Unusual spud gun fuels

[-Jack]

Me and a friend of mine recently put together a spud gun (potato launcher, spudzooka, it goes by many names) which we had some fun with blasting trees, a couple broken appliances, etc. with. We used the usual simple design: two PVC pipes (barrel and chamber) and some other ignition parts with a little aerosol starter fluid as fuel.

Now, I'm looking for some stronger, more exotic fuels, but not so strong that they'll blow the shit out of the gun or ammo (even though spuds can be substituted with something more durable, like tennis balls or baseballs if we make a new barrel). Maybe something like a very, very small amount of APAN in the chamber. No matter what we end up with, we'll probably fire it electrically from a safe distance, so the only concern is that we don't strip the pipe after accidentally blasting off the cap on the chamber or something.

So, any suggestions?

[Anthony]

High explosives are not good propellents - they are far too brisant! A projectile launcher requires a progressive "push" up the barrel, not peak pressure in a few microseconds.

The amount of APAN that would be required to not shatter your PVC pipe will produce a pathetically small volume of gas, that'd probably be lucky to propell the projectile out of the barrel at all.

[VX]

You could always make yourself some good quality blackpowder.

That should keep you busy for months! seriously, it's easy enough to make explosive compounds, but making good quality BP is an art (well at least it's as close to art as anything iv ever done) The process is generaly more involved than a simple organic synth (most explosives).... Then you can call your spud gun a cannon :)

[MightyQuinn®]

About the black powder... Would schedule 40 PVC handle the pressure? I'd be sketchy firing it up close.

I was going to suggest Acetylene, then I thought better of it and employed a search engine to keep me from making nO06 mistakes.

I found this with a Google search: Advanced Spuds (http://www.advancedspuds.com/)

And Fuel Page (http://www.advancedspuds.com/fuel.htm)

Some basic fuel advice for using aerosol propellants:

"Less fuel will often make your spudgun shoot farther. Always experiment with different amounts of fuel. It seems strange but when you combust a fuel inside of a closed container, such as a spud gun chamber, if you have too much fuel you will not have enough oxygen to ignite the fuel mixture.

Remember less is more!

Propane : Direct propane injection and meter

Right Guard : The choice fuel for aerosol propellants

Chamber Fan: More fuel efficiency

"Ghetto Propane Meter": Cheap, yet accurate fuel meter

Do not use high powered fuels such as acetylene, hydrogen or oxygen. If you do you will die. PVC is nowhere capable of withstanding the extreme power of these fuels, and will explode with much PVC shrapnel."

[Jacks Complete]

I second the exploding PVC thing. Using Hydrogen would be bad, as the PVC would shatter. Same with Acetylene, which has more oomph than Hydrogen/air, and can blow a 500ml coke bottle to bits. Don't forget that you can get a stuck projectile, which will cause a pressure overload.

With butane, you tend to get a fast burn, a whoosh rather than a bang.

[Bert]

When I was young and foolish, I disregarded advice to NOT use PVC Sch. 40 for launching aerial shells with black powder- A similar projectile profile to a potato, at least in 3". I usualy got 4-8 shots before they blew up... But I wasn't holding onto them! If I had, I'd have lost parts.

I used acetylene in "beer can cannons" (like a spud gun, but no projectile, just a noise maker) Even with no back pressure and not using Oxygen, the detonations were insanely loud and destroyed the cannon after a few dozen shots. Acetylend has a very wide range of mixtures that will undergo true detonation- Not a good propellant, but a hell of a bomb.

[meselfs]

I've used hydrogen in small quantities and find that it works miracles. I haven't launched a potato in years, but where I left off the best fuel I came up with was ether, it had more energy then propane and was more forgiving to bad mix proportions. The ether was dispensed VERY conviniently: It's just the starting fluid sprays they sell in the automotive departments. Look on the back of the can if in doubt.


But seriously, the only reason you'd want to use an "exotic" fuel for spud propulsion would be for you to say to your friends "D00ds! I haev a assetylyne powred spud launchinatorr!" Anything more powerful is likely to desroy your gun.

[cyclonite4]

I agree with meselfs. From my experience, ether (apparently a car starting fluid) is a very good fuel, but make sure you use strong piping, and don't keep firing constantly, take a break every so often, otherwise the pipes will burst or get damaged.

I've tried hydrogen and havn't found it to be as powerful as expected. Acetylene is definitely a no-no, I've heard reports of cannons going off like massive pipe-bombs when using ethyne.

A good, cheap fuel is butane. I simply refill an empty deo can with butane from lighter refill cans, it gives you a can of low-pressure aerosol butane, works nicely.

[grendel23]

If you want more power than a combustion spud gun, build a pneumatic one. Mine will easily shoot a frozen potato through 1/2" plywood.
If made properly, air powered guns are safe. Note I said IF, improper materials or assembly can cost body parts.
A couple of years ago I wanted to build a large pneumatic gun with an adaptor on the barrel to attach the 2" barrel to a 6" section to launch a cabbage.
Once I priced the PVC at about $100, I decided I didn't need it that bad.

