jpg.html)

[Crasherfromwayback]

Love yer work.

[Grumph]

Ideally, you'd use deep drawing steel sheet. After much asking, it seems that it's no longer imported into NZ - at least for public consumption.
I finished up using bright mild 20G and annealing all over once it was welded.
I was looking for a way to mass produce them so investigated continuous arc welding at a company here in ChCh. Afrer truing up their wheels - and adding a fence to one wheel to keep the weld seam aligned with the edge...Fail. Even with the amps turned up to max the seams split.
So back to TIG...Which worked.

I used a hand pump. Marsheng on here imported a box of them. Used with a one way valve in line they work very well indeed. I'm pretty sure he's still got a couple of them if anyone is interested.
I also welded in fittings at each end. Steel pipe at the input end to suit the one way valve. A machined stub at the exit end tapped for a small lever tap.
Pump through till no air, close the tap and pump...Go back and reweld splits, resume as before....

[AllanB]

So you weld up the 'flat' unit then pressure fill it with water to get the roundness desired?

[Drew]

So you weld up the 'flat' unit then pressure fill it with water to get the roundness desired?

Seems easier than what I imagined hydroforming to be.

Now it makes sense where someone said to Chop the seam off after forming, and butt welding afterward.

[Sketchy_Racer]

After a little bit more research I have found some more notes and photos.

From the "Practical Machinist" forum


I visited Pete Gibson when he was in Romford, UK in 1994.

I flew all the way from South Africa so that I could learn how he hydroformed an exhaust. I will outline the common mistakes. I used this technique for about two years making racing 2-stroke exhausts.

Common misconception is that the process is dangerous. Water can't be compressed like a gas can, so all that will happen is that the water will fall out and make a mess.

The trick is working out what radius the exhaust will end up once it is formed. Trial and error will give you an idea what to allow for the radius tightening up.

You also need to allow about 2% extra for stretch during forming.

If you TIG weld, use thin mig wire to prevent porosity in the mild steel. Gas welding is preferable as the weld is not so hard after welding.

The edge of the two halves needs to be bent over using a bead roller or sheet metal Jenny. This gives you the correct joint for welding and what it will end up after forming, butt weld and not an edge weld if you welded them flat together.

Allow extra both ends for attaching the water pump and a bleed valve.

I used a old hydraulic jack which I cut in half and welded fitting on to the various inlet/outlet holes of the jack. I used an old motor cycle brake line as the hydraulic line. Only issue with this choice is it takes ages to fill the exhaust before it starts to form.

Fill the exhaust with water, and bleed all the air out using the bleed valve. Now you need to stop the large area expanding first by placing the exhaust in a hydraulic press between two steel plates.

Gradually expand the exhaust, making sure the small areas obtain correct shape before you fully expand the large section.

You will reach a point where the exhaust has taken final shape but has unacceptable wrinkles. This can be dressed out whilst under pressure with either a plastic THOR hammer or steel planishing hammer.

Heat can be applied to the wrinkles to make them expand out. You will need to drain the exhaust to apply heat, otherwise the water will soak the heat out. Once you have applied heat to the low spots, re pressurize the exhaust and the heated areas will expand first.

I also experimented with making steel dies for the large parallel section to give it better definition. Make two halves in the lathe and make them so that you can bolt the two halves together. This will give the exhaust better definition in the areas where the exhaust would normally end up with a radius.

[AllanB]

Very interesting method. Done well the final result looks impressive. It appears to be similar in 'work' to welding up a pile of cones. Any measurable difference in the final product on the bike?

[husaberg]

I stole this off the Pitlane thread where your photos came from
Howard should be contactable via a few sites I might ask him to post something more
The major points I gleaned were
The bending of the edges prior to joining
The amount of stretch
The banding just areas can only grow so much
The way he coaxes the ripples out.



I beg to differ! I have developed a technique (sort of a reverse engineering) that allows me to hold a tolerence of less than .5mm anywhere on the pipe. My hydroforming technique produces a ripple free pipe that does not have any sharp edges that can disrupt the wave. Even if a pipe is lazer cut and uses computer generated layout there is still an abrupt change in direction everytime the wave transitions from a straight section to a curved section.
I use simple tools a torch a pressure washer and a hammer. The metal I use is 19 gage .041 forming metal. The secret is in the design of template and how it is blown up. On the bottom of page 40 of this thread there is a picture of a pipe I built using this process.

Hydroforming is not easy but with good forethought and good craftsmanship along with good process results can be repeated with good consistancy. I use an accurate weigh scale to know exactly how much water is in the pipe so I can duplicate the volume of each pipe exactly. I use a lot of construction lines in the prototype stage and measure each line circumference to see how far off the drawing the pipe has stretched to. I then adjust the template accordingly until I get the results that match the drawing within .5mm circumference. I can also vary the volume with the same design to test different volumes. I record the weight so I know the exact volume of each pipe and test each design to find the sweetspot. It is both a science and an art

My investment in making a pipe is extremely low compared to a CAD designed stamp. A sheet of white cardboard is under a dollar and is what I invest in the template. My time of course is an investment but I would rather design a pipe than sit in a pub drinking beer complaining. I was taught how to hydroform by a very good friend by the name of Alex Mayes. He was a craftsman and reminds me a lot of Frits. Unfortunately he had a bad heart and he was a chain smoker. When he suddenly died I was left to either find another pipe builder or start making my own. By the way frits your first try at hydroforming looks surprisingly a lot like my first attempt. I have got very wet a few times and it took about a year before I could say my pipes were as good as Alexes pipes. I have probably made 200 sets of hydroformed pipes since and every time I finish a pipe I get excited to try it. I will gladly answer any questions if anyone wants to attempt it.

The difuser usually starts out as a 3 stage straight cone design because that is what my software spits out and that is how nmost pipe designs begin life. I make a full size straight line drawing of the actual finished pipe. I then use a french curve to blend the intersecting cones so as to make a smooth transition. Sometimes I blend the cones almost 1/3 of their entire lengths to make a more or less parabolic curve. I have found that a straight cone difuser at near the center section delivers the best powerband. A more parabolic continuous curve gives a more peaky power band with a little more peak horsepower. Just to let you know the template drawing is typically 1.5" smaller than the finished diameter. The metal stretches that much. That is the secret to getting very smooth finished products. Also to achieve high pressure in the pipe I use sleeves that exactly match the finish diameter of the center section. This only works on pipes that have a defined straight belly section. THe pipe expands into the sleeve allowing me to build pressure in the rest of the pipe to remove any ripples or dents. For a pressure source I use a standard piston type pressure washer with a standard wash handle fitted with a hydraulic fitting. It is vital that the handle be leak free and is able to control the flow. it is also vital that there be no pinholes. A lot of the time is spent with a pressurized pipe on your lap hammering away with a small ball peen to dolly out the ripples. With about 300 - 400 psi in the pipe it allows you to work dents and ripples by tapping around the dent. It is also vital (and may save your life) that you ensure there is no air at all in the pipe when blowing it up. Even a small trapped pocket of air can store enough energy to do serious damage if it were to rupture. With no air the rupture gets you wet, thats it! People ask me about the weld. If you can't weld then dont try to blow up a pipe. Practise and get good at welding with acetylene first. I have tried several types of filler rods and the best I have found by far is 19 gage "Mechanics" wire. Yes the stuff used to twist things together. it is cheap and most importantly it is malleable even when welded. The outside seam actually shrinks quite a lot so you need a soft weld that will shrink with the metal
I use 19 gage (.041") cold rolled steel ,nothing special.
I use a home made hand driven roller to roll the edge. I also use a small press that has an adjustable relief valve to allow the pipe to expand automatically in the press. The prssure setting depends on the size of the pipe . I press the pipe between two plates of steel covered with plywood. The press allows the entire pipe to expand evenly. Without it the center expands first and creates some horrible ripples. Everythin g is done cold. I do not recommend heating the pipe at all with any pressure in it.

