Spud Gun Ignition System

[jowrose]

no no no, you use it to surround the solid pvc of the real combustion chamber. it's just a little safety thing i thought might help in case of an explosion... the air would escape through the holes but the shrapnel would be contained. or maybe the shrapnel would just tear right through the holed stuff, i'm not sure. never really felt like testing it...

[Callipygous]

ok. i get that part. the problem is how do you build it with that around it? you just have it loose and try to keep it covered up while your pumping and shooting?

[jowrose]

you can get the drain pipe (if that's what it is) to be about an inch thicker in diameter so you just slide it around the regular pvc and it's endcap/transition piece (forget what you call that...)

[Callipygous]

you can get the drain pipe (if that's what it is) to be about an inch thicker in diameter so you just slide it around the regular pvc and it's endcap/transition piece (forget what you call that...)

 

 

so not fully enclosed, just kind of a shell around it in the hopes of catching most of the shrapnel?

[jowrose]

exacticully.

 

i went to ace hardware and the 4" drain pipe fits somewhat snugly around the end cap and transition piece of the 3" pvc. it wouldn't do anything if the end cap decided to blow off, which i suppose is the ultimate weak spot in the gun, so it isn't the best safety system. but if you really wanted to be safe you probably wouldn't be building a combustion gun in the first place...

[Callipygous]

exacticully.

 

i went to ace hardware and the 4" drain pipe fits somewhat snugly around the end cap and transition piece of the 3" pvc. it wouldn't do anything if the end cap decided to blow off' date=' which i suppose is the ultimate weak spot in the gun, so it isn't the best safety system. but if you really wanted to be safe you probably wouldn't be building a combustion gun in the first place...[/quote']

 

the weak spot should be halfway down the chamber.

 

the glue that holds the pieces together should be about as strong as the plastic itself, if not stronger, assuming you did it correctly. the place where the pieces come together has two layers of plastic instead of one, which puts the weak spot midway down the chamber (farthest from a reinforced spot) or depending on what you used for a valve, at the bike valve itself.

[jowrose]

for a pneumatic gun, you are probably correct. But i was talking about a combustion gun, where I believe the threading from the end cap would provide the weakest spot in case of a malfunction. The end cap to my gun has blown off twice in the past week. Although that could be because i only give it about half a turn because the threads are coated with combusted deoderant... hmm maybe i need to do some fixing soon.

[Callipygous]

for a pneumatic gun, you are probably correct. But i was talking about a combustion gun, where I believe the threading from the end cap would provide the weakest spot in case of a malfunction. The end cap to my gun has blown off twice in the past week. Although that could be because i only give it about half a turn because the threads are coated with combusted deoderant... hmm maybe i need to do some fixing soon.

 

 

yeah... you should definately fix that.

 

you shouldnt ever have any problem with explosions with a combustion gun, since the weakest point by far should be the potato.

 

jesus... what were you thinking? you cant twist your endcap in all the way but you fire it off anyway? even after it blows off once? do we have a "stupid things i did for others to learn from" thread?

[YT2095]

yer best bet would be either clean it up or start again and make a new one, this time use some sealant, silicone is fine, and make sure it`s screwed on properly.

from there you should always muzzel load it, forget the end cap from now on.

self tapping screws are also a good idea, 4 of them through the cap into the tube will be just fine.

I`ve made more of these than I care to count as a youth, never once had a problem

 

well... apart from the one that launched a 12oz speaker magnet with a black-powder charge from a 5 foot scaffolding tube and knocked me clean on my a$$ after dislocating my shoulder!

[Callipygous]

well... apart from the one that launched a 12oz speaker magnet with a black-powder charge from a 5 foot scaffolding tube and knocked me clean on my a$$ after dislocating my shoulder!

 

NICE.

 

the most fun i have had with these things is punching a d size battery through both sides of a pumpkin and my friends wooden fence : P

 

i feel left out.

