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trying to design BBQ gas tank hybrid

A place to ask general spud cannon related questions.
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trying to design BBQ gas tank hybrid

Unread postAuthor: coconut helmet » Mon Oct 31, 2005 8:56 pm

Basically ive never built a spudgun, but 2 weeks ago my bro in law, showed me a combustion one and fired off a few rounds - great fun.
i never even knew about them before so ive been spending heaps of time on the net looking at all the different types and havebecome interested in the idea of using household items that store pressure to make a gun ...eg fire extinguishers or gas BBQ tanks instead of pvc, to increase pressure.and all steel design
basically i have no experience (so its probably very flawed) but im just trying to think of different ideas for one. would any of my plan be viable, could it work, how could i make it work?
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Unread postAuthor: Ballad_Black » Tue Nov 01, 2005 12:04 am

It looks pretty good for a first gun idea, in fact, ver very detailed. Also, before I go on, a rant insues. 9 people before me have looked at the diagram and not one posted, as of yet any how. That always got to me, just weird I know.

Back on track, very nice, detail, and nice ideas. Personally, I have never mesed with any hybrid type gun. So I cant tell if it would work or not, but from reading around it should. There would be trial and error, as well as figuring out perfect air/fuel ratio, but thats gonna be a task in most guns involving combustable fuels.

Get more input before going build crazy, I'd trust anything Pimpmann, PCguy, or spud shot said. They know thier stuff (not saying all those not mention know nothing.)
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Unread postAuthor: CS » Tue Nov 01, 2005 1:20 am

BLB actually should be on the top of your "trust" list he freakin knows everything. Literaly he has a equation for everything! Back to the topic you seem to know your stuff Coconut Helmet but im sure you heard this several times but Ill say it again ((echo)) Due to the power created by a hybrid and the complexty of a hybrid cannon DO NOT build one. Now im suprised by your nowlegde and your only a noob but I gaurntee there is something you havent learned that you should learn that could prevent personal injury/ cannon failure. Before attempting a hybrid make a few of both combustions and hybrids.

About the diagram I dont know if I would use a propane cylinder becuase im not sure if they even hold that much pressure. When the propane is in the cylinder it is a liquid so there for there isnt a need to hold high pressures. I must admit I dont fully understand your spring contraption. A fire extingusher would be a better choice of a chamber. You also need some way of measuring your propane input. Besides that it works on paper until the spring things and since I dont fully understand whats going on there I cant tell you if I think it can work.
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Unread postAuthor: spudshot » Tue Nov 01, 2005 6:39 am

those propane tanks are made to hold propane only, they will probably fail when you detonate a mix creating 300 PSI inside it, i believe propane in those tanks is around 120 PSI, so the tanks arent made for much more than that (a little more due to temp. shift).
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Unread postAuthor: Ballad_Black » Tue Nov 01, 2005 12:32 pm

See, this is why I said listen for input from pimp and spud, lol, makes my post almost useless. But I even learned a few things now, not that I wanna attempt something like this.
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Unread postAuthor: boilingleadbath » Tue Nov 01, 2005 3:32 pm

BLB = me
Equation for everything... Many of those are composed on the fly, so be sceptical if I hint at having done that...

Personaly, I don't see the need to construct a combustion cannon before attempting a hybrid. The only thing you'll need to learn are fuel meters, and they are rather simple... if you feel you need experience with them, you can just opperate your hybrid as a sch 80 combustion for a while.

As to the cannon it's self, here are the problems I see:
Ignition scource location; current location will result in a poor burn and similar muzzle velocity.
The ball valve will restrict the flow, as it won't be open by the time the projectile is gone.
The current gauge system will be inacurate.


I would avoid using a propane container as a pressure vessle, as they are intended to hold 120 PSI. The pressure rating will only be decreased by tapping a hole in it... it'd probably be safer to use sch 40 (4" is rated to 220)
It should be noted that sceince this is not NASA, the tank will most likely fail at 500 PSI, or roundabout. However, if you have a defective tank it's going to get you.
(NASA doesn't belive in saftey margins... if a tank is going to be used at 100 PSI, it will fail within a few PSI of that. That's one reason why it costs so much to do anything; this is really high quality merchandise.)
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Unread postAuthor: saladtossser » Tue Nov 01, 2005 7:17 pm

spudshot wrote:those propane tanks are made to hold propane only, they will probably fail when you detonate a mix creating 300 PSI inside it, i believe propane in those tanks is around 120 PSI, so the tanks arent made for much more than that (a little more due to temp. shift).


last time i checked, a tank like that comes with a 300psi relief valve

that is a neat igniton idea!!
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