FANG 2
Updates to this project will be posted under the "fang2" category of the blog.
There are threads at Spudfiles and NerfHaven about this project. There also are a few comments at the bottom of this page.
I've written a page on the safety of FANG 2 that I suggest anyone who believes FANG 2 is dangerous reads.
Note that the writing below is my plans as of February 2009. As the first prototype is nearly complete, this page will be updated relatively soon with new information, new goals, and the results so far.
FANG 2 will be enormously different from any previously done Nerf blaster, even ones made by manufacturers like Hasbro and Buzz Bee Toys. The goal is to make an efficient, powerful, durable, safe, and lightweight semi-automatic Nerf blaster. This goal will be achieved through a detailed development process involving multiple tests, statistical analysis, constrained optimization, 3D modeling, structural analysis, and computer simulation. FANG 2 will be an engineered Nerf blaster, perhaps the most engineered Nerf blaster conceived yet. My intention is to apply much of what I've learned so far as an undergraduate mechanical engineer, learn some new things in the process, and share what I have learned and developed with others.
Also, FANG 2's development will involve much tweaking of darts for efficiency. I have noticed that barely anyone is interested in aerodynamic darts, which will easily reduce the amount of energy required to achieve a certain range by 50% or more. I hope to develop a simple process to create a great number of aerodynamic darts for cheap, though, this part of the development cycle may be put on the backburner until I can do more analysis of the aerodynamics.
Overview of the planned design
The planned design at the moment is a simplified Eclipse, which itself is a scaled up SuperMAXX 3000. Like the SuperMAXX 3000, FANG 2 will have a automatically rotating barrel assembly rather than a rotating clip like the Eclipse. Unlike the SuperMAXX 3000 and like the Eclipse, the barrel assembly will be advanced by a cam actuated by an air cylinder.
The reason to use the rotating barrel approach rather than the dart pushing approach of the original FANG is reliability. This approach I know is easy to make reliable. Pushing darts introduces problems because the darts themselves aren't completely solid.
The 3/8" NPT Deltrol QEV used in the original FANG was a cheap and powerful primary valve and will continue to be used. However, I plan on using a Clippard MJVO-3 valve as the pilot valve because the pilot valve on the FANG had a very low flow rate, was somewhat expensive, and was larger than the Clippard valve.
Unlike FANG 1, I do not intend to use an HPA tank, rather, I intend to use a lightweight (and cheap) aluminum air tank as a stock. Combine that with a lightweight pump and we're golden. The HPA tank approach is expensive, heavy, and inconvenient. Pumping every 50-100+ shots is much more convenient than visiting a paintball store every 2000-3000, especially if the blaster is optimized for energy efficiency so less energy input is required.
Eventually a FANG 3 will be made which will use a more efficient HEAR valve to improve efficiency further. The plan is to make the entire blaster from aluminum and use a minimum amount of off-the-shelf parts. This may or may not be ever completed, but it's something to think about.
Efficiency as a goal
...is something I have not read about before. Efficiency, not the semi-automatic operation, will be the killer feature of FANG 2. An efficient blaster will get more shots for the amount of energy put in. A quantum leap in efficiency such as that the FANG 2 will bring will make a clear distinction between engineered blasters and everything else.
Despite how poor the efficiency of most pneumatic blasters are, I have not been able to find much about improving it, and the few remarks on improving efficiency either are misleading or nearly inconsequential nitpicking. Very few people seem to have a good idea of what is efficient and what is not. And I have not even seen a good classification of different efficiency goals.
When improving the efficiency of a pneumatic blaster, there are 3 possible goals: improving energy efficiency, reducing the gas used per shot, and improving the number of shots you can extract from a gas tank. All approaches yield different ideal configurations, but there is much overlap between acceptable configurations, so much so that it is very possible to optimize for all 3.
The only practical way to examine efficiency directly is through computer modeling. That's where BAGS comes in. I basically have a modified version of BAGS designed to loop through different configurations to find ideal ones. I could describe the loop in more detail (and I have before), but it's too complicated for this overview and will be described later on a page about optimizing pneumatic blasters.
Features
The exact features that will be in FANG 2 is not completely clear at this stage of the design process, however, these are the features I'd like the see.
- Semi-automatic operation
- Hand pump
- Low pressure air tank as a stock
- Various safety features such as multiple pressure gauges, multiple safeties, check valves, and release valves
- Comfortable handles (one in front, one primary handle, and one on top)
- Iron sights
- Dart storage on the blaster
- A pleasing aesthetic
Design process
The design process is easier said than done but should be effective in developing an improved semi-automatic Nerf blaster. These steps don't necessarily go in this order either.
Steps 4 and 5 will be skipped to save time and simplify the development process. I'll be pushing the final version of the FANG 2 back so I can experiment a good deal with a non-semi-auto version.
- Write computer models of the internal and external ballistics of a Nerf blaster and dart, respectively. (This step is complete).
- Build a test prototype for empirical tests.
- Perform empirical tests to help calibrate internal and external ballistic computer models.