The templates are made "old school" on a drafting board. I make a centerline using an aluminum yardstick bent roughly the shape of the bend of the pipe and mark it off in 1 inch segments. I transfer the measurements from a full scale straightline drawing. I connect the dots with a flexible curve. I number each segment on both the template and the drawing and transfere the construction lines to the metal for future reference

[Lightbulb]

Ideally, you'd use deep drawing steel sheet. After much asking, it seems that it's no longer imported into NZ - at least for public consumption.
I finished up using bright mild 20G and annealing all over once it was welded.
I was looking for a way to mass produce them so investigated continuous arc welding at a company here in ChCh. Afrer truing up their wheels - and adding a fence to one wheel to keep the weld seam aligned with the edge...Fail. Even with the amps turned up to max the seams split.
So back to TIG...Which worked.

I used a hand pump. Marsheng on here imported a box of them. Used with a one way valve in line they work very well indeed. I'm pretty sure he's still got a couple of them if anyone is interested.
I also welded in fittings at each end. Steel pipe at the input end to suit the one way valve. A machined stub at the exit end tapped for a small lever tap.
Pump through till no air, close the tap and pump...Go back and reweld splits, resume as before....

Is Greens industries who used to make wheel burrows still in business. They would have been made from such steel. I will have a phone around on monday. Can this process also be done with Aluminium ? if so, what grade could anybody suggest please. I find this all very interesting.
Neil

[Grumph]

I note he says early on, "19 gauge,.041in forming metal"
Then later, "19 gauge cold rolled steel, nothing special"

In my limited experience, you don't see a lot of stretch, if any, with normal cold rolled mild steel (20G, or thinner than his...). You might very well see it with 'forming metal' which i take to be deep drawing steel.

If he's still around Husa, and you can contact him, it's worth clearing up just what steel he is using.

[Grumph]

Is Greens industries who used to make wheel burrows still in business. They would have been made from such steel. I will have a phone around on monday. Can this process also be done with Aluminium ? if so, what grade could anybody suggest please. I find this all very interesting.
Neil

You'd need to find someone doing a lot of presswork. Do Fisher and Paykel still do any in this country ?
I'd doubt if alloy could be used, I'd think it would tear too easily in the light gauges used.

[jasonu]

You'd need to find someone doing a lot of presswork. Do Fisher and Paykel still do any in this country ?
I'd doubt if alloy could be used, I'd think it would tear too easily in the light gauges used.

I'd be surprised if F&P did anything more than assembly in NZ.

[husaberg]

I note he says early on, "19 gauge,.041in forming metal"
Then later, "19 gauge cold rolled steel, nothing special"

In my limited experience, you don't see a lot of stretch, if any, with normal cold rolled mild steel (20G, or thinner than his...). You might very well see it with 'forming metal' which i take to be deep drawing steel.

If he's still around Husa, and you can contact him, it's worth clearing up just what steel he is using.

http://www.kiwisteel.co.nz/services-and-products/stock/hot-rolled-steel/

[Sketchy_Racer]

Interesting info there Husa. I saw in the pitlane thread about the use of regular cold rolled steel so that is what I will start with. I have a sheet of 1mm turning up on Monday.

The tool I am going to lack in the process is a swaging jenny to do pre bend the edges to get a nice butt weld. I might look at making a specific one just for doing this job as it should be pretty easy to make. Failing that I might just use a hammer and beat it over a former.

I'm just about to start getting the dimensions together from Frits' pipe formula, however I am not sure what percentage I should add to my measured RWHP to get my crank HP. Are there any common factors that people use to assume this?

[richban]

Interesting info there Husa. I saw in the pitlane thread about the use of regular cold rolled steel so that is what I will start with. I have a sheet of 1mm turning up on Monday.

The tool I am going to lack in the process is a swaging jenny to do pre bend the edges to get a nice butt weld. I might look at making a specific one just for doing this job as it should be pretty easy to make. Failing that I might just use a hammer and beat it over a former.

I'm just about to start getting the dimensions together from Frits' pipe formula, however I am not sure what percentage I should add to my measured RWHP to get my crank HP. Are there any common factors that people use to assume this?

I thought 10% was the go. So plus 10% of 85hp for the 300.

[jasonu]

Interesting info there Husa. I saw in the pitlane thread about the use of regular cold rolled steel so that is what I will start with. I have a sheet of 1mm turning up on Monday.

The tool I am going to lack in the process is a swaging jenny to do pre bend the edges to get a nice butt weld. I might look at making a specific one just for doing this job as it should be pretty easy to make. Failing that I might just use a hammer and beat it over a former.

I'm just about to start getting the dimensions together from Frits' pipe formula, however I am not sure what percentage I should add to my measured RWHP to get my crank HP. Are there any common factors that people use to assume this?

'Failing that I might just use a hammer and beat it over a former.'
No need to get too flash. The above method will do just fine. Use a plastic or similar faced hammer.

[husaberg]

Interesting info there Husa. I saw in the pitlane thread about the use of regular cold rolled steel so that is what I will start with. I have a sheet of 1mm turning up on Monday.

The tool I am going to lack in the process is a swaging jenny to do pre bend the edges to get a nice butt weld. I might look at making a specific one just for doing this job as it should be pretty easy to make. Failing that I might just use a hammer and beat it over a former.

I'm just about to start getting the dimensions together from Frits' pipe formula, however I am not sure what percentage I should add to my measured RWHP to get my crank HP. Are there any common factors that people use to assume this?

I thought 10% was the go. So plus 10% of 85hp for the 300.
...................................

I can understand that. What I would do: assume a 5 % power loss for every set of gears, for the chain, and for the deformation of the tire on the drum.So what you would measure, is 0.95 (primary drive) * 0.95 (gearbox) * 0.95 (chain) * 0.95 (tire) * crankshaft HP = 0.8145 * crankshaft HP. Or, the other way around: crankshaft HP = drum HP / 0.8145.
Granted, this is not exact, but it's an honest approximation. In any case it is way better than calculating with coast-down losses that you know are not representative of the real losses.
hopefully you noted I spoke of drum HP. That is not the same as rear wheel HP. About 5% of rear wheel HP is lost between tire and drum and what really accelerates the drum, is drum HP. And something which you may not know: Dynojet-readings are already compensated for this loss, and then some. We once did a comparative test at Ten Kate's (umpteen times Supersport world champion, just around the corner from my house). It turned out that the Dynojet is 11% optimistic.

[husaberg]

I have PM''ed Howard asking him to contribute here.
316318316319316320316321316322316323
Here is a few more posts off pitlane.


I have been around long enough to see a pipe failure or two as well. Thin pipes (under .035") tend to have shorter life spans. Most of the failures I have seen were due to vibration. Cracks appear within inches of the cylinder or where the tail pipe welds on. Also the weld-on fittings for temperature sensors seem to be a source for cracks to develop on thin wall pipes. Going to .040 or thicker reduces the likelyhood of pipe failures.


I manufacture hydroformed pipes and I agree with Jan that 1mm or 19 gage cold rolled steel works best. Going thinner especially on bigger engines that tend to vibrate more will result in a shorter life span for pipes and they will crack. Going to thicker metal adds weight but does make the pipe more durable. Thicker pipes need more warm-up time to stabilize the temperature and come up to full revs. Thin pipes do tend to heat up an cool faster which is good for a drag racer but not for a track engine.

[Cheesy]

You'd need to find someone doing a lot of presswork. Do Fisher and Paykel still do any in this country ?
I'd doubt if alloy could be used, I'd think it would tear too easily in the light gauges used.

No idea if they still do but when I was working there 10 years ago there was more than one package of deep drawing steel sent form Dunedin to Auckland where it ended up as exhausts, it was only used in the ovens.

