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Semi-automatic Air Gun.


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#1 Vereiah

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Posted 23 May 2010 - 09:05 AM

So, I've been interested in working on a fully homemade nerf gun for ages... Probably about two years, but I've never had the time or money (yes, I'm that poor). Recently, though, I've been seeing possible ways to get the materials I need - In other words, I've got a half-decent job.

I've only modded a pair of Mavericks, and it's some basic modding too - Air restrictor removal, tightening the opening in the plunger tube, and filling the plunger for some more effective air compression.

I'm currently working on a miniature air compressor to mount to the back of a nerf gun for semi-automatic fire, similarly to a Paintball gun, in order to completely replace the usual bike-pump solution. As of yet, I only really need a 9v DC motor to make it run. The pressures should be around 50PSI in the tank, since any more than that would most likely slip through the intake valve (homemade PVC Air Compressor ftw), and only a small portion of that would be used to actually fire the dart - Thus, allowing for semi-automatic fire.


Again, I'm dirt poor, so I can't take pictures of the Semi-Automatic I'm working on yet. It's still mostly just a concept. Will post MS Paint diagrams after I get my house a little more painted today.



I'm also experimenting with ammo a little bit for the time being. I've noticed that a ~1/4" stefan with a copper BB and hot glue in the tip with a ~1/8" hollow in the rear will perform just as well as a more standard size, so I've been making extra small stefans. This has the added benefit of being able to double or triple load them for a shotgun effect. I would NOT recommend loading them up to the length of a standard size stefan, due to the weight issue... Though this could be countered in a system with much more pressure. Only tested with Mavericks.

Edited by Vereiah, 23 May 2010 - 12:33 PM.

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#2 ModSquad

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Posted 23 May 2010 - 09:50 AM

I would suggest you start on a simpler spring gun apposed to your proposed gun which seems pretty complex.
P.S. It would be easier to buy the compressor that SgNerf used on his magstrike.
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QUOTE
"Roger Ten Niner, we got a rainbow four klicks out. I'm casting the rod."
"Roger Squad Leader. Sending in back up."
"Roger Ten Niner. We have a confirmed bite. I repeat, a confirmed bite"
"Good job boys, lets real it in and go home"

#3 taerKitty

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Posted 23 May 2010 - 10:44 AM

I see this is your first post, Vereiah. Welcome to the Haven. You'll find people here to be very knowledgeable and eager to share their knowledge, albeit forcefully at times.

Congrats on getting a job, so you can progress in the hobby (or obsession, depending on who you ask.)

I'm with ModSquad on this one - airguns are much more complex than springers, and probably not a good first homebrew. Then again, we all start somewhere, so good luck if that's your plan.

By the way, nothing wrong with 'basic modding' if you're just playing with friends or coworkers. If you're going to Nerf with people who are serious, such as a 'war' with people on this site, you'll find that you'll need to 'step up your game'. Then again, from what I've read and seen, most wars seem to have someone kind enough to lend out decent blasters if what you brought wasn't up to the job.

Speaking without any knowledge of how your PVC air compressor works, may I suggest you use a rubber bladder system if you are planning to use a PVC 'tank'? PVC is not rated for gases under pressure. The problem isn't the 100 PSI stamped on the side - it's the fact that a length of 100 PSI water is only slightly larger in volume than 14 PSI water, so the pipe would crack and leak; but 100 PSI of gas is significantly more (someone said 5x?) than 14 PSI of gas, so the pipe would explode.

I'd love to see how your homebrew compressor works. MS Paint is a poor substitute for actual photos, though. In fact, I've found that pictures are expected - some treat them as required. Better a (not blurry, please) cell phone camera pic than an MS Paint schematic.

The 1/4" stefan sounds interesting, but where do you get your foam? I've never seen foam that size.

As you've probably found, a Maverick isn't a very good blaster. It's fun to look at and all, but performance is pretty poor. That said, I'd like to see how the 1/4" and 1/2" stefans perform in other context, too. If you have any decent length of 1/2" barrel material, you can get a passable comparison of their performance against standard stefans if you use the barrel as a blowgun.

Anyhow, welcome to the Haven. Looking forward to your next post (with pictures! :P )

PS: Lose the 'concepts' in your title. Concept threads are very much extremely erotic, and some members seem to get off on flaming newbies who post 'concept threads'. It sounds like your PVC air compressor is actually underway, though. Looking forward to seeing it.
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#4 Vereiah

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Posted 23 May 2010 - 11:28 AM

The 1/4" stefan sounds interesting, but where do you get your foam? I've never seen foam that size.

As you've probably found, a Maverick isn't a very good blaster. It's fun to look at and all, but performance is pretty poor. That said, I'd like to see how the 1/4" and 1/2" stefans perform in other context, too. If you have any decent length of 1/2" barrel material, you can get a passable comparison of their performance against standard stefans if you use the barrel as a blowgun.


