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HELP Im a Newb And i Wanna Build A Large Scale Cannon

Post questions and info about combustion (flammable vapor) powered cannons here. This includes discussion about fuels, ratios, ignition systems, safety, and anything else relevant.
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HELP Im a Newb And i Wanna Build A Large Scale Cannon

Unread postAuthor: spec4soldier » Thu Nov 22, 2007 7:55 am

ok people i am new to this very new....... so new that im still in Iraq and dreaming up my new invention(s) when i get home. im needing suggestions on a large scale combustion cannon. and when i say large scale im thinkin cannot be carried by one person. i want more like a towed cannon.

I need serious help on how to go about designing this beast of a spud gun ive dreamt up and i need to know the basics and what is best for this kind of project. Message me back please... this is very important.

thank you for your time[/b]
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Last edited by spec4soldier on Thu Nov 22, 2007 2:17 pm, edited 1 time in total.

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Unread postAuthor: watto » Thu Nov 22, 2007 8:25 am

Welcome to spudfiles,

What route you wanna take with your gun depends largely on your DIY skills and what tools you have. Since I'm not a fan of combustion cannons I would encourage you to look towards pneumatic guns they are more powerful and reliable generally.

That said If you want something real simple, just get some real long pressure pipe screw a cap on one end of it put a sparker on it and spray deoderent inside. Doesn't seem like much fun to me though, all that fumbling round screwing the cap on quickly before the deoderent 'expires' Good for some cheap laughs but youde get bored of it.

I think the best thing for you would be a big arse 'over-under' piston cannon, basically its a piston housed in a tee joint, the piston pushes up against the barrel and seals it because of the pressure from the fill valve building behind it, when you exhaust a small amount of air from behind the piston it gets pushed back and lets the air into the barrel quickly.

Theres probably a website where you could buy a pre-made valve that opens real quick which would eliminate the need for a piston and make it real easy to make.

Maybe something like this?
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Unread postAuthor: psycix » Thu Nov 22, 2007 8:37 am

A large scale combustion?
Just get HUGE PVC pipes and one hell of a long barrel.
But get multiple spark gaps and keep the ratio under 1:1.
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Unread postAuthor: spec4soldier » Thu Nov 22, 2007 8:37 am

well let me tell ya what im thinkin about. i want a cannon that is towed like behind my 4 wheeler . i want it to look like a 155mm towed howitzer...... dont ask me why but i want to make a bad ass cannon that fires a good distance without having the knowledge of building the complex pneumatics or the hybrids and since im new i dont really know the difference in many of these except that some use air and some use flamable sprays. im making the towed frame outta metal and the cannon its self outta pvc. its gonna take a while to do this . and as far as that goes i dont know any of the ratio measurements that i need ,,,, something about the size in the picture you posted im guessin

If i go pneumatic what all would i need to make it function ,,,, what types of stuff is recomended?
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Unread postAuthor: watto » Thu Nov 22, 2007 9:11 am

Building a pneumatic can be a bit daunting, but once you understand the concepts of how they work you can scale them up to any size really. If money is not an issue then buy one of these overpriced but high performance valves http://www.bcvids.com/store/product_info.php?cPath=23_29&products_id=52 then you just need to make a chamber that connects to one side of it and a barrel to the other and you cant go wrong. Obviously you need pressure rated pipe, I only use Australian class 18 pipe, which is similar to American Sch 80 pipe (not cheap but safe).

I think you should do a bit of reading on piston cannons, god knows I'm not the right person to explain it to you :lol:, start here maybe http://www.spudfiles.com/spud_wiki/index.php?title=Piston_valve
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Unread postAuthor: psycix » Thu Nov 22, 2007 9:30 am

If you really want it to be an combustion, get a 6" and 4' long chamber, combined with a 4", 10' long barrel.
Make it a over/under design.

This design is norhing more than a basic (but HUGE) combustion design.
Get as much spark gaps as you can get, spreaded out as much as you can.
Like 3 spark gaps placed on 1/4, 1/2 and 3/4 of the length of the chamber.
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Unread postAuthor: wangpushups » Thu Nov 22, 2007 9:43 am

Ok first off there's a thing called a caps lock key, turn it off. Second off, there's a search tab, use it.
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Unread postAuthor: Fnord » Thu Nov 22, 2007 10:08 am

If you want a barrel of say, 10'x4", you might want to use one of those 5 gallon portable air tanks for a chamber. It'll probably save you money on fittings, and you don't have any chance of it getting damaged and exploding.

As for attaching the barrel to the tank, well, you'll just have to improvise. You could weld on a 4" coupler, or a slightly bigger metal pipe and sleeve+bolt the barrel inside it.

I'd try a combustion before a pnuematic. Building a big pnuematic cheaply* means making your own valve, and isn't really something you want to attempt when you start out. Unless you're an engineer.