[Grumph]

Re the Kiwisteel link...I did speak to them, I actually found someone who'd been there long enough to remember drawing/forming steel sheet.
I was assured that, no, sir we haven't carried any of that for years now....BUT, if you cared to order at least a ton....

I spoke to every steel importer i could find. Most had never heard of it.......I spoke to every company i could find left in the SI doing presswork. All told me that they weren't doing enough deep pressing to justify getting any in.

Just because they have it listed on their website, it doesn't follow that they'll carry it - or the yoof who answer the phones will know anything about it...

[husaberg]

Re the Kiwisteel link...I did speak to them, I actually found someone who'd been there long enough to remember drawing/forming steel sheet.
I was assured that, no, sir we haven't carried any of that for years now....BUT, if you cared to order at least a ton....

I spoke to every steel importer i could find. Most had never heard of it.......I spoke to every company i could find left in the SI doing presswork. All told me that they weren't doing enough deep pressing to justify getting any in.

Just because they have it listed on their website, it doesn't follow that they'll carry it - or the yoof who answer the phones will know anything about it...

No doubt they too have a minimum order I just googled it to see what it was.
I would say find someone or something that has deep pressings ovens esp trays I guess is one maybe fridges.

[Grumph]

No idea if they still do but when I was working there 10 years ago there was more than one package of deep drawing steel sent form Dunedin to Auckland where it ended up as exhausts, it was only used in the ovens.

I met a guy who teaches welding at Otago Polytech. His family had a presswork company and he reckoned most of the deep drawing steel came in through Dunedin. He asked around, I asked around, and it's stopped coming in....

[Cheesy]

I met a guy who teaches welding at Otago Polytech. His family had a presswork company and he reckoned most of the deep drawing steel came in through Dunedin. He asked around, I asked around, and it's stopped coming in....

The other one I can think of is SAFA tool boxes but havent seen them for years either. It not just the lack of materials that is a problem (in the wider scheme of things), there is a lack of technical skills left in the country too. I was designing some stamped/pressed stuff awhile ago but didnt find anyone in NZ to get advice from and even had another company ask us for help....

[husaberg]

I met a guy who teaches welding at Otago Polytech. His family had a presswork company and he reckoned most of the deep drawing steel came in through Dunedin. He asked around, I asked around, and it's stopped coming in....


The other one I can think of is SAFA tool boxes but havent seen them for years either. It not just the lack of materials that is a problem (in the wider scheme of things), there is a lack of technical skills left in the country too. I was designing some stamped/pressed stuff awhile ago but didnt find anyone in NZ to get advice from and even had another company ask us for help....

I'm picking most of those space heater and so forth are no longer made on Dunedin?

[Sketchy_Racer]

Right so I sat down and had a go at the FOS exhaust concept.

I think i've got it right, the only variable i'm not 100% sure on is the speed of sound. I pick that this will be the speed of sound at the exhaust operating temperature? After a quick google I found that most suggested that I use 550m/s

I'm open to any peer review on the numbers to make sure I haven't made a hash of them.

316327316328

[husaberg]

Right so I sat down and had a go at the FOS exhaust concept.

I think i've got it right, the only variable i'm not 100% sure on is the speed of sound. I pick that this will be the speed of sound at the exhaust operating temperature? After a quick google I found that most suggested that I use 550m/s

I'm open to any peer review on the numbers to make sure I haven't made a hash of them.



There is a site I will post in a few seconds that does this as a spreadsheet based on the basic Frits formula.
http://www.kiwibiker.co.nz/forums/showthread.php/93220-Bucket-bits-wanted-amp-services-needed/page81?p=1130535174#post1130535174
The site the spreadsheet is in the post
http://www.underdogsracing.com/fospipe/
the default used is 550.
they also have a software program for doing the cones as per the tygr or as Wob does them
https://www.conelayout.com/ that's not free though

[Tunisti]

Seems like that somebody had time to make this thread first.:laugh:

But, I hope I won´t be banned because of this (maybe too long?) report. At first I´m going to introduce the designing principles I have, and after that the manufacturing itself.

The design:

First off, I´ll start with this Excel sheet that uses Blair´s design principles: http://www.mediafire.com/download/t87d51tpgo3mbvg/BlairExhaustII.xls

That´s the most common design tool used in Finland, it´s been made by this mysterious Finnish two stroke guru "Sarvi-Perkele". After the basic values have been inserted into the sheet, the measures are copyed into MOTA file of the motor being builded. First simulation is run through, and with "gray matter" simulator (aka. the brains) the dimensions of the pipe are altered into better direction. With Suzuki EPO type engines the transfer timing is usually quite high, so coarse modifications to measures given by the sheet are somewhat easy to deduce without MOTA´s help. MOTA gives different dynamic pressure/velocity/purity etc. graphs, which assist the brain-simulator´s functioning. After figuring out some (many) different exhaust pipe measures to copyed files, the simulation continues. The best simulations are selected, graphs are expounded, measures are modified with reasoning and brain-simulation and new files are made, with altered dimensions. This algorithm goes on and on until the prediction of MOTA doesn´t get any better with changed measures. This takes about 100...200 seperate MOTA files, which are simulated and expounded one by one. This takes huge amounts of time and coffee.

So, you have the measures, now you´ll have to choose whether to make pipe out of cones or to hydroform it. If you decide to take cones, there is not much to talk about, when it comes to the drawing. "Cone layout" is the best option at that case. You can also save the Cone layout´s spreaded cones into .dxf form and open them as a group in AutoCAD etc. It will help you save a lot of paper when you can put many cones onto one paper.:psst: The angles and lenghts are easy to measure and determine with bikes frame and bended steel wire etc. You can also make projection of bike´s sideview onto cardboar etc, to ease up the designing.

If you go for hydroforming, things get more complicated. You´ll have to determine the "wireframe route" of the pipe, use steel wire etc. Then you must decrease all the angles just the "right" amount, this is the part where you need the experience and gut feeling. I´d say take 20 degrees off, if the turn is 90 degrees. Pipe´s radius, "expansion angle" and the diameter vs. lenght will affect the need of loosening the bendings. A good rule is that "you can easily make loose turn into tighter, but not the opposite way". Note that the errors you make, tend to have cumulative effects on the pipe´s fitting.

Now you can start drawing, either by hand or with some CAD softwares. I used to draw by hands, but now I´m into CAD since I can use those softwares. The only rules I can give to you are these:
1) Multiply all diameters with PII/2.
2) Be accurate, errors can be cumulative.
3) Measure lenghts with "bending" measures (ie. plastic ruler), since you tend to get big errors if you try to measure lenght of and arc with non bending measure.
4) When drawing small diameters, add some exrta, when large diameters, take some off. Experience helps in this case.
5) Whenever possible, take advantage of using circles etc. simple geometrical forms.
6) BE PRECISE AND AVOID ANY SHARP EDGES!

