Designing and manufacturing of exhaust pipes

[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/Giff...00004979745390

[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-...-rolled-steel/
This one still has deep drawing steel by the look of it
not sure what the minimum order is.

[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-c...00inst-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.

[Flettner]

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

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.