[The_Rsert]

I'm using usually a deodorant called "8x4 Pro Active". I tested some fuels. Benzine fuel for cars, benzine for lighteres, eher, ethanol/methanol, a mix of 70% butane and 30% propane, acetone, hair sprays, deodorants,... by my grandparents because the next neigbours to them are living 600m away, the country is shoal and they have a special rule for measuring long distances but the best is the "8x4 Pro Active" deodorant.
The potato can reach 300m with it if the conditons (temperature, dosage,..) are perfect. (One time the potato reached exactly 322m)
-
One time I added about 1g AP as propellant with the result that a part of my potatagun shattered. :(
I heard of one who's using a spudgun made of aluminium. Maybe this would better work for AP!
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I think it should be possible to NC as a good propellant, beacuse it does usually not detonate....

[-Jack]

Thanks for all the help, but I'm really looking for fuels that easier (cheaper) to buy and easier to make (if necessary at all). That's why I mentioned APAN at first, even though I realize it was a really dumb idea.

So that rules out black powder and the like. I have no guns, no shells, and no license to buy either.

Quinn's link was a little useful though. Apparently RightGuard works better than ether. I'm still looking for something that packs a little more punch though. Propane is a little expensive (the whole system and everything), but I was wondering how good ole' gasoline would perform through a spray bottle. I guess not many of you have probably tried this before?

[tom haggen]

I think a lot of pyros use polyurethane for launching shells. That would probably be a good starting material for making a high powered potato gun.

[Jacks Complete]

The_Rsert, you didn't read any of the posts on this board about NOT EVER using high explosive as propellant, then?

There is a big thread where some idiot wants to get a homemade cannon to 5000m/s using a huge chamber and high explosive, and a massive steel container was the result. He's probably dead by now, since the microfractures in the steel will have added up until the lot blew to bits. Aluminium wouldn't be any better.

Have you got a laser rangefinder? 322 meters is a long way for a tape measure!

tom, I've not heard of anyone using polyurethane as a propellant. Doesn't it give off really nasty fumes? http://roguesci.org/theforum/showpost.php?p=40143&postcount=17 by Tuatara says it does. Or do you mean as a containing structure, instead of PVC pipe? In which case, I still wouldn't want to breathe that nasty shit after fireing!

[MightyQuinn®]

tom, I've not heard of anyone using polyurethane as a propellant. Doesn't it give off really nasty fumes?


Not to mention the killer residue it would leave. The link I posted talks about most of the fuels mentioned here...Including deodorant which is purported to be the best fuel with almost no residue left in chamber. That guy also uses a fan in the chamber for effective fuel/air mixing. :D

[tom haggen]

I meant using polyurethane as a container not as a fuel :p
I helped some licensed pyros launch some shells last summer, and I'm pretty sure he said they used polyurethane rather than PVC. But don't quote me on that :rolleyes:

[sdjsdj]

How about Nitromethane?

[knowledgehungry]

I have thought about using a mixture of flammable gas, i.e. propane and oxygen. This would be very powerful but there are safety issues, also this would allow you to make a "semi-automatic airgun".

[The_Rsert]

The_Rsert, you didn't read any of the posts on this board about NOT EVER using high explosive as propellant, then?

There is a big thread where some idiot wants to get a homemade cannon to 5000m/s using a huge chamber and high explosive, and a massive steel container was the result. He's probably dead by now, since the microfractures in the steel will have added up until the lot blew to bits. Aluminium wouldn't be any better.

Have you got a laser rangefinder? 322 meters is a long way for a tape measure!



One time I added about 1g AP as propellant with the result that a part of my potatagun shattered. :(


Sorry, I didn't used the right word for "propellant" :rolleyes:
I meant as "fuel" of course.

I used no real HE as fuel, only AP... :rolleyes:
Anything I wanna say is that a usual potatoguns will explode if there's a HE used as fuel (even a little amount).

And yes that's a long way for a tape measure... my grandparents are peasants (I hope this is the right English word) and have got a special metal rule for measuring long distances which looks like this sheme:
Sheme for measureing long distances (http://www.infernolabs.co.uk/filehost/measuingoflongdistances.jpg)

[trinitride3]

Hey Tom, I think what you were referring to is HDPE High Density Poly-Ethylene not polyurethane. It is an extremely strong material that looks similar to regular PVC but dark gray in color. When used as a mortar to launch arial shells it won't shatter if a shell explodes while still in the pipe, it will burst but stays mostly in tact. The stuff is expensive but would work great to make a spud gun with.

[knowledgehungry]

It tells me to get my own fucking bandwidth.

[Pb1]

I used no real HE as fuel, only AP... :rolleyes:
A crappy HE is still an HE.