[jowrose]

Oh i always muzzle load the potato, i just spray the deoderant through the endcap... And it got sticky so i could never screw it all the way on. Come to think of it, that probably wasn't the most intelligent thing to do. Does anyone know of any other ways to make a hole to spray in the propellant? When i tried (and failed) to make a butane-powered gun (using lighters of all stupid things) I tried using metal pipe valves but they didn't work well. Any ideas?

 

Yt, you made a cannon? that's not even a spud gun anymore, that's ghetto-artillery! holy crap that thing must have gone a mile. where did you get the black powder for it? empty some shotgun shells or make it yourself?

 

wow.

[jowrose]

hahaha. d cell batteries. that's probably the best use i've heard for them. I rarely see people using those anymore, everything is rechargeable nowadays.

[bang69]

hay i am trying to make a spud gun i have made the gun but i need a way to ignite it. im trying a spark plug but i dont no how to make it spark. anny ideas ?

[big314mp]

If you can get an ignition coil, you can pulse 12V power through it and it will spark (same way a car works).

 

I would use a piezoelectric igniter, like the ones found on gas grills.

[bang69]

kool thans i will try both of them ideas what would be the best to set it off?

[big314mp]

My seventh grade science teacher used the piezo igniter (he just pulled it off of an old gas grill). He was using cheap hairspray for propellant.

 

I've never heard of anyone using a spark plug, but it would theoretically provide a hotter spark. I don't know if that is really relevant in this application, however.

[frosch45]

I can speak from expierence on this one, because I have made one of these that can shoot a potato about 75 meters, believe it or not

 

although, this is nothing compared to a pumpkin cannon

 

Anyway, its really not an issue here for getting a hotter spark because you gas that you are putting in your combustion chamber is already so flammable (or at least should be) that you shouldn't have a big problem getting it to go. From experience, if it doesn't go on the first click, you either don't have enough fuel inside or you don't have enough oxygen inside.

 

I just use a piezoelectric sparker. 15 bucks at home depot, and its held out for years.

 

and don't forget your silencer!!!!

http://www.advancedspuds.com/silencer.htm

 

it really works significantly. instead of sounding like a bomb, its kinda like a soft "funf---"

[person]

I would strongly sugest that you dont try anything in that book before consulting someone who has had some chemistry expirience or the forum. Wile the book is nice to read through to get ideas or inspiration from not all the articles are safe or acurate .

 

Sory my last post is quite ambiguous i was refering to the "anarchists cook book"

[hydraliskdragon]

I can recommend you two products.

 

1) A propane torch cup ignitor (Obtainable at hardware store)

2) Make a small 1 Joule Capacitor bank from a camera flash unit then have a Rotary Spark gap to cause the ignition.

 

It is not all that hard to obtain a piezo barbecue lighter. It would be less of a hassle to get this instead of all the other methods.

 

For my first spud gun, my fuel was a normal butane spray but now I switched to propane gas with oxygen enrichment. Do Not Use MAPP gas as the high Acetylene content of the fuel could result in a dangerous explosion.

[Camaro350]

I nabbed a 100,000 personal stun gun off eBay. It was like 10 bucks plus 8 bucks shipping. Took it apart and put the guts in your typical radio shack project box. Coming off the 2 electrodes is thick sheathed wire from CRT flyback circuits (Crack open any old TV or computer monitor and you will see it suction cupped to the glass tube). These go to 3 sets of screws wired in series with the electrodes screwed into the PVC pipe. Gives a very hot spark, several times per second. Ignites my propane every time. Runs on a 9V battery.

 

http://i371.photobucket.com/albums/oo151/andrew61987/P1020850.jpg

 

http://i371.photobucket.com/albums/oo151/andrew61987/P1020851.jpg

 

(Before I added the 2nd and 3rd spark gap)

http://i371.photobucket.com/albums/oo151/andrew61987/zap.jpg

[confused]

i recomend tazer

[Mark Rian]

Well, as for me, I have the tazer. It's running a wiring system that helps to produce four sparks, but, at the end, it burns all the chamber' fuel.

 

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