28 replies to this topic

[CO]

No piney, I know what you're thinking and I have way better things to do than post for the sake of posting. I'd like to do something more with my life. I'll let it slide but for the reccord, it was light-hearted and just... I dunno, something that caught my eye as a possible source for kicks... perhaps I have a bad sense of humor... whatever. I liked the thread you refrenced... true commedy is hard to find but you're right, the dude's idea in all its vague uncertainty shrouded in a false sense of knowing a great truth which can be summarized as HPA = GOOD is freakin' hilarious. I somehow have avoided these threads over the past month.
By the Way, what's the max PSI of a 3" PVC tank? I've read of some debate over how this changes for different types of PVC (furniture vs piping PVC) but assuming it's simply PVC ground piping... does anyone know?
On another topic relative to the mechanical operation of the gun, what would you all say to this verbal explanation of a firing mechanism... feasible? crappy? better idea? could be improved upon with ___x___?
In its rest position, the breech lies open and a hollow bolt lies farther towards the back of the gun. The valve opens and air is allowed into the back of the bolt sending it shooting towards the front of the gun. The bolt's movement primes the firing mechanism by scooping up the next shell (with dart inside) and forcing it forward against a slight ramp headed towards an o-ring which rests at the rear of the barrel/front of the breech. As the bolt accelerates inside its air-tight sheath, the spring which binds the rear of the bolt to the sheath is being streched. Finally, the bolt stops abruptly as the front of the shell makes contact with the o-ring and is pressed into a tight fit. Simultaneously, the bolt reaches a point where a perhaps 1/2" long (measured parallel to the barrell) groove in the sheath allows air out from the rear of the bolt and into another area previously locked off between the rear of the bolt, which contains the compressed air, and a secondary chamber just ahead of this. The secondary chamber is just as wide as the bolt and is solidly connected to the bolt, but has a hole in the front to allow the air to escape into the shell. If yo've followed me correctly, the air now gushes out around the sides of the bolt and into the aforementioned groove and then out of a hole, centered, in the front of the bolt. The shell lies tightly clamped between the front of the bolt, and the rear of the barrel. OK??????
That's the exciting part... after that, the valve is closed, the bolt is pulled back by the spring, and as it retracts (closing off access to the groove in the sheath) another shell is pushed up by a spring-fed magazine.
This is the image I drew on my tablet of what I just described



Most of this process came from watching those flash videos on the workings of a gas-powered machine gun and thinking about the plungers and bolt mechanisms for some of boltsniper's guns.
-co
PS I'll work on posting a picture in the next edit for all you visually inclined people like me... And this post is only about 500 words so I'll only post a half of a picture to keep things fair and all.


hey inkjet I wrote this as you were writing your last post, does this mean I get a hat?

In response to elf_avec_gun, yeah that would add weight, but it's a moot point.

Edited by C.O., 20 October 2006 - 12:20 AM.

[InkJet]

Well, I halfway understand it, but i'd say you get a hat. Good job on that mechanism. But that was one of the easiest parts, now comes making it!

[Meaker VI]

This site will tell you everything you need to know about PVC piping; you can get it rated to 1300 some odd psi, however it is only 1/4" inner diameter and therefore might be difficult for your gun's HPA chamber-making. 3" gravity piping is unrated and won't hold pressure.

And I'm not so sure I understand your mechanisim; could you clarify it a little bit? Right now it's looking perpetual-motionish with the air being compressed by the spring that it just compressed...

Edited by Meaker VI, 20 October 2006 - 01:08 PM.

[CaptainSlug]

I'm not too keen on your mechanism. Having air do mechanical work at lower pressures will lead to a very slow cycle speed and your bolt may simply hang in the midpoint of the cycle unless the extension spring is the right rating.

3" SCH40 PVC pipe tank is rated up to 200 psi but don't fill it beyond 140psi. PVC is a really poor tank material because it will shatter instead of warping at failure. It's only saving grace is afforability.
And you won't be able to fill your tank beyond 60psi unless you have a compressor and a check valve.

Here are my opinions on automatic Nerf.

1. Shells are bad. They lead to a longer reload time and you have twice as many things you need to pick up after shooting. They're also really picky and won't allow you to use a variety of stefan lengths.
2. A high rate of fire means nothing if you don't have a supply of ammunition that can keep up with it. If you can empty an entire clip quickly, great. But if none of those hit anything then you're no better off than the players with single-shot guns.
3. Everything you're proposing has been discussed at length. But nobody gets around to doing it because it all requires so much time, experience, money, and tools. I was working on an actuated breech weapon that could potentially be made full auto, but I decided it wasn't worth the time involved when I could simply alter a magstrike to do the same thing.
4. If you want full-auto you'll also have to consider that at higher rates of fire a 20-round magazine can be emptied in a few seconds. So you may want to forget using a magazine and instead come up with a hopper or gravity clip system of some kind that will allow for a higher capacity and faster reloading.

These are the few means of supplying darts to a nerf gun reliably that i can think of.
@ Spring-feed box magazine + bolt - involves tight tolerances and not very easy to make in an effective manner.
@ Gravity-feed + breech - Can be simple and effective. But I'm finding ways of complicating it for specific use in CSHG.
@ Actuated Clip with integrated barrels - the magstrike clip, at3k turret, maverick, and firefly all do the same thing. The clip or turret hold the darts and act as the barrel. These require some precision, but are far less complicated and faster to reload than a spring-feed box magazine.
@ Manual Turret - Like above, but cycled by hand inbetween shots.
@ Manual - Either by breech coupler or muzzle loading. This is the easy-out option.

Edited by CaptainSlug, 20 October 2006 - 06:39 PM.