HP steam cannon

[DYI]

Well I've set myself two cannon building goals for the summer. The first is to make some sort of mortar cannon that feels like someone punched you in the chest when you set if off, and the other is a 200 bar steam gun. As the title suggests, this thread is about the 200 bar steam gun. The design is as simple (and therefore cheap) as possible.

Here's the plan:

Chamber: 2" SCH 160 black steel with a thin layer of high temperature ceramic cast on the inside to circumvent rusting. The ceramic material is designed to be conductive of heat, so transfer shouldn't be any problem. The fittings will be all threaded, so I can coat them individually. I discovered a graphite based thread sealant rated for 800 degrees Fahrenheit, which I will be using on the threads instead of teflon tape, which would actually melt at the temperatures I'm planning on (almost 700 degrees F).

Valve: Customised 2" 6000psi rated black steel union. The male sealing face will be machined flat, and I'll create a spacer to fit in the female sealing face that will make it flat. I'll use thin annealed aluminum sheet to act as both a gasket and a sealing face. My only worry here is that the ceramic spacer will crack somehow, but the can is 10 pounds of casting compound, so if one breaks eventually I can always make another one. The compounds are on page 3531 of the McMaster-Carr online catalog, and I'm leaning toward the alumina ceramic right now.

Barrel: I don't really know yet. I'm guessing seamless steel or SS pipe, probably 4 feet or so. This should be enough to hit 2000 fps with a golfball. The high speed velocity f*ck ups of GGDT may be messing with this result (does anyone know the speed of sound in 700 degree F steam?), but apparently it could fire in the hypersonic range with a 10g projectile and a 1" bore barrel 12' long. Any suggestions on the barrel that are actually achievable are welcomed.

Gauging: As far as I know, none. Too expensive, vulnerable, complicated, etc...

If anyone sees any flaws in this design, for God's sake, point them out now. I don't want to die before I build a working thermonuclear warhead

[judgment_arms]

How you going turn the water to steam?

How long is your chamber going to be?

Forget the sound barrier; try putting a 2” steel ball through plate steel, or a car.

Go for as large diameter of barrel, and heavy a projectile, as possible; forget muzzle velocity, go for maximum muzzle energy, imagine what 30,000ft-lb of energy would do to a car.

[Velocity]

Sorry if I missed it, but how to you plan to heat the gas to 800 degrees Fahrenheit?

On a very distantly related note, what kind of a place do you go to get your stuff machined? I only wonder because I fear that if I brought something into a machine shop around here, they would bombard me with questions and concerns regarding safety, cost, etc.

[willarddaniels]

Sounds good, so far.
One item to remember: I am assuming it is true with steel as it is with PVC that the PSI rating of any threaded fitting is 50% that of the pipe rating. Just something for everyone to keep in mind when doing high powered guns.

The spacer is a real concern, but I think you will be fine if you use multiple layers of light weight burst disks as opposed to one layer of something thicker. eg tin can lid. I have also been looking at making several rings for the same purpose, but I was going to fashion it out of Belzona. I can't imagine that would break. (I have 7 or 8 1.25" black iron unions I am itching to use in something)

[DYI]

Essentially, I'm going to build a big fire, and throw the thing in. I'll have steel handle welded on so that it can be positioned after it's in the fire.

I'd love to make this thing on some ridiculously large scale like MIT did, but it was supposed to be a summer project. I'll do this small scale version first, to see how well it works. If it proves feasible, I can do a big version next year sometime.

I was planning on using an 18" long chamber, or maybe 24".

Most of my custom stuff gets done by the local welder. He likes my hobby, and I send him the videos every once in a while. For things involving a manual lathe, I can stay after school and work on it then in the metal shop. For things that need a mill or more intricate work, there's a machine shop that I can pay large sums of money to for simple jobs. For complex things, lets just say that shipping costs from Sweden are worth it.

[judgment_arms]

Aww… but I wanted to see a 2” steel ball impact the hood of a car and put the engine in the drivers seat…

Big fires always get the job done, put a leaf blower up to it to get it hotter faster. 8)

I missed your line on the thermonuclear warhead, they’re not all they’re cracked up to be; go for a large strategic bomber and several tons of incendiaries, turn ‘em to glass with out nuclear winter, although nuclear winter would solve global warming...