And some pictures to help understanding:

Radius changing principle in hydroforming
http://i893.photobucket.com/albums/ac137/Tunisti/KiwiBike%20Hydroforming/th_tehoputkixxx13oi_zps7e4kiilo.jpg (http://s893.photobucket.com/user/Tunisti/media/KiwiBike%20Hydroforming/tehoputkixxx13oi_zps7e4kiilo.jpg.html)

Left: Hand drawn hydroforming "middleline" with loosened corners, assisting picture and assistant. Right: Middleline & assisting picture=cutting template.
http://i893.photobucket.com/albums/ac137/Tunisti/KiwiBike%20Hydroforming/th_2020-10-25-379_zpszdqcgdcf.jpg (http://s893.photobucket.com/user/Tunisti/media/KiwiBike%20Hydroforming/2020-10-25-379_zpszdqcgdcf.jpg.html)http://i893.photobucket.com/albums/ac137/Tunisti/KiwiBike%20Hydroforming/th_2020-10-25-386_zpsrpzhmaa3.jpg (http://s893.photobucket.com/user/Tunisti/media/KiwiBike%20Hydroforming/2020-10-25-386_zpsrpzhmaa3.jpg.html)

Some old hand drawn assisting pictures (so called straight pipe with PII/2*diameter):
http://i893.photobucket.com/albums/ac137/Tunisti/KiwiBike%20Hydroforming/th_ftghjdjf_zpsrnpradyg.png (http://s893.photobucket.com/user/Tunisti/media/KiwiBike%20Hydroforming/ftghjdjf_zpsrnpradyg.png.html)

The cone way via Cone layout & CAD:
http://i893.photobucket.com/albums/ac137/Tunisti/KiwiBike%20Hydroforming/th_kaddia_zpsdmttsd0p.gif (http://s893.photobucket.com/user/Tunisti/media/KiwiBike%20Hydroforming/kaddia_zpsdmttsd0p.gif.html)http://i893.photobucket.com/albums/ac137/Tunisti/KiwiBike%20Hydroforming/th_fsghdfhfhg_zpsvdag66bh.png (http://s893.photobucket.com/user/Tunisti/media/KiwiBike%20Hydroforming/fsghdfhfhg_zpsvdag66bh.png.html)http://i893.photobucket.com/albums/ac137/Tunisti/KiwiBike%20Hydroforming/th_ewrgewrgew_zpsfzfq8dxb.jpg (http://s893.photobucket.com/user/Tunisti/media/KiwiBike%20Hydroforming/ewrgewrgew_zpsfzfq8dxb.jpg.html)

And the CAD way of making hydroforming templates (this is quite tricky for a novice):
http://i893.photobucket.com/albums/ac137/Tunisti/KiwiBike%20Hydroforming/th_gsdhftgjj_zpsl4td6fdc.png (http://s893.photobucket.com/user/Tunisti/media/KiwiBike%20Hydroforming/gsdhftgjj_zpsl4td6fdc.png.html)http://i893.photobucket.com/albums/ac137/Tunisti/KiwiBike%20Hydroforming/th_dfhjhfkjgj_zpsy4nylnov.png (http://s893.photobucket.com/user/Tunisti/media/KiwiBike%20Hydroforming/dfhjhfkjgj_zpsy4nylnov.png.html)http://i893.photobucket.com/albums/ac137/Tunisti/KiwiBike%20Hydroforming/th_sdfhfsjghgjkhfk_zpsf9beeg7j.png (http://s893.photobucket.com/user/Tunisti/media/KiwiBike%20Hydroforming/sdfhfsjghgjkhfk_zpsf9beeg7j.png.html)http://i893.photobucket.com/albums/ac137/Tunisti/KiwiBike%20Hydroforming/th_2015-06-03-1590_zpsi0rlnyaw.jpg (http://s893.photobucket.com/user/Tunisti/media/KiwiBike%20Hydroforming/2015-06-03-1590_zpsi0rlnyaw.jpg.html)


The manufacturing:

Via Cones (& universal cutting experience): Not much to explain, cut the spreaded cones on the paper on the lines. Glue those templates onto sheet metal with paper glue (0,75mm sheet metal is my favourite!) and start cutting with air nibbler/sheet metal cutting shears/sheet metal cutters/plasma cutter/angle grinder/fret saw. You can also cut the pieces a bit oversize and grind them with bench grinder etc. into accurate dimensions, it´s actually quite quick. When cutting whit sheet metal scissors bevare of cutting in such way, that the jaws get together all the way, it will make a nasty twist on the sheet being cutted. Cut a little, move the jaws, cut a little... Makes much cleaner cutting surfaces. My favourite method is to first cut the raw shapes with air nibbler, leaving about 2-3mm of "extra metal" around the template. After that it is easy to cut the final shape with sheet metal scissors, since the cutting of narrow slice won´t warp the final template at all. Btw. it´s a good idea to write an identification number on each cone...

Next thing is to remove the glued papers and start rolling the cones. If you want, you can do some grinding on the edges of the templates before it. The easiest way is to put pipes of different diameters into vise, and bend the cones with bare hands against them, until they´re all round and beautiful. This is the part where you realize, that YOU SHOULD NOT MAKE TOO LONG CONES. Long cones are really hard to get bent, and they require hammering, sweat and tears of masochism.

Btw. I made this DIY cone roller, works just fine.:yes:
http://i893.photobucket.com/albums/ac137/Tunisti/KiwiBike%20Hydroforming/th_2015-10-03-2814_zpscunpz0tx.jpg (http://s893.photobucket.com/user/Tunisti/media/KiwiBike%20Hydroforming/2015-10-03-2814_zpscunpz0tx.jpg.html)

After the cones are finished, start tacking them into right positions one after another. If you are uncertain of you welding skills, I recommend that you won´t tack the whole pipe into one solid piece. Make it in three....four seperate pieces, and you are still able to grind off any burn throughs inside the pipe, if such would occur during welding. You can also use duct tape etc to hold the cones on line when tacking the pieces.

This is the same pipe, as above in section "The cone way via Cona layout & CAD:
http://i893.photobucket.com/albums/ac137/Tunisti/KiwiBike%20Hydroforming/th_sfdfdfdfdfdfdfdnh_zps8bv239pw.jpg (http://s893.photobucket.com/user/Tunisti/media/KiwiBike%20Hydroforming/sfdfdfdfdfdfdfdnh_zps8bv239pw.jpg.html)

And this is the aluminium version of it (not welded yet, material is ½ hard 0,70mm aluminium sheet):
http://i893.photobucket.com/albums/ac137/Tunisti/KiwiBike%20Hydroforming/th_xfgsfgnfg_zpstuozcynt.jpg (http://s893.photobucket.com/user/Tunisti/media/KiwiBike%20Hydroforming/xfgsfgnfg_zpstuozcynt.jpg.html)http://i893.photobucket.com/albums/ac137/Tunisti/KiwiBike%20Hydroforming/th_ghjkjhk_zps2znf95vg.jpg (http://s893.photobucket.com/user/Tunisti/media/KiwiBike%20Hydroforming/ghjkjhk_zps2znf95vg.jpg.html)

Via hydroforming: I like to use regular 0,75mm thick sheet metal, it´s cheap. When it comes to welding, I use my old Kemppi MAG welder with 0,80mm wire and CO2 as shielding gas. I also have a TIG, mut here in Finland the argon is so insanely expensive, that I won´t use it on exhaust pipes. The refill of 20 litres and 200Bar container costs at worse roughly 180 Euros. I have made one pipe with TIG, and the hydroforming was ridiculously easy...

