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please help me making a pneumatic cannon (noob here)

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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please help me making a pneumatic cannon (noob here)

Unread postAuthor: eggbom » Thu Jul 23, 2009 10:06 am

hello,

i just wanna make a 'basic' pneumatic cannon with all metal stuff.
but the problem is that this is my first build.
and i dont know if it's possible but i like to build the gun with a pump on it.

can anyone please help me to build the cannon, what stuff i need or a good site where i can find that.
thanks in advance,

eggbom

(sorry for the bad english)
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Unread postAuthor: geardog32 » Thu Jul 23, 2009 10:26 am

uh.. well first you should look around the forum and cannon showcase to get some ideas. Then you should go to a lowes, home depot, ace ect... and see what parts you have available to you. most importantly look around on the forum.
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Re: please help me making a pneumatic cannon (noob here)

Unread postAuthor: suburban spudgunner » Thu Jul 23, 2009 10:28 am

eggbom wrote:hello,

i just wanna make a 'basic' pneumatic cannon with all metal stuff.
but the problem is that this is my first build.
and i dont know if it's possible but i like to build the gun with a pump on it.


You mean like a bike pump? In that case, all you would have to do would be to use a schrader valve as your fill valve and keep the pump connected to your gun.

If you're looking to make a shock pump, there are plenty of tutorials on this site. As far as connecting one of them, you could probably do the same as I suggested with a bike pump.
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Unread postAuthor: eggbom » Thu Jul 23, 2009 10:44 am

i mean a pump with a cable on it, or a bike pump.
doesnt matter, here is a good example:

http://www.youtube.com/watch?v=5KAUBOfjcYM


(Here is quick pic i've made)

i dont know it's working but if it's working then i dont know how to build the valve on it,
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Unread postAuthor: geardog32 » Thu Jul 23, 2009 1:48 pm

do you know how to solder? if not i would recommend building it out of pvc. the most basic you can get would be a ball valve. just get like a 10 foot section of pressure rated pvc, a ball valve and cap to match, and a schrader valve and gauge if your pump doesnt have one. then cut the ten foot section in half put the ball valve in between. then thread the schrader and gauge into the end cap and glue it all together. and you will need some pvc primer and glue. thats as simple as i can think of.
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Unread postAuthor: jrrdw » Thu Jul 23, 2009 3:09 pm

You can also use a check valve inbetween the pump and chamber. Have you spent any time looking in the "Wiki", the button is at the top of the page. Lots of great information in there to help you.

Welcome to Spudfiles.
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Unread postAuthor: eggbom » Thu Jul 23, 2009 3:10 pm

ok thanks but i really need one from metal, and no i cant solder.
but is there no other way without solder to make one with a valve for a bike pump?
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Unread postAuthor: jrrdw » Thu Jul 23, 2009 3:13 pm

Look at my post above, you probly missed it. You can thread all your parts together.
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Unread postAuthor: eggbom » Thu Jul 23, 2009 3:46 pm

jrrdw wrote:Look at my post above, you probly missed it. You can thread all your parts together.


ok thanks dude, i'm going tommorow to the market to looking around for stuff.

but one question, if i have a 'chamber' that is 30mm x 300mm long, is that possible to shoot something?

thanks anyway
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Unread postAuthor: roboman » Thu Jul 23, 2009 3:48 pm

It all depends on your barrel volume...if the volume of your barrel is less than that of your camber, it leads to reduced efficiency...ideally, you want about a 1:1 C:B ratio.

Just out of curiosity, why does it have to be made out of metal? PVC is much less expensive, and quite a bit easier to work with.
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Unread postAuthor: jrrdw » Thu Jul 23, 2009 4:17 pm

I like a 2:1 ratio myself, thats your chamber should have 2 X the volume as your barrel. Where are you from?

@roboman, if he's not from the USA, PVC pipe can be costly and hard to get.
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Unread postAuthor: Technician1002 » Thu Jul 23, 2009 4:18 pm

roboman wrote:It all depends on your barrel volume...if the volume of your barrel is less than that of your camber, it leads to reduced efficiency...ideally, you want about a 1:1 C:B ratio.

Just out of curiosity, why does it have to be made out of metal? PVC is much less expensive, and quite a bit easier to work with.


That statement is a generic rule. The real world will need to make changes based on operating pressure and valve efficiency. With a 1:1 ratio and slow heavy projectile, at 1 bar pressure, the projectile will leave the barrel at 0 bar pressure. With a faster lighter projectile, the valve inefficiency will require either a shorter barrel, larger chamber, or higher pressure. Pumpkin cannons operate at low pressure and benefit greatly from oversize chambers.

On the other end of the pressure range and with a fast high flow valve, great performance can be achieved with a small chamber. The small chamber high pressure guns are a prime example of this.

Here is a recent example, the Decimator.
Image
It is in this thread.
http://www.spudfiles.com/forums/decimator-video-update-07-20-09-t18647.html
Thanks Jeepkahn for the excellent example. :cheers:

I have test data on a in barrel launch where at low pressure, a 1:1 volume ratio is a poor choice because the projectile slows down prior to leaving the barrel.

Below is a chart with a low pressure launch. The blips are located for every foot of travel in the barrel. Peak velocity is achieved at about 3 feet and then drops off for the remainder of the distance in the barrel.

I like a 2:1 ratio myself, thats your chamber should have 2 X the volume as your barrel.

Funny, If I have to hand pump it, I like it the other way around. It's less work and not much drop in performance at higher pressure. :D With the small compressor I use, the large tank cannon is about 10 minutes between shots at 60 PSI. With the little cannon, it's 80 PSI shots as fast as I can reload. For raw power, it is true the large chamber does perform better.
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Projectile is slowing in the barrel at low pressure.
Last edited by Technician1002 on Thu Jul 23, 2009 7:26 pm, edited 3 times in total.
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Unread postAuthor: eggbom » Thu Jul 23, 2009 4:20 pm

roboman wrote:It all depends on your barrel volume...if the volume of your barrel is less than that of your camber, it leads to reduced efficiency...ideally, you want about a 1:1 C:B ratio.

Just out of curiosity, why does it have to be made out of metal? PVC is much less expensive, and quite a bit easier to work with.


because in my country (holland) i cant find all stuff to work with,
and i have made a wooden weapon, where i want to put the metal barrel on for the looking.

and pvc is dangerous for me :(
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Unread postAuthor: inonickname » Thu Jul 23, 2009 6:49 pm

1:1 C:B ratio is rubbish.. Most of my guns sure aren't 1:1, and they seem to work fine..

There are really no risks with rated PVC.

Maybe threaded malleable iron fittings for this?
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Unread postAuthor: roboman » Fri Jul 24, 2009 5:17 pm

Maybe threaded malleable iron fittings for this?


That would probably be the only way to go, without having to solder it...

If you intend to make a "basic cannon" using all metal parts, your valve will be the weakest point in your design, unless you go with a metal valve, which can get costly...

but one question, if i have a 'chamber' that is 30mm x 300mm long, is that possible to shoot something?


GGDT will help you find the answer to that. I can almost guarantee that it will "shoot something" with that size of a chamber, but, again, how far it shoots depends on the size of your barrel.
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