hi I had some great links on applying water pressure inside
of welded sheet metal parts to expand them like a balloon of metal
One guy made a exhaust pipe for his motorcycle
Another woman was making pillows looked real but where metal
There was a link that said how to do this
And I can’t find the information on my computer anymore
And I have a little project in mind that this would be the best method for
I know you are not supposed to post some links but if someone could let me know something if they have the information like search words I cant find it and I know it was something simple like welding the metal
Then hooking a hand pump to it and pumping it up like a balloon
Thanks I know its here on my computer in this 20 gigs somewhere
But no search worked yet or on the internet help please thanks

I believe this is the right forum as it bends the metal

Well off the bat....the water pressure required to deform metal is probably beyond your capabilities.....geesch just think of the safety issues.....I seriously doubt that a hand pump will do anything more then give you a workout.....now add a bit of heat....yeehaaaa....we have a boilermaker.......

I believe the term is hydroforming. Most of the apps for it that I know of though use either explosives or submerged arc to generate a shock wave that forms the metal against a shell mold.


Tiger

Yes possibly I was not remembering it right
I found one link to the pillow artist
www.calsmith.org/news2.html
There is a pillow on the bottom and they say
Inflated with air I wish I could find the place with the guy that made his motorcycle exhaust he explained it all very well how he did it from the welding to the finished product and the pump he used how there was not much risk involved for a small volume
My memory is not that great but
I know there is a way to make what I have in mind
I have seen it pretty straight forward without spending forever
I think you weld it inflate it hammer it just a little then cut off what you don’t use he made a
Tapered pipe that came out nice then he welded a mounting bracket on it
I will keep looking but have been at it for hours it is driving me nuts
I think I got it on rec craft metal working news group
Just thought someone might know what I was looking for

I believe the term is hydroforming. Most of the apps for it that I know of though use either explosives or submerged arc to generate a shock wave that forms the metal against a shell mold.Tiger

Yes it is hydroforming and what WhiteTiger is referring to is, I think, called explosive forming. Hydroforming is used for making chassis side rails by Magna International, one of the larger auto-parts subcontractors. A steel tube is put inside a mold and inflated. Much the same as blow molding plastic but at a much higher pressure.

Regarding inflating it with air I suppose it is possible if you are completely out of your mind.

Some manufacturers of solar water heating panels use the water pressure technique to form the waterways in stainless steel sheet. They weld lines to join two sheets together then use water pressure to 'blow' the non-welded areas apart.

Martin

Hi All
Just a couple of points, don't be tempted pump it up with air, if you do and a weld fails, it will be like a bomb gong off. If you use water it is safe, because as soon as you get leakage the pressure plummets. Because water is incompressible there is virtually no stored energy to dissipate. For the same reason it is easy to create and maintain high pressures since you only need to be able to pump small volumes. If you use a small bore (say 3/8” bore) hand pump you should be able to create 300/400 psi without any problem

Hey guys: 300-400 psi is dangerous in a pressurized vessul whether you're using water, air or duck feathers.

Even A pin hole leak with that much pressure behind it could LITERALLY cut you in half... if it doesn't erode and explosively try to exit through same leak point...

Explosive forming is NOT the same as hydroforming. I've seen hydroforming of tubes and other products for automotive use and they use hydraulic oils applied by massive pumps for the pressure mediums. The parts are in closed dies when formed - they're NOT laying there and swelling like balloons or inner tubes.

Keep in mind that you are deforming to YIELD and unless you "guide" the part into forming the way you want, the expansion will occur randomly and usually with quite a bit of uncontrollable randomness - IE: explosion.

Hydroforming is NOT something that should be played. The forces involved can be LETHAL if they get out of control. Half baked, half finished, half fast attempts at duplicating the process improperly are QUITE ILL ADVISED. They could be your LAST project.... literally.

Working with hydraulic assist is a proven method for doing many things. It can be deadly serious. Hydroforming is NOT something to be casually attempted. Saw a guy try to do something like it only with grease gun for pressure - hose ruptured and shot a wad of grease into his hand/arm. Lost both due to mandatory amputation 'cause they couldn't get the grease out...

A lot of the process involves proprietary techniques and/or equipment. Although the concept is simple enough (blow molding only with much more OOMPH), I'd hardly think that the true "secrets" associated with the process would be readily "findable" as a freebie on the internet.

Be REALLY REALLY careful if you try it - you have been warned....

I am familiar with hydraulic forming of metal parts using process like in link
www.bonnydoonengineering.com
HTH
Carl

Hi All
Just a couple of points, don't be tempted pump it up with air, if you do and a weld fails, it will be like a bomb gong off. If you use water it is safe, because as soon as you get leakage the pressure plummets. Because water is incompressible there is virtually no stored energy to dissipate. For the same reason it is easy to create and maintain high pressures since you only need to be able to pump small volumes. If you use a small bore (say 3/8” bore) hand pump you should be able to create 300/400 psi without any problem

Pauluk; When you get to the pressures needed for hydroforming water is compressible. I think the number is something like 12% volume reduction at 25,000 psi. You will need a very sophisticated hand pump to get to this pressure region of course.