But, let´s get into it. First you take the paper template and glue it onto the sheet metal (beware of making too much waste pieces!). Now you´ll have to add some more material at both ends, since else it wouldn´t form nicely and there would not be enough space for the filling adapter and air extractor.
http://i893.photobucket.com/albums/ac137/Tunisti/KiwiBike%20Hydroforming/th_20150604_144434_zpsfjr7z4si.jpg (http://s893.photobucket.com/user/Tunisti/media/KiwiBike%20Hydroforming/20150604_144434_zpsfjr7z4si.jpg.html)

Cut it. I like my own style, explained in the cone section.
http://i893.photobucket.com/albums/ac137/Tunisti/KiwiBike%20Hydroforming/th_20150604_145810_zps6yckbxw1.jpg (http://s893.photobucket.com/user/Tunisti/media/KiwiBike%20Hydroforming/20150604_145810_zps6yckbxw1.jpg.html)

Copy the other half and cut. Pictures positioned on the right are from other pipe projects... Grind edges if necessary.
http://i893.photobucket.com/albums/ac137/Tunisti/KiwiBike%20Hydroforming/th_20150604_160013_zpsmrp8ctq1.jpg (http://s893.photobucket.com/user/Tunisti/media/KiwiBike%20Hydroforming/20150604_160013_zpsmrp8ctq1.jpg.html)http://i893.photobucket.com/albums/ac137/Tunisti/KiwiBike%20Hydroforming/th_20150604_171140_zps8lfvbghn.jpg (http://s893.photobucket.com/user/Tunisti/media/KiwiBike%20Hydroforming/20150604_171140_zps8lfvbghn.jpg.html)http://i893.photobucket.com/albums/ac137/Tunisti/KiwiBike%20Hydroforming/th_DSC00878_zpszgpekj3n.jpg (http://s893.photobucket.com/user/Tunisti/media/KiwiBike%20Hydroforming/DSC00878_zpszgpekj3n.jpg.html)

Bend the edges. Don´t bend too much, 60 deg. is good, avoid sharp edges. If you bend too much, you´ll end up with poor fitting when the halves must be alinged, since you can´t hammer them so well together. I have these DIY bending pliers, I recommend them tho anyone who´s into hydroforming.
http://i893.photobucket.com/albums/ac137/Tunisti/KiwiBike%20Hydroforming/th_20150604_173930_zpsndlflgjo.jpg (http://s893.photobucket.com/user/Tunisti/media/KiwiBike%20Hydroforming/20150604_173930_zpsndlflgjo.jpg.html)http://i893.photobucket.com/albums/ac137/Tunisti/KiwiBike%20Hydroforming/th_2012-09-29-018_zpsuemkfx03.jpg (http://s893.photobucket.com/user/Tunisti/media/KiwiBike%20Hydroforming/2012-09-29-018_zpsuemkfx03.jpg.html)http://i893.photobucket.com/albums/ac137/Tunisti/KiwiBike%20Hydroforming/th_2020-10-25-388_zpsv8v0vfhg.jpg (http://s893.photobucket.com/user/Tunisti/media/KiwiBike%20Hydroforming/2020-10-25-388_zpsv8v0vfhg.jpg.html)

This is the fun part! It always seems like that: "These won´t fit at all!". Relax and position the halves onto each other as good as you can. Tack them together on few points. Take time to think, hammer the edges carefully together and tack. If the edges overlap, pull them apart with screwdriver and hammer them into line. Grind the tacks as much as you can, since they´re masters of causing wrinkles, remove all welding splatters. You should end up with something like this (last picture of another pipe):
http://i893.photobucket.com/albums/ac137/Tunisti/KiwiBike%20Hydroforming/th_20150604_185839_zpsxde4ocod.jpg (http://s893.photobucket.com/user/Tunisti/media/KiwiBike%20Hydroforming/20150604_185839_zpsxde4ocod.jpg.html)http://i893.photobucket.com/albums/ac137/Tunisti/KiwiBike%20Hydroforming/th_20150604_211630_zps5azndlww.jpg (http://s893.photobucket.com/user/Tunisti/media/KiwiBike%20Hydroforming/20150604_211630_zps5azndlww.jpg.html)http://i893.photobucket.com/albums/ac137/Tunisti/KiwiBike%20Hydroforming/th_20150604_211607_zpstblcmdpo.jpg (http://s893.photobucket.com/user/Tunisti/media/KiwiBike%20Hydroforming/20150604_211607_zpstblcmdpo.jpg.html)http://i893.photobucket.com/albums/ac137/Tunisti/KiwiBike%20Hydroforming/th_2020-10-25-392_zpso5iq8g5q.jpg (http://s893.photobucket.com/user/Tunisti/media/KiwiBike%20Hydroforming/2020-10-25-392_zpso5iq8g5q.jpg.html)

Time to weld it up! If you can, use TIG or gas welder. If you can´t you should do MIG/MAG tacks one after another, unless you are a good welder. But by my experiense is that the line of tacks tends to act nicer when hydroforming. They won´t also leak so easily. Beware of making too high beams, they´ll cause wrinkles. Drill some 5mm holes on the each ends of the pipe. Weld nut onto the other end, and filling adapter on the another end. (Two last pictures of other pipes.)
http://i893.photobucket.com/albums/ac137/Tunisti/KiwiBike%20Hydroforming/th_20150604_215539_zpsvof0v9gw.jpg (http://s893.photobucket.com/user/Tunisti/media/KiwiBike%20Hydroforming/20150604_215539_zpsvof0v9gw.jpg.html)http://i893.photobucket.com/albums/ac137/Tunisti/KiwiBike%20Hydroforming/th_20150604_215453_zpsllslwclh.jpg (http://s893.photobucket.com/user/Tunisti/media/KiwiBike%20Hydroforming/20150604_215453_zpsllslwclh.jpg.html)http://i893.photobucket.com/albums/ac137/Tunisti/KiwiBike%20Hydroforming/th_20150604_221716_zpswrhrpqpj.jpg (http://s893.photobucket.com/user/Tunisti/media/KiwiBike%20Hydroforming/20150604_221716_zpswrhrpqpj.jpg.html)http://i893.photobucket.com/albums/ac137/Tunisti/KiwiBike%20Hydroforming/th_2020-10-25-399_zpsdmt32uxo.jpg (http://s893.photobucket.com/user/Tunisti/media/KiwiBike%20Hydroforming/2020-10-25-399_zpsdmt32uxo.jpg.html)http://i893.photobucket.com/albums/ac137/Tunisti/KiwiBike%20Hydroforming/th_P7110152_zpsuinivcl9.jpg (http://s893.photobucket.com/user/Tunisti/media/KiwiBike%20Hydroforming/P7110152_zpsuinivcl9.jpg.html)

Give some softening heat treatment to the hard MAG welds. Aluminium melting furnance works just fine for this step...
http://i893.photobucket.com/albums/ac137/Tunisti/KiwiBike%20Hydroforming/th_20150605_152709_zpswtcgst0c.jpg (http://s893.photobucket.com/user/Tunisti/media/KiwiBike%20Hydroforming/20150605_152709_zpswtcgst0c.jpg.html)

Connect the pipe to pressure washer with something. I use this High-End DIY billet connector, "push&turn!".
http://i893.photobucket.com/albums/ac137/Tunisti/KiwiBike%20Hydroforming/th_2015-10-03-2820_zpsygpkxrbi.jpg (http://s893.photobucket.com/user/Tunisti/media/KiwiBike%20Hydroforming/2015-10-03-2820_zpsygpkxrbi.jpg.html)http://i893.photobucket.com/albums/ac137/Tunisti/KiwiBike%20Hydroforming/th_270620121027_zps5qwarn1v.jpg (http://s893.photobucket.com/user/Tunisti/media/KiwiBike%20Hydroforming/270620121027_zps5qwarn1v.jpg.html)

Let the water flow into the pipe, make sure there is no bolt attached to the nut at the other end of the pipe. Turn the pipe into different directions, until you are sure that there is no air at all in the pipe (air comes out from the nut). Install bolt to the nut and pull the trigger. If you are going to hydroform the pipe in one piece, put the middle section in a strong vise, between thick planks and secure with something VERY durable rope etc. Start hydroforming. When the header is almost formed, remove the pipe from the vise and continue forming. Use ball end hammer to get rid of those wrinkles. The hammering might take a lot of time and patience, but keep hammering until you´re just too tired. The pipe may "explode" quite a few times during hydroforming, so safety goggles should be used (it won´t be too dangerous, if there is no air in the pipe). When it explodes, weld it together, fill the pipe with water ONLY and repeat until you are too tired to weld it together anymore.

