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Combustion spudgun made of EU pvc

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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Combustion spudgun made of EU pvc

Unread postAuthor: ozoncqp » Mon Mar 30, 2009 6:14 am

Greetings.
Am new to this forum tho i browsed it quite alot recently.
I got a few questions i hope i can get satishfying answer on here.
I've had my spudgun for about 4 months now. It started out after my brothers and I decided to try this as it sounds like great fun!
So we drove to the local vvs dealer and bought some pvc pipes and reductions etc to make the standard, danish orange cannon!

The model was a basic. 110mm chamber 50cm long, 75mm barrel 1-1.5m long.
Assembling it with duct tape and having 2 ppl to hold it while a 3rd fires it with a lighter was fun the first 2 days. Then i decided to make it a 1 man shooter.
So i began my research of various sites and forums. Nothing much could help me as most spudguns are made from US pipes, diameters and thickness doesnt match in any way compared to danish/european pvc pipes.
But after some time i've come up with this.

Image
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Able to do this on 30meters distance.
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Now, the pipes im using should be pressure safe uptill 130-150 psi according to the dealer. Tho the wall thickness is only about 2-2.5 mm i forgot the exact number atm.
I just came by another type of pvc called; pvc/pp ht1 PP should just indicate its made by recycle pvc tubes/plastic. And the dealers says it takes the same pressure. Now i just wanna be sure that this can be used as a cannon material as its only 1/3 the standard prices of the usual pvc/drainpipes im using.

I just came by This topic And i did some calculation and well the numbers kinda says using these pipes would be safe no matter what propellant im using. Atm im using any hairspray with all the good stuff in it and no aqua.
Sadly i haven't got a vid of the thing in action atm, but a 72mm 220gram orange shot straight up will go out of sight for a few secs. And the gun packs a massive recoil.

If these pipes can be approved ill make a new gun as this is still "recycle" parts of our original gun. Better power strips, new fan, better wiring, most parts will be glued. And ill work on making a breechload system with threads. As our pipes wont have threads just stupid O-rings im using screws atm for testings.

I might exchange some of the chamber with a cleanout T-pipe, for injection/fan venting.
And if ppl think that the 130psi pressure ratings will be sufficient for propane injection ill make a system like that. Any onehand weed burner tank of 450ml would last for a while i guess.
And i cant find any hard info regarding a straight cannon vs the Ubend cannon.

I came by some who claimed that Ubended is best for Phneumatics. Im open to suggestion. But all fair i think i've reached the power im looking for. Now i just want to tweak it for safety/reliability/looks. The duct tape will be replaced by a paint job of some sort. and better handles.
oh i allmost forgot. The c:b ratio is 1.5-1 chambers holds 6 liters of water barrel takes 4.
I hope i landed in the correct section of the forum ;)
/michael
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Unread postAuthor: psycix » Mon Mar 30, 2009 6:53 am

Nice!
You should indeed try to lose the black tape, it looks a bit messy.

Your pipes will probably hold the pressure of a normal combustion. Just do not use acetylene or hydrogen (not because of the pressure, but because of the shockwave)

Straight is more powerful, but as long as your U-bend is not too small, it usually doesnt matter. It is however a problem that your flamefront also needs to reach into the U bent to burn the fuel there, this slows combustion time a little. And because of the Ubend cannon being compact, you can make up for this (very small) power loss by using a longer barrel.
Another downside of over/under cannons though, is that the barrel needs to be supported: make a piece of wood or something for between the barrel and the chamber and then clamp em together. If not, the recoil will put a lot of stress on the elbows and cause failure.

Oh and you should've posted this into the "Combustion cannon showcase" not the discussion. Just ask a mod to move it.
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Unread postAuthor: inonickname » Mon Mar 30, 2009 7:00 am

Hydrogen and acetylene burn rates double and quadruple propane rates (acetylene is roughly double) and are both prone to DDT'ing in the right circumstances. Trust me, you do not want DDT. DDT will literally blast the living PVC out of that.

Anyway, awesome. Was that grip inspired by the one on the locotus or whatever? I believe he even had a how to on his webpage.