For inflating stainless steel solar collectors or metal pillows probably between 1000 and 4000 psi would do and a well made hand pump could get to this quite easily. I used to test acrylic filter housings to 2500 psi with water using a home made pump.

Although inflating something the volume of a pillow could be tedious; my pump discharged about 0.2cubic cm per stroke; how many liters in a pillow?

One of the sites that has some info about hydroforming exhaust pipe is at eurospares. If you can't find it with google let me know and I'll try and find the link. I have done some motorcycle expansion chambers and it is fun to watch the pipe form as you pump it up. I borrowed the plumber's pump from the guy that has the eurospares web site. It took about 100 psi to form the 20 guage sheet metal.
Gary

HPbyGD thank you so much with your info that sounded familiar
I was able to track down the site
http://www.eurospares.com/frame8.htm
You guys should see this look at the article and check the pictures very interesting for some applications
Hope it works for what I have planned
Would sure save me a lot of work thanks again

Hi Eat
Your welcome. I have a couple of thoughts one is to use a motorcycle mastercylinder for a pump. The other idea that I had was to use a pressure washer but a guy would have to be really careful and not apply to much pressure to quickly. The plumbers pump that some of the guys use for hydroforming is about a one imch bore if I remember corectly and the go for about $100.. Like I said it took about a hundred psi to form 20 guage sheet metal.
GD

The other idea that I had was to use a pressure washer but a guy would have to be really careful and not apply to much pressure to quickly.

:eek: :eek: :eek: :eek: :nono: :nono: :nono:

Not a good idea.

Yes I was thinking of something hydraulic I would most likely put it in a cage like they did the old split rim truck tires use a something like a hydraulic hand pump if I could fill it with water something high pressure low volume
I want to do some shapes that I could start with globe shapes just weld some circles around the rims a couple times and pump them up then I think well a couple dies with holes clamp them together
Pump it up inside but by the time I am at that much work since I want to use aluminum
I mite as well just use the dies and pour hot aluminum in spin it around as it cools and pop my part out
Well too much thinking.
Back to what I am working on right this minute thanks for all the input

Don't even THINK of putting any liquid in or near molten metal of ANY KIND. You could kill yourself with that experiment - ask anybody who works in a foundry what happens when liquids and molten metal react with each other.

If you want to make globe shaped items, look for someone who does metal spinning. Even the guys on Mythbusters, had metal globes spun by an outside firm when they were making VanDegraff generators and they usually make all kinds of trick stuff themselves in an obviously very well equipped and funded shop.

Sometimes, it is easier and cheaper to have some things made by an expert than to do them yourself - especially if the technology might involve something that could be on the dangerous side, like trying to centrifically pour molten aluminum into a spherical something or other to try to generate a globe shape.

I was talking about a completely separate process to
Achieve the same form something like centrifugal casting
Seems like everyone wants to tell people what not to do
not how to help them accomplish
There goal

I was talking about a completely separate process to
Achieve the same form something like centrifugal casting
Seems like everyone wants to tell people what not to do
not how to help them accomplish
There goal

Possibly if you described your goal you might find people will give advise on how to get there. As it was many if not all your posts did not express a goal but talked about distinctly hazardous processes.

Actually I think I just hurt to much from work and it is making me grouchy
As I achieved my goal when I was helped and was able to find the link I lost
No offence meant spirit of brother hood and all thank you

I know of the motorcycle link. The fellow used the process to make the muffler for his Norton. He used a plumbers hydraulic pump used to test plumbing systems. The article went extensively into using pure water wth no air bubbles. Air acts like a spring and causes explosive decompression. Water on the other hand doesn't compress. When a rupture occurs the pressure is immediately released with a very small amount of fluid loss due to this incompressibility. The trick is purging all air from the system with a secondary outlet you can plug once the air is purged. Pumping on the plumbers test pump will generate the pressure you need and you can control the amount of deformity with pump strokes. Gentle hammer work around creases before they start forming will help shape the part you are trying to make.

There are interesting threads about the explosive force of compressed gases in the plastic mold forum. Some folks have used pressure cooker pots to aid in bubble free plastic mold making. A very worrysum undertaking. Fluids and their incompressible natures react differently than the wound spring of a gas under pressure.

When one posts on a message board, the ONLY thing one sees is what is posted - we're NOT mind readers. Thus, if you say "I intend to start a fire in my living room", taken literally, this means you're going to set fire IN MY LIVING ROOM - period.

However, if there is a fireplace in your living room, you intend to set a fire THERE, the actual meaning is entirely different than what you initially wrote. But how would/should we or anyone know that????

Having provided phone support for any number of years as a service engineer, I"m quite wary of responding to some of the questions that get posted. Thus, I preface the ones outlining a dangerous process with appropriate caveats because one never knows if the guy is REALLY going to set fire to his living room. I've been burned (no pun intended) by too many people who don't mean what they say or say what they mean. Thus, you tend to give advice defensively or to the lowest common denominator to protect someone from hurting themself or someone else from doing something dumb.