Cut the pipe´s ends in right lenght. You should end up with something like this. Again other pipes on the right...
http://i893.photobucket.com/albums/ac137/Tunisti/KiwiBike%20Hydroforming/th_20150605_181539_zps4ts6lgk9.jpg (http://s893.photobucket.com/user/Tunisti/media/KiwiBike%20Hydroforming/20150605_181539_zps4ts6lgk9.jpg.html)http://i893.photobucket.com/albums/ac137/Tunisti/KiwiBike%20Hydroforming/th_20150605_181521_zpsvtrt2ruc.jpg (http://s893.photobucket.com/user/Tunisti/media/KiwiBike%20Hydroforming/20150605_181521_zpsvtrt2ruc.jpg.html)http://i893.photobucket.com/albums/ac137/Tunisti/KiwiBike%20Hydroforming/th_270620121027_zps5qwarn1v.jpg (http://s893.photobucket.com/user/Tunisti/media/KiwiBike%20Hydroforming/270620121027_zps5qwarn1v.jpg.html)http://i893.photobucket.com/albums/ac137/Tunisti/KiwiBike%20Hydroforming/th_PC090083_zpspa47rr65.jpg (http://s893.photobucket.com/user/Tunisti/media/KiwiBike%20Hydroforming/PC090083_zpspa47rr65.jpg.html)http://i893.photobucket.com/albums/ac137/Tunisti/KiwiBike%20Hydroforming/th_PC090080_zpswyni5jj1.jpg (http://s893.photobucket.com/user/Tunisti/media/KiwiBike%20Hydroforming/PC090080_zpswyni5jj1.jpg.html)

Depending on the design, cut the pipe into sections. Weld the pieces together into right positions, add stinger, flange and attaching components. (Last moped not mine, though the pipe is made by me.)
http://i893.photobucket.com/albums/ac137/Tunisti/KiwiBike%20Hydroforming/th_20150605_191327_zps0fs6ukso.jpg (http://s893.photobucket.com/user/Tunisti/media/KiwiBike%20Hydroforming/20150605_191327_zps0fs6ukso.jpg.html)http://i893.photobucket.com/albums/ac137/Tunisti/KiwiBike%20Hydroforming/th_20150605_193103_zps5iqlfwf8.jpg (http://s893.photobucket.com/user/Tunisti/media/KiwiBike%20Hydroforming/20150605_193103_zps5iqlfwf8.jpg.html)http://i893.photobucket.com/albums/ac137/Tunisti/KiwiBike%20Hydroforming/th_20150605_221418_zpslhykbbzb.jpg (http://s893.photobucket.com/user/Tunisti/media/KiwiBike%20Hydroforming/20150605_221418_zpslhykbbzb.jpg.html)http://i893.photobucket.com/albums/ac137/Tunisti/KiwiBike%20Hydroforming/th_2015-06-05-1600_zpsl45uubi2.jpg (http://s893.photobucket.com/user/Tunisti/media/KiwiBike%20Hydroforming/2015-06-05-1600_zpsl45uubi2.jpg.html)http://i893.photobucket.com/albums/ac137/Tunisti/KiwiBike%20Hydroforming/th_06072012003_zpsvmgiq1db.jpg (http://s893.photobucket.com/user/Tunisti/media/KiwiBike%20Hydroforming/06072012003_zpsvmgiq1db.jpg.html)http://i893.photobucket.com/albums/ac137/Tunisti/KiwiBike%20Hydroforming/th_DSC00892_zpsrw8zke6n.jpg (http://s893.photobucket.com/user/Tunisti/media/KiwiBike%20Hydroforming/DSC00892_zpsrw8zke6n.jpg.html)http://i893.photobucket.com/albums/ac137/Tunisti/KiwiBike%20Hydroforming/th_2014-04-25-620_zps03pdfdkx.jpg (http://s893.photobucket.com/user/Tunisti/media/KiwiBike%20Hydroforming/2014-04-25-620_zps03pdfdkx.jpg.html)http://i893.photobucket.com/albums/ac137/Tunisti/KiwiBike%20Hydroforming/th_20140506_162607_20140530T135931-233_zpstclmg8me.jpg (http://s893.photobucket.com/user/Tunisti/media/KiwiBike%20Hydroforming/20140506_162607_20140530T135931-233_zpstclmg8me.jpg.html)

And here are some useful tools:
http://i893.photobucket.com/albums/ac137/Tunisti/KiwiBike%20Hydroforming/th_2015-10-03-2815_zpsyn16gc7s.jpg (http://s893.photobucket.com/user/Tunisti/media/KiwiBike%20Hydroforming/2015-10-03-2815_zpsyn16gc7s.jpg.html)

And some pipes, not all though. (Most of these were lend by Finnish moped tuners, we organized this charity dyno-day to get knowledge of these pipes)
http://i893.photobucket.com/albums/ac137/Tunisti/KiwiBike%20Hydroforming/th_2015-06-12-1618_zpswaxwgnoy.jpg (http://s893.photobucket.com/user/Tunisti/media/KiwiBike%20Hydroforming/2015-06-12-1618_zpswaxwgnoy.jpg.html)http://i893.photobucket.com/albums/ac137/Tunisti/KiwiBike%20Hydroforming/th_2015-10-03-2819_zpsqt2dtihf.jpg (http://s893.photobucket.com/user/Tunisti/media/KiwiBike%20Hydroforming/2015-10-03-2819_zpsqt2dtihf.jpg.html)

Btw. it takes about 1 day to do one hydroformed pipe. From hand drawing to first start.:bleh:

PS. Sorry for my bad English!

[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.:cool:

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.:cool:

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 ?? :crazy:

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 ?? :crazy:

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.:cool:

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 300316329316330

[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

[mr bucketracer]

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 uncontrollablyyip you get water comimg out of pin pricks in the weld and it drives ;you nuts , but you get strong arms after a wail lol

[Sketchy_Racer]

So a little bit more work done. I've taken the dimensions from the FOS exhaust concept and created my chamber in Solidworks. So far it's looking good. I used the a spline tool to create very smooth transitions between the changing diameters.

I will have to wait until tomorrow evening when I can use the 2015 solidworks to generate the flat pattern from this but I think it should be fairly straight forward.

[Bert]

yip you get water comimg out of pin pricks in the weld and it drives ;you nuts , but you get strong arms after a wail lol

Here you go...


http://youtu.be/qB6DR4YT-j0

[Sketchy_Racer]

Love it!!

You shoud take some detailed pics of it so I can "study" it.... and maybe copy it to make my own. I can see having to have a few attempts at the hydroforming......

[Mental Trousers]

Title of thread changed as requested by the original poster.

[jasonu]

Here you go...
]

Nice machine.
You might want to watch just how close you get your shirt and hair to the top wheel...

[mr bucketracer]

Nice machine.
You might want to watch just how close you get your shirt and hair to the top wheel...thats what bert told me lol

[Sketchy_Racer]

Well I had a fairly productive evening. So many other jobs to do but I couldn't get the Pipe out of my mind so I went and welded the flat pattern together.

With a bit of luck will pump it up tomorrow and see how it comes up.

[mr bucketracer]

Well I had a fairly productive evening. So many other jobs to do but I couldn't get the Pipe out of my mind so I went and welded the flat pattern together.

With a bit of luck will pump it up tomorrow and see how it comes up.good stuff , warning it can become a obsession lol

[Sketchy_Racer]

Well, not a bad start at all! It is remarkable how much the metal stretches through the center section!

I decided to simply do the template by multiplying the diameters by (d*pi)/2 and then took a stab in the dark regarding the header angle change.

Because the metal stretched so much through the center it made the material ripple a lot more than I was expecting.

I didn't bother putting a relief valve on the fitting for this attempt I thought I'd give it a go with out it. Needless to say I really need a relief valve as well as a pressure gauge.

Anyway enough with the words, here's the result. Time to have a measure up and a second attempt.

[Bert]

Well, not a bad start at all! It is remarkable how much the metal stretches through the center section!