[Acdcmonkey1991]

Man this is going to be one hell of a cannon. A couple of questions...
Has anyone else done HP steam before?
How are you going to move this thing after its hot?
What is 200 bar in psi?

[judgment_arms]

What is 200 bar in psi?

200bar is approximately 2900psi.

[SpudUke5]

200 bar = 2900.75476 psi

Edit: Damnit!

Well i think this would be one hell of a project. That energy transfer from those particles would have alot of energy.

I am just beginning thermochemistry in my chem class right now and from my current knowledge in it, this would be one powerful cannon that no one can image.

From what i know, since particles at 700 degrees have more energy than ones at room temperature, its going to get harder to reach mach 2 because at higher temperatures and pressures, you need to produce more energy to get at mach 1.

For example, in New Orleans, an egg boils at 105 degrees Fahrenheit and in Denver, a egg boils at 85 degrees fahrenheit. This is because New Orleans is below the sea level so there is more atmospheric pressure so the needs to be more energy to get that water to boil to overcome the pressure (energy) acting against it. In Denver, the atmospheric pressure is less because it is above sea level and therefore needs less energy to boil to overcome the pressure (energy) acting against it.

But the water boiling in New Orleans is still going to have more energy because is it at a higher temperature.

Refer to this wikipedia article for more information on calculating the "Mach number" possible with this cannon.

I know i didnt explain this well, because i forgot some of the reasoning.

[Pyro Ninja]

What is 200 bar in psi?

According to an online converter 200 bar = 2900.7541psi

judgement and LikimysCrotchus5 beat me

[D_Hall]

May I make a suggestion?

Forget the "throw it in a fire" approach. I've seen it tried for steam rockets. It's a royal PITA that doesn't work horribly well.


Try this on for size....

Insulate the interior of the pipe so that it DOESN'T transmit heat.

Heck, insulate the exterior too. In short, insulate the pipe as best you can....


...Then use an electric heating element INSIDE the gun (like a water heater).


MUCH more efficient system (due to insulation). MUCH more reliable (it's as reliable as your source of electricity).

[judgment_arms]

judgement and LikimysCrotchus5 beat me

Dang it, after I removed it from my signature people stopped calling me Judge...


DYI, I just thought of a possible problem:
What temperature does aluminum melt at? You might have a bit of a problem with the burst disk melting in the union and steam and molten aluminum blowing out everywhere and your union seal together…

[Lentamentalisk]

Issue that I see: most fittings are given their ratings for up to 180F or so, they do not even mention what it will do if heated above that, and 700F is a fair amount over what they are standardly measured to.
As for heating, I suggest that you make a little brick forge for your cannon, and get a big 20lb propane tank and just fire away till it goes boom! They have instructables and such on how to make a brick forge.
Also, with such high amounts of force, it is almost completely necessary that you mount the thing on something really heavy so it doesn't fly away and send your fire all over the place.

[Acdcmonkey1991]

200 bar = 2900.75476 psi

Edit: Damnit!

Well i think this would be one hell of a project. That energy transfer from those particles would have alot of energy.

I am just beginning thermochemistry in my chem class right now and from my current knowledge in it, this would be one powerful cannon that no one can image.

From what i know, since particles at 700 degrees have more energy than ones at room temperature, its going to get harder to reach mach 2 because at higher temperatures and pressures, you need to produce more energy to get at mach 1.

For example, in New Orleans, an egg boils at 105 degrees Fahrenheit and in Denver, a egg boils at 85 degrees fahrenheit. This is because New Orleans is below the sea level so there is more atmospheric pressure so the needs to be more energy to get that water to boil. In Denver, the atmospheric pressure is less because it is above sea level and therefore needs less energy to boil.

But the water boiling in New Orleans is still going to have more energy because is it at a higher temperature.

I know i didnt explain this well, because i forgot some of the reasoning.

Acording to my calculations using this formula
c={sqrt(v*[P/x])}
Where v is the constant of pressure divided by heat
P is the pressure
x is the density of the gas
And c is the speed of sound at that temperature and pressure
I got that the speed of sound should be reached at 1872.42872 fps
Which is higher than in just air

Not sure if I'm right though because I just finished 8th grade chemistry and Algebra with a B-

[D_Hall]

Has anyone else done HP steam before?

Even in the 1800s.

Very little around here is new.