Example: my dad caught my mom hosing down the fuse panel with water one day because it was "dirty and HAD to be cleaned". God apparently had a special purpose for my mom cuz she didn't get eletrocuted doing something that was so totally dangerous and outright stupid but seemingly totally necessary in her mind.....

Perhaps if one took the "here's what I want to do and here's how I plan to do it" approach when asking a question, one might get more positive responses.

At some point, one has to 'splain how not do do something, especially if the semi-lucid idea is downright dangerous and/or life threatening. Preferrably this will be done BEFORE the person sets fire to their living room rather than after the house is half burned to the ground.

Then again, it should be intuitively obvious by that time (house on fire) that starting a fire i the living room may have been the smartest thing you've ever done. In that sense, would you have preferred us telling you so BEFORE or AFTER the house was ablaze that LITERALLY setting a fire in the living room was a bad idea????

You guys with thousands of pounds of pressure scare me to death. Yes hydro forming is safer (much) than using a compressible such as air!

Elisabeth Brim (the woman that makes the pillows and other shapes) cuts two identical pieces of sheet metal, welds them together except for a small hole that gets a small piece of tubing welded in. She then heats the sheet metal in a gas forge to about 1500 deg F EVENLY on both sides at the same time, and then she removes the item from the forge and inflates it with A HAND BICYCLE PUMP AT a PRESSURE OF ABOUT 3 PSI!!! Until the desired "PLUMPNESS" is achieved. I have watched her do the process in person at a blacksmithing conference about 10 years ago.

This is not to say that everyone can do the process, as in the post above, your level of skill, tools and knowledge of metal working along with safety precautions are the variables. I provided the above info as insight only as to how one person achieved the results sought after by the first poster. If you try it on your own, YOU are responsible for any and all results and consequences.

Wouldn't you say that a couple of thousand pounds water pressure on one hand is more or less equivalent to 1500 degrees F on the other in terms of safety? :) Both need a good degree of respect.

I must say though that it is nice to know that the steel pillows are made using finesse rather than brute force; thank you for that information.

Dear Cal:

Here is what some people got from your post:

blah blah blah WELD TOGETHER SHEET METAL blah blah BICYCLE PUMP blah blah INFLATE blah DESIRED PLUMPNESS blah blahSHEET METAL PILLOWS.

You might as well talk to the computer screen as to explain the details (blah blahs) because some people don't/won't/can't listen to the details inbetween - they can't be bothered cuz it doesn't fit their agenda.

I once read a tongue in cheek article on how safer cars prevented some members of the species from meeting their untimely demises (aka thinning out the herd). The article then went on to say that the aircraft industry had a ruthlessly efficient way to dealing with bad pilots and we should cosider relaxing safety standards to do the same thing with cars. Ruthless but effective.

I'm not advocationg THAT but, really, maybe we just ought to let people do more learning by experiencing mistakes first hand.

Having felt the wrath of bad decisions with regard to office politics more than once in my career, the learning process taught me what not to do the hard way and NOBODY warned me of the consequences before hand.

Fore warned is fore armed and doing dumb things with high/ultra high pressures will either educate or kill you.....

Enjoy

Dear NC Cams.

It is very true that I am new to the board today; thus, I do not know the culture of this board. I am not quite sure how to understand your post to me.

I think it said that many but not all of the people here just skim for information and then go off on a tear doing what they think was said and not understanding what was intended to be communicated.

If that is true, that is sad indeed as there are many here I am sure that have experience and head smarts to help those who otherwise scan for basics, to understand what they are trying to do and to achieve a positive result.

I for one am glad to offer my experience and knowledge that I gained from over 25 years in the aircraft tooling industry and more than 15 years of blacksmithing. I will continue to try to impart the skills I learned through many others and by my trials. Those who will listen will gain, those who don't, won't. I know there are things here for me to learn and I will take what is said here, compare it to what I do know and if it matches, then I have learned something valuable.

Thank you for your welcome here, it is always nice to receive one.

Cal

Yes, my comment was a welcome.

The "blah blah" part was the sound of people who might be READING the article IGNORING the details they found inconvenient - clearly the WRITER (you) spoke clearly and distinctly on how the process (pressure formnig) was done in reality.

Sort of like talking to my friend's dog -

blah blah blah BALL blah blah blah FOOD blah blah blah OUTSIDE.

Contributions are always welcome. Explanations are perhaps more beneficial overall then simple answers yet there are thos who only want the answers - not the solutions or procedures.

Next time I'll just not reply since there are to many "lawyers" here!
Gary

Cal welcome to the site.

on to the technical side of this thread, I can't see why it takes high pressures to shape the metal, i could, but its going to vary a lot on what's being formed. A couple of hundred psi pressure test on a boiler will change its shape - the pressure required going to depend on the force required to cause the whatever bending is at hand, right? Second, iirc, there is very little danger in in a pressure vessel letting go that is filled with a liquid (ok Geof, not so sure at 25,000 psi :) ) PROVIDED there is not a sustained source for the pressure (ie a submarine @ 400') This is why boilers are static tested with water and if a hydraulic line bursts generally people don't die. There is very little energy stored compared that with compressed air or, many times worse, water in a boiler @235 degrees. fill those metal pillows up with water and pump away! (i may never have typed a sentence before that seems to make less sense than that one) but not with a compressed gas

Dear HP

It is hard to determine if people ask some of the questions they do because of a lack of education (ignorance) or simply not caring to do things properly (stupidity) after being properly instructed. This is why some of us go to the extreme to educate people about the dangers of some practices.

