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Portable electric air cannon

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#1 Arvex

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Posted 23 February 2013 - 11:38 AM

EDIT: Shoot, misread the New Member guide and thought this is where I would post this... My mistake. If a mod can just move this thread to the right category, I would appreciate it very much.

Hello, I've been working on a design for a while now and I needed to find a few pieces of information before I can start building this. I figured I would turn to you guys for answers.

What I thought of trying to do was use the Nerf Titan Mega Missile as the projectile for something else or at least creating a projectile close to it in dimensions. I wanted this to be carried the same manner as a heavy weapon from a certain game and it would behave similarly with the charge up time and firing a large projectile (the Forge Gun from the Dust 514 beta if any of you know what I'm talking about)

The concept is basically a PVC air cannon with a battery powered air compressor attached to it and a 12V solenoid wired up to the trigger. I'm also going to add a pressure regulator to prevent it from being overcharged to a point where it could hurt someone at the intended range and a second safety valve that will prevent it from reaching pressure that could seriously damage the air tank.

Design concept(Image)

Some of the parts don't look anything like what they're supposed to because I didn't know what they looked like at the time I made this. I'm working on an updated model and I will post it as soon as I think it's done. As I figure out what I'm going to order, the updated versions will slowly be to scale and more like the actual parts.

What I am uncertain about is how much power this thing should have/will need. I'm trying to find out the mass and size of my projectile so I know how much pressure is needed in the air tank and how big of an air tank I will actually need to provide that pressure long enough to provide the projectile with enough acceleration. Theoretically, I could build this now (minus shipping times for parts,) but I fear I would make it either too strong to the point where it's not safe to fire on anything or lack the power to fire the intended projectile effectively if at all.

I'm also a little worried that the air pump I bought for it might be a little weak, but I won't know until I get the cannon assembled. I might be able to counteract this by using a smaller tank, but that means I might be giving up some firing power as well.

And I do have an external shell planned for this, but I'm going to wait until I have this design closer to being finalized before I actually start to design it.

What I was hoping to find out from you guys were the following:
-Mega Missile inside diameter and length (to figure out the barrel dimensions, I'm also going to base my homemade projectiles on this if possible)
-Mega Missile weight (to figure out the optimal firing pressure)
-Confirmation that the Nerf Titan's optimal recommended firing pressure is ~35 PSI. I read it on this forum, but I wanted to make sure that what I read was correct before I take it into consideration.

With this information I should be able to figure out the rest on my own. I can calculate some of this stuff, but I need a few unknowns cleared out.

My primary concern with this is safety, I want this to be able to fire at people without seriously hurting them unless they're being stupid (i.e. close range with a Titan.)

A few minutes before I started typing this post up, I won a Nerf Titan on Ebay, but it probably won't be shipped out until Monday at the earliest.

Edited by Arvex, 23 February 2013 - 11:02 PM.

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#2 BlackBoarderV

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Posted 23 February 2013 - 12:14 PM

Mods don't like concept threads, I guess you didn't read the Code of Conduct.
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#3 Arvex

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Posted 23 February 2013 - 12:17 PM

Mods don't like concept threads, I guess you didn't read the Code of Conduct.

Then where am I supposed to post the questions I have? I thought I read in the code of conduct that this is where you ask questions for making homemades.

Nevermind, I just read the New Member guide again and realized I misread it... My mistake...
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#4 Daniel Beaver

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Posted 23 February 2013 - 12:35 PM

Mods don't like concept threads, I guess you didn't read the Code of Conduct.

We also don't like backseat moderating


What I am uncertain about is how much power this thing should have/will need. I'm trying to find out the mass and size of my projectile so I know how much pressure is needed in the air tank and how big of an air tank I will actually need to provide that pressure long enough to provide the projectile with enough acceleration. Theoretically, I could build this now (minus shipping times for parts,) but I fear I would make it either too strong to the point where it's not safe to fire on anything or lack the power to fire the intended projectile effectively if at all.

...

My primary concern with this is safety, I want this to be able to fire at people without seriously hurting them unless they're being stupid (i.e. close range with a Titan.)

From the quick overview you gave, it seems like it will be massively overpowered. But go ahead and build it anyways - overpowered blasters are fun to play around with in your backyard, and you'll learn a lot in the process.
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#5 Doom

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Posted 23 February 2013 - 02:39 PM

Hi Arvex,

You can use this computer model to simulate your air cannon and get a better estimate of how it will perform. Alternatively, you'll figure out what works rather quickly from a few tests. You probably won't get it right the first time, but buy enough material to build a few and design your gun such that parts can be reused and you won't find this is a problem.