- Build an improved prototype much like the FANG 2 is planned to be, but with a manually rotated barrel assembly (essentially a FANG 2 beta). Use empirical data and preliminary computer modeling to help design FANG 2.
Test FANG 2 beta in wars. Note strengths and shortcomings.- Choose desired range, taking into account terminal ballistics (i.e. safety of the dart) and energy requirements.
- Use external ballistics model to find dart configurations and velocities that achieve the designed range. Note optimal configuration and what configurations are practical.
- Use internal ballistic model, varying dart configurations, optimizing for both shots per tank and energy efficiency. Note acceptable configurations.
- Make CAD model of FANG 2. Design FANG 2 to be structurally stable, durable, safe, and lightweight.
- Use a machine shop and rapid prototyping equipment to fabricate FANG 2.
You should be able to see that the development of FANG 2 will be very involved, which is why I'm taking it slow. FANG 2 should be complete some time before summer 2009. You should see the FANG 2 experimental version without semi-automatic operation within two months and the completed semi-automatic FANG 2 anywhere from a few months to a year after that.
Comments
1
2
I have recently become very interested in this project and was wondering exactly how much that LPA cylinder and the bushing cost.
3
Hey there analogkid.
I could say exactly how much it should cost, but I'm not certain if Catalina Cylinders would approve. They usually do not sell less than 25 units in an order, but a single unit is not a problem if you call them and are honest about your project. Don't expect to pay more than $35 for the cylinder I have and the bushing.
P.S. Check your email.
4
So, how is this going?
5
I haven't had much time lately due to school, however, I finished my semester a few days ago and have began working on parts of this project.
Over the next few months I'll be doing extensive testing to generate data to calibrate my simulation. This requires the right sensors... conveniently I finished the first electronics/instrumentation course required for my mechanical engineering degree, so making a pressure transducer and a chronometer is relatively easy.
War testing with a preliminary blaster should begin relatively soon (at least if I can get a ride to DCNO). I intend to use more traditional barrel assemblies like a breech or flip-barrel (or whatever it's really called) just to get an idea of what muzzle velocity is appropriate.
I also will experiment with different advancement mechanisms. What I did with FANG 1 was interesting but not particularly reliable. I believe I can fix these problems, however, I am interested too in a rotating turret solution. Both approaches will be tested.
I'll try to keep everyone updated.
6
Hey there btrettel. I've seen your work on spudfiles and we've shared some ideas on nerf guns in the past. It took me this long to realize you had a website! Everything looks great, especially your progress on the FANG 2.
I just wanted to ask whether or not you bought the Clippard MJVO-3 pilot valve yet. So far the only place I've found them available is directly from Clippard, but their shipping and handling charges are pretty rough. If you've found it for a better price somewhere else I'd appreciate it if you could share the name of the store.
You might have seen the pilot valve I've been using on my projects. It's a Pneumadyne A11-31-44. It does the job but it's a bit too bulky and I'm having trouble configuring it in a way that keeps the gun streamlined. The Clippard valve is a lot smaller and has a slightly higher flow rate.
Good luck on the FANG 2, I can't wait to see the finished product. My own project is almost finished as well.
Mark
7
Hey Mark. Yes, I did buy a MJVO-3. I found one on eBay after noticing the same ridiculous shipping charges from Clippard directly. Clippard suggests looking for local distributors too. I believe their website lists some and they might be even cheaper than eBay. I also considered buying one from a surplus website, but I can't seem to recall the website URL.
You can see the valve in this image: http://trettel.org/fang2/021.jpg
That image is in this blog post: http://trettel.org/blog/48
The plan at the moment is to go back to something like FANG 1 and what you've tried. Details are here: http://trettel.org/blog/66
I actually did some preliminary ballistic testing for this and I'll be crunching the numbers tonight. I want to know the drag coefficient of the common "Slug darts" with reasonable accuracy.
8
You mean you're not going with the rotating barrel setup and instead revisiting the "projectile pusher" design? How do you plan on solving the problem of pinched darts? If I recall, that was the difficult part of that design.
Also, do you know any good sources of foam backer rod besides the people from the nerf community? I've looked online but I can't tell which is the right stuff. The Frost King type sold at Home Depot and Lowes is garbage. I'm looking for something with higher density.
9
Read this blog post and you'll see what made me decide to switch back: http://trettel.org/blog/66
I basically noticed a (supposedly) successful design and decided I could run with something similar (or an improved version of my own--all that matters is that something like this can work).
The pinching problem (on either side of the thinner part) I believe can be addressed by simply not allowing the part to pinch it. This means there'll be flow restrictions unless I design it differently. A flow path through the rod should be good.
The foam I use is available from the local Lowes, the local Home Depot, and McMaster-Carr. I believe the brand name is M+D. The McMaster-Carr part number is 93295K33. There's also the far longer 250' length 93295K43, which I believe is essentially the same, though it is made by a different company (for more information visit here: http://nerfhaven.com/forums/index.php?s=&showtopic=13301&view=findpost&p=178459 ).
Frost King is too variable from what I've read, so yes, it is garbage. I've also been meaning to try some colored foams but I figure I already have enough problems so I'll worry about that later.