Like: you shouldn't use a hair drier in the shower, you shouldn't smoke while washing parts with gasoline or lacquer thinner, and don't inhale phosgene gas.

Thus, those of us who have learned by our mistakes or from our education are only trying to share our knowledge to prevent people from UNNECESSARILY hurting themselves. Or, perhaps even worse, we may prevent them from hurting others or a helpless kid standing by watching (and trying to learn from) a poorly educated parent.

No matter what the reason, this is not a place where we should teach or condone the teaching by others on how to thin out the herd....

If someone wants to ignore my or anyone else's advice, they are welcomed to do so. In the mean time, in reviewing the thread, I didn't see where you contributed (one way or the other) prior to your post offering not to reply next time.

And your contribution that you chose NOT to give was what again???

he was the one who actually
gave me the information that I was looking for in the original post
and helped me.
I thank him.
Oh and welcome to the new guy I found your information
quite interesting
the information on how the other process was done with air
was interesting and the guy who said something like
you remember what you learn from your own mistakes was good
personally some of the stuff said just pissed me off
but whatever makes you feel like a big man I guess
I was trying not to post onto this thread I started again
As it has turned into something of a monster that wont die

eat: Glad you got what you needed. I got something out of this.

NC Cams, Cal, Geof, and all.....

It is true, "some" people only read the words on a page they think will fit in with thier agenda.

I tend to be the opposite and I read every word, sometimes more than once!

A lot of claims have been made in this thread (And I'm Paraphasing Here On Purpose)

Such as:

Three or four hundred pounds of pressure escaping through a pinhole could cut you in half (Or sever a limb, or cause an injection injury for that matter)

Is that the correct figure? Is it really three or four hundred pounds? Or is it fifteen hundred pounds? Or is it something in between? How much Hydraulic pressure does it take to break the human skin? Was this idea expressed by someone working within their field of expertise, or outside their field of expertise?

Or Such as this:

A closed vessel pressurised with nothing but liquid in it (Water Or Oil, NO AIR OR GAS) could explode if a weld breaks or if the material fails. Is this the truth? Will it explode? Or when that weld breaks, will you just hear a little "Tink" type noise and see water dripping on the floor? Has anyone with some expertise and experience in this area chimed in on this?(A boilermaker would be the person to consult)

I tend to read much, and read carefully, because I have to wach out for dissinformation that does none of us any good.

When I see such widely differing expressions in one thread (And being argued about!) I have to wonder.

All great questions
I have tested big fuel injectors before in collage
and know there is some danger in working with some things
But I think that most of the people here are intelligent
The funny thing is I work all day doing tree work on any given day I am up cutting 40 foot logs
Fitting them into a 60 foot lot between houses so they can be used for market
Or something similar I live on a island and work banks also all of it hanging from ropes
Swinging a chainsaw around all day I have been doing this since I was a young
And find common sense and a little thinking before hand will let you
Do amazing things

I first saw the pillow forming test for roller welding. Two square sheets are rollerwelded together and pumped up until the weld gives up and the pressure is noted as a quality number for the weld. As all shapes under pressure will go ball-shaped (Law of Pascal)there is a lot of deformation in the process.

If you want for example make a pipe using this process, using two sheets with tapered ends, which are later removed, you are basically using the force to (if it is the size of a tin can) to bend a tin can. Only when you want to fixate it to the circular form, you are entering the higher pressures. I did this and it's fun.

Leaking: if this little free forming system is airless then a leak will be an overflow valve. So first a drop will form and if you continue it will piss 10 cm (4") and with a handpump you feel that you lost the pressure. It will be a different ballgame if you do this with an high volume, high pressure pump. But with this the goal, which is a end-pressure just above bending, would be overshot anyway.

If you want to shape forms, you enter the area of stressing the metal and for this method you need closed forms and higher pressures. For example, you could make a central heating panel with the inward shaped ribs with this method. This is an entirily different area. Don't do this at home.

I worked in a factory where they also made vessels and some would go in the hydraulic range. For testing they were filled with water and gradually brought to the testing pressure. Leaks were spotted because you saw "wet spots". Larger vessels would piss a little. If you would continue pumping (useless) the gap would open thill input=output. And sorry, thats all.

If you compare this with a blocked boiler, which I once experienced, it's different. The boiler had a lead meltdown fuse. Let's assume a melting point of 200C. The water pressure is then approx 20 bar. If the fuse melts you have water of 200C which can cool down all the way to 100C forming steam. That's a reasonable basic design for a rocket. It's plain scary, especially if you do the numbers.

I never investigated in bringing injury's with hydraulics. But as you need shaped nozzles, overcome air resistance and gravity I don't see it usefull in warfare.

