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new copper QEV marble blaster

Built a pneumatic cannon? Then post it here! This section is for completed, finished cannons that you have built. Please include pictures and information.
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Unread postAuthor: jook13 » Fri Oct 17, 2008 8:52 pm

HAHAHA.... epic is good.
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Unread postAuthor: i-will » Fri Oct 17, 2008 8:57 pm

if u want damage than ur on the right track. i'd like to see pics of that.
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Unread postAuthor: jackssmirkingrevenge » Sun Oct 19, 2008 12:20 pm

POLAND_SPUD wrote:it would make sense if you compared two projectiles that have the same diameter but different weight.. for example 15mm marbles and 15mm ball bearings... anyway I think it's better to discuss it in that thread since jook might not want me to hijack his thread


It's a relevant discussion of interest to many, so why not ;)

You're right that projectile diameter is an issue, in fact penetration gets better as sectional density increases (ie weight per unit of frontal area), not weight on its own.

It is a complex matter as mentioned in the other thread, one must also consider projectile hardness too. A steel BB at a given velocity weights less than a lead BB of the same dimensions and therefore has less energy, but by virtue of its greater hardness will likely penetrate better than the lead in a tougher medium.

there is no proof in that thread that higher velocity = more penetration...


Higher velocity means the target medium has less time to react and deform to absorb the blow and therefore the kinetic energy cannot be dissipated and the medium fails, allowing penetration. It's an equation which has to be balanced though, as I mentioned before. For similarly sized projectiles fired at the same velocity, the heavier one will slow down less quickly and therefore penetrate further. However, fired from the same launcher, a heavier projectile will have a lower velocity, so you've changed another variable, so the above doesn't apply.

It does not necessarily mean that you won't have better penetration - for example, from any one of my 6mm launchers, a 1 gram lead pellet penetrates better than a 0.12 gram airsoft BB, even though the latter flies out at sometimes almost double the velocity - but it's not a guaranteed solution to penetrating further either.

The projectile I suggested is relatively light - therefore it will give good velocity - but by virtue of its low cross-secional area, has a high sectional density, which is very good for penetration. It also uses a steel nail that is harder than most things likely to be fired at, so all in all it optimises all areas relevant to penetration depth within the confines of our amateur resources.

I like the idea of the sabot nail with fins, a lot. any suggestions for attaching fins like that? I doubt JB weld or epoxy would hold something like that, and I have no welding experience.


I used araldite - roughly the same as JB weld - for mine and they held up fine :)
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Unread postAuthor: Crna Legija » Tue Oct 28, 2008 3:26 am

hay nice gun really good set up and where did you get your QEV
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Unread postAuthor: nivekatoz » Wed Oct 29, 2008 6:19 pm

Thats a cool cannon. Thats what Im tying to make,... not your design but the power you are putting out. Where the hell do you get a QEV llike that?? I have only used sprinkler valves and ASCO diaphram valves. I have always thought that diaphram valve were the same,..or close to QEV's
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Unread postAuthor: jook13 » Wed Oct 29, 2008 8:36 pm

http://www.fastenal.com/web/products/de ... ku=0443031

thats where I got mine. I dont know about the diaphram valve, never used one. but this qev is awesome.
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Unread postAuthor: jackssmirkingrevenge » Thu Oct 30, 2008 1:03 am

nivekatoz wrote:I have only used sprinkler valves and ASCO diaphram valves. I have always thought that diaphram valve were the same,..or close to QEV's


In this case, the power has more to do with the fact that he's using 350 psi that the use of a QEV. Force on the projectile is pressure x projectile base area, in this case he has over three times what typical spudguns use, hence the impressive performance.
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