*Still very expensive
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Unread postAuthor: trae08 » Thu Nov 22, 2007 10:20 am

you need more help on how to hake your posts rather then how to make a cannon.
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Unread postAuthor: schmanman » Thu Nov 22, 2007 10:33 am

building a big pneumatic is not a cheap thing to do, but if you do it right, it is worth it. it's harder to assemble, put the fittings together, ect.


to build something that cannot be carried by one person, it took me over $500.
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Unread postAuthor: LikimysCrotchus5 » Thu Nov 22, 2007 10:38 am

Well in my theory, i would say you need to start small so that you can get a great performing big cannon after you know enough on building a small one. So i would start out with a combustion because they are somewhat harder to mess up on. Once you get that concept, you should try an advanced combustion. Then, if you are successful, try a large scale cannon. All you would have to do is take that smaller advanced combustion, then just multiply the length and the chamber, but still keeping it less than 1:1 C:B ratio, then you would have the calculations you need. Then you build it and would have a beautiful amazingly powerful cannon. To say the truth, you will be much more successful if you work your way up. Don't start from the top, you'll mess up and waste money. And look up info using the search
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Unread postAuthor: spec4soldier » Thu Nov 22, 2007 12:40 pm

TRAE08 and WANGPUSHUPS

Well first off since im NEW AND IN IRAQ SERVING MY COUNTRY!!!!!!!!!! i figured i could make my letters large in the Subject of my forum in order to get replies and suggestions on how to make a spud cannon. I get enough remarks against my character on a daily basis and i sure dont need them from you as well , since all i was asking for was help you could have been nice about it but instead you wanna treat me, a complete stranger, like this

TO EVERYONE ELSE

To those who gave proper input on the subject posted thanks for the input [/b]
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Unread postAuthor: Ragnarok » Thu Nov 22, 2007 1:38 pm

spec4soldier wrote:i figured i could make my letters large in the Subject of my forum in order to get replies and suggestions on how to make a spud cannon.

Although it gets attention, it is against the forum rules to post in ALL CAPS to boost your thread's views - threads shouldn't be replied to on the basis of whether the poster used CAPS LOCK for the title. It would be courteous for you to alter the title to fit the forum rules, and it would avoid a moderator needing to do it for you.I don't wish to cause any offence to you, but the rules are there for a reason.
I have the utmost respect for serving soldiers, regardless of whether or not they are from my country, but it doesn't affect how you should act on a forum.

Last but not least, use of poor grammar makes it harder for me to respect you as a good forum member, as well as introducing some doubt that you really are the mature adult you claim to be.
As I once remember reading: "A member's building skills, safety and maturity have a high correlation to their posting ability".


You may notice the text in italics... please read it, it's not in italics so it can be easily ignored, it's that way to divide the two halves of the post.

All that aside, I would suggest a large propane metered combustion. Large well built pneumatics are more powerful, but far more complicated - not to mention large charging times, even with a meaty compressor, and limited mobility.
A large combustion needs a propane bottle and a few batteries. A large pneumatic needs a compressor or HPA tank which it will eat like candy.

There are enough different guides to building combustions, but I suggest looking round Burnt Latke.
It's a nice and very comprehensive site, with information on chamber fans, propane metering, multiple ignition, and stungun spark control.

If you can read around, and take in all their suggestions, then you will be able to create a very considerable cannon.
On these forums, there are many very ingenious improvements that could also be applied, including breech loading, and there were suggestions for combustion efficiency improvement ages back if I remember.

I include the customary warning that all PVC pipe and fittings you use should be pressure rated. This involves a stamped rating, and NSF-PW markings in the US.
A DWV marking is a possible indicator of no/low pressure ratings (although not always), and should be eyed suspiciously to find a pressure rating on it.
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Does that thing kinda look like a big cat to you?
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Unread postAuthor: cwazy1 » Thu Nov 22, 2007 2:06 pm

i love hoow only one person has told this guy to use the search. im most topics where the poster knows nothing about soemthing, ppl start spamming "use the search" but not in this topic. interesting.

i would say that because you obviously know nothing on the subject of potato guns and etc. to look at some of the posted showcases of pneumatic and combustion cannons and see what you like instead of just getting opinions of what other ppl like. also, using the search is a great tool because it gives you all the info you really need.

just why do you really want a huge cannon? you know that it will cost you more money in the short and long run, and it prolly wont shoot as far as a nicely build small cannon.

if you decide to build a combustion, most combustion cannons are deemed "firearms" in many cities and thus you wont be able to tow it around and show it off. on the other hand, building a pneumatic is not terribly hard to do on the component scale. the only thing that might mess with you is the valve on the thing, creating a huge cannon requires a huge valve or else it'll be like creating a small cannon with huge volume. on the con side, you would need a huge compressor or a massive amount of HPA to charge the thing. you know those pumpkin chuckin contests? those cannons in the pneumatic section of the contest, those things take about an hour of charging to pump it up.

if i were you, i would consider re-thinking your idea of making a huge cannon, think more about making a smaller cannon and make it efficient and powerful.
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Unread postAuthor: psycix » Thu Nov 22, 2007 5:11 pm

Start small, start basic and work your way up to the big advanced cool stuff as you gain more and more experience in spudding.
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