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Semi Auto Nerf Gun

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: daberno123 » Tue Oct 21, 2008 5:33 pm

If a three-way valve is still an option here is one on eBay for $10.99 + shipping. It has 1/8" NPT connections and says it can be set up normally open or normally closed.

Just throwing that out there if you decide not to use the slide check.
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Unread postAuthor: PVC Arsenal 17 » Tue Oct 21, 2008 6:51 pm

daberno123 wrote:If a three-way valve is still an option here is one on eBay for $10.99 + shipping. It has 1/8" NPT connections and says it can be set up normally open or normally closed.

Just throwing that out there if you decide not to use the slide check.


Only problem with that is that it's a solenoid valve. I want to avoid electronics.



Also, here are some parts loosely arranged in one possible configuration:
Image
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Unread postAuthor: VH_man » Tue Oct 21, 2008 7:09 pm

looking good.

Thats one strange Qev...

One thought though... Place the Air cylinder on the side of the Barrel so you can still sight down the barrel.
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Unread postAuthor: PVC Arsenal 17 » Tue Oct 21, 2008 7:26 pm

VH_man wrote:looking good.

Thats one strange Qev...

One thought though... Place the Air cylinder on the side of the Barrel so you can still sight down the barrel.


Considering it... but that would set off my symmetry OCD! Plus I was going to use those nickel plated fittings connecting to the cylinder as platform for some type of iron sight.
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Unread postAuthor: VH_man » Tue Oct 21, 2008 8:00 pm

Ah. In that case, Nevermind. In my Paintball Version of this Mechanism, the cylinder will be on the side. I guess it works either way.

this mechanism is so useful. In fact, i might have to re-create my Shell Ejection system......... As this will work perfectly.
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Unread postAuthor: daberno123 » Tue Oct 21, 2008 8:56 pm

What sort of clip are you planning on building? A clip for nerfs could get difficult because they're rectangular.

How many rounds do you plan on having it hold?
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Unread postAuthor: SEAKING9006 » Tue Oct 21, 2008 9:45 pm

Nerf clips don't have to be rectangular. Check out Boltsniper's (Nerfhaven's equivalent of Larda, or maybe JSR) SCAR-N. It uses an AR-15 magazine containing stefans in copper shells.
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Unread postAuthor: Lentamentalisk » Tue Oct 21, 2008 9:48 pm

ok, I'm having a little trouble with scale there. What size is all of that?

I would just forgo the stock, to make it more portable and all.

Other than that, it looks great!
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Unread postAuthor: POLAND_SPUD » Tue Oct 21, 2008 11:05 pm

you might consider building it in a different way... becasue there is a lot of deadspace and it seems it might be difficult to use the pilot valve

something like this (it's not exactly what you should do but it should give you a rough idea how it can be arranged )
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Unread postAuthor: Lentamentalisk » Tue Oct 21, 2008 11:33 pm

well the slide valve actually works best in the position that it was in, given a trigger mounted to it or something. It is almost impossible to use when mounted vertically, though your method of mounting the cylinder is great.
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Unread postAuthor: POLAND_SPUD » Wed Oct 22, 2008 12:05 am

I think that it is possible to make a trigger with a slide valve mounted vertically.. sure it won't be as easy as making a trigger with horizontally placed valve...

I still think it's a better idea to use a 3way valve and I am sure that there are dozens of places where he can buy it.. but of course I was considering using a slide check valve myself

well one way or another i think that the design has to rearranged.. his design has way too large dead space, short barrel (while having long overall lenght) and the magazine tthat has to be placed far away from the shooter (near the muzzle).
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Unread postAuthor: vovka351 » Mon Oct 27, 2008 1:02 pm

So, is this project going anywhere?
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Unread postAuthor: judgment_arms » Tue Oct 28, 2008 9:37 am

okay...
I may be missing something, but...
wouldn't the breach open as the chamber dumped?
and if you were running low on input pressure, would the breach be able to fully close?

still, it's a very interesting design...
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Unread postAuthor: Ragnarok » Tue Oct 28, 2008 9:57 am

judgment_arms wrote:wouldn't the breach open as the chamber dumped?

No, not if the spudgun were run at adequate pressure.
If the force from the chamber pressure exceeds whatever return force there is, then the cylinder won't start cycling.

I imagine that the chamber pressure won't fall low enough - with an adequate C:B ratio - for the cylinder to start movement until well after the dart is gone.

When I (hopefully) use the design on 3vo, the loader design may require an additional system to be added to delay the cylinder further - 3vo will run across a very wide pressure range (likely 50-500 psi), and may as such need it to ensure correct operation across an order of magnitude, but I doubt it's needed here.
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Does that thing kinda look like a big cat to you?
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Unread postAuthor: judgment_arms » Tue Oct 28, 2008 10:25 am

humm...
if you've got all that extra volume that must be dumped, well there goes efficiency and ROF will be limited also...

there's a lot of timing to get this thing singing, and in the end it still has an efficiency issue...


since you've already got a ram, why not just throw in a 3-way and run it autococker style, with the trigger controlling the firing valve and the cycling?
Image


by the way, is the new LRC done yet? :D
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