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Understanding Air Guns


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#1 DartSlinger

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Posted 16 March 2013 - 01:56 PM

First of all, many thanks go to Ben Trettel (Doom), who got me interested in air guns, and who, along with roboman, provided most of the purchasing information.

In the NIC, air guns do not receive nearly as much attention as springers do. This is possibly because people do not understand how they work. I did not understand how the different designs worked until I started researching it. In my quest, I have found many useful diagrams and articles that will help other people to understand how air guns work.

A basic understanding of valves is crucial to designing, building, or troubleshooting any air gun. Wikipedia defines a valve as "a device that regulates, directs or controls the flow of a fluid (gases, liquids, fluidized solids, or slurries) by opening, closing, or partially obstructing various passageways." Here are some excellent guides on valves.



Check Valves

One of the simplest valves is the check valve. It allows airflow only one way, therefore eliminating backflow in a system.

How one works

An extremely simple one built by Zorn's Lemma

Purchasing: PVC check valves are available from most hardware stores. 46835k54p1l_zpsbdd75a7c.png They are available in threaded and unthreaded. These are somewhat expensive, though, so McMaster's 7757K43 should do the trick. Check valves can also be acquired for free from Ark-Plas—see the Guides, Tips, and Tricks section of this post for more information.



Over Pressure Valve

An over pressure valve, or pressure relief valve, is basically a check valve that vents after a certain pressure is reached. They are to be used with tanks to ensure that the maximum working pressure is not exceeded.

How one works

Homemade, adjustable, over pressure valve There is also a thread here that is about where to use them on air guns.

Purchasing: McMaster's 50265K23 works well and is the cheapest over pressure valve that I have seen.



Directional Control Valves

Directional control valves are used as pilot valves (basically the trigger) for exhausting air tanks. Here are explanations of their workings.

CaptainSlug's explanation of how three-way directional control valves work. This is an excellent guide to them. It is where I found out how they worked.

Animated explanation of two, three, and four-way directional control valves

Purchasing: McMaster's 6464K11 and Clippard's MJVO-3 MJVO-3 is much better than 6464K11. It has a higher flow rate, is smaller, cheaper, and can attach to trigger style buttons. The only reason to use the McMaster-Carr valve is if you can't buy Clippard valves.



Solenoid Valves

A solenoid valve is any valve that is controlled by electricity instead of manual input. For example, a solenoid directional control valve is a directional control valve that uses electricity instead of manual operation to switch the ports.



Quick Exhaust Valves

The Spudding Handbook gives an excellent definition complete with animated picture right here.

Ben Trettel posted an excellent article on a homemade that he built that utilizes a quick exhaust valve and a directional control valve. This was the article that got me into air guns.

Purchasing: McMaster's 6646K33 and 6646K11, and Clippard's JEV-F2M2. Both 6646K33 and JEV-F2M2 will work for Nerf guns. However, your power with JEV-F2M2 will be somewhat limited. Doom has not yet tried 6646K33, but he suspects that like the larger McMaster-Carr valve (6646K11), it is overkill. Either is fine depending on a project's goals. If you want power, go with 6646K33 or the even larger one. Here is the data sheet of McMaster-Carr QEVs. Ebay is also an excellent source for QEVs, and you can usually find a 1/2" one in the range of $10 or so.



Piston Valves

Piston valves, also known as back-pressure valves and back-pressure tanks, are the valves that are most often used in factory-made dart blasters. They are a type of quick exhaust valves that differ in form but not function.

The Spudding Handbook once again has the best diagram for piston valves here.(Be sure to click the play button under "Phase 0" to start the animation.) You can learn almost unlimited amounts of information about pneumatics by hanging around Spudfiles.

There are also several good articles on NerfHaven pertaining to piston valves.

The Nerf Secret Strike Internals This contains excellent PowerPoint drawings of how the internals work.

The Autopsy Pictures Thread This contains images of many cut-open pistons from factory-made dart blasters.


Now that you understand piston valves, let us move on to some examples. Buffdaddy has created multiple valves, with varying levels of success, such as Adventures in Air Guns, and the B.U.F.F.