Pretty good work, but the black tape is a downer to it. It would look much more streamlined and nice without it. It wont be doing much to stop explosions, that pipe will be fine with "standard" fuels.

Good work..I'm sure a mod can shift it.
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Unread postAuthor: ozoncqp » Mon Mar 30, 2009 7:01 am

ahh well i posted it here as i had some questions aswell. Rather make a combi post than 2 seperate, but im lazy. Ya the tape will go off, but its just on its beta test atm.
But youre quite sure that it can hold the pressure of a protane injection system ?


****Edit #1
About the tape just to calrify it. The pipes are gray and orange, and its been affected by tons of silicone in one way or a nother. Reason i applied tape to it more or less.
Bout the handles nah i cant say i got inspired i just grabbed whatever i could find in the garage of random pipes n things.
Im curious about the DDT, this is short for?
Oh and if it helps im a blacksmith by proffession, so i can get my hands on rather nifty items, but i just dont wanna fill it with nipples n shizzle.
In a week i should have my clean, remade model of this posted. Straight tube and maybe slightly bigger due new muffs n fittings.
The batery on it is by the way, from one of them 75cm remote controlled cars. 12v 2.5Ah. Should support a 80mm fan for a lifetime ;)
Its now packed in tape n stuff to support it. Ill make a glassfibre casing for it. And i might make all the handles in fibre aswel.
Cant wait till my nxt posting. That will however go into the showcase, and hopefully with a vid of it.
****Edit #1

****edit #2
psycix wrote:Straight is more powerful, but as long as your U-bend is not too small, it usually doesnt matter. It is however a problem that your flamefront also needs to reach into the U bent to burn the fuel there, this slows combustion time a little. And because of the Ubend cannon being compact, you can make up for this (very small) power loss by using a longer barrel.
Another downside of over/under cannons though, is that the barrel needs to be supported: make a piece of wood or something for between the barrel and the chamber and then clamp em together. If not, the recoil will put a lot of stress on the elbows and cause failure.

Well if youre familiar with the cannon Themonkeybase has made, it'll be roughly the same messurements im thikning in using a Ubend cannon.
But by adding a longer barrel do you mean change the C:B ratio? im planning on keeping it at 1.5-1 that suite me fine.
***edit #2


Edit note collapsed multiposts to keep it clean
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Last edited by ozoncqp on Mon Mar 30, 2009 10:33 am, edited 2 times in total.

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Unread postAuthor: ozoncqp » Mon Mar 30, 2009 7:13 am

merged, thought i could delete posts
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Last edited by ozoncqp on Mon Mar 30, 2009 10:36 am, edited 1 time in total.

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Unread postAuthor: ozoncqp » Mon Mar 30, 2009 8:43 am

Shameless merge
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Last edited by ozoncqp on Mon Mar 30, 2009 12:15 pm, edited 1 time in total.

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Unread postAuthor: ozoncqp » Mon Mar 30, 2009 12:15 pm

Ok i don't know if I violate anything but here goes. I just made a fast paint drawing. Just to make sure that were talking about the same thing here. And also as our pipes are different i hope that i could get a suggestion or two on how to make an effective breechloading system. I've got a few idea and ill add the drawing asap.
Just gotta get my old cad/cam tools again
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All fair i must say i like the Ubend alot more when it comes into how handy it is. But im somehow a sucker for the straight cannon aswel. But thats due the fact that the barrel is easy to take off.
As mentioned before im planing on some fibreglassing it to hold battery, custom handles etc. I could fibre in a 75mm "slide connector" for the barrel to slide in on the Ubend version for a breechload. And use the 3point bolting system im mentioning on the drawings.
But im gonna go to my old workshop and see if i cant find some 90mm nylon rods to work on, for threading and stuff ;)

again this is just a fast drawing, the wires are for my pleasure only, it'll be simplified alot before its complete.
And the measures on the drawing are random. Its just a quick hmm this might work drawing ;)

