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steam cannon

A place to ask general spud cannon related questions.
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Unread postAuthor: judgment_arms » Tue Apr 10, 2007 9:57 pm

They used to use leather all the time as seals, works better than rubber in some situations, like when working with steam.

just hade the greatest idea, make a big fire and wait for the coles to settle, then heat i up in there, the pull it out with pliers and gloves, then put it in a vise and fire. that would kinda work, and the fuel would be free.

For me I’d just throw the thing in the forge well I’m workin’ steel,
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Unread postAuthor: hi » Tue Apr 10, 2007 11:13 pm

i didnt know leather worked. why did you quote me and whoever? a fire will get it red hot, a forge would almost melt it.
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Unread postAuthor: judgment_arms » Tue Apr 10, 2007 11:21 pm

Na, a forge won’t melt it, it’ll get it hot fast though. My forge is basically a hole in the ground filled with charcoal, I use the air compressor as a blower. Not going to get hot enough to melt it…

oh and I quoted you because I already said that, that’s what the other quote is,
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Unread postAuthor: hi » Tue Apr 10, 2007 11:33 pm

I just thought of something, I couldnt use teftlon tape could I? It would melt. is the only thing i can do to make it air tight to screw it on and tighten it really really tight? i doubt i could glue it.
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Unread postAuthor: frankrede » Tue Apr 10, 2007 11:39 pm

You could use teflon paste?
Or lock tite on the threads.

Or maybe even jb weld on the threads the screw it together.

Or weld along the joint?
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Unread postAuthor: hi » Tue Apr 10, 2007 11:44 pm

would any of those stand up to the heat? maybe i could put some cement in it, but that wouldnt be very practical and would take a week or so to dry. welding isnt an option for me. i think ill put a blow torch to some JB Weld and see how it does, but if that fails, any other suggestions?

yea, 200th post, only 999800 to go and ill have a million!
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Unread postAuthor: lukemc » Wed Apr 11, 2007 7:49 am

judgment_arms wrote:First off to answer you question, provided the ball valve doesn’t fail, yes.

Now here’s an idea:
Make a coaxial out of gas pipe, make the piston from wood (undersized to allow for the expansion of wood), and use leather for the seal face. Have a heavy spring behind the piston to keep it closed until it hits the desired pressure, about 500PSI, fill the area in front of the piston (what would normally be the pressure chamber) two thirds full of water and load it with a projectile such as a steel ball bearing. For me I’d just throw the thing in the forge well I’m workin’ steel, I suppose you could use a blow torch, but I’m not sure if that’ll give you enough heat. When the thing hits the “popping pressure” it’ll fire the gun, kind of like a burst disk, only slower and reusable.
Whadoyathink?


the spring wouldnt work it would reach the desired pressure and the spring would move a tiny bit allowing a bit of pressure out then would close again almost instantly because the amount of pressure it let out made the spring stronger than the pressure again. this would keep hapening until all the steam was slowly let out
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Unread postAuthor: judgment_arms » Wed Apr 11, 2007 11:29 am

And that just goes to show how tired I was last night… it’s a miracle I got my how-to done… good thing it wasn’t on steam cannon…
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Unread postAuthor: boilingleadbath » Wed Apr 11, 2007 6:22 pm

The service temperature of PTFE is about 500*F
That can give you steam pressures just shy of 600 PSI

That's more steam than you want to play with, considering the pressure rating and temperature derating factor of your pipe... discounting the possibility of buying some fancy-shmancy SS pipe of doom<sup>(R)</sup>.

And J-arm's spring-loaded piston <i>could</i> work, because the area under the barrel that is exposed when it opens will help keep it open... albeit not very well.
It'd require both a high C:B ratio and a large pilot volume, but it could be done.
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Unread postAuthor: chaos » Wed Apr 11, 2007 8:01 pm

boilingleadbath wrote:some fancy-shmancy SS pipe of doom<sup>(R)</sup>.


are you talking bout Stainless Steel BLB?
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Unread postAuthor: boilingleadbath » Thu Apr 12, 2007 4:45 pm

Yes, that's what I was using the acronym SS to mean.

The time before last time someone mentioned building a steam cannon, they where planning on using 1.5" sch 160 type 316 SS pipe (rated at about 3000 PSI) with burst disks that'd rupture at about 2000 PSI.
(mcmaster carried it)
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Unread postAuthor: Hotwired » Thu Apr 12, 2007 7:54 pm

A 2000psi burst disk sounds like a great way to lose your hearing...

Probably end up cheaper to have used HPA instead of generating that kind of pressure with steam :?
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Unread postAuthor: hi » Thu Apr 12, 2007 10:00 pm

thats a great idea.... not 2000 psi, but burst disks are.

maybe like 10 layers of aluminum foil or something.
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Unread postAuthor: mark.f » Fri Apr 13, 2007 9:36 am

Blitz, do some modeling with GGDT to see why steam would be a good idea.

I also think a ball-valve would be shorting yourself. If you're gonna work on a steam cannon, might as well make some sort of high-temperature piston valve, (investigate into some high-temp gasketing materials for the seal), and get the most "bang" for your buck. From what I hear from Navigator7, steam is pretty mean even at relatively low pressures. Also, the pressure is easier to acquire than compressed air. No moving parts like a bike pump to break, and no expensive air compressors. Everybody and their brother can buy a bag of charcoal, and has some sort of foot pump to provide an air blast to bring the heat up when they feel like it, (although not too much).

EDIT: goshdammit, I didn't see there were three pages. BLB already said why steam is better than air on page two, for anybody interested. Also, I was talking to "Blitz" on page 1 in the beginning of my post.

EDIT2: Here's a theoretical layout:

<img src="http://www.markfh11q.net/images/steamcannon.png">

"A" is a pressure gauge. "B" is a temperature gauge. The piston and sealing face are silicone. Charcoal is dumped into the hole, and a shop-vac exhaust is fed into the hole. The temp. shouldn't be allowed to exceed around 350 F. That will keep everything within ratings, hopefully. Everything is iron, and the bushing at the front is a "double-tapped bushing" from McMaster-Carr. The back is a regular bushing.
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Unread postAuthor: Bubba05 » Fri Apr 13, 2007 12:32 pm

the whole thin is flawed you saw what they had to do to get those results. and look at the size of the thing!! even a small down scale version wouldnt be mobile coz youd have to sit around for about two hours after you finished fireing waiting for the damed thing to cool. they also have a warning at the begining of that episode that it was quite dangerouse and dont attemp any of it at home...... They dont show you every step in how they made it and they may have put in a few miss leaders in there so you go astay.

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