Carel

Elisabeth Brim (the woman that makes the pillows and other shapes) cuts two identical pieces of sheet metal, welds them together except for a small hole that gets a small piece of tubing welded in. She then heats the sheet metal in a gas forge to about 1500 deg F EVENLY on both sides at the same time, and then she removes the item from the forge and inflates it with A HAND BICYCLE PUMP AT a PRESSURE OF ABOUT 3 PSI!!! Until the desired "PLUMPNESS" is achieved. I have watched her do the process in person at a blacksmithing conference about 10 years ago

I've done a least a few dozen of those things with Elizabeth, what a good time. We used compressed air at about 100psi. Works great. Sure a seam would pop now and again, but by and large it was fine. Blacksmiths do alot more sketchy stuff than that on a daily basis.

... We used compressed air at about 100psi. Works great. Sure a seam would pop now and again, but by and large it was fine....

Your casual phrasing reminded me of the time I bronze welded a crack in a motor cycle gas tank for a friend. Sure, it blew, just straightened out all the dents in the tank. We thought we had it full of water right up to the crack but some drained out while we were working. Never did that again.

Not that I'm recommending you monkey with this, but, the new volkswagen / audi FSI gasoline direct injection motors generate almost 20,000psi of fuel pressure. Perhaps that pump might last for short periods of experimentation and be available at reasonable cost from a european boneyard. (www.car-part.com)

I would probably add something to the fluid your using to lubricate the pump or I doubt it would last too long.

And for gods sake stand behind something thick!

Hey eat! go for it. It's great fun. Have done some test with hydrofroming and its really fun. weld together and weld in a hydraulic fitting in one end and a Nut in the other end. plugg the nut with a screw with a bronse washer. Then you fill up with water. connect a handpump pump in a little pressure and let the air out of the part. Go on pumping to the right form apears. The result is incredible good.

I used an hydraulic handpump had no problem with that. Used 1mm steelplate.

some advices: no air in the part, Lay down the part on the floor with a litttle space around, do not have your hands on the part while pressure goes up. no sharp radiuses in the flat part. Because then the stress at this point will tear it apart before the rest have formed completly, if it cracks just emty the part and weld the crack and back on pumping.

My parts have cracked many times, But since theres only water the pressure falls at once. Have never had any scary experiences with this. The moust dangerous part of this projects have been driving my car to buy more steel ;-)

http://www.smoregrava.net/hydroforming.htm

This is my webpage but unforunally only in norwegian

One thing that I found when trying to make a round part is to bend the edges of the material so as it expands it is not trying to unfold the weld.
Gary

the method used by the lady who makes the pillows is exactly how they fix dents in 2 stroke expansion chambers. plug one end, apply air pressure, and heat the dent till it pops out. I think this hydroforming technique sounds neat, and we finally hear from someone who does it and says that cracks arent dangerous.

The comment, "..and we finally hear from someone who does it and says that cracks arent dangerous..." is an over simplification that borders on irresponsibility of highest order.

ANY metal that cracks under pressure can be dangerious to the bystanders DEPENDING ON THE RATE OF CRACK PROPOGATION AND THE VIOLENCE OF CONCENTRATION OF THE EXPANDING/LEAKING LIQUID AS IT IMPINGES ON ADJACENT BODY TISSUE.

If you've ever seen a steel drum expand under pressure, that is one thing but to see it expand and then burst at at the seams or rupture ponit is another thing entirely!!!!.

I know of a case where a guy tried to use grease pressure to expand something much like one might use hydraulics to "hydroform". This trick is also done to expand bearing retaining sleeves on certain shafting.

Fortunately the steel parts stayed perfectly intact - Sadly however, the hose ruptured and sent a shot/jet of grease RIGHT into the guys hand. Oops. He didn't think much of it until his arm started to get real ugly looking from blood poisoning.

No big deal.

The insurance covered the cost of for the limb amputation. Why amputate?

There was no way to get the grease out of the wound and to stop the resultant infection/blood poisoning from grease migration into his blood stream.

His lawsuit essentialy got tossed out of court because the product liability lawyer showed that what he was doing was a gross misapplication of the equipment he was using. He lived, but with one arm and his life as a technician ended as he knew it.

Having seen REAL hydroforming done, it is done within a closed die and under careful conditions with safety of the utmost concern. Yes, you can pressurize and reform a muffler chambers or some small thin vessels via the use of air or water pressure.

You can literaly coax a shape into an alternate form using "hydroforming techniques". BUT It all depends on what you're trying to form and the thickness of the metal that you're trying to reshape and the extent of the reshaping.

The point that some of us are trying to convey is that care MUST be taken when using this practice.

Moreover, ANYONE who says that cracking metal isn't dangerous is grossly oversimplifying the dangers that CAN AND ARE INHERENT TO THE PROCESS to the point of gross irresponsibility.

People can and will do stupid things.

Hydroforming via the "if a little pressure helps, more should help better and faster" method could result in a very unpleasant, life altering or ending stupid experience. Irresponsible hydroformers need to aware that they are playing with a potentially dangerous and/or lethal forces.