As for safety, read this article about KED, the safety measure Hasbro uses. It's kinda technical, but it needs to be.

I don't know any of the dimensions of the ammo you want to use, but I do want to say that I don't think there's any such thing as "optimal pressure." You can show via computer simulations rather easily that both performance and energy efficiency increase monotonically with pressure. So the higher, the better performance-wise (assuming that your material can handle the pressure, and that there are no other safety concerns).
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#6 Arvex

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Posted 24 February 2013 - 05:51 PM

From the quick overview you gave, it seems like it will be massively overpowered. But go ahead and build it anyways - overpowered blasters are fun to play around with in your backyard, and you'll learn a lot in the process.


I'm trying not to make it overpowered, but I can easily counteract that. If I have this system set up right, I might be able to make it as safe or as dangerous as I want just by swapping out for a larger/smaller air tank and higher/lower pressure limit on the regulator (the one I'm looking at looks like it can be adjusted by swapping out a spring inside.) I can also make sure the homemade ammo has a lot more padding. Making it adjustable is part of how I figured I could make it safe.

Hi Arvex,

You can use this computer model to simulate your air cannon and get a better estimate of how it will perform. Alternatively, you'll figure out what works rather quickly from a few tests. You probably won't get it right the first time, but buy enough material to build a few and design your gun such that parts can be reused and you won't find this is a problem.

As for safety, read this article about KED, the safety measure Hasbro uses. It's kinda technical, but it needs to be.

I don't know any of the dimensions of the ammo you want to use, but I do want to say that I don't think there's any such thing as "optimal pressure." You can show via computer simulations rather easily that performance and energy efficiency increases monotonically with pressure. So the higher, the better performance-wise (assuming that your material can handle the pressure, and that there are no other safety concerns).


I think I chose the wrong word. I meant to ask what the recommended firing air pressure for a Nerf Titan was, where it's not going to damage the air tank or doing serious harm to someone. But perhaps I was also asking the wrong question, maybe I should have been asking what the muzzle velocity of an unmodified Titan was.

I'll probably make tanks of a few different sizes and try adjusting the regulator to get everything working at the levels I need. I will be firing this alongside the Titan I ordered and work my way down until it makes comparable firing performance with a Titan.
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#7 Daniel Beaver

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Posted 24 February 2013 - 06:36 PM

I meant to ask what the recommended firing air pressure for a Nerf Titan was, where it's not going to damage the air tank or doing serious harm to someone.

Generally speaking, nerf guns are okay up to 35psi or so.

A Titan isn't "safe" in the first place, unless you're shotgunning.
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#8 Arvex

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Posted 25 February 2013 - 06:15 PM

My Nerf Titan arrived today (thought it was going to be shipped out today... Glad to be wrong on this one.) I'll post the info on the stock missile in case anyone else in the future is ever looking:

Nerf Titan Mega Missile (without fins)
Weight: 1.25 oz
Inside/barrel diameter: 1-1/2 inches
Outside diameter: Just shy of 2-5/8 inches (missile is a little squished, so this might be off.
Lengths:
-Black foam: 10 inches
-Grey: 3/4 inches
-Orange tip: Roughly 2 inches if measured all the way to the rounded end.

I'll probably try to come up with replacement fins for it or just use homemade missiles if I can get better accuracy out of them.

Now I just need to figure out the kind of solenoid I need to purchase and I can start ordering parts to build it, specifically the diameter on the ends. I need to figure out how fast the air will flow out the 1/4" and 1/2" solenoids when opened or I might too much or not get enough acceleration before the projectile leaves the barrel. I should be able to figure this out now that I have more information on the projectile itself. If not, I'll order both and design everything so that I can swap them out and find a use for the one I don't use.

A Titan isn't "safe" in the first place, unless you're shotgunning.


As for the safety, maybe the Titan I'm using was just worn out or something, but it didn't seem that dangerous. I had my brother shoot it at me a few times with it from about 15 feet away and I barely felt it the one time it actually hit (fins seem to make a difference.) Is there something I am missing as far as safety? Or were you referring to a modified Titan? Then again, maybe other people pump it past maximum (on the little gauge) and that's why it seemed safe to me.
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#9 Daniel Beaver

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Posted 25 February 2013 - 08:59 PM

Or were you referring to a modified Titan?

