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imported_Sgt_Starr
August 6th, 2001, 12:04 PM
Hey Guys,

I was pondering over the remains of what used to be a nice spudgun(it just decided to fall apart, The ignitor doesnt work anymore and the chamber cracked which scared the mfin piss outa me) Anyone ever tried to used 1/4in Steel? I was thinkin of using 1/4in steel in this way,

Barrel:
1/2 in Diameter
2ft length(plus ABS flash supressor)

Chamber:
2-3in Diameter
1ft length


From this I was thinking of fuels and I came up with a somewhat dangerous but inticing fuel injection system, Why not hook up a tank of Propane and a Tank of Oxeygen to a double valve(correct Name?) that would be welded to the barrel at a small port in the mid to mid-front of the chamber, Now for ignition, Ive gotten tired of my Peizio although when it does work it works great and I think it might still be the way to go, I was thinking maybe have a Capacitator (sp?) hooked to a 6v battery then to a spark gap, The Capacitator and spark gap being housed inside a PVC pipe mounted inside of the chamber. I was thinking maybe make it a break barrel to fit the ammunition in with more ease. That being it for the gun I was thinking, Would it be possible (using a nice Blow torch) to melt down aluminum foil into like a 35mm shell (wrapped at the base with Prefit Cardboard for compression and to protect the barrel) Any input? This is just a hypothetical idea untill I work out all the kinks and get some more feedback from you guys(btw all testing I do is dont behind a 3ft wide by 4ft tall Plexiglass shield about 10 ft from The gun)

------------------
"Oh Sh".::BOOM:http://theforum.virtualave.net/ubb/smilies/frown.gif(later
in front of saint peter))
"it"

[This message has been edited by Sgt_Starr (edited August 06, 2001).]

Mastermind
August 13th, 2002, 03:00 PM
I used an electrical ignitor on my spudgun, but it got wet with the fuel and wouldnt work. I usually could get one or two shots, and that was after alot of tries, so I'd stick with other things, but i might have done something worng

vulture
August 13th, 2002, 04:00 PM
Take a look at the powerlabs website and then start makin ALOT of nitrocellulose..... :D

xoo1246
August 13th, 2002, 04:45 PM
I have been looking and I'm really impressed, NC must me a very good fuel for improvised mortars, and clean burning too.

bonnsgeo
August 13th, 2002, 05:19 PM
hmmm i'd like to ask a stupid question ... :rolleyes:

the nitrocellulose "Lacquer", nitrocellulose in acetone, is still an explosive after all the acetone evaporate ? because its like a paste...

thx to answser this question. (there absolutely no topic on NC on this forum and i didnt want to start a new one with a stupid question like that)

xoo1246
August 13th, 2002, 05:45 PM
Well, the NC is dissolved by the aceton, and when the aceton is evaporated it's still NC. But the NC in the laquer has low nitrogen content(thus not at all usefull as a H.E., possibly as a binder and in not so fast burning pyrotechnical devices).
You don't know this? And you are working with RDX? Could someone please explain this?

bonnsgeo
August 13th, 2002, 07:22 PM
thx xoo for your answer.

yes i play with rdx,petn,picric and all those things :)
but i really never play with NC ! i made NC two times ans that's all.I absolutely ignore this explosive because it is really useless for me ...
maybe its a mistake !

bye and thx for your answer.

kingspaz
August 13th, 2002, 07:25 PM
well i can't explain it!
bonnsgeo it would be a good idea if you read some chemistry and some quality books like 'the chemistry of powder and explosives' for example. check the links section under chemistry pages for chemistry reading or search the web. i am seriously recomending you do this as i'm sure you don't want to be stumpy. the way not to get injured doing this is to know EXACTLY what you are doing. not just what you are going to do and how but why somthing happens when you mix two chemicals.

McGuyver
August 13th, 2002, 08:37 PM
Okay, off the NC cannon, I don't think aluminum foil melts too well, try lead or solder something along those lines.

As for ignition, I've found electrical(not piezo) and flint ignition are the best. Right now I am using a lantern ignitor. This ignitor is a turn type ignitor and can be found at Wally world in the camping section. No, jee I hope it will light the gas, these things are really reliable.

Another thing- hooking a capacitor and a 6 volt battery together isn't going to do a whole lot. A better way would be to get a high voltage step up transformer like a magneto or an ignition coil.

