13mm Marble ghetto gun!

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.
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psycix
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Mon Jun 25, 2007 7:45 am

Hi all,

This is my first post here and also my first gun. It is not a real spud gun, its a smaller caliber. It was a nice project to gain some experience with spudgunning and soon ill be going on to the real work.

About the gun:
It is a 1,5L coke bottle attached to a PVC pipe (13mm diameter, 49cm long)
I made a hole in the cap and fitted the pipe thru it

The ammo were small glass marbles with a few layers of duct tape around em.

Inside was a spark strip made by a small plastic tube from a pen with 10 bugs on it, each about 1mm from eachother. The first and last bugs were connected to a piezo sparker. This resulted in a nice 9-spark ignition.

Shooting sequence:
-The cap+pipe is unscrewed from the bottle.
-Put duct tape around ball until it could not fit into pipe
-Bash the taped ball into the pipe (from the backside, where the cap is)
-spray hairspray in
-quickly screw cap on
-aim (or don't)
-FIRE!

The results were nice!
I shot it around in my backyard a few times. The damage done:
-Left an imprint in my wooden fence.
-Left a very small imprint in the metal pole of a street light
-I shot through the plexiglass window of my barn.
:D Im really proud on the damage especially on the hole in the window, my mom was not.... :roll:

The gun is broken now, when one of the screws for the spark contact started leaking a real lot of heated air was squeezed through and in a few shots it all melted away. My next project will be a real combustion spudgun.


Well that was it, I just wanted to show this to you guys!
Thanks for watching and leave a reply if you want. :)

psycix :wink:
Attachments
Two marbles, one of em taped in and the backside of the barrel with the bottle cap. You can see the pipe became a bit burned.....
Two marbles, one of em taped in and the backside of the barrel with the bottle cap. You can see the pipe became a bit burned.....
All parts together
All parts together
Close-up of chamber.
Close-up of chamber.
The gun with barrel attached to the chamber.
The gun with barrel attached to the chamber.
Last edited by psycix on Fri Jul 13, 2007 10:52 am, edited 2 times in total.
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demilus
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Mon Jun 25, 2007 7:55 am

Holy ghetto! Nice first combustion though. Next time, I suggest that you use ABS for combustion, and PVC for pneumatic (compressed air powered) cannons. Good luck and welcome to spudding!
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spudbud101
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Mon Jun 25, 2007 7:58 am

Very nice!

Why ABS for combustion? I would think that the way ABS fails it would be a safer pipe for pneumatics...
Rawr.
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psycix
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Mon Jun 25, 2007 8:03 am

Thanks for the answer.

I just wanted to add the following:
This thing has a C:B ratio of 15! :P

And about the ABS-PVC:
ABS has chemical resistance, PVC doesnt
Though PVC is stronger....
I think ill be using PVC in my realy spud.
Im using hairspray as fuel (i know there are better fuel but hey im still a noob just experimenting to get experience)
I hope the hairspray wont eat the PVC....?
Spedy
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Mon Jun 25, 2007 9:52 am

Hairspray won't eat the pvc, but it WILL put a layer of gummy stuff on the inside of you gun, and eventually you will have replace the electrodes.

Nice first gun btw, I haven't even made mine yet (on vacation no pvc :( )
e1337
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Mon Jun 25, 2007 3:17 pm

Cool, Can you see the flames in the bottle?
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psycix
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Mon Jun 25, 2007 3:20 pm

e1337 wrote:Cool, Can you see the flames in the bottle?
yup, it gives an orange flash and the bottle gets very warm

the flames last for a very short time and arent really bright, it are more darker orange flames
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spud yeti
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Tue Jun 26, 2007 1:57 pm

Flip its ghetto, I love it! :D
I would think that the way ABS fails it would be a safer pipe for pneumatics...
If you ever try using ABS for pneumatics, youre probably going to land in hospital! Apparently ABS is more suited towards combustion and PVC for pneumatics, but I'd rather only use PVC! :wink:
But nice gun all the rest! :lol:

btw, you can get see-through PVC if you still want to see the flame! :twisted:
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paaiyan
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Tue Jun 26, 2007 2:39 pm

Well i can suggest Static Guard to you as a fuel. It's pretty good, I get a pretty consistent 200 yards out of it, sometimes I get upwards of 275 on a good day.
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psycix
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Tue Jun 26, 2007 4:52 pm

i just figured out my future gun will get a propane metering device :D
so then im surely in for PVC :)

i've been designing the gun the past few days i think i will go buy the parts tomorrow or the day after tomorrow.
Then, its CONSTRUCTION TIME :D
*exciteness*
And then its DESTRUCTION TIME :twisted:
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lukemc
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Tue Jun 26, 2007 5:08 pm

well as spray fuel goes right guard used to be the best but the formula changed so now best thing to do is get an off brand can or it that says "like right guard" of "comapred to right guard". other wise just look at the ingredients. look for butan, heptane, propane, and other stuff that i cant think of right now
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psycix
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Wed Jun 27, 2007 4:52 am

i im going for a pure propane tank, no spraying cans anymore

I HATE spray and prey and find out you injected too much or too les fuel clicking the ignitor thousand times.... :evil:

So im going to the store right now to buy parts for my new spud.
Specs:
-1meter long barrel, 1 1/2" or 2" dia. (detachable)
-4"dia by 10"long chamber
-propane metering device
-chamber fan
-2 or 3 spark gaps in front and back chamber (maybe also one mid)
I hope it all stays UNDER 80 euros...... :|
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spud yeti
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Wed Jun 27, 2007 5:34 am

Flip that sounds like a lethally decent gun! What are the real advantages of using propane though? Isnt it expensive?
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psycix
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Wed Jun 27, 2007 7:36 am

I hate the local store....
They didnt have all parts i wanted...
The propane meter device will come later..
And I couldnt find anything to make the barrel detachable

I just brought with me:
-2 meters of 50mm pipe (barrel)
-1 meter of 110mm pipe (chamber)
-2 couplings
-1 110mm to 50mm reducer (stupid looking one, just flat with 50 mm hole in it, wich isnt in the center)
-1 110mm screw adapter + cap (only item i am very happy with, since it took me a LONG time to find and the screw-on cap was included

It took me over an hour to accomplish this all :P
But they didnt have anything for a propane tank adapter :(

@spud yeti
Propane is 100% clean fuel, it doesnt give sticky electrodes like hairspray will.
Also its easy to meter: With a perfect fuel-air mix you wont have much misfires anymore.
Furthermore, its powerful and not really expensive i believe.
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chaos
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Wed Jun 27, 2007 7:46 am

psycix wrote:I hate the local store....
They didnt have all parts i wanted...
The propane meter device will come later..
And I couldnt find anything to make the barrel detachable

I just brought with me:
-2 meters of 50mm pipe (barrel)
-1 meter of 110mm pipe (chamber)
-2 couplings
-1 110mm to 50mm reducer (stupid looking one, just flat with 50 mm hole in it, wich isnt in the center)
-1 110mm screw adapter + cap (only item i am very happy with, since it took me a LONG time to find and the screw-on cap was included

It took me over an hour to accomplish this all :P
But they didnt have anything for a propane tank adapter :(

@spud yeti
Propane is 100% clean fuel, it doesnt give sticky electrodes like hairspray will.
Also its easy to meter: With a perfect fuel-air mix you wont have much misfires anymore.
Furthermore, its powerful and not really expensive i believe.
sorry but me being me, i must point out that its only a clean fuel if it burns in the right atmosphere.
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