Yes, I was referring to Titans modified to shoot darts.
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#10 Arvex

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Posted 22 March 2013 - 10:12 PM

Update time.

I purchased a cheap air compressor for the prototype build and went looking for materials for the barrel and ammo (I wanted to make sure I bought ammo material and pipe that fitted to each other.) Unfortunately, my search hasn't been very fruitful, apparently they don't make any foam tubing anywhere close to the dimensions I need (at least not at any hardware stores in my area.) I have considered trying to use a pool noodle, but if memory serves, they are made of a much denser foam and I worry that could give the projectile a little too much mass for the size and amount of force I intend to apply to it. Has someone else tried making homemade Titan missiles using pool noodle before and is it roughly the same in performance as the stock missile and mass?

If all else fails, I can probably scale down the intended projectile and barrel, but I could end up having to rescale all of the other parts as well depending on how far up or down I go with the projectile.

I have located the types of solenoids I intend to use and will purchase one as soon as I have some cash to spare, but I can't really buy any tank materials until I have a solid idea of what my prototype ammo will be made of and what is going to be used to connect everything together.


Help requested:

I'm going to continue my search for a material to use for my projectile, but while I search, I was hoping someone could at least point me in the right direction. I'm trying to make a projectile that has roughly the same dimensions (more concerned about the inside diameter than the outside) and mass as a stock Nerf Titan missile as I was originally hoping to make the ammo interchangeable between the cannon and the Titan without needing to modify the Titan. If I can't, I will go back to the drawing board and try to redesign it with an alternate ammunition in mind.
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#11 Daniel Beaver

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Posted 22 March 2013 - 11:27 PM

I'm trying to make a projectile that has roughly the same dimensions (more concerned about the inside diameter than the outside) and mass as a stock Nerf Titan missile as I was originally hoping to make the ammo interchangeable between the cannon and the Titan without needing to modify the Titan. If I can't, I will go back to the drawing board and try to redesign it with an alternate ammunition in mind.


Draconis' rockets are probably what you're looking for. I could sell you a few pre-made ones if you wanted (they're not really easy to come by). I forget what materials he's using exactly, you'll have to ask him.
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#12 Dart Slammer

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Posted 24 March 2013 - 03:55 AM

This reminds me of a project I had a while back...

Posted Image

It fires mini vortex howlers. At 70psi it reached 295 feet when angled at about 45o

Posted Image

Uses a modified sprinkler solenoid valve power by 2 9v batteries.
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#13 Blood Angel

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Posted 24 March 2013 - 06:52 AM

From my experience, this may not be the best place to ask your questions. Not just because your question(s) are full of variables; but because there are only a handful of people who can recognize and process the concepts you are posing (without the trial and error already done).

As for your question(s), there are some things that need to be made clear first. It took a while, but it is clear (now) that the ammunition you plan to use is the large missile type.

The performance of your blaster is only as good as the ammunition you use. For consistent performance, you will need consistence in ammunition and a way to make your blaster fire the same way every shot.

The psi vs. muzzle velocity will depend on your ammunition. Example: mini vortex howlers have more mass, are made to spin, conically shaped, and launch well at 70 psi. Stock elite streamline darts are about 1g, donít spin well fired, flat tipped, and fire from air blasters well from 35-40 psi (depending). Foam missiles, have a medium amount of mass, fin stabilized, flat or cone tipped, and launch well at varying psi depending on the material they are made out of. Ball ammunition is very tricky. It can have various masses, can be smooth bore, no bore, or rifled barreled. The ball can spiral spin for stability, backspin for range, or have no spin at all.

Generally speaking the more pressure your blaster produces, the more mass (or weight) your ammunition needs to have. This is not always the case though. Also, donít forget that the higher psi tends to mean more velocity and with more mass tends to mean more KED (F=ma^2=KED).

Since you are not using an outer barrel, your muzzle velocity is the speed at which the missile leaves the tube. From there it stops being about pneumatic cannon performance, and starts being about ballistic physics. The characteristics of your ammunition take precedence over the GGDT projections. Every projectile has a terminal velocity, optimal velocity, or maximum speed at which it can travel before over pressure or excess air resistance causes it to travel a little wonky. I highly recommend that you fin stabilize your missiles. It will increase range, accuracy, and KED.