Point made and hopefully taken. Do whatever you want and however you want to do it using whatever means.

You've at least been warned. Caveat emptor.

My parts have cracked many times, But since theres only water the pressure falls at once. Have never had any scary experiences with this. The moust dangerous part of this projects have been driving my car to buy more steel ;-)


smoregrava, have to agree with you. when a pressure vessel lets go, its has nothing more to play with that the stored energy - thats obviously huge if its compressed gas, but not with water. if you evacuated almost all of the air, theoretically you could pump it up to very high pressures with half a stroke of a small hand pump - there is a very low level of stored energy. why NC's cautionary message is good is to stop the guy that goes off and tries using compressed gas (that means air!) etc. as I said in my earlier post hydrostatic testing of pressure vessels is standard and safe, but you have to have a clue and understand what you are doing. still I'd be wearing safety goggles and gloves, maybe even braces and a belt

smoregrava, have to agree with you. when a pressure vessel lets go, its has nothing more to play with that the stored energy - thats obviously huge if its compressed gas, but not with water....

Correct up to a point. When you are dealing with low tensile material you do not have much stored energy with a liquid under pressure but it is a different matter if your vessel has a high yield strength. It is possible even with a hand pump to store significant amounts of energy in elastic deformation of the container; when a small leak occurs this deformation can produce a dangerous high pressure stream.

An analogy is to take a piece of mild steel 1" by 1/8, grip it in a vise and haul on the end. It will bend and if you bend it back and forth it will get hot and eventually break. All your work went into heating it and eventually creating a fracture. Now take a file around the same dimensions and treat it the same (actually don't do this, this is a thought example). The file will not deform plastically, all the effort you put into it goes into elastic deformation and if you push hard enough it will fracture. Now all the stored energy goes into making lots of fragments of file spraying out from the fracture zone in an explosive manner. Quite apart from the fact you have fallen forward and impaled yourself on the broken part in the vise or fallen backwards and split your skull on the concrete floor.

One thing that I found when trying to make a round part is to bend the edges of the material so as it expands it is not trying to unfold the weld.
Gary

I agree if you bend the edges and weld. Then the finnished result is even better.

To you people who still is discussing the safety around this. when a part with water(no air) cracks and you have a very little hole. You got very high pressure and the water could cut/be sharp like a knife. But thats why I state "Lay down the part on the floor with a litttle space around, do not have your hands on the part while pressure goes up" Because the waterjet from this could not travell 300-400mm trough air and still be able to cut. The water just vaporize. if you want a long jet not to vaporize it must have a greater diameter but then the pressure will fall at once.

Safety have to come from your head. Your workshop is filled up with dangerous things.I' have heard about a man that lost his hand on a CNC mill. Should I stop using CNC equipment? On this forum we build CNC machines, this process could be realy dangerous if you don't use your brain. Have respect for your life and evaluate the safety around it.

Please let us who want to do hydrofroming talk and exchange experience

This process is greate to produce 2 stroke exhaust look at this link
http://www.two-stroke-addicts.freeserve.co.uk/mick/hydropipe.htm

....Please let us who want to do hydrofroming talk and exchange experience....

When you have the knowledge and experience you can do it safely. However go to the Today's Posts page and you will see two columns: 'Replies' and 'Views'; as I type this the number of Replies is 42 and Views is 1,176. How many out of the 1,134 difference have your experience and knowledge and how many do not but might be prompted to experiment on their own by what they read in the thread?

Hi, one of the methods the model engineers use to test small copper boilers is to completely fill the boiler with water, leaving no air at all , seal it and then apply heat to the water.
The water expands and can produce tons of pressure for little heat.
The copper boilers are normally tested to 1-1/2 to 2X working pressure. This isn't much by your requirements but if the heat is applied it soon goes up, literally.
Ian.

Hi, one of the methods the model engineers use to test small copper boilers is to completely fill the boiler with water, leaving no air at all , seal it and then apply heat to the water.
The water expands and can produce tons of pressure for little heat.
The copper boilers are normally tested to 1-1/2 to 2X working pressure. This isn't much by your requirements but if the heat is applied it soon goes up, literally...Ian.

Yes and if you get it too hot and something springs a leak you have a nice jet of superheated. With all due respect, I think this approach is idiotic; it might work successfully many times but only needs to go wrong once for possibly horrible results.

Hi, one of the methods the model engineers use to test small copper boilers is to completely fill the boiler with water, leaving no air at all , seal it and then apply heat to the water.
The water expands and can produce tons of pressure for little heat.
The copper boilers are normally tested to 1-1/2 to 2X working pressure. This isn't much by your requirements but if the heat is applied it soon goes up, literally.
Ian.

