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Boom! The classic potato gun harnesses the combustion of flammable vapor. Show us your combustion spud gun and discuss fuels, ratios, safety, ignition systems, tools, and more.
thekiller578
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Wed Oct 26, 2011 8:14 pm

Alright i finally did some rework on the cannon,
now the only problem is the chamber,
i really dont know where to get my pvc pipe clearly but let me know what you guys think!
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Ive added a 3" coupling inside the 4" combustion chamber, i really dont know if this would help at all, but if in my mind it holds a bit more pressure
Ive added a 3" coupling inside the 4" combustion chamber, i really dont know if this would help at all, but if in my mind it holds a bit more pressure
link.JPG (22.31 KiB) Viewed 3798 times
I recently added 4 screws where the reducer is and the female thread
I recently added 4 screws where the reducer is and the female thread
Cannon.JPG (37.54 KiB) Viewed 3798 times
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Gun Freak
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Wed Oct 26, 2011 8:29 pm

Few things:
  • -coupling in the chamber probably isn't doing any good.
    -The ball valve should be tapped in a double layer.
    -Putting screws in the chamber doesn't strengthen it.
    -Bell reducers aren't pressure rated but you should be ok.
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thekiller578
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Wed Oct 26, 2011 8:36 pm

the ball valve is on a double layer, the whole inner chamber has the couplings, i added since the pipe isnt pressure rated, couldnt find any,
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Gun Freak
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Wed Oct 26, 2011 8:45 pm

Oh... Hm well are the couplings airtight at their sides? If not, then they still probably aren't doing much, other than providing a double layer. But I would still feel safe with it even though the pipe isn't pressure rated. since it's only a combustion.
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thekiller578
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Wed Oct 26, 2011 8:51 pm

yes i sanded down the little nub the couplings had, took me a while to put them in the chamber! thanks for your input :D
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Gun Freak
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Wed Oct 26, 2011 9:00 pm

You're welcome. Why did you sand down the nub? Did you put a piece of 3" all the way through?
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evanmcorleytv
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Wed Oct 26, 2011 9:23 pm

Yeah, I have to agree with gun freak.. BUT, I do like it, and it has VERY clean construction!! Great cannon!!
thekiller578
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Wed Oct 26, 2011 9:37 pm

i didnt i only had 2 3" couplings and i cut one in half so i could use a double layer to hold a dual fan at the end of the cannon, and the second one i used for the mid section, where the ball valve goes in, just for security,

thanks i tried my best! :P
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mattyzip77
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Thu Oct 27, 2011 9:33 am

Thats a weird place to put a ball valve, but other than that not bad! For future reference, you can get those bell reducers pressure rated, but you gotta order them on line. They are a biitch to find locally. Its a combustion, so I wouldnt worry about the DWV pipe and fittings. Great job man, is this your first???
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wyz2285
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Thu Oct 27, 2011 10:32 am

looks clean, you should paint it
I would also suggest you to change your topic title to a clear one
SpudBlaster15
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Thu Oct 27, 2011 12:54 pm

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Last edited by SpudBlaster15 on Wed Jul 14, 2021 9:48 pm, edited 1 time in total.
thekiller578
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Fri Oct 28, 2011 12:03 pm

mattyzip77 wrote:Thats a weird place to put a ball valve, but other than that not bad! For future reference, you can get those bell reducers pressure rated, but you gotta order them on line. They are a biitch to find locally. Its a combustion, so I wouldnt worry about the DWV pipe and fittings. Great job man, is this your first???
its actually my 3rd i had to rebuild this same cannon 3 times,
but thanks!
thekiller578
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Fri Oct 28, 2011 12:06 pm

SpudBlaster15 wrote:Gluing the couplings inside the chamber should significantly strengthen the areas which have screws/fittings threaded through them. I've used this method previously to achieve double layering near the center of 4" diameter chambers, and it does work well.

The rest of the cannon looks pretty clean, but you may want to consider replacing the electrical tape holding the electronics housing on with something more secure such as a large hose clamp. Also, it appears that you do not have a switch for the fan power supply, so it would be a good idea to add one.

Your chamber should probably be shortened if you plan to continue using the 3ft barrel mentioned in your other thread, but it depends entirely on how much you value energy efficiency. It will certainly still fire well if the air and fuel are mixed properly.
the tape is actually temporary, because of the button i had for the fan switch broke :(
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