As for safety, if you use stock ammunition; then you will have no problem with safety. Stock ammunition is designed to be safety for ages 6+ and should start to be less functional when it exceeds terminal velocity. If you are making custom ammunition then you must find the median KED of stock ammunition and not exceed its KED by more than one standard deviation (http://en.wikipedia....ndard_deviation).

For the stock Titan missile I would predict 50-55psi would work well (depending on the design specs). Try to plug the data into the GGDT and see if you can reverse calculate the optimal psi. From there, calculate ballistic trajectory based on the characteristics from the Titan missile.
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#14 Draconis

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Posted 25 March 2013 - 02:43 AM

I have considered trying to use a pool noodle, but if memory serves, they are made of a much denser foam and I worry that could give the projectile a little too much mass for the size and amount of force I intend to apply to it. Has someone else tried making homemade Titan missiles using pool noodle before and is it roughly the same in performance as the stock missile and mass?


Yep I do, they work well, but require some modification. I chose to use a different barrel size, which makes the rockets compatible without modification with roto-rockets and Estes Air Rockets.



Draconis' rockets are probably what you're looking for. I could sell you a few pre-made ones if you wanted (they're not really easy to come by). I forget what materials he's using exactly, you'll have to ask him.


Thanks for the shou out. I am gearing up to start selling them again but have to get a few things sorted first.

From my experience, this may not be the best place to ask your questions. Not just because your question(s) are full of variables; but because there are only a handful of people who can recognize and process the concepts you are posing (without the trial and error already done).


That's silly. There are plenty of people here.

Arvex, take a look at some of the contest entries from http://nerfhaven.com...1&#entry319253' class='bbc_url' title='External link' rel='nofollow external'> last year's contest for some more info and pointers regarding rockets. The biggest limitation I have found is pressure. Tube style ammo tends to rupture when used with peg-type barrels. Take the Airtech line, for example. That is part of why we rebarrel them. Rockets will do the same. To get around this problem, we bought sleeves to go inside the rocket bodies, which increases the working pressure a LOT. That said, the caps weren't welded on well and will still break if over pressurized.
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[15:51] <+Noodle> titties
[15:51] <+Rhadamanthys> titties
[15:51] <+jakejagan> titties
[15:51] <+Lucian> boobs
[15:51] <+Gears> titties
[15:51] <@Draconis> Titties.
[15:52] <+Noodle> why is this so hard?

#15 Blood Angel

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Posted 25 March 2013 - 08:07 AM

Honestly, I would change the ammunition to arrow type:
http://www.amazon.co...r/dp/B004QNX9OG
http://www.toysrus.c...oductId=4008539
http://3btech.net/thpaoffomifo.html
http://www.amazon.co...r/dp/B001JBCKV6

It is lighter, smaller, and commercially available to buy. That mean more consistency.
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#16 Draconis

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Posted 25 March 2013 - 05:20 PM

Honestly, I would change the ammunition to arrow type:
http://www.amazon.co...r/dp/B004QNX9OG
http://www.toysrus.c...oductId=4008539


I am insult. The problem with arrows is exactly the same kind of maximum pressure limitation that rockets have. Except that nobody has spent a year and over a thousand dollars solving it for arrows. Just saying.


http://3btech.net/thpaoffomifo.html
http://www.amazon.co...r/dp/B001JBCKV6

You know that these two are smaller than normal micro darts, right?
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[15:51] <+Noodle> titties
[15:51] <+Rhadamanthys> titties
[15:51] <+jakejagan> titties
[15:51] <+Lucian> boobs
[15:51] <+Gears> titties
[15:51] <@Draconis> Titties.
[15:52] <+Noodle> why is this so hard?

#17 Daniel Beaver

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Posted 25 March 2013 - 10:44 PM

The problem with arrows is exactly the same kind of maximum pressure limitation that rockets have.

Truth. Standard arrows get ripped apart by high-powered blasters, and are completely inadequate for this project.
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#18 Blood Angel

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Posted 26 March 2013 - 05:04 AM

When I look at blasters, there are a few things I consider.