Pneumatic Cylinders

Pneumatic cylinders, often called air cylinders, extend and retract under pressure. These are usually used for breeches when used in homemades. Some examples being FANG 1, and Abp5k. The Abp5k also uses a homemade directional control valve. Reading that entire thread will gain you vast amounts of knowledge about air guns, valves, regulators, and high pressure tanks.

How they work



Pressure Regulators

Pressure regulators regulate the pressure from a high-pressure source to a lower-pressure destination while keeping the pressure constant.

How they work

Another guide to how they work This one has an animated explanation of one and two-stage regulators.

Purchasing: Clippard's MAR-1NR is an adjustable, non-relieving pressure regulator that has been tested and works well. Harbor Freight has flow (not pressure) regulators around five dollars. Two examples are this and this. These Harbor Freight regulators are what is called "flow regulators" and are little more than ball valves. They are used to reduce flow rate, not pressure, so be advised.



Air Tanks

Quite a few air-gun designs utilize a larger, usually higher-pressure tank that charges a smaller tank that fires the blaster. Depending on size and personal preference, a designer will choose to integrate one with the blaster or to carry it on his back.

External air tanks are also often used with factory-made Nerf blasters to remove the necessity of pumping it up manually.

Paintball Tanks with Nerf

DIY: External Air Tanks

People have had an obsession with modifying Magstrikes to take external air tanks for years. CaptainSlug did the first here, and two other notable examples are this and this.

I mentioned this air gun before, but it is relevant here also. Ben Trettel's air gun here uses an integrated hard tank, as do FANG 2, and Pepé.

Purchasing: These tanks are absolutely fantastic. They have a working pressure rating to 125 psi, with a burst rating to 500 psi, and they're polyethylene, so they are pretty light. The brackets you can buy with them are awesome also, because they have a bolt hole already in them, and the tanks just snap in.



Guides, Tips, and Tricks

Buying Clippard Components

You can request a catalog from Clippard. They'll send you a very nice glossy printed catalog. This catalog contains all their products and a lot of technical data.

NPT dimensions This will give you the real (not nominal) dimensions of the National Pipe Thread Taper.

You can receive samples of many Ark-Plas products such as valves and polyurethane tubing for free. Use the sample request form that is under the item. An example is check valves. The sample request button is under each item that it is available for.

Harbor Freight and hardware stores such as Lowes and Home Depot carry many pneumatic items such as brass barbed fittings.


This is a guide on how to use latex tubing for air bladders.

Converting Flow Rates



Further Reading and Must-Read Articles

If you are interested in air guns, there are many interesting articles for you.

Homemade Magstrike Piston and Write-up

JSPB-The Mad Ghost This is a very simple air gun with an extensive write-up. Oh, and it is by 3DBBQ, who is one of the greats. You should read it. This explains how the triggers on his air guns work.

WNTS This is very similar to the 3DBBQ trigger system. It uses American parts though, so it may be helpful to you.

Dchap-1 This stands for "Dirt-cheap homemade air-powered," and it describes it exactly. It is simple and cheap.

Dchap-2 The second dirt-cheap homemade design.

Introduction to Pneumatics and Pneumatic Circuit Problems

S.C.U.N.B.A.G. This is a simple design with an in-depth write-up.

Semi-Automatic Valve


If you find any mistakes or would like me to add anything, send me a personal message.


Edited by DartSlinger, 06 March 2019 - 09:33 PM.

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#2 Doom

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Posted 16 March 2013 - 02:17 PM

Excellent work DartSlinger. This is a great summary. Air guns are less popular in part because there are less intro-level guides. Hopefully this will fill that gap.

I would suggest adding some links to safety valves, check valves, directional control valves, QEVs, pneumatic cylinders, and pressure regulators on McMaster-Carr.

Several other Nerf guns have used pneumatic cylinders. My own FANG1 did (scroll down to see), as did several other guns by PVC Arsenal: RR, RSP-Skeleton (photos and info deleted), and TFS-Semi.

