Coke Bottle Combustion

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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PCGUY
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Sat Feb 12, 2005 5:13 pm

<div align="center">COKE BOTTLE COMBUSTION

Provided By - GalFisk

This is my first spud gun, built only from parts I found around the farm. It began as a bottle with two screws in it connected to an old monitor, and a piece of dubious PVC pipe. It has been modified and improved countless times since then, the only part I'm still using is the fly back, which I eventually ripped from the monitor and built a driver circuit onto. Features: 28mm ID x1.5m HDPE barrel, 1500cc combustion chamber (C:B ratio ~1.7:1), breech loading, breech knife, wooden handles, fly back ignition w rechargeable 9V battery and capacitor battery booster, shoddy muzzle porting, easy disassembly. All cold-resistant materials. The cannon is best fired from the hip or shoulder. I use butane for fuel, or a butane/propane mix in the winter, and a bike pump for venting, or compressor if available. Good projectiles are carrots, small spuds, 1" marbles w. burst disks, 1" bouncy balls, throwing darts w. wadding.

Provided By - GalFisk </div>
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cfront.jpg
cfront.jpg (8.6 KiB) Viewed 7565 times
The cannon can be disassembled, by disconnecting the breech, screwing off the handles and disconnecting the battery. All parts except the barrel fits nicely in a shopping bag, along with ammo, fuel, bike pump and other accessories.
The cannon can be disassembled, by disconnecting the breech, screwing off the handles and disconnecting the battery. All parts except the barrel fits nicely in a shopping bag, along with ammo, fuel, bike pump and other accessories.
disassembled.jpg (19.88 KiB) Viewed 7565 times
The ignitor, powered by a 9V battery and using a fly back driver for voltage source. A 4700uF capacitor is connected in parallel with the battery to provide a current boost for the circuit, allowing it to function even when the battery is running low. The electrodes (one M3 and one M4 bolt) are self-threaded into the plastic. The electronics are held onto the bottle with a sewn-together handkerchief, so that it can be slid off and placed on a new bottle if the chamber needs to be replaced.
The ignitor, powered by a 9V battery and using a fly back driver for voltage source. A 4700uF capacitor is connected in parallel with the battery to provide a current boost for the circuit, allowing it to function even when the battery is running low. The electrodes (one M3 and one M4 bolt) are self-threaded into the plastic. The electronics are held onto the bottle with a sewn-together handkerchief, so that it can be slid off and placed on a new bottle if the chamber needs to be replaced.
ignitor.jpg (19.53 KiB) Viewed 7565 times
This is the mechanism for opening and closing the breech, disassembled. Apologies for the fuzzy picture.
This is the mechanism for opening and closing the breech, disassembled. Apologies for the fuzzy picture.
breech.jpg (14.11 KiB) Viewed 7565 times
A better picture of the bottle neck.
A better picture of the bottle neck.
neck.jpg (8.96 KiB) Viewed 7565 times
The parts connect together like this.
The parts connect together like this.
breecconnect.jpg (12.28 KiB) Viewed 7565 times
and are secured with a shaft pin.
and are secured with a shaft pin.
breechsecure.jpg (15.16 KiB) Viewed 7565 times
a better view of the connected breech.
a better view of the connected breech.
breechsecure2.jpg (13.93 KiB) Viewed 7565 times
The marble burst-disk ammo is loaded by placing the finished ammo over the neck of the bottle
The marble burst-disk ammo is loaded by placing the finished ammo over the neck of the bottle
marbleload.jpg (9.06 KiB) Viewed 7565 times
and locking the breech in place over the plastic, like this.
and locking the breech in place over the plastic, like this.
Last edited by PCGUY on Mon Jun 12, 2006 7:21 pm, edited 1 time in total.
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darthtator
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Sun Jul 10, 2005 10:08 am

Thats a pretty interesting meathod. All in all pretty nice cannon. how far does it shoot? How much psi do you use? Or how much until the disk goes?
Your hands can't hit what your eyes can't see, float like a butterfly sting like a bee. *Ali*
spudshot
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Sun Jul 10, 2005 3:53 pm

its a combustion using a burst disk, not a pneumatic, it has to burst below about 50 psi, since thats what most combustions create, you can see his burst disk marble ammo in the how to section
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GalFisk
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Thu Sep 15, 2005 5:49 am

It shoots maybe 80-180 meters/yards depending on ammo. The longest shot was with a hunting arrow, I'd estimate carrots to 100 and marbles to maybe 130m on average. But as we all know, range estimates can be wildly inaccurate.
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toza
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Tue Oct 11, 2005 4:08 am

i reckon it looks pretty compicated and dosent look like an easy feat but u made most things replaceable which is smart i imagine the coke bottle wouldn't last very long though.by the way what ammo did u use and do u still use it?
wesjac
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Wed Oct 12, 2005 1:42 pm

i just gained an interest in spud guns and posess very little knowledge in it. When u use this spud gun gun do u fill it up totally or half full, and with what? benzene, parrafin?
spudshot
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Wed Oct 12, 2005 3:01 pm

what? all you do is spray some fuel in and put the barrel on with a potato inside, its just like any normal cannon.
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beebs111
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Wed Oct 12, 2005 3:46 pm

i dont think he has any clue what ur talkin about spudshot. what you do is spray some right gaurd deoderant or other fuel and press the igniter or spin the flint wheel and it goes boom
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toza
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Sun Oct 16, 2005 6:44 am

i'm from australia and cant get a barbecue lighter or lantern lighter what do you guys sugest?

by the way what is a fly back driver and is it cheap?
UAE_gunner
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Wed Nov 09, 2005 1:23 am

for u in aus u could buy a lighter that instead of spining the thing on flint that it clicks. you can take out a little thing inside that makes a spark if you squeeze both ends. then on the inside of the combustion chamber glue a piece of metal and put the wire through thatmakes a spark and there you go.
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toza
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Thu Nov 17, 2005 4:39 am

thanks alot youre a legend
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julz
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Wed Dec 21, 2005 10:16 pm

mmm, coke...

a mate and i made 2 cannons in 10 minutes yesterday. we got one 1.25L bottle and a big 2L bottle, one was 1.5" diametre barrell and the other was 2.5".

we just duct taped the barrell and chamber together, then we drilled a hole at the end of the chamber. to shoot we just held the bbq lighter at the hole and lit it, since it didnt work when we put the lighte 'in' the hole there was a lot of flame shooting out the back of the cannon as well :)

we managed to shoot a plastic thing about 100m and another pool ball 50m.

they were pretty fun lol
cardinals08
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Fri Dec 23, 2005 10:09 pm

man, all I have built are two mini guns(my dad says I cant build big ones till I have my own money to do it with), I made the pill bottle one, and made one with a gatorade bottle and wiffle ball bat, the farthest I shot anything is about 75 feet, that was a K'Nex piece with a piece of tissue in the barrel with the pill bottle. I use AXE as fuel, and dont know what I can be doing wrong to not get the gatorade one to do better. Maybe its because the barrel is only about 6 inches long and a little more than an inch inside diameter
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Andrew52
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Tue Mar 28, 2006 11:31 pm

well i have a gatorade mini sometimes if u get the right mixture its loud and powerful i have a barrel maybe 16 inches of half inch conduit im not a nube for the conduit it doesnt really matter its a mini i can shot a grape about a 100 yards
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jjk92
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Fri Apr 21, 2006 7:45 am

what is a flyback driver?
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