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First post, first mini spud gun.

Discuss miniature cannons built from things such as pill bottles and pen caps.
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First post, first mini spud gun.

Unread postAuthor: VirusX » Thu Oct 01, 2009 1:37 pm

Hi,

I'm new here. First I have to say, that I'm not American, so my English is not so good, but I try my best.

Ok, here are some pictures of my first mini spud gun:

I used the tube of "vitamin pellets" as combustion chamber and a brass pipe (<6mm diameter) as barrel. On the backend I glued on the breech of a bottle. The electric sprakle comes from a piezo connected to screws, which reach in the tube. My ammos are 6mm steel bullets.

ImageImageImageImage

At the end of the barrel I glued on a light magnet so the bullets can't roll in the combustion champer. I take deodorant as "fuel".

OK now some issues I recognized:

The screws get wet very fast because of the deodorant. Do you have any tips to prevent the problem?

I used a power glue called "henkel superbond" and silicone but it seems to me, that the mini spud gun isn't really close at all. Which glue would you recommend?

So thats it so far. What do you think about my first mini spud gun?

I'll add some videos tomorrow of my mini and my big spud gun.
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Unread postAuthor: jackssmirkingrevenge » Thu Oct 01, 2009 1:49 pm

Not bad for a first effort, but on a launcher so small you shouldn't be using deodorant.

Image

Get yourself a can of lighter gas and a small syringe. Calculate 4% of your chamber volume, fill the syringe with this quantity of butane gas, inject it into your chamber et voila :)
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Unread postAuthor: jimmy101 » Thu Oct 01, 2009 2:35 pm

What JackSR said. You can also use a cheapo butane lighter as the gas source.

Butane will eliminate the problem of stuff gunking up the inside of the chamber.
http://www.inpharmix.com/jps/Fuel%20Met ... ghter.html
http://www.inpharmix.com/jps/Hacking_lighter.html
Image

BTW, VirusX welcome to the board.
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Unread postAuthor: VirusX » Thu Oct 01, 2009 2:46 pm

Hi,

Thanks for the tips!

I can't get such a syringe or long-tipped lighter in a rush. Would it also work, when I put a lighter in the chamber and press a little bit on the button, so there's just gas coming out?
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Last edited by VirusX on Thu Oct 01, 2009 2:47 pm, edited 1 time in total.

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Unread postAuthor: jackssmirkingrevenge » Thu Oct 01, 2009 2:47 pm

Thanks Jimmy, I keep forgetting there's an even easier way of going about it hehe.

Are spuds part of the animal kingdom :D

Would it also work, when I put a lighter in the chamber and press a little bit on the button, so there's just gas coming out?


The problem is you won't know how much gas you've put in, too little or too much means it won't fire.
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Unread postAuthor: VirusX » Thu Oct 01, 2009 2:58 pm

Would the hole mini cannon (+ my hand?) explode, if I take too much gas from a lighter?
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Unread postAuthor: theBOOM » Thu Oct 01, 2009 3:20 pm

Virus to answer your question the answer is no, if there is too much gas from the lighter going into your chamber it simply wont ignite beacause the fuel mixture isnt metered to the correct fuel and air ratio.... Simply, too much fuel.

Like others said I would try a small metering system... I've heard of people using expoy syringes or cooking syringes the same as normal medical ones.... msg me or answer me here if you have any questions on the metering system.

If you want a good glue I would try finding some marine epoxy or some jb weld or some other type of loctite. If you dont know what epoxy or these are just google it and you will find plenty of info.

Also dont use deodorant for 2 reasons, it will gunken up your electrodes (screws) REALLY fast... prolly like in 10 days their gonna be covered in gunk and things that will make it hard for your spudgun to work, second it smells bad and it makes your potato cannon unreliable.

Last is.. your barrel looks kinda off centered with your chamber you can easily use pvc as a chamber and some other fittings to get a better assembly on the barrel beacause having a crooked barrel affects accuracy... not like minis are accurate.. .but still :P

Good mini for a start man ;) Especially for a first, Might want to look into inonickname's work as he is pretty good atbuild small guns... I'm into small guns myself :P
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Unread postAuthor: VirusX » Thu Oct 01, 2009 3:38 pm

theBOOM wrote:Virus to answer your question the answer is no, if there is too much gas from the lighter going into your chamber it simply wont ignite beacause the fuel mixture isnt metered to the correct fuel and air ratio.... Simply, too much fuel.