Range - maximum distance
Accuracy - maximum effective range
Speed - velocity of projectile
Portability - ease of carry and sling
Firepower - shots per minute
Reload - ease of feeding and re-feeding

All of these things factor into something called "Philosophy of Use" (PoU). I guess my question would be, "what is this blaster for? what is the purpose of making this?"
The type of ammunition that would be ideal for this blaster would depend on that answer.
Smaller rockets = less maximum applied pressure, but the size of the arrows means more can be carried. Bigger rockets = less can be carried in the same volume, but more applied pressure.
From the OP design and theory, I was thinking this would make a great "wye" hopper feed dart machine gun. The amount of pressure is not an issue. He can always put on a regulator, over-pressure valve, or use barrel porting/vents to control/regulate pressure output.

Based off of my considerations, the range of the blaster is far, the accuracy is low (not shoulder fired or sight aimed), the speed is ammunition is dependent, and the blaster is bulky; there is a potential for high level firepower and the reload seems to be relatively the same either arrow/rocket or hopper feed dart system.

I make and modify blasters specifically to be used to fill a role in a nerf battle. Example: Our battles are very fast paced. So lighter, small to mid sized, high level firepower, and quick reloads are preferred.

Avrex is concerned about injury from KED. From my experience, I have never had or ever heard of stock ammunition as a safety issue (assumed eye protection worn). Modified or custom ammunition may be or appear safe, but there is always a question. Is there a possibility of this electric air cannon potentially being powerful enough to launch a Draconis rocket hard enough to knock someone out? Yes, no, maybe? The last nerf game I went to had children as young as 7 playing. If that is a concern, then maybe this will be a lower powered blaster (then there won't be a worry about arrows ripping apart).

So, like I said. It really depends on what this blaster is for. From what I gather, it is clear Avrex plans to shoot people with this blaster, otherwise he wouldn't be concerned about safety. If a Draconis rocket rips apart before becoming KED dangerous, then there is also no issue. Or Avrex may plan to only use this blaster at safe/limited pressure output levels for Draconis rockets. Either way, it seem bad to give ideas for a theory base blaster without knowing what it is for.

I have no problem with Draconis Rockets: http://nerfhaven.com...15 I think shooting a giant happy face at someone is rather amusing. I was merely looking at this project from MY point of view, for what I would use it for, in the nerf battles I play. Avrex might just be using it for something completely different.
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#19 Arvex

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Posted 26 March 2013 - 04:29 PM

From my experience, this may not be the best place to ask your questions. Not just because your question(s) are full of variables; but because there are only a handful of people who can recognize and process the concepts you are posing (without the trial and error already done).

As for your question(s), there are some things that need to be made clear first. It took a while, but it is clear (now) that the ammunition you plan to use is the large missile type.

The performance of your blaster is only as good as the ammunition you use. For consistent performance, you will need consistence in ammunition and a way to make your blaster fire the same way every shot.

The psi vs. muzzle velocity will depend on your ammunition. Example: mini vortex howlers have more mass, are made to spin, conically shaped, and launch well at 70 psi. Stock elite streamline darts are about 1g, donít spin well fired, flat tipped, and fire from air blasters well from 35-40 psi (depending). Foam missiles, have a medium amount of mass, fin stabilized, flat or cone tipped, and launch well at varying psi depending on the material they are made out of. Ball ammunition is very tricky. It can have various masses, can be smooth bore, no bore, or rifled barreled. The ball can spiral spin for stability, backspin for range, or have no spin at all.

Generally speaking the more pressure your blaster produces, the more mass (or weight) your ammunition needs to have. This is not always the case though. Also, donít forget that the higher psi tends to mean more velocity and with more mass tends to mean more KED (F=ma^2=KED).

Since you are not using an outer barrel, your muzzle velocity is the speed at which the missile leaves the tube. From there it stops being about pneumatic cannon performance, and starts being about ballistic physics. The characteristics of your ammunition take precedence over the GGDT projections. Every projectile has a terminal velocity, optimal velocity, or maximum speed at which it can travel before over pressure or excess air resistance causes it to travel a little wonky. I highly recommend that you fin stabilize your missiles. It will increase range, accuracy, and KED.

As for safety, if you use stock ammunition; then you will have no problem with safety. Stock ammunition is designed to be safety for ages 6+ and should start to be less functional when it exceeds terminal velocity. If you are making custom ammunition then you must find the median KED of stock ammunition and not exceed its KED by more than one standard deviation (http://en.wikipedia....ndard_deviation).

For the stock Titan missile I would predict 50-55psi would work well (depending on the design specs). Try to plug the data into the GGDT and see if you can reverse calculate the optimal psi. From there, calculate ballistic trajectory based on the characteristics from the Titan missile.