I was referring to length.
If you hollow out the back end of a substantially shortened stefan, it reduces the weight of that end (duh) for the surface area in direct contact with the air it's flying through. If anything, it might reduce accuracy (slightly) with (slightly) increased ranges.


As for the Maverick... It's mostly for fun. I was going to go to Lowes later to get some larger pieces of PVC to replace the slide with a pump setup and possibly give it a larger plunger.




I also have a spring gun that I was going to work on, but I'm lacking the spring. Right now I just have some bits of material I'm using for the air compressor.

Piston pumps air in, opening the intake valve and closing the discharge valve; Piston pumps air out, doing the opposite. Piston is pretty much a PVC endcap with a couple of O-rings (well greased, of course) and a hinge in the middle, with a smaller section of plastic running to a flywheel. Still working on this component, since it's easily the most important (and I'd love to see how well it works out).
Only making my own because I would prefer to not spend any more money than I have to.
As for compressed air in PVC, I had a 150PSI 25mm Potato Gun a while back made out of PVC. Wonderful little thing, but I never wanted to go beyond 150PSI because despite 200 being the pressure rating, it seemed like it would be more likely to explode. 50PSI is nothing :P

Still working on painting the house. May go to Lowes later and grab a few more necessary components - I know what I'm doing here, but I'm at an embarrassingly early stage in development :D
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#5 ModSquad

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Posted 23 May 2010 - 11:59 AM

Your pump design seems to be lacking a check valve.
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QUOTE
"Roger Ten Niner, we got a rainbow four klicks out. I'm casting the rod."
"Roger Squad Leader. Sending in back up."
"Roger Ten Niner. We have a confirmed bite. I repeat, a confirmed bite"
"Good job boys, lets real it in and go home"

#6 Vereiah

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Posted 23 May 2010 - 12:29 PM

Your pump design seems to be lacking a check valve.


Exactly what do you mean?
If I'm not mistaken, a check valve is a one-way valve. If that's what you're talking about, then there are two of them. If you're talking about something to limit the pressure in the pump and tank, then that's already more or less taken care of as well - Between a pressure gauge, an on-off switch, and the semi-faulty PVC pump mechanism (only machining can make a perfect seal), there's a VERY low chance of the tank/pump exploding.
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#7 taerKitty

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Posted 23 May 2010 - 01:10 PM

Also, springs aren't the only white meat. I've recently started bungeeing my blasters, and am pleasantly surprised at the yield. Sure, it looks super-primitive, but, let's face it - if we're going to wave around what are effectively foam zip guns, we're already in the primitive zone - it's just a matter of degrees.

Bungees are great - you don't have to worry about finding the right length, and if you want more oomph, just add a few more runs.

Off-thread:

I'm experimenting with two different 'methods' - one is to use a few of the mini bungees stretched to the limit, and the other is to use more runs of the 'regular' stuff. Both have crazy-heavy pulls, but I'm interested in plunger speed (my only method is to measure empirically through performance, unfortunately), durability, and maintenance costs over time.

I'm pretty sure the minis will wear out quicker, but wanted to see how quickly, if the regular thickness ones do wear out, how quickly, and how much it would cost to replace them as they do.

Get that house painted already - I want to see your compressor. I'm always stoked to see new stuff.
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#8 ModSquad

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Posted 23 May 2010 - 02:46 PM

I mean the one way valve so the pressure in the tank isn't spilled out the pump or the pump doesn't come flying out of your gun.
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QUOTE
"Roger Ten Niner, we got a rainbow four klicks out. I'm casting the rod."
"Roger Squad Leader. Sending in back up."
"Roger Ten Niner. We have a confirmed bite. I repeat, a confirmed bite"
"Good job boys, lets real it in and go home"

#9 Vereiah

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Posted 24 May 2010 - 08:06 AM

Also, springs aren't the only white meat. I've recently started bungeeing my blasters, and am pleasantly surprised at the yield. Sure, it looks super-primitive, but, let's face it - if we're going to wave around what are effectively foam zip guns, we're already in the primitive zone - it's just a matter of degrees.


Idea here. Get some 1+1/2" or 2" PVC (can't remember which) and cut two slits on an even plane, and a third, larger slit at a right angle to those two. Put a ram in there and get the Bungees attached (to the ram) in any way possible, while placing a grip in the third (last time I did a bungee blaster, I had that grip working as a sight too). Put in a simple trigger system, preferably NOT a pistol grip, which makes it less effective in close range (between reloading, cocking, and firing, you're probably going to be holding it at the hip). Throw some arms out front - PVC is shockingly effective for a foam bow application, stick the other end of the bungees to those, and BAM. Instant (not quite) crossbow.