I decided to simply do the template by multiplying the diameters by (d*pi)/2 and then took a stab in the dark regarding the header angle change.

Because the metal stretched so much through the center it made the material ripple a lot more than I was expecting.

I didn't bother putting a relief valve on the fitting for this attempt I thought I'd give it a go with out it. Needless to say I really need a relief valve as well as a pressure gauge.

Anyway enough with the words, here's the result. Time to have a measure up and a second attempt.

Looks great for first run.

Scotty suggested fulling with water again and tap with hammer or sealing and adding air ~30psi then heat the ripple areas and they will pop out...

Also note the belly will expand about 2-5% more the template/design.

[AllanB]

Well done - that is very cool. Nice effort for the first time out.

[TALLIS]

seem to easy. but seriously... looks good for the frist time!

[Tunisti]

Nice job Sketchy!

Did you try the middle section support method, in the beginning of hydroforming? It´s somewhat dangerous method, if the vise decides to crack under the huge load... But that´s what the wrapping of vise with durable rope is for! With that method I´ve been able to get the belly streching somewhere bethween 2-4%.

[Drew]

Can ya not make some sturdy bands to go around it to stop it stretching?

[Flatout]

if you want to know how to do hydroforming I will answer any questions. I have been hydroforming pipes for over 15 years and i have it figured out quite well.
Go to my facebook page gifford brothers hudroformed pipes to see pics

[husaberg]

if you want to know how to do hydroforming I will answer any questions. I have been hydroforming pipes for over 15 years and i have it figured out quite well.
Go to my facebook page gifford brothers hudroformed pipes to see pics

Thanks Howard.

https://www.facebook.com/people/Gifford-Brothers-Hydroformed-Pipes/100004979745390

[Sketchy_Racer]

if you want to know how to do hydroforming I will answer any questions. I have been hydroforming pipes for over 15 years and i have it figured out quite well.
Go to my facebook page gifford brothers hudroformed pipes to see pics

Hi Howard,

Thank's for contributing to the forums!

I'm not sure if you have had a look at the rest of this thread but I recently had my first go at hydroforming. Went better than I was expecting to be honest!

A couple of questions to get started :P

Material: What grade steel are you using? I am trying to use 1mm cold rolled mild steel. I believe this is the same as .040" which I read somewhere is what you were using?

Pump: What are you using as a means to pump it up? My first go I used my power washer, but this doesn't have any real control so I was going to look at making a hand pump instead.

Template: I have seen that you simply draw out your template on a piece of paper then cut it out. I did the same and got my dimensions from (D*pi)/2 I didn't make any adjusments for the stretch or radius change in the template. Are there any rules of thumb that I can use here to try get a better starting point?

Thanks again for your input. I must get back into experimenting with these as my re-welded tyga chambers are costing me over 5hp now!

-Sketchy

[Flatout]

If you are using 1mm cold rolled steel that should be fine. I use either 20 gauge .036 or 19 gauge .041 plain cold rolled steel. Be sure you cut your pieces with the longest part parallel to the grain of the material. Otherwise the material stretches differently. To calculate how much the metal stretches is hard. basically the whole pipe stretches a bit but the center section stretches the most sort of like a balloon. When I make a pipe that has a finish circumference dimension of 17" in the center it actually stretches over an inch so I simply make the template 1/4" smaller on both sides of the centerline to compensate. The stretch diminishes down where at a circumference of 10" there is almost no measurable stretch. It is a bit of reverse engineering to get it perfect. I make construction lines on my first pipe that correspond to the drawing so I can measure them after the inflation to see if they match the drawing. If so great but if not I record the differences of each line and adjust the template accordingly. Also remember that your centerline will bend about 10 to 15 % more than the template so compensate for this in your template. Again make a test pipe and see how it fits and adjust the template with more or less bend as needed.
Here are some tips to help you
1. Use a 000 tip to weld the halves together
2. Use 19 gauge mechanical wire as your welding rod. I simply roll it off the roll and give it a stretch and then cut it into about 24" pieces to weld with. The mechanical wire or "mechanics wire" as it is referred to is very soft and does not crack. It also allows the metal to shrink or stretch without being brittle.
3. roll your edges before welding. I made a hand operated crank roller that has about a 1/2" radius. You dont need to roll it to 90 degrees. 45 to 60 degrees will do. Using a big set of pliers and a small 4 oz hammer you can tack weld and pinch while hammering the rolled edge together. I think there is a picture on my facebook demonstrating this.. Make sure the tack welding is perfectly aligned and flush. I usually thake about an hour to fully tack weld the halves together
4. Use a neutral flame when welding and use the filler rod on the full weld. Make the weld as small and neat as possible. There can be no pinholes. If you stop and restart the weld make sure you start about 1/4" back to make sure there are no pinholes. It usually takes 45 minutes to do the seam weld.
5. use a hand rag in the vice to stop unsightly scratches on the pipe. After all you want it to look nice when done.
6. Once it is welded cut off about 1" of the end of the baffle cone. I use a tapered punch to make the hole round and wire wheel it. You will be brazing in a male 3/8" pipe thread fitting in the hole. This will be cut off after inflation and is used to connect to the pump
7. The pump i use has about 1500 psi output and has an unloading valve. I use the pressure wash gun to control the flow of water into the pipe.
8. When filling the flat pipe simply leave the fitting loose and pump water into it intermittently. When you stop pumping water into it the air escapes around the loose fitting. Make sure that you allow all the air to escape. Give the pipe a shake and allow some water to escape to make sure no air is in the pipe and then tighten the fitting.
9. I use a 10 ton press to inflate the pipe evenly. I have 2 big plates of steel and plywood that i sandwich it in the press with. My press has a relief valve on it that allows it to open when I start inflating the pipe. It probably opens with around 16000 lb of force and I stop pumping once it is about 3/4 to 7/8 inflated. The amount of force required to evenly inflate the pipe is something you have to experiment with. Too low asnd you will get all sorts of wrinkles and too much and it will turn out like a pregnant guppy.
10. Once I take it out of the press I add some more water until the center is fully round but I wrap a tape around it to make sure it is still under size. I use a small hammer to dolly out any wripples or dents. I then place a sleeve over the center that has been machined to the finish diameter and inflate the pipe into it. The sleeve must be at least 1/4" thick to keep everything perfectly round. With the sleeve on the stretch is now stopped . (welol aslmost) and you can apply a bit more pressure without going oversize. The extra pressure allows you to dolly out any remaining imperfections. I usually allow 1/2 hour on my lap to do the final dollying. Remember that if you have any leaks. Evven a small pinhole, stop and drain it and fix the leak and refill the pipe to pressure. Make sure again there is zero air in it for your own safety. You need to maintain good pressure to do the dollying.
11. Pipe building is an art and a reflection of the craftsmanship of the builder and can not be rushed or shortcut. The first few pipes you build will most likely have flaws and will not match your drawing but with patience and some sustained thought you will become good at it. Hydroforming is not for everybody. You need to have the equipment and be a good welder. (real good welder) If you want to mass produce hydroforming is not the way. If you want to build a few sets and experiment it is great. I always weight the pipe before and after inflation. This will give you the volume with a few calculations and will assist you in your experimentation and in your duplication of a sucessful design
Ok now go and build some pipes!
6.

[husaberg]

Ok Cold Drawn sheet is still made in NZ.
http://www.nzsteel.co.nz/products/cold-rolled-steel

looks like here is one of the few suppliers left is this place.http://www.easysteel.co.nz/
http://www.kiwisteel.co.nz/services-and-products/stock/hot-rolled-steel/
This one still has deep drawing steel by the look of it
not sure what the minimum order is.