I've been looking at that tool, but it seems to run under the assumption that the ammo is inside the barrel instead of over the barrel like the Titan. Or is there something I am missing in the options? Or does this difference even have a significant effect the displayed results?

Arvex, take a look at some of the contest entries from http://nerfhaven.com...1&#entry319253' class='bbc_url' title='External link' rel='nofollow external'> last year's contest for some more info and pointers regarding rockets. The biggest limitation I have found is pressure. Tube style ammo tends to rupture when used with peg-type barrels. Take the Airtech line, for example. That is part of why we rebarrel them. Rockets will do the same. To get around this problem, we bought sleeves to go inside the rocket bodies, which increases the working pressure a LOT. That said, the caps weren't welded on well and will still break if over pressurized.


Thanks, I'm checking it out now. If I can make the ammo durable and cheap enough price or make them easy to fix/reuse parts, I don't think that will be too much of a problem. I plan to make ammo for this in fairly large quantities.

Is there a chance of you giving me the measurements of the Draconis missiles so I can design this to fire them? I read on the page that it fits a 1" OD barrel, but I was hoping to get the length and mass of it. That way if my homemade ammo doesn't work so well, I can buy some of yours when you do the next run of them.

Honestly, I would change the ammunition to arrow type:
http://www.amazon.co...r/dp/B004QNX9OG
http://www.toysrus.c...oductId=4008539
http://3btech.net/thpaoffomifo.html
http://www.amazon.co...r/dp/B001JBCKV6

It is lighter, smaller, and commercially available to buy. That mean more consistency.

I'd rather make my own ammo than buy off-brand stuff. I was originally going to track down the ammo for the Nerf Titan on eBay, but people are massively overcharging for the missile by itself or selling it with a Titan and I don't want to have a bunch of unused Titans sitting around.

When I look at blasters, there are a few things I consider.

Range - maximum distance
Accuracy - maximum effective range
Speed - velocity of projectile
Portability - ease of carry and sling
Firepower - shots per minute
Reload - ease of feeding and re-feeding

All of these things factor into something called "Philosophy of Use" (PoU). I guess my question would be, "what is this blaster for? what is the purpose of making this?"
The type of ammunition that would be ideal for this blaster would depend on that answer.
Smaller rockets = less maximum applied pressure, but the size of the arrows means more can be carried. Bigger rockets = less can be carried in the same volume, but more applied pressure.
From the OP design and theory, I was thinking this would make a great "wye" hopper feed dart machine gun. The amount of pressure is not an issue. He can always put on a regulator, over-pressure valve, or use barrel porting/vents to control/regulate pressure output.

Based off of my considerations, the range of the blaster is far, the accuracy is low (not shoulder fired or sight aimed), the speed is ammunition is dependent, and the blaster is bulky; there is a potential for high level firepower and the reload seems to be relatively the same either arrow/rocket or hopper feed dart system.

I make and modify blasters specifically to be used to fill a role in a nerf battle. Example: Our battles are very fast paced. So lighter, small to mid sized, high level firepower, and quick reloads are preferred.

Avrex is concerned about injury from KED. From my experience, I have never had or ever heard of stock ammunition as a safety issue (assumed eye protection worn). Modified or custom ammunition may be or appear safe, but there is always a question. Is there a possibility of this electric air cannon potentially being powerful enough to launch a Draconis rocket hard enough to knock someone out? Yes, no, maybe? The last nerf game I went to had children as young as 7 playing. If that is a concern, then maybe this will be a lower powered blaster (then there won't be a worry about arrows ripping apart).

So, like I said. It really depends on what this blaster is for. From what I gather, it is clear Avrex plans to shoot people with this blaster, otherwise he wouldn't be concerned about safety. If a Draconis rocket rips apart before becoming KED dangerous, then there is also no issue. Or Avrex may plan to only use this blaster at safe/limited pressure output levels for Draconis rockets. Either way, it seem bad to give ideas for a theory base blaster without knowing what it is for.

I have no problem with Draconis Rockets: http://nerfhaven.com...15 I think shooting a giant happy face at someone is rather amusing. I was merely looking at this project from MY point of view, for what I would use it for, in the nerf battles I play. Avrex might just be using it for something completely different.