NO NO NO, please don't do this! In fairness to Ian, I know he's not giving instructions, but this is a potentially deadly act that should not be done...

every boiler, copper or steel needs testing prior to steaming but you never use heat, you use a pump. this way there is almost no energy stored. if you use heat, as pressure goes up, the water temp goes beyond 100C, but its still water - if the boiler cracks, pressure drops back to atmosphere, but you've got a volume of water at some temp above 100C that instantly wants to be steam and occupy 100x its previous volume. this is otherwise the definition of an explosion and why a boiler exploding is many times worse than say an air compressor letting go - its like a stick of dynamite! you must test to some multiple of the normal working pressure and that can only safely be done hydrostatically. you cannot do this test with the safety valves in place and should NEVER heat the boiler with them not in place.

btw its the drop in pressure that triggers a boiler explosion, they've happened in past from taking steam too fast.

there are specific rules imposed by insurance co's and model engineering clubs (important if you are demonstrating at a club or if its a locomotive and you want to take it to a track) on hydrostatic testing - sometimes required to be done in the presence of the club inspector. These procedure are safe and common, but not if you only get 75% right - don't mess with pressure vessels if you arent' sure

Hydrostatic = low energy, safe
compressed gas = medium energy - this can kill
boiler letting go = huge energy, will completely ruin your day

.....boiler letting go = huge energy, will completely ruin your day

Clearly I am redundant.

But I do take issue with the above; you may not have a day left to ruin. But it is the likely to the the first day of a ruined rest-of-life for your family.

Exactly the expansion of a bunch of superheated water turning into steam because the pressure just fell to atmospheric is NO fun. At least with ~room tempurature water used if it bursts it stays as water and doesn't expand vastly...

Check out a steam table to see how screwed you could be.

Honestly the safest way to do this although possibly more expensive then others will be a high high pressure pump and a liquid. This way there is little potential for expansion (explosion!) in the event of a failure.

I would also suggest either setting it up so you can be relatively far away from this as it happens- or behind something tough as hell. This way you are well out of harms way in the event of any jets (which will be short lived) or shrapnel should it actually "explode".

For a homegrown approach I really would look into using an automotive diesel pump or direct injection fuel pump, even some power steering pumps all generate relatively high pressures... At least a place to start on google anyways! Problem I see with all 3 of those is none are designed to operate with water and likely won't last long without the lubrication provided by their intended fluids... Granted, they are designed to last a couple hundred thousand road miles in automotive use, and running one for a few minutes at a time for your purposes you might find the lifespan acceptable anyways.

PS I would be really interested in seeing some DIY approaches to hydroforming a part using a set of dies and everything! I have seen some aluminum intake manifold plenums for turbocharged 4 cylinders which have been hydroformed (two halves and welded) and it produces extremely nice, natural curves.

I suppose similar shapes could be easily made by stamping but this is just how they chose to do it.

http://www.hypertune.net/ Those are the intake manifolds i'm on about...

Clearly I am redundant.

.

nah, just more succinct and quicker on the keys, btw if it wasn't the clear the ruin your whole was a studied understandment

nah, just more succinct and quicker on the keys, btw if it wasn't the clear the ruin your whole was a studied understandment

Flatterer.

Yeah, I did figure it was something like that.

For a homegrown approach I really would look into using an automotive diesel pump or direct injection fuel pump, even some power steering pumps all generate relatively high pressures... At

just use a homemade piston type hand pump, with air evacuated it'll only take a a couple of strokes to bring it to pressure. you have to have one anyway for boiler feedwater, so just make it first :) for boiler testing you need a pressure gauge attached and a lot of control, with a mechanical pump the pressure would increase to rapidly because there would be negligible flow before the pressure went off the scale.

There might be potential for those mechanical pumps for your hydroforming idea where the volume would be changing so you'd need a lot more flow. come to think of though, even with that you might want the control a hand pump gives., guess it depends on how big you are going with it

Now that the troubled waters have subsided, the heating of the water is done to a LOW degree, certainly not up to 100 deg, which would be daft.
I read about this method in a model engineering magazine, some years back, and the important part to observe is that the boiler is completely filled with water. The small amount of heat required to raise the water pressure to 150lb/sq " is negligable, and as the water is incompressible it exerts enormous pressure for little heat rise.
There is a plan for an engine that works on the same principle, but in this case a metal rod is heated and the resulting expansion, which is also tremendous for little heat, moves a gear wheel which is geared up a lot to enable the small amont of expansion to produce a lot of movement.
I'm not sure what the co-efficient of linear expansion is for various metals, it'll probably be in the Machinery's Handbook, but it also applies to a liquid. Both are incompressible, well probably not alluminium which will mushroom if the force is contained.
So to put a figure on the theory, what is the expansion rate per degree for water.
I suppose an experiment with a 100cc's of water in a jar having a pipe pointing vertical and calibrated to show the increased volume per degree would put some light on an otherwise dark subject.
A boiler, with a capacity of 100cc's, and completely filled with water, and then having 1cc pumped into it would show a pressure increase of 100 times what?
I suppose the elasticity of the metal container, as it's not a sphere, would be a factor hard to define.
If the container was a sphere then the metal would just go on stretching till it ruptured, or in the job at hand, till the metal stretched and filled the moulded shape and flowed to all corners.
The pump required to make this happen would have to have a small ram, proberly 1/4" diam and a leverage of 100:1. this would give 100lb on the ram for every 1lb applied to the handle.
The difference in volume from the tubular shape to the finished item would determine the stroke length and so the amount of pump strokes you would have to do.
The big problem is no matter which method you choose there is going to be a high pressure to stretch metal to any degree, and the metal container will itself resist the pressure like a spring loaded piston.
So you would not want to be around when this was taking place, even under controlled conditions.
The mold cavity would also have to be larger to allow for "spring back" due to the elasticity of the metal.
Some metals work harden and this just increases the "spring" factor.
Ducking for cover as I can hear the old breech loaders clanking shut to deliver a broadside.
Ian.