10
Building a flow path through the rod (or bolt) would be possible, but you probably couldn't keep the air cylinder inline with the barrel. Instead you may need to mount it above the barrel and connect it to a tube within the barrel which would serve as the flow-through bolt.
To prevent pinching, the solution might be as simple as using a thicker barrel material (I suggest 1/2" sch80 PVC but weight might be an issue) and then chamfering the breech opening to create a "ramp" that will allow the dart to slide inside easier without getting caught.
I probably didn't explain those two things clearly so take a look at this picture to see what I mean:
http://i237.photobucket.com/albums/ff155/PointBlank017/sabr2.png
Thanks for the link to the FBR, I'll be ordering some soon.
Again, good luck with your project.
11
Your design would have possibly too much dead space, though, I am yet to quantify how much is bad so it may be acceptable or even optimal (some dead space increases performance).
I'm not sure if you looked at FANG 1, but the air cylinder was inline with the barrel and it worked fine. I intend to use this approach again because it's simple and compact.
12
Yes, the air cylinder was inline with the barrel, but you were not using a flow through bolt. Instead you mounted the QEV outlet perpendicular to the barrel just ahead of the breech opening (behind the advanced dart). Both of our early designs were similar in that respect. http://www.spudfiles.com/forums/semi-auto-nerf-gun-t16254,start,60.html
As for dead space, I don't think it matters much. We're dealing with extremely light projectiles and even the slightest puff of air gets them moving. Just for the hell of it, I set a nerf dart in the end of an 18 inch barrel, with the outlet of my QEV at the opposite end. At 18 inches apart, the range it achieved was about equal to what it achieved when the dart was directly in front of the outlet. Not to mention the range was still far greater than any stock nerf gun.
To me, it's not a big deal. I can see how it might matter in your project though since you're quite concerned with efficiency. Still, I wonder if it's even worth focusing so much on efficiency.
13
Ah, I can see that I had not explained what I meant by flow through the bolt. This design is essentially the same as FANG 1 except that the front of the bolt is 1) wider and 2) has two holes drilled through it to permit flow (one in the end of the "rod" and another at an angle to connect to the valve). This should eliminate pinching and only have a minimal effect on flow rate.
You're probably seeing efficiencies in the 5% to 15% range, while I'm shooting for 50% and higher. This makes a significant difference. ;-)
Anyway, as I said, more "dead space" might be better for performance (hence the quotes). I haven't crunched the numbers yet.
14
Yes if you could find out exactly that would be helpful. I wouldn't even know where to begin if I had to figure that out. With any luck, the volume of dead space created by 3" of PETG is optimum! That is an almost unavoidable part of one of my designs.
15
It appears that you are trying to take this project to a professional level, too bad that probably rules out using an soda bottle for your air tank, they really are a pneumatic hobbyist's best friend, soo light and good up to 100psi, though I keep them below 90.
so when you mean safe do you mean "stock gun" safe , cause if you do you really ought to consider increasing the caliber
and how do you plan to prevent the HEAR valve from rapid firing or how do you plan to slow it down, I believe clide had to increase the weight of his piston to slow it down, imagine the amount of input flow compared to volume in clide's gun from a compressor, compared to a direct tank input for a micro sized valve!
16
You probably don't want to hear this, but soda bottles are your enemy, not friend. They're not designed to hold gas under pressure for an extended period as soda obviously has a limited life. For safety I would suggest switching to a sturdier aluminum tank.
(Note that aluminum and expensive are not synonyms. I was surprised by how low the cost was, but due to my desire to protect what might have been a one time deal I won't publicly state how much I paid. Ask a manufacturer like Catalina about how much 1 cylinder would cost.)
Somewhere in this guide I discuss why not to use soda bottles in detail: http://trettel.org/nerf/ne.html
I'll make it clear that after trying an aluminum tank I'm never going to return to anything else that's not temporary, even for a "ghetto" simple project. I don't necessarily think soda bottles are ghetto and would consider using a properly designed plastic bottle if such a thing existed.
The air chamber is intentionally small. I don't want to give ignoramuses who want to ban pneumatics a reason to think this gun is dangerous (see the safety page linked to above). At the same time, I've looked at how to improve efficiency. Small chambers can achieve very high performance with higher efficiency than equivalent performance large chambers (in general). Given that knowledge it is likely that I'll decrease the size of the chamber for the finished product. This will allow me to get very significantly more shots from the gas chamber.
I'm not too familiar with how clide operated his valve. Mine will be semi-auto if I decide to go the HEAR type valve route. I'm more interested in the concept of closing the valve earlier to improve efficiency than his exact setup. HEAR type valves don't necessarily improve efficiency but as I recall in most scenarios the most efficient HEAR configuration was about 2% more efficient than the most efficient normal configuration.
©2007 - 2010 Ben Trettel
Last modified on 2009-04-04 14:34:27.
If anyone has any comments, ideas, criticisms, or anything to say please let me know either publicly here or privately by email. The goal is to create an extremely good Nerf gun and thus any thoughts are welcome.
Posted by on 2009-02-13 15:40:15