Like others said I would try a small metering system... I've heard of people using expoy syringes or cooking syringes the same as normal medical ones.... msg me or answer me here if you have any questions on the metering system.

If you want a good glue I would try finding some marine epoxy or some jb weld or some other type of loctite. If you dont know what epoxy or these are just google it and you will find plenty of info.

Also dont use deodorant for 2 reasons, it will gunken up your electrodes (screws) REALLY fast... prolly like in 10 days their gonna be covered in gunk and things that will make it hard for your spudgun to work, second it smells bad and it makes your potato cannon unreliable.

Last is.. your barrel looks kinda off centered with your chamber you can easily use pvc as a chamber and some other fittings to get a better assembly on the barrel beacause having a crooked barrel affects accuracy... not like minis are accurate.. .but still :P

Good mini for a start man ;) Especially for a first, Might want to look into inonickname's work as he is pretty good atbuild small guns... I'm into small guns myself :P


Hi, thank you for your help! :wink:

Is there a working plan for a mini cannon with pvc pipes? I dont really know which I should take.

Ad ehm ... who is "inonickname" ? :oops:
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Unread postAuthor: theBOOM » Thu Oct 01, 2009 3:46 pm

Hm a working plan not... in minis its all about the creativity and fun but there are some examples of minis... just look in the mini cannon showcase and just find topics with the name inonickname he's built pretty cool cannons :P
Right now im replicating one of the small cannons that he built... it has a 1/2 pvc chamber and will be used at a 2x mix maybe 3x if I can hydrotest my chamber to more than 400 psi...Will include a mini fan and a spark strip... Just a small prototype of a hybrid cannon I plan to build.. I suggest you read the Spudwiki which is at the right at the top of the homepage... or any page... just soak up all the info :P

inonickname is a member in the forum that builds small guns .. AND HAS A 4000 DOLLAR LATHE! :lol:

Edit: Also if you decide to use pvc pipe or even metal pipes once you get better at building guns you can use higher pressures or fuels that generate more pressure... PVC or galvanized or brass fittings are already pre-made fittings that only need to be welded or threaded so that you can build your gun.. no more finding stuff in the house to make minis, (even though that's how we all start, atleast I did)...
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Unread postAuthor: jackssmirkingrevenge » Thu Oct 01, 2009 4:05 pm

VirusX wrote:Is there a working plan for a mini cannon with pvc pipes? I dont really know which I should take.


If you're into mini cannons and want some decent power, forget combustions and make yourself a real one :D
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Unread postAuthor: theBOOM » Thu Oct 01, 2009 6:18 pm

COMBUSTION MINI GUNS !!!!
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Unread postAuthor: inonickname » Thu Oct 01, 2009 10:11 pm

2x mix maybe 3x if I can hydrotest my chamber to more than 400 psi

The burst pressure of schedule 80 1/2" PVC is around 2500 psi iirc. Not sure on sched. 40 but it's around 2000 I believe. Never mind, found the table. This assumes rated pipe of course.
Image

As boom's brought it up, stuff I build.
This was all before I got my lathe...theres some wicked stuff coming.

Another option to fuel it would be to use the inbuilt venturi in a torch head to pre-mix the fuel, and purge the chamber with the mixture.

Nice work.

If you've got the patience and materials, pneumatic miniatures are many times more powerful.
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Unread postAuthor: theBOOM » Thu Oct 01, 2009 11:23 pm

Hm inonickname I sleeved the sch 40 pipe rated to a working pressure of 600 psi in some 1/2 nsf-pw pressure rated couplings THEORTICALLY giving me a wokring pressure of like 1000 or sometihng well just assuming that the fittings are also rated to the same as the pipe... im sure it will be safe at a 3x mix seeing it will only generate 300 psi tops with a burst disc bursting at 110 psi or so.. I'll be careful.
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Unread postAuthor: jackssmirkingrevenge » Fri Oct 02, 2009 1:06 am

theBOOM wrote:COMBUSTION MINI GUNS ARE PATHETIC NEXT TO PNEUMATICS !!!!


Agreed ;)
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Unread postAuthor: VirusX » Mon Oct 05, 2009 10:07 am

Hey,

I went to a bigger store (like Wallmart in USA) and bought epoxy glue (Uhu plus 300). After unpacking I read the manual and there stands, that the glue is only temperature-resistant from -20°C to +100°C (-4° to 212° Fahrenheit, I think).

Is + 100°C enough for a spud gun?
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I'm sorry, my English is not so good but I'll try my best!

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