This post has now definitely become recursive; it started on blowing metal balloons, deviated into high pressure hydroforming, wandered off into a never-neverland of rant and rave, went quiescent for a while, then was revived blowing metal balloons and has now re-deviated into hydroforming. I wonder what the next six months will produce.:)

We have done 2-stroke performance exhausts by "hydroforming" with home made pumps in finland for a long time. its really not that hard and its also safe. by the way don´t try that expanding with air or heating sealed thing filled with liquid.
http://www.motot.net/galleria/showphoto.php/photo/16063/si/putki/what/allfields here is few made by "sarvi-perkele"
http://www.motot.net/galleria/showphoto.php/photo/9261/what/allfields/name/kalpi and here´s one from kalpi

I am not familiar with air over water to form motorcycle exhaust systems it sounds very dangerous,however i have made a few expantion chambers for motor cycles using hydraulics and its quite safe and the finished product looks very good .I have also seen the end product with air and heat to repair 2 stroke expantion chambers and without the correct procautions taken its down right dangerous be very very carefull regards greg b

BTW, if you want to see the tremendous force exerted by the incompressible force of water at LOW temperatures, completely fill a glass bottle with water and close with a screwed cap, then place in the sun for a while.

Three glass fruit juice bottles of water burst after 15 minutes exposure, however there was no earth shattering explosion, with massive loss of life, sorry doom watchers, just a small crack, and a puddle of water.

This is not recommended for trial at home, due to the dick heads that would be holding it in their hands while trying it out.

Provided the container is FILLED with water and no air space is left, then the item to be expanded will expand at a given rate as the temperature is raised.

The temperature should not be raised more than a few degrees otherwise the water will become superheated steam when the pressure is released.

It is probably common knowledge that if you heat water it will expand at a rate according to the temperature rise, and if you cool water it will contract also at a rate dependent on the temperature drop, but not a lot of people know that water will EXPAND from 4 deg C down to 0deg C as it freezes.
This is why steel water pipes can burst when they freeze.

To clarify this, if the water is at 100PSI and the temperature is at 300 or 400 degree C then you have a bomb on your hands, but if the water temperature is only 10 degrees above ambient then in a totally filled container with no air space it will only fizzle, no big drama.

It all depends on the expansion rate of the water per degree.

Taken to it's ultimate conclusion, if you haven't grasped the fundamentals of temperature and pressure with regard to liquids or gasses, research on the subject, or don't piss about with something you don't know about,
SIMPLE innit?
Ian.

greetings,

i have to concur . . . . . . now that the "explosiveness" of some of
the replies has subsided we can all learn & enjoy an excellent
practice. in an early 80's issue of the Motorcycle Mechanics (English
trade magazine) there was a most excellent article on a fellow who
used a water pump to create some beautiful muffler/megaphones
for a Honda GP replica road bike. they were astounding in shape
& the article was extremely straightforward in its descriptive
form. to this day i can remember that article & how impressive
it was upon my creative energies. and i must also stress the
importance the article took to explain the very nature of pure water to
instantly lose its working pressure when unbridled.
if one has the need, i will be most happy to retrieve the volume number
& year of that respective issue from my storage bins.

Hi Archi, I bet waterforming would beat spinning when you have a mould to press the item into, especially if there were a few humps and bumps on the surface that couldn't be done by spinning.

The hardest part would be making the mould as it has to be internal to form the part pressed into it, but here is where CNC comes in.

I take it the mufflers and megaphones were in steel, and to get the stretch, without splitting, the steel would have to be annealed not cold rolled, the type used for deep drawing in press work etc.
Ian.

hi Ian,

good thoughts on the mold process, but referring back to the motorcycle
article for the mufflers, the gentleman duplicated the very same process
as described in one of the earlier posts regarding 2 stroke expansion
chambers. he created his shapes in sheet steel, bent the perimeter,
applied an entry & stop loss point; welding the 2 halves together
& then applying the necessary water apparatus to pressurized the
vessel. as the vessel's water content expanded the circumference
he initiated some deft hammer blows to begin removing the dimples
& to even out the surfaces. some great photography details
delineated quite well, each step of his process. i almost want to
dig the article out of storage just to reread the abstract.

would also like to add a thumbs up to your unequivocal dissertation to
the thermodynamic characteristics of heat, pressure & metal when involved
in such a process as described. i enjoyed reading your essays & got
a lot from them. you wrote clearly & i was able to follow with just
as much success. glad you stuck thru the mess & didn't give up.

hope to see more of your contributions in the future.