I can add i just spoke to the dealer selling the PP/pvc pipes. He guarantees that its pressure tested for 130-150 psi. And it didn't really take him long to figure out what i was gonna use it for, so he added;" Not long ago we sold 3-5 set of pipes and ignitors aday, I can assure you it'll work for the spudgun"
My concern still lies in the fact that its gonna be glued up, but whats the difference between 3 ppl holding it together or it being glued ? I guess aslong as the slug can be pushed by hand it'll pass through the barrel aslong as its not too long.
/michael

Oh and if this is indeed in the wrong section please move it. Or should I PM a mod ?
**edit fixed typos i hope**
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Unread postAuthor: psycix » Mon Mar 30, 2009 12:38 pm

I meant that the difference between inline and over/under is very small, almost nothing.
With over/under, you can have more barrel length (and chamber length) because over/under shortens the gun. So because it becomes more compact, you can make the gun larger, while the overall length stays the same.

My concern still lies in the fact that its gonna be glued up, but whats the difference between 3 ppl holding it together or it being glued ?

You should glue it with solvent weld glue.
If not, the cannon WILL blow the fittings out, unless they are threaded.

Oh and if this is indeed in the wrong section please move it. Or should I PM a mod ?
You can PM a mod yes.
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Unread postAuthor: starman » Mon Mar 30, 2009 12:52 pm

If you're using proper PVC cement and primer, it will be like the parts grew together. I'm not sure what you mean by 3 people holding together. I hope and pray it was cemented together then as well... :shock:

I've seen the orange and gray PVC used before here in MushiYoshi'sguns...he's in Norway.
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Unread postAuthor: ozoncqp » Mon Mar 30, 2009 1:40 pm

Ya mushi and I would be using more or less the same type of material.

Well holding it together with 3 ppl would be something like this.
[youtube]http://www.youtube.com/watch?v=E8fFGFyBdaA[/youtube]
This is not me or my brothers just some random rednecks :D

Well without the fancy clambs and stuff you guys got the danes start to think creative ;)
But i got a big tube of epoxy glue, i recon thats what we used back in the days when i went to blacksmith school :P
For some od reason the pvc cement costs a fortune, unless [This] is strong enough. And i think i might just have found a 75mm threaded pvc fitting that will fit both ends :o looking like [this] I'll call the shop tomorrow and ask for the inside diameter.

I just ordered the parts for the over/under model, i might jo go with it aslong as it fits my trunk im happy. And well it would be cool if its easy to conceal, these aren't exactly legal in many european countries. Doesn't make it less fun tho. Luckily i live far far away from most civilization
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Unread postAuthor: ramses » Mon Mar 30, 2009 1:57 pm

that is not suitable cement. did you check ebay for pvc cement? It shouldn't be more than a few dollars.
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Unread postAuthor: ozoncqp » Mon Mar 30, 2009 2:17 pm

The tube in the pic or epoxy?
But ill get the stuff in the tincan with the spunge on it. I might be able to bum something from my old workshop.
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Unread postAuthor: starman » Mon Mar 30, 2009 10:01 pm

OK, that's one of the more crazy things I've seen this year. Anything less than the tractor wheel for a brace could have been trouble for those guys.

PVC cement...in the US it's only $3 or so for a small can...the primer another $3. In Denmark, I guess it costs what it costs but you should use the proper products. Here is the product we typically use here. I'm not sure of its availability there.

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Unread postAuthor: ozoncqp » Tue Mar 31, 2009 2:05 am

hahah crazy or not thats how a spudgun works in these outlaw countries. Nah we havent got the brand, but i might be able to find something similar.
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Unread postAuthor: inonickname » Tue Mar 31, 2009 3:30 am

DDT is an extremely rare case (probably never happened in a 1x propane combustion) where the flame front exceeds mach (speed of sound relative to your area) creating a massive pressure wave. As fuels such as acetylene and hydrogen burn much faster than propane this is more likely to occur. (Not that you should use acetylene anyway, you'll kill yourself). I wouldn't aim to contain DDT with a PVC chamber, no PVC on earth will hold back this kind of force. It won't happen in a 1x anyway

Good luck on find primer/cement..try a plumbing or hardware store.
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