(Edit: sp)

<small>[ August 13, 2002, 07:39 PM: Message edited by: McGuyver ]</small>

duke of hazmat
September 3rd, 2002, 12:39 PM
In the past week i have made a spudgun out of a length of 4" X 4' PVC and a 6' length of 2", i know from reading info on the net
that the idea ratio is 1.5:1 so i know it is WAY under the maximum efficiency possible. But i can still get a tomato out to 300 yards without having to wait for ideal conditions and aiming at 45 degrees,
i'm planning on buying a 20' length of 2" and a few reducers to make a potato gun "SD" barrel (like the hkmp5sd series of sub-machine guns <img border="0" title="" alt="[Wink]" src="wink.gif" /> ) .Does anyone know if they do work WELL for a potato gun? :confused:

I stupidly mounted the piezo about mid way down the combustion chamber, but it works well as it sparks as i go to pull it tight to my shoulder (acting like commando here). Btw, i use waitrose 'own brand' underarm deoderant, and it is the most powerful stuff short of acetylene (which i have tried b/c my dad has a Oxy/acetylene cutting torch hanging around) but im not brave or rich enough to try a oxy/acetylene mix (as im sure the cannon will just blow)

and does anyone know the legality of spud guns in england??
I dont want to end up havning to ask a politz and being frog marched to the nearest station and interrogated for being the next 'osama spud laden' (maybe another time when tony blair is within that gold 300 yards :D ).

<small>[ September 03, 2002, 11:41 AM: Message edited by: duke of hazmat ]</small>

zaibatsu
September 3rd, 2002, 02:50 PM
Spudguns are most definately illegal in England/UK, they're either oging to be classed as firearms due to combustion, or firearms due to the high power (greater than 12ftlb, by just a bit <img border="0" title="" alt="[Wink]" src="wink.gif" /> ) Just don't threaten to shoot anyone, and do it a LONG way from anywhere, and if all else fails, claim its a physics project or something.

Ctrl_C
September 3rd, 2002, 03:55 PM
spudguns can be VERRRY powerful. Mine, for instance, will put a potato through 1" thick oriental strand board (similar to plywood). That's just where the fun starts though...bolts, chains, nuts, nails (flechettes!) and other household goodies. As soon as I rebuild my (sick) spudgun, I am going to build projectiles with stabilizing fins/cone and sharpened rebar. It WILL be able to kill an elephant, this I am sure of.

duke of hazmat
September 3rd, 2002, 06:34 PM
LOL, i dont think im in any danger of elephant attack in england and im sure that zaibatsu can back me up on that :p

I am quite aware of the power that i wield when i start swinging it around, and im not inclined to allow p.c. plod the chance to zero in on me (it was in the local papers about a frozen tomato making a serious dent in a car bonnet that was well within the range of where testing coud have been :D )

btw, can i advise a plaster or concrete sabot around a steel bolt
as i have found this sufficient to penetrate a car door (window rolled down) up to about 80 yards, but the design needs a bit of attention so that a propper gas seal is created for maximum power

i wonder what sort of ft/lb's i'd be getting......

maybe i should ask the police for a fac :p , but i can imagine the conversation as to where i keep the ammunition for it
P.C. " so where is the ammunition kept when not at the range?"
ME " next to the frying pan " :D

as an idea for a really sneaky munition, how about a frozen carrot?
could resemble flechette (sp?) wounds from nam'

Anthony
September 3rd, 2002, 07:59 PM
I'm pretty sure of the specific pipe you're using and oxy-anything, let alone acetylene would be almost certain suicide.

If you do want a ball park figure on the projectile energy your gun is putting out, do a websearch for "ballistic pendulum". It can be as simple as a slab of wood/metal/concrete, a tree and some rope or thick string.

duke of hazmat
September 4th, 2002, 01:31 PM
im not thinking of doing anything as idiotic as holding the blasted thing while im testing it, i have all ten fingers that i was gifted with at birth for a very good reason,

I THINK SAFETY !!

even when i first started out in anything that this forum speaks of, i made sure that testing was completed in a polycarbonate box that i had made for the purpose (with a supposed blast-proof fibreglass plate as the base) and i had access to a lot of nicrome wire that 90% of time was able to reach the ignition temp of whatever i was testing
(or a long bit of string)

i may not know all there is in the field of explosives but i know all there is to know about safety with explosives, and the gold word being distance! :D

live to fight another day and all that.....

and i intend to test the chamber pressure created using a handy piezo electric job i picked up from a catalogue a while ago, and if it reaches 90% max pressure then i scrap the idea, or i'll find the failiure pressure of the pipe with a hefty layer of duct tape (mans fourth best friend after explosives and a nice pair of swedish twins :D )

X-Wulf
September 4th, 2002, 03:25 PM
Well, 1/4" steel spud-guns do work, a little on the difficult side to make though (have to rust-proof ... for obvious reasons!!).

The one I built is designed mainly to be a pneumatic cannon, it uses a piston design, but with a little modification could quite easily be adapted to propane-oxygen ignition mixtures. Should hold under the pressure, though if it were to fail, I'd have metal shrapnel to contend with. Easier to locate on x-rays though.

Only problem is that this thing would look and sound like an artillery piece (and I'll probably be arrested on sight for using it, let alone building it!)

Ctrl_C
September 4th, 2002, 03:49 PM
well when you start talking metal and oxyacetylene, you are no longer talking about a spudgun, at least not of the pneumatic type. Instead, it now becomes a cannon. If you're going to build a cannon, you might as well do it right. Thick metal and a good explosive. See supersonic golf ball cannon/video at <a href="http://www.powerlabs.org" target="_blank">http://www.powerlabs.org</a>

<small>[ September 04, 2002, 02:50 PM: Message edited by: Ctrl_C ]</small>

vulture
September 4th, 2002, 03:57 PM
You'd better not use copper(valves!) or silver parts in your cannon, because otherwise it might explode when filling it!

