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I just made my first spud gun the other day but in my excitement I did not pay attention to the pipe specs. This is my gun, from clean-out to barrel:
4" cleanout adapter and plug -> 4" bushing -> 4" Diameter 14" long chamber -> 4"x2" coupler -> 2" Diameter 36" long barrel
I have a BBQ ignitor through the bushing
The chamber is PVC sch 40 DWV cellcore
The barrel is PVC sch 40 DWV solid
I had read that the optimum ratio was 1.5:1, so I calculated the length of the chamber to 14" to match the 36" barrel. But I did not include the bushing or adapter volume, so now my ratio is greater than 1.5.
I did one test shot and I was very surprised by how loud it was. Is my ratio okay? I am also afraid that the chamber is going to explode in my face since it is cellcore. I only use deodorant as fuel, so will it hold together?
If the PVC is not safe, is there a way to dissolve the PVC cement and disassemble the gun and replace the pipes?
Last edited by corrosion on Thu Mar 29, 2007 8:29 pm, edited 1 time in total.
The max pressure you get in a combustion is around 80 psi. That is in the perfect conditions. You should be safe enough just don't drop the gun and if you see any crack stop using it.
For pneumatics never use DWV. no one like pvc shrapnel in their leg.
The strength of cellcore varies wildly with the brand, and we can't honestly say that it's safe... but it probably won't blow up, destroy your testes, thus causing hormonal problems, and leave you to live your life as a man who wears a 36-B brassier and speaks in a high voice.
Now, I'm the type to always wear my seat belt... so I'm going to personally suggest that you get new pipe.
1) There are, in a sense, multiple optimum ratios; the most efficient (not 1.5:1 for a combustion - as evidenced by the loudness of your launcher [efficient launchers are quiet]... it's acctualy about .8:1), the most powerful for a given launcher length (calculate with EVBEC), the quietist, what your uncle Ron told you is a good trade off between power and loudness...
...but most of the time, they mean the first one in this list, which 1.5:1 is not.
(fortunately, the energy loss is fairly small)
lol that was pretty f*cking funny.
And i found the loudness of a cannon to be one of the most redeeming qualities of it, but thats just me.
Anyways, getting new pipe would be in your best interests in my opinion, but i think as long as you stick with deodorant you should be fine.
well cellular core wont blow up in a combustion within 10 shots....BUT cell core is made from foam...foam melts...easily...this has happened to me before and i got a huge ass rip in a prototype combustion and 2nd degree burns on my chin and chest...plus i ruined my favorite dvs shirt....
4" piston valved cannon-half done..( i spilt my cement...)
Hybrid- 75% done. need to build propane holder and drill/tap sparkplug hole..
Cut the chamber twice, about 3-4 inches from each end, and cement a coupler on the cut ends. Get pressure rated pipe and glue it into the couplers. Now you have a safe combustion that will be louder because of the extra chamber space.
Uh Spudthug, cellular core is not made from foam, it is made from pvc like any pressure rated pvc pipe, except that the manufactur blows air bubbles into it while it is being extruded (formed) into pipe, which results in an extremely light pipe that is cheaper to make (because pvc material is displaced by air).
It will not melt like foam but will actually burn and become malluable much like regually pvc does when it is exposed to heat or an open flame.
Actually noname thats a really good idea for saving his cannon while making it safer.
Make sure the coupler that you use is pressure rated or at least not cell core. I think you already knew that but I just wanted to make sure. BLB that was hilarious!
I will most likely shoot it off some more this weekend, and then I will tell you how it goes. If I don't post after the weekend, then watch my story on the 10 o' clock news.
I use the same exact core with no problems, just dont use propane or butane to be on the safeside. hairspray, deoderant, or some airfresheners my favorite (keeps the gun smelling nice) they will all provide plenty of kick.
Hold up. Corrosion, you mentioned primer, but not glue. Did you not use PVC cement? If you only used primer, that's bad. Start over completely new. If I can toss a $35 chamber because I simply wasn't happy with it, I'm sure you can toss a $10 one for safety reasons.
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Did I not mention it? Don't worry, I am not that stupid. I used primer and cement, and gave it plenty of time to dry. I think I would get a little suspicious if the gun fell apart just by touching it. You can sleep easy tonight.
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