Also, there are many companies that specialize in miniature pneumatic components that work excellently for Nerf guns. My favorite is Clippard. On Spudfiles I posted a guide about buying Clippard parts because they can be hard to find "cheap." (Definitions of cheap vary. Others might call this approach "cheaper.")

I'll add more to this post as I think of it.

Edit: I added a link to this thread in the General Reference thread for Homemade Blasters. This will not be added as a sticky to prevent cluttering the stickies.

Edited by Doom, 17 March 2013 - 06:09 PM.

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#3 CigarBaby

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Posted 16 March 2013 - 02:20 PM

Great guide DartSlinger! I was also a bit confused on how air blasters worked at first. I'm sure this will be really helpful to some of the newer members as well as some of the older ones.
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#4 Alfatrooper

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Posted 16 March 2013 - 03:29 PM

Great guide. Explanes a lot real fast. So if you are just releasing air out of the tank, then you can dry fire it? Should this be pined?
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#5 DartSlinger

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Posted 16 March 2013 - 04:34 PM

So if you are just releasing air out of the tank, then you can dry fire it?

Yes.

Thank you everyone for the compliments.Posted Image

I edited the post slightly, and I'm working on getting McMaster part numbers. If you know of parts that worked for you, it would be very helpful if you sent them to me. Try to make it a message though, so this thread doesn't get cluttered. Thanks again everyone.Posted Image


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#6 Ivan S

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Posted 16 March 2013 - 05:57 PM

I think one of the things that keeps people from building air guns is the fear that they're too complicated. I think it should be noted, just for beginners, that you don't need to understand most of this stuff if you just want to make a good Mad Ghost, TH^2, WNTS, or similar. The essential things to understand are check valves and over pressure valves.
You may also want to add this link to the oprv section, it has some crucial information on how to use them.

Edited by Ivan S, 16 March 2013 - 06:12 PM.

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#7 Buffdaddy

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Posted 16 March 2013 - 07:03 PM

Just a heads-up: the homemade Pulsestrike isn't a piston-type tank. You're still just opening the airway to the barrel, like in an At2K or Titan. It simply has the added benefit of an extra force input for building pressure.
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#8 DartSlinger

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Posted 16 March 2013 - 07:40 PM

Just a heads-up: the homemade Pulsestrike isn't a piston-type tank.

Thank you. I amended that section.


You may also want to add this link to the oprv section, it has some crucial information on how to use them.

Thank you. I added it. So far, the input and suggestions I have been receiving are good. So thank you all.

I think one of the things that keeps people from building air guns is the fear that they're too complicated. I think it should be noted, just for beginners, that you don't need to understand most of this stuff if you just want to make a good Mad Ghost, TH^2, WNTS, or similar. The essential things to understand are check valves and over pressure valves.


I agree. Analogously, I didn't understand everything about springers when I built my first one, but building it gave me confidence of my craftsmanship, and helped me to understand the function of springers in general.



I am currently working with Doom on adding part numbers of parts that have been tested and work. If anyone has any parts that have worked, please send their part numbers to me and I would be much obliged.

Edited by DartSlinger, 16 March 2013 - 08:55 PM.

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#9 Super0dp

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Posted 17 March 2013 - 02:10 PM

Very, very nice work. Air guns are not as well known in the community and now people can have more information on a very cool topic.
I think it should be sticky, Mods?
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#10 Hammy

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Posted 18 March 2013 - 02:40 AM

Nice guide.

But playing with compressed air can be highly dangerous.
And if one is using incorrect materials to construct an air-blaster, this could lead to very serious injury, in the event the tank explodes and fragments.
So bear that in mind.
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#11 ShaNayNay

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Posted 18 March 2013 - 11:10 AM

This is a very nice guide, thank Dartslinger. I feel like this would be a great place to repost this thread as it is a means for modders to create semi-auto valves for standard air tanks (or with simple changes backpressure tanks) using cheap and easily acquirable parts most already have.

SEMI-AUTO VALVES

It seems air tank blasters have declined greatly since 2010, so hopefully this will help them return.


Playing with compressed air can be highly dangerous.