Already did that :ph34r:
...Unless you were talking about getting some bands on the back of the bolt? O.o
Ball crossbows are pretty effective in my experience, at least when compared to a Ballzooka MP150's ranges.




Still haven't gotten to Lowes/Home Depot. Transportation is somewhat difficult, though I might be able to get there tonight... -.-
Will start working on the stock/grip today, since that's the part with the most readily available components. Not going to carve out slots for the pieces until I actually get those pieces built, put together, and tested.



As for the check valve... I was talking about having a check valve at both intake and discharge. The pump is effectively a 6-inch 2"PVC tube, capped at one end, with some 3/4" end caps drilled into and attached to that cap.
A small rod goes through each of the endcaps to approx. halfway between the endcap and the 3/4"PVC I'm using to connect the endcap to the pump. On the ends of these small rods, I have a rubber disk, similar to the SNAP plunger heads. Intake, the edge of the disc is inside the tank end, and discharge, the edge of the disc is inside the endcap. A length of vinyl tubing is attached to each one of the 3/4" endcaps.

Plans I've made call to place the pump inside the stock and the tank directly in line with the barrel.

Edited by Vereiah, 24 May 2010 - 08:14 AM.

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#10 Kabigon

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Posted 24 May 2010 - 02:28 PM

As for the check valve... I was talking about having a check valve at both intake and discharge. The pump is effectively a 6-inch 2"PVC tube, capped at one end, with some 3/4" end caps drilled into and attached to that cap.
A small rod goes through each of the endcaps to approx. halfway between the endcap and the 3/4"PVC I'm using to connect the endcap to the pump. On the ends of these small rods, I have a rubber disk, similar to the SNAP plunger heads. Intake, the edge of the disc is inside the tank end, and discharge, the edge of the disc is inside the endcap. A length of vinyl tubing is attached to each one of the 3/4" endcaps.

Plans I've made call to place the pump inside the stock and the tank directly in line with the barrel.


If I understand what you're saying, you made a homemade check valve? My Home Depot sells pre-made PVC check valves. Maybe yours will sell them too. Buying one from there, if they have it, might be alot easier than making your own.

Anyways, I'm looking forward to see this get completed. It sounds very interesting.

Edited by Kabigon, 24 May 2010 - 02:31 PM.

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QUOTE(Tannman500 @ Aug 14 2008, 08:17 PM) View Post

CDdts r great u new to nerf if u dont know how to make them
NOOB


#11 PVC Arsenal 17

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Posted 24 May 2010 - 03:49 PM

Vereiah, keep checking this forum in the coming days. I have a semi-auto of my own in the works and initial testing looks very promising. You might find my project relevant to your interests.

Posted Image

The idea is not far fetched by any means, you don't have to be Captain Slug or Boltsniper to make a properly functioning Nerf gun on your own, and you especially don't need access to machining equipment.

It sounds like you're looking to start out by addressing the problem of what to use as an air source and you've already decided on a homemade onboard compressor. First I will ask: Have you considered a high pressure air (HPA) or CO2 tank? If not, I would like to be the first to point out the benefits. An HPA tank is very simple to incorporate into a gun. About as simple as connect and go. No manual pumping, no noisy compressor or complicated and messy wiring. Best of all, regulating the pressure going into your gun is very easy (and of course necessary), giving you complete command over the safety of your gun. (Pneumatic and dangerous are not synonymous).

If you do insist on a compressor system, I would suggest avoiding PVC or plastic for any parts that will handle pressure. It's not that PVC can't handle high pressures - trust me, it can - it's that PVC has low impact strength and if you take a fall with a plastic tank under pressure, the tank could easily explode. Compressed air stores large amounts of potential energy unlike water.

Aside from the issue of the air source, have you thought yet about what mechanism you'll use in the gun itself? It sounds like you plan to use an existing toy Nerf gun but I'm not sure. If instead you're going to build your own gun from the ground up, share your ideas here and we can offer more input. There are a few of us (including myself and Doom) who have lots of experience in that area. You can also head over to SpudFiles if you'd like to learn more about how to incorporate cylinders and directional control valves into semi-automatic guns.


Good luck with your project and please keep us posted. I'm vey interested in seeing what you plan to do.

Edited by PVC Arsenal 17, 24 May 2010 - 03:55 PM.

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#12 taerKitty

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Posted 24 May 2010 - 08:20 PM

On the topic of air tanks, what's a good material to use, and how would you work it? I'm guessing ABS is in the same no-no category as PVC, right?
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#13 PVC Arsenal 17

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Posted 24 May 2010 - 08:56 PM

Copper is always good. I know Doom used lightweight aluminum low pressure cylinders in his FANG 2 project. Those seem like a great solution. You can also buy volume cylinders. I would try to avoid plastic unless you can guarantee you won't fall and smash it. At least sleeve it in something metal.
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