The original goal for the air cannon was to get it to match the performance of a stock Nerf Titan (assuming the user stops pumping once the gauge maxes out,) but have it charge up its air tank electrically instead of being hand pumped like the Titan. However, after owning one for a while and seeing how it performs and letting my brother shoot me with it a few times, I think I might be able to safely surpass the Titan's firing power. Part of this under performance might be because the seller/previous owner lost the fins on the missile that came with it.

An air tank based machine gun is something I have been considering for another project, might not be hopper fed. This is still a far away project as I haven't even purchased all of the parts for this one, so let's not derail the topic on it.

As for the PoU, I like the list format you did so I'll fill it in there.
Range - More concerned about the effective range, anything past that is icing on the cake.
Accuracy - I was hoping to be able to reliably hit targets at about 30-40 feet in outdoors conditions, expecting better accuracy indoors where wind isn't an issue. (roughly 10-13 meters for those outside the US)
Speed - Not too concerned about this, long as it isn't going so fast that the impact could be dangerous.
Portability - Far from it. This is going to be a bulky weapon, shoulder strap optional.
Firepower - As fast as you can load them plus the three seconds charging. I don't know how fast that is. If I could make this work with a clip system, I might consider that for a Mk. II or something.
Reload - The reload is just sliding a new rocket on the barrel and holding the charge button until you hear the pressure regulator leak (would mean you've reached full pressure)

It probably won't see much use sadly, this is more of a "for fun"/"because I can" project since I don't think there are any Nerf wars in the part of Ohio I live in (not much of anything fun out here unless I want to drive for more almost three hours to get there.) The only HvZ event that I have been to only allows unmodified* Nerf and off-brand blasters and even then there are ones they restrict use of (only person allowed to use a Nerf Titan was a special zombie) The other one is run by a group of local college students and I haven't had much luck finding out if they are open to non-students and what they will/will not allow because I don't know anyone in it.

I probably won't achieve the target charge time (aiming for full pressure in three seconds) with the $8 air pump I bought, but it will work to test everything else. Once everything else is figured out, I can swap out the cheap air compressor for a better one. I could probably get a quick charge with the better air compressor and a smaller air tank, which works because I wanted it to empty the air tank almost completely and need to recharge between shots.

For those wondering, this weapon is the inspiration for the blaster I am working on. The charge and fire system and the size are based on it, but I'm going to make a shell of my own design when the internals are finished. It is going to double as a costume piece for some futuristic armor I was going to design and build later on.



*Very lightly enforced.
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#20 Blood Angel

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Posted 26 March 2013 - 06:06 PM

Answers a lot.

So if Draconis Rockets nerfhaven.com/forums/index.php?showtopic=22982&st=0&p=320315&#entry320315 are the way you are going (and I think you should). Then you might need a little more psi to achieve optimal effective range. Those rockets are a little heavier, but I still think 50-55 psi is a good range to start with. You can trial and error all the way to about 65 psi (**I think**). **I'm assuming a safe KED range for point blank impact to the throat.

To achieve desired pressure by target time is not a difficult problem. There is, however, a certain consideration regarding pressure equalization and the exit valve. Think of it like soda that was shaken inside a bottle. If you open a tiny dime sized cap vs. a giant Gatorade sized cap the gas and soda will escape at different rates. Also the type of bottle (as in shape and size) of the tank/expansion chamber matters. In extreme cases, a giant tank with a tiny hole vs. a tiny tank with a huge gaping hole.

Check out thins link:
http://nerfhaven.com...showtopic=23762

Then check out this link:
http://nerfhaven.com...?showtopic=8234

$8.00 for an air compressor? Just add two air compressors for $16.00. Or you can make the tank shorter/smaller. Or both. This will, no doubt, change your initial design a little; however, your basic components will remain the same.

The reason speed is a factor in my consideration is because of the vortex series. The disc have some nice range but tend to be slower and easier to dodge. This means that distance and velocity are NOT in direct correlation; and that ballistic physics/trajectory is just as important as blaster modification. In short, your blaster is only as good as the ammo you fire.

In game considerations:

Portability - This might sound silly, but think about adding a top handle, side handle, and leave room for a place to put your hand underneath. Consider adding a "stock" type counter balance opposite the barrel end. And a place to attach a sling.

Picture holding this thing in your hands. Trigger in right hand, handle in left. Great, you've fired it. Now what? I'm guessing you swing/push the barrel towards you placing the blaster vertically on its stock on the ground (pointing at the sky). You then reach into your pocket, pouch, or backpack for another rocket and reload with your right hand (maybe?). The only other way I can see involves a sling. Otherwise you have to drop the blaster.

