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HP steam cannon

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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Unread postAuthor: swinging_dic_tater » Sun Apr 27, 2008 11:32 am

Regardless of what he meant, he isn't correct.
You can use this calculator and the information on the NOAA site for both Denver and New Orleans.

Today in Denver water boils at 203.281°F or 95.156°C

In New Orleans it boils at 212.275°F or 100.153°C
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Unread postAuthor: POLAND_SPUD » Sun Apr 27, 2008 11:34 am

he said 'below sea level' it doesn't really matter whether New Orlean is below sea level or not but it shows that he knows more less how it works...
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Unread postAuthor: DYI » Sun Apr 27, 2008 12:22 pm

And no matter what it shows, it has absolutely no relevance whatsoever to the topic. :roll:
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Unread postAuthor: rp181 » Sun Apr 27, 2008 12:34 pm

i think you should look into electric heating, it gives a presice controll of tempeture. I got water to boil with a 7W 260ohm resistor in mains voltage, i think it would be easy with actuall heating elements, home depot sells water heater elements.
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Re: HP steam cannon

Unread postAuthor: Ragnarok » Sun Apr 27, 2008 12:39 pm

DYI wrote:Does anyone know the speed of sound in 700 degree F steam?

Around 615 m/s (2020 fps), although I didn't have an exact ratio of specific heats for steam at that temperature, but it would seem to be around 1.29.

Unfortunately, I can't find my book of steam tables, or I'd give you a more accurate answer.

@Judge: If you want a couple of corrections:
Those fireless locomotives would only normally operate at around 400 psi at most - and I know US steam locomotives are a lot more substantial than the ones that we had in this country, but a 1000 ton locomotive sounds way off the mark.
Even the largest of UK locomotives were only around 100 tons in working order. I can imagine a US locomotive being a lot more than that, but not 10 times.

As I think you were saying, the real danger with steam vessels is that they contain superheated water. If they rupture, the pressure drops.
This dropping of pressure will lower the pressure that water is under.
This allows the water to "flash" into steam, and rapidly vaporise.

This means that the volume of steam you are dealing with is vast. When water turns to steam, it's volume increases around 1700 times (IIRC, might be wrong).
Essentially, the safety advice here is to use the minimum amount of water possible in a steam cannon, otherwise the water will rapidly flash in the case of any rupture.

However, I was thinking about this some time ago (in one of the "articles" I write myself, watch this space*) - You could vastly increase the potential of a steam cannon by deliberately exploiting this effect.
If you had a reserve of superheated water in the chamber that would flash into steam when the pressure dropped (i.e. when steam moves through the main valve), the chamber's pressure could be kept near constant, essentially like having a very high C:B, but without the disadvantages or corresponding efficency losses.

You could use the effect to allow a proportionally very small chamber, and if done right, you could get high power without too much of a safety risk.

*Or perhaps a different one, as any extra information on the subject is unlikely to be edited into this post.
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Last edited by Ragnarok on Sun Apr 27, 2008 2:58 pm, edited 1 time in total.
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Unread postAuthor: sniper hero » Sun Apr 27, 2008 1:39 pm

I'm not an expert but just want to help
if you have a test tube put water in it and heat it for a while it breaks right? (ofcours there might are that doesn't)
so you have keep it moving to have all water the same temperature.
does this have an effect on heating the not moving gun?
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Re: HP steam cannon

Unread postAuthor: judgment_arms » Sun Apr 27, 2008 2:08 pm

Sorry, locomotive weight was only 600 tons; I had the line from “The Silverton” stuck in my head:
“…and she weighed about a thousand tons”

The locomotive was a 4-8-8-4, I think…

Once again, Ragnarok had the answer I was looking for… :)

Also, another case of a boiler explosion from a 4-8-2, or something of that size, blew apart the round house and derailed two other locomotives of similar size.
This blast was caused by the fireman forgetting to fill the water tank before lunch, the water level dropped below the top of the firebox and the fire weakened it to the point of failing: KA-BOOOM!!!
The blast was compared to a 500lb bomb, by the local news of course… :roll:
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Last edited by judgment_arms on Sun Apr 27, 2008 2:38 pm, edited 1 time in total.
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Re: HP steam cannon

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Unread postAuthor: Deli » Sun Apr 27, 2008 2:37 pm

If you still don't have a heat source, you could consider Thermite, assuming you have the equipment to make/handle it. That might be too unstable for your needs though.

Some types of thermite are made to burn through tank armor though, so be careful.
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Unread postAuthor: judgment_arms » Sun Apr 27, 2008 2:42 pm

Deli wrote:If you still don't have a heat source, you could consider Thermite, assuming you have the equipment to make/handle it. That might be too unstable for your needs though.

Some types of thermite are made to burn through tank armor though, so be careful.


Thermite! :shock: Talk about blowing open the gates of Hades with a ton of nitro…

Naw, a good sized fire and a blower should do nice; run it off presto-logs, burns 30% hotter than wood. (Back to the Future III reference)
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Unread postAuthor: JDP12 » Sun Apr 27, 2008 2:47 pm

yea, thermite might just be a bit excessive...
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Unread postAuthor: Deli » Sun Apr 27, 2008 2:48 pm

If you want water at 700 degrees celcius, thermite is about the only way I know of. If you want Fahrenheit, thermite is a little overkill.

There are many types of thermite, ranging from tank killers to welders. Some is just hot enough to melt steel but not vaporize it. Look into that. It's also pretty cheap to make low grade thermite. It'd burn pretty quick though, so a log might be better if you are wiling to wait.
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Unread postAuthor: D_Hall » Sun Apr 27, 2008 3:02 pm

Deli wrote:If you want water at 700 degrees celcius, thermite is about the only way I know of. If you want Fahrenheit, thermite is a little overkill.

700 F is roughly the temperature of dry steam so I'm gonna guess he meant F.

That said, if you can't think of a way to reach 700 C without thermite, you need to get out more.


Oh, and I'll go ahead and say it: Thermite is a STUPID idea for this application.
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Unread postAuthor: Deli » Sun Apr 27, 2008 3:08 pm

Oh, and I'll go ahead and say it: Thermite is a STUPID idea for this application.


Yeah, but if you are planning on just dumping the gun into a fire, this is a little smaller and managable. I can see the problems with my method though.
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Unread postAuthor: bigbob12345 » Sun Apr 27, 2008 3:20 pm

I can see the problems with my method though.



Well ill go list a few for you

1. price
2. burn time(it wont burn long enough to suffeciantlly heat the water)
3. the chamber melting :lol:
the list goes on and on
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Unread postAuthor: D_Hall » Sun Apr 27, 2008 3:50 pm

Deli wrote:Yeah, but if you are planning on just dumping the gun into a fire, this is a little smaller and managable. I can see the problems with my method though.

The biggest problem is that the word "managable" apparently doesn't mean to you what it means to the rest of the world.
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