And so is working with utility knives, hack saws, power tools, toxic fumes in paint and PVC, and everything else Nerf modders use in the modification process. If you are dumb enough to hurt yourself by blowing up an air tank then you are dumb enough to cut off a finger with a saw or utility knife and you just shouldnt bother modding nerf blasters.

Edited by ShaNayNay, 18 March 2013 - 11:25 AM.

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#12 Tangerle

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Posted 18 March 2013 - 04:52 PM

Nice thread, now I finally understand the sspb and panther. At first you bugged me a little but wow, this is really useful (and a slight halt to all of the "iffy" posts). How long did it take to make this?
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#13 DartSlinger

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Posted 18 March 2013 - 08:35 PM

How long did it take to make this?

I created it over ten days, and I estimate that it took me about eight hours. It is difficult to estimate, though, so I could be off.

Edited by DartSlinger, 18 March 2013 - 08:35 PM.

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#14 Tangerle

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Posted 18 March 2013 - 08:47 PM

I created it over ten days, and I estimate that it took me about eight hours. It is difficult to estimate, though, so I could be off.

Well, nice contribution. I wish this was posted 1 and a half years ago when I first got into air guns.
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#15 Hammy

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Posted 18 March 2013 - 11:55 PM

With knives and cutting tools and sharp edges one can see the danger, but it is not so obivious with compressed air.

And so is working with utility knives, hack saws, power tools, toxic fumes in paint and PVC, and everything else Nerf modders use in the modification process. If you are dumb enough to hurt yourself by blowing up an air tank then you are dumb enough to cut off a finger with a saw or utility knife and you just shouldnt bother modding nerf blasters.


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#16 Eik

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Posted 19 March 2013 - 02:33 AM

With knives and cutting tools and sharp edges one can see the danger, but it is not so obivious with compressed air.


In addition, all those other dangers listed only impact the individual. Compressed air failures impact anyone who is in the blast radius.
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#17 Doom

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Posted 19 March 2013 - 05:24 PM

With knives and cutting tools and sharp edges one can see the danger, but it is not so obivious with compressed air.


I disagree. Determining whether a compressed gas gun is dangerous is usually easy. If the gun uses non-pressure-rated PVC pipe and/or fittings, it is potentially dangerous. If PVC primer was not used, or the PVC cement or primer was used incorrectly, it is potentially dangerous. I'd go as far as to say if PVC pipe was used at all then the gun is potentially dangerous, simply because PVC pipe is not meant for compressed gas. Compressed gas requires that a more ductile material be used to prevent the generation of shrapnel. (Soda bottles are no good either. I've discussed them several times before on NH.)

Most compressed air components have stated pressure ratings. Sometimes these ratings are printed on the pipe! So in those cases, checking whether a system is potentially dangerous is trivial. Just compare the pressure to the rating.

If only metal components are used, the gun is likely overwhelming safe assuming that the pressure ratings are respected. And if you exceed the pressure rating, likely the worst case scenario is that you'll see a leak. The shrapnel risk of PVC is basically gone for aluminum, steel, and brass (they are much more ductile materials than PVC). People generally don't use metal out of convenience, unfortunately. That and metal's usually more expensive than plastic.

Bladders actually pose worse safety concerns. A bladder bursting is about as loud as a shotgun firing. That can cause very real hearing damage. I know because I did some research into the failure of bladders, and I made sure to use hearing protection after the first burst. Ouch. I suggest hydrotesting instead of testing with air.
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#18 snickers

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Posted 19 March 2013 - 10:07 PM

Unless your using the sprinkler vale/solenoid valve for sprinkler systems, most people just modify them into quick-exhaust valves. The majority of the videos I have seen of people using air guns made with a solenoid valve, the valve is modded.

Just a tid bit I thought I should add.
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#19 ShaNayNay

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Posted 19 March 2013 - 11:36 PM

Bladders actually pose worse safety concerns. A bladder bursting is about as loud as a shotgun firing. That can cause very real hearing damage. I know because I did some research into the failure of bladders, and I made sure to use hearing protection after the first burst. Ouch. I suggest hydrotesting instead of testing with air.

