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My first project.

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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Unread postAuthor: john bunsenburner » Mon Apr 06, 2009 3:36 pm

ok, makes sense, i only have a 5mm barrel(20mm is better to work with) so really it doesn't make much difference, even a few moderately big hoses will provide good flow.
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Unread postAuthor: Night Hawk » Mon Apr 06, 2009 3:47 pm

You have a 5mm barell? You making a bb gun? If im piloting to a blow gun, can i use a smaller hose as its just to equlise the pressure?
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Unread postAuthor: Night Hawk » Sun Jun 07, 2009 1:57 pm

Ok boys back on track here.

Have a diagram and a price list now, any thoughts and comments muchly appreciated :D


Image

Thoughts??

Oh and the barell will be longer, how long im not sure but is there a ratio to barell and chamber volume?
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Unread postAuthor: Biopyro » Sun Jun 07, 2009 3:33 pm

You'll have to fill it from where the ball valve is, behind the QEV.
This post should help you understand why the fill valve has to be on the fill port of the QEV.

I would definately attempt to solder it. It's neater, lighter, and a good skill to learn (also good fun!). In the long run (more than one cannon) it is also cheaper.

Why are you using a 28x22 reducer for the endcap? It would be much less expensive and lighter to just get a 28mm endcap. Even if B&Q don't stock them, check out for other places (especially more specialist plumbing places). If you know a builder/plumber they'll probably get you one for a fair price too.

This is my QEV cannon. It is effectively the same, but it uses some 45* bends to take the 22mm chamber a little closer to the barrel.

I regret sacrificing size and ergonmics for power though (it is easily taken apart, but I don't have time right now).

The barrel length depends on your operating pressure.
Download Gas Gun Design Tool (By D_Hall) and use it to model your cannon.
This guide by Ragnarok should help you use it.
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Unread postAuthor: Night Hawk » Sun Jun 07, 2009 5:03 pm

Ahh thanking you so much :).

Yeah im not sure why i whacked the scralder there, ive seen that post on pistons before :S. Overall this makes things easier tbh.

- Ok well this is a quick update,

after various thoughts this is what i have in theory on paper, any comments you peeps?

Image
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Unread postAuthor: jackssmirkingrevenge » Sun Jun 07, 2009 11:18 pm

Why did you put the projectile diameter as 1.5cm when the bore is 2cm? Try adjusting that and you should see a significant jump in projected performance ;)
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Unread postAuthor: Biopyro » Mon Jun 08, 2009 5:00 am

Your dead volume should be a little higher, maybe 15.
Your inner diameter should be 0, that's only for coaxial cannons.
Your chamber is waaaay too long. It should be shorter than the barrel (the volumes will work out when you remove that inner diameter value).
I don't know what you're imagining as your projectile, but finding something 3gm which fits well will be difficult!
Also schrader has no L in it ;)
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Unread postAuthor: Night Hawk » Mon Jun 08, 2009 1:46 pm

Cheers for the spelling tip :P, as for the projectile, i was planning on using marbles which weigh in at 3g and are about 15 mm accross. My next question was any suitable ammo, i will check the ammo forums at some point though so do not feel obliged to comment.

Thanks for the inner diameter tip too, i was wandering why the barrel was so much shorter than the chamber, i always thought it was the other way round!!
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Unread postAuthor: covey12 » Mon Jun 08, 2009 1:49 pm

hey by any chance are you nighthawkinlight on youtube, just wondering
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Unread postAuthor: Night Hawk » Mon Jun 08, 2009 2:30 pm

No im not, but they obviously got their cool name from me.

The only stuff related to me on the web is my graphics design work. Check it out :D

http://nighthawkgraphics.deviantart.com/

pm me if you want any work doing :P, i specilise in flash and photoshop web design and applications.
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Ok well i just got my qev, now looking for a 3/4(male) to 28mm compression elbow, any ideas?
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Unread postAuthor: Night Hawk » Thu Jun 11, 2009 5:38 pm

UPDATE:-



Ok guys, i drew up the plans over the last three nights, funtimes.

Image


Here is the result, the two bits of hose from the base of the qev to the T above the airgun and the hose from the split run coming out the check valve are not drawn in due to me not being able to draw a consistant line 8mm apart.

Some measurements


QEV = 3/4"
Hose = 8mm
Barrel = 22mm
Chamber = 28mm

i aim to be pressureising it at about 8bar.


The drawing is supposed to be to scale but i have nothing to go off apart from the thickness of copper pipe and the hose im using. I do have alot of pictures though.

Comments?
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