316665

[mr bucketracer]

.8 to 1mm deep Drawn sheet is what i used , did use the other and seemed ok , they told me after 100 and something days it changes to deep drawn steel so don't know how much true is in that. but that was 20 years ago

[Michael Moore]

A hand pump works fine and is not slow IF you prefill the exhaust with line-pressure water. The pump I have lets the water run straight in and then check valves let you pressurize it to higher levers with the hand pump. Knocking the edges over with a hammer and dolly works fine. I made a custom hammer that helps to knock the two edges into each other once the initial tacks are done. Details and photos at

http://www.eurospares.com/frame8.htm

cheers,
Michael

[husaberg]

A hand pump works fine and is not slow IF you prefill the exhaust with line-pressure water. The pump I have lets the water run straight in and then check valves let you pressurize it to higher levers with the hand pump. Knocking the edges over with a hammer and dolly works fine. I made a custom hammer that helps to knock the two edges into each other once the initial tacks are done. Details and photos at

http://www.eurospares.com/frame8.htm

cheers,
Michael

Great post Michael, do you have pics of the "Custom Hammer" that one has me intrigued.

Found this today
http://www.mickabbeytuning.co.uk/
www.mickabbeytuning.co.uk

Note the simple garden tap. Tt is both the pressure regulator and the air expeller, genius


I will copy out the page so if the page link disappears it will still be able to live on.

[Michael Moore]

No photo needed. I took an old ball pein hammer and welded a 1-1.5" length of 1" round stock to the flat hammer face, perpendicular to the handle.

The round section hits the high spots on both sides of the joint and goes into hollows and helps to push the two sides together. I had gotten frustrated trying to use a regular flat-face hammer when I ran into the concave sections and figured that the elderly hammer I modified wouldn't be missed if it didn't work.

Of course, if you take some care when knocking over the edges to start then there's less "nudging" that is needed.

Having a bead roller/jenny would probably be a superior solution, but I made do with what fell readily to hand (if not foot).

The air bleed doesn't need to be anything more than a pipe plug at the far end. Once the chamber/megaphone is full of water and expanded as much as the mains pressure will do ( a surprising amount) then it doesn't take long for the hand pump to make some serious changes.

cheers,
Michael

[Michael Moore]

http://perfectoproducts.net/hydro-static-test-pumps/

http://s500727864.onlinehome.us/wp-content/uploads/2013/06/P-1000inst-web.pdf

That's the kind of pump I have, with a parts description.

Note the incoming mains pressure goes into a check valve and then there is the pump shaft and then another check valve on the exit. Opening the household spigot lets water run straight through both check valves, bypassing the pump mechanism. Once you've bled the exhaust and it has bulged as much as the mains pressure will do, then start pumping.

The first check valve prevents the higher pressure from the pump from going back to the mains. The second check valve prevents the exhaust from bleeding back into the pump when the next stroke is made.

This pump has a cast aluminum body, but it seems to me that it could be replicated with various plumbing fittings and some kind of ad hoc pump, whether a repurposed bottle jack, master cylinder, etc for less money than they sell for new.

cheers,
Michael

[Grumph]

That's very similar to the pump I have. Mine is UK origin and if anything, rather neater in layout. No check valve though, but a manual shutoff to hold pressure in the pipe.
As I said earlier in the thread, Wallace at marsheng may well have a couple avilable for sale already in NZ.

[Flettner]

So, after all this, who has built a pipe from information on this thread? How did it go? How different was the finished product from the cut out pattern? I'd like to have a go at a pair of pipes for my sleeve engine but would be interested to know some of the real world pitfalls.
I made a dishing machine years ago for making dished ends for mufflers, convex and concave anvils with one adjusted by hand on a lead screw and the other motorized crankshaft, 2mm offset bigend ie 4mm stroke, through a LS2 conrod to the sliding mechanism holding one of the anvils. A motorized hammer. It was lent out and came back with funny looking anvils, for a rolled edge it looked like. I didn't know what they were for, took them out and disposed of them (went into the abyss under the bench) now I realize what they were for, Making chamber edges for hydro-forming, what a dumb ass, do you think I can find them now.

[lodgernz]

OK, here's my first attempt at hydroforming.
I decided to only try and make headers this way, as the following cones are easily made and aren't too hard to fit on the bike. Headers are always my biggest issue.
First photo is of a pair of headers back-to-back. Anyone with experience in hydroforming will immediately spot that I have made the typical rookie's mistake of underestimating the extra curvature that will result from the process, as demonstrated by the second photo. The original pattern had a centre-line radius of 150mm: The final product has a radius of about 100mm.
Second major error was not rolling the edges before welding. Scott Griffiths told me he doesn't bother anymore and just welds the two halves flat. I imagine that works OK for bigger components than mine, which are for a 50.
Hoped-for diameters were from about 24mm up to 36, but as you can see from photo3, it's impossible to get the pipe to a round profile with such a small amount of expandable steel.
Also, every time I got the pressure above 400psi, some welds would burst. Again, limits on the expandibility of the body meant more strain on the welds. Steel I used is 0.75mm. I think that's 22 gauge.

Next attempt I'll fold the edges a little before welding.



325229325230325231

[Flettner]

Next attempt I'll fold the edges a little before welding.



325229325230325231

Yes do that, it helps.

[Niels Abildgaard]

Is it really important that header pipe is cirkular?
Exhaust leaving cylinder during blow down time is very rectangular.
Pressure in exhaust systems does not exeed 2 bar absolute.
To my eyes it can be made of four very funny shaped pieces of steel edge welded together and then blown with water.

[diesel pig]

Is it really important that header pipe is cirkular?
Exhaust leaving cylinder during blow down time is very rectangular.
Pressure in exhaust systems does not exeed 2 bar absolute.
To my eyes it can be made of four very funny shaped pieces of steel edge welded together and then blown with water.

Well history tells us flat sided two stroke exhausts do not handle the pressures present in a two stroke exhaust very well at all. The first TZ750s with all four pipes under the bike had flat sides so they would all fit, in the first Daytona 200 they raced in almost all of them cracked before the end of the race.

[Hemi Makutu]

AFAIR, header pipe is important to flow - in being shaped regular section/smooth internally/focussed into exhaust nozzle..

Dents, weld spatter-lumps adhering, irregularities & what-not in the fat section do not matter so much..
..this factor was tested by dyno - on dirt bikes.. .. if interested, maybe check 'motocross action mag' site?

[Hemi Makutu]

www.amsnow.com/how-to-tech/2016/03/2017-ski-doo-inside-look

Latest hi-po 850 twin, uses 2-into-1 with header making geometric/conformal change from port to junction.

[Hemi Makutu]

http://l3s9113.zeus09.de/RD350/Auspuffbau_V2_englisch.pdf

The bloke credits a couple of the 'brains trust' regulars here too, as it happens.

[aljaxon]

http://l3s9113.zeus09.de/RD350/Auspuffbau_V2_englisch.pdf

The bloke credits a couple of the 'brains trust' regulars here too, as it happens.

i know this is an old post but i have been making my own pipes since 2012 for my rd350A and lately for 50 and 70cc mopeds. i just wondered if anyone can recommend good cheap software? at first i used Blairs calcs in his book and since then tried FOS, and 2t calc. the pipes work well but only just compare to universal off the shelf pipes such as doppler streetcups. yet i am inputting precise info. i can now tig weld a pipe and it has zero leaks. i can roll them so there are no gaps. i get my cones dxf files cut by a local laser company.
with me baing a diy hobbyist i cannot justify forking out for $400 software. plus the cylinders im using are poorly designed with little scope for improvement in various areas so any simulation software would be bigging them up too much and i'd get an inflated simulation and skewed output for any pipe.

a pal showed me torqsoft which has a handy header angle altering facility almost real time changes the angle at part of the downpipe saving me hours doing it with autocad and a calculator.

has anyone used torqsoft pipe designer? or any other software?
cheers