I have heard countless debates regarding the safety of PVC tanks and otger materials, but never regarding the safety of bladders. Thanks for bringing this up and letting us know. What was the pressure at which your's failed? Was it anywhere near what a modestly overpumped Ms or rf20 bladder reaches?
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#20 Asamere

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Posted 19 March 2013 - 11:39 PM

I am very impressed by all the information. It helped me understand the concepts and gave me a peak at some useful information for modifications.

As for the phobia of the dreaded air blaster I understand it, however I feel its a limitation. While "some" airguns are far too powerful for standard purposes. Homemade blasters are made to the specifications of the one building it. There are numerous homemade versions for air guns. I do believe there is a homemade air tank for the Air tech 2000 by Roboman.

Spring guns. They are cool they are wonderful, they have tons of variants.

Air guns. powerful and wrongly feared (At least in my opinion which probably doesn't matter). They have a bunch of good models that show proper restraint. I would love to see more models of air guns. I feel they have the ability to take on a multitude of different shapes and can give a greater variance in RoF, Range, and size. They just need to be crafted safely.

The more that are built the more they will be accepted. Great thread again! However. After all your research. It begs the question. Do you have a homemade air gun in the works for us?
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#21 Doom

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Posted 20 March 2013 - 07:31 AM

I have heard countless debates regarding the safety of PVC tanks and otger materials, but never regarding the safety of bladders. Thanks for bringing this up and letting us know. What was the pressure at which your’s failed? Was it anywhere near what a modestly overpumped Ms or rf20 bladder reaches?


Bladders fail because they develop microtears that (with enough expansions and time) become large tears where the burst occurs.

Bladders have approximately constant pressures as a function of the volume pumped in (which is why they are used), so the pressure at which the bladder failed can not be used as a safety guideline. Also, the tubes I tested were unusual. I was testing several higher pressure latex tubes that you could buy off McMaster-Carr. I found that the thickest tubes (with measured pressures in the 40s and 50s of psi) had a tendency to slowly tear and eventually burst from simply being slightly full. You could hear the tearing while it occurred. It sounded very similar to tearing paper. And then the boom occurred suddenly.

So it seems that bladders can burst under three circumstances: when they have a tendency to burst anyway (hard to know), when they have been used so many times that the microtears become too large, and if you pump too much volume into them.

I do not suggest “overpumping” a bladder under any circumstances. That sounds seriously dangerous to your hearing. I don’t know why someone would do such a thing, but if more volume and/or pressure is wanted, just buy a better latex tube to replace the original with. I’ve used latex tubing as bladders for Nerf since 2004 and I’m still continually amazed by how few people use it for homemade Nerf guns and modifications.

Given that, DartSlinger, I suggest adding a link to this guide about latex tubing to the first post. These tubes can be used to make completely homemade bladders.

Edited by Doom, 21 March 2013 - 04:47 PM.
Corrected reported tube pressures.

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#22 imaseoulman

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Posted 07 April 2013 - 02:28 PM

Very nice aggregation of information. I never thought that there was this much misunderstanding about "air guns" but from reading the comments it's clear that there is. As for reasons people aren't making many air guns, there are a couple of other factors at play.

First is that for a long time, homemade air guns have not been allowed at many NH advertised wars. This was because of safety concerns. The possible hazards of poor construction have already been discussed, and dart speed/pain inflicted was also a concern. It's very simple to up the pressure just a little bit or make the tank just a little bit bigger and be shooting darts so hard it's unpleasantly painful.

And then there's the +bow. It was a veritable air gun killer. I recall playing at a Deal war in NJ a few years ago and being the only one not using a +bow/modified xbow. With the advent of the hopper (1/2" PVC wye) a pump action springer had almost unbeatable range and rate of fire. I had to play very athletically and carefully to keep up while using my old school SM1500.

I still prefer the slight pop of an air gun over the slam of a springer any day, but it's hard to find a "war legal" air gun that competes with a well built hoppered springer. In fact a lot of the currently accepted war regulations are based on the use of hoppered springers. Hoppered springers really changed the way the game was played.
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