Mick
September 7th, 2002, 12:08 PM
dam...i creamed my duds when i saw that NC cannon.

i am so going to build one of them.
all i need to source out is a hydraulic ram, and some nitric acid.
the ram will be the easy part, cause with any sort of luck i'll be able to pick a rooted one up at the plant equipment joint near here. if that fails i'll just pinch one off a backhoe at the roadworks site 10kms from here(easy enough to steal, there only held in with split pins most of the time)

however, getting hold of some nitric acid is going to be next to impossible.
is anyone in australia able to get hold of nitric acid?
i've tried all the art suppliers, engravers etc near me and none of them sell it. short of making it - which i don't really have equipment to do so, i'm fucked if i know what to do...

anyways, this will be one of those "backburner" projects.
i'll either get so bored one day that i go "fuck it" and find all the bits i need and build it in a day, or eventually after some months i'll have or the bits i need.

as for PVC spud guns, i don't fuck with them anymore. had 2 blow up in my hands so far. great fun for a while, but they get too weak after a while, and the barrels deform and jam, then eventually go bang, or if you don't use it for a while they go brittle, then bang.

sure you can build them out of ABS, but you still end up with the same problems eventually and plus ABS is $$$.

<small>[ September 07, 2002, 11:10 AM: Message edited by: Mick ]</small>

X-Wulf
September 7th, 2002, 04:14 PM
Vulture, I fully agree with the thick metal, the thicker the safer, and safety is everything, but the explosive propellant ... The only decent one to use is NC, as most of the others will leave a nasty residue, or the excessive heat will damage the chamber. And then there's the making of the NC, nitric and sulfuric acid are hard to come by here (if not entirely impossible).

The other problem is that if you get busted for operating illegal weaponry, you certainly don't want to give them reason to get a warrant to search your house and find your lab, and using NC as a prop will certainly give them that reason.

When I do modify my spud-gun into a cannon, I'll probably use an oxygen-propane fuel system. Acetylene could become quite expensive after a while, and may burn a little too hot in the chamber for my liking. I'm working on a remote valve operating system, so that I can charge and fire the thing from a safe distance away and behind some good cover <img border="0" title="" alt="[Wink]" src="wink.gif" />

As for determining the internal pressure of your cannon, there are 2 ways. The first involves some seriously expense and delicate equipment (i.e. you'll blow to hell after the first shot). The second involves determining the inertia of the projectile, but this relies on knowing it's velocity.

Anthony, the ballistic pendulum works quite well, but can be pretty inaccurate if your projectile is not aerodynamic. So if you do decide to use this method, carve the spud a little to give it a cone shaped nose (it'll help significantly). Another method would be use two infra-red "gates", when attached to a computer running an oscilliscope program (or if you can afford it, an actual oscilliscope). The gates are connected to the computers sound card, and upon being triggered, will "spike" the oscilliscope. The time difference between the two spikes is then known, and so is the distance between the gates. Thus you have the velocity :)

Sorry about the length, got a bit carried away there.

Anthony
September 8th, 2002, 09:14 PM
I realise that it isn't the most accurate method of measuring projectile energy, but it is arguable the simplest. When using this method I have always done so at point blank range, so aerodynamic loses aren't going to be much.

Using a 'scope or your computer, you can replace the IR beams with strips of baking foil to simplify things a little.

Mick, that cannon video is awesome (well, the audio mainly), but at roughly 1/2lb of NC per shot it's going to be expensive to run!

<small>[ September 08, 2002, 08:16 PM: Message edited by: Anthony ]</small>

Fl4PP4W0k
September 14th, 2002, 09:22 AM
A teensy bit off topic... but here goes
Some of you would be aware of X Inventions Forums, and while the pyrotechnic board has the reputation as 'k3wl', the Pneumatic Cannon board is actually rather good.

<a href="http://pub9.ezboard.com/fxinventionspneumaticcannons" target="_blank">http://pub9.ezboard.com/fxinventionspneumaticcannons</a>

We really need more regular posters, so if any of you are interested in spudguns, air cannons or anything in that realm - please check it out.
Many people have been turned away by X Inventions in the past due to the lack of moderators... Fortuanately, that has been resolved. There are now a few mods, Me, Nika452 and Drac0nic. This has caused the amount of inane \ kewl posts to almost vanish.
The pyro forum still *cough* needs some... work.

Take a gander.

l8r,
rob

jimwig
December 21st, 2002, 03:32 PM
WHAT!!! no elephants in Piccadilly... what's this world coming to.

someone, what's the proper procedure for

a full auto spudgun
a fail safe green pea grenade
a life of fun that doesn't involve dangerous pursuits

Yeah, you're going to have to make a little more sense than that - a little clarification please?

<small>[ December 21, 2002, 06:46 PM: Message edited by: Anthony ]</small>