Well, it this is just for kicks; I guess it doesn't really matter. I'm just trying to imagine something like this in one of my games. If you are making this just to see if it is a viable blaster; I would say it is not only possible, it opens up new possibilities.

Edited by Blood Angel, 26 March 2013 - 06:11 PM.

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#21 Arvex

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Posted 27 March 2013 - 03:14 PM

Multiple air pumps, why didn't I think of that? If I can't achieve the fill times I want with my cheap compressor, I'll start weighing the options of a second pump or one bigger pump.

Does anyone have a Draconis missile on hand? I just need to know length of the inside of one of them so I can figure out long I need to make the barrel. I just bought some parts for the prototype, going to start working on the first air tank this weekend. My intent is for the air tank to drain out entirely when fired so you don't accidentally store it while the tank is pressurized (I'm considering adding a manual air release if that doesn't complicate the design too much.) And yes, I plan to put a pressure gauge in there as well, just need to find one that I can fit on my PVC system or put it between the compressor and the tank. I'm also going to try to plug it into GGDT to figure out the tank requirements to get one of these moving.

The big bottleneck in the airflow works is the solenoid, largest opening I could find for a 12V solenoid was 1/2" threaded connectors unless I want to buy something bigger (rated for industrial use and about five times more expensive), so the largest inside diameter of the works is kind of fixed for now. The only unknown variables right now are the specs of a Draconis missile and the required volume for the tank to achieve the firing pressure long enough for the projectile to leave the barrel entirely.

I also discovered a wonderful thing in the world of PVC pipes called bushings, this will make connecting everything to the tank so much cleaner. I'm going to use a bushing with a half inch female threading and all of the interconnecting parts are going to be 1/2" PVC with threaded male adapters on all of the ends to match up to the solenoid. On the other hand, the connection of the air compressor might be a little bit difficult unless I want to replace the hose or find a bike tire inner tube (or two if I go the dual compressor route) to cut up. Or do they make threaded adapters that can hook up to my PVC air tank via threaded bushings and adapters?

This one is more of a "because I can" for goofing around, but in the future I might make an upgraded version that would be more practical for games.

Though, you did get me thinking about ammo carrying. I made a quick 3D mock up of what I had in mind, basically just take a sheet of sintra or similar sheet plastic, cut out a piece of armor and shape it to your leg, take some PVC pipe and glue/strap them to the armor plate and strap the plate to your leg. Nothing is to scale, it's just a mock up to give an idea of what goes through my head. That makes three easy to reach shots (or four if I can fit a fourth one on there, might depend on the size of the wearer's leg) the rest can be stored elsewhere and transferred there when you're behind cover. The large grey cylinder is a placeholder for a leg since I don't have any 3D models of a human to fit my armor parts to.
Posted Image

EDIT: And yes, it's going to have multiple handles to make carrying and reloading easier.

Edited by Arvex, 27 March 2013 - 03:16 PM.

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#22 DartSlinger

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Posted 27 March 2013 - 05:44 PM

Or do they make threaded adapters that can hook up to my PVC air tank via threaded bushings and adapters?

What kind of adapters do you mean? What kind of compressor are you using? One for a bike? If so, it probably has a Schrader valve coming off of its hose, so you would want to drill a hole in your PVC air tank and screw an adapter like this into your air tank.

You probably already know this, but since you are using threaded unions, be sure to use Teflon tape on your threads before assembling them.



Edited by DartSlinger, 27 March 2013 - 05:46 PM.

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#23 Ivan S

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Posted 28 March 2013 - 12:56 AM

The big bottleneck in the airflow works is the solenoid, largest opening I could find for a 12V solenoid was 1/2" threaded connectors unless I want to buy something bigger (rated for industrial use and about five times more expensive), so the largest inside diameter of the works is kind of fixed for now. The only unknown variables right now are the specs of a Draconis missile and the required volume for the tank to achieve the firing pressure long enough for the projectile to leave the barrel entirely.

There are bigger solenoid valves than that at reasonable prices, but they're usually sold as "sprinkler valves" which is maybe why you had trouble finding them. Here and here are examples. Keep in mind that most solenoid valves aren't full flow, so in a 3/4" system for example, a 3/4" solenoid valve may still be a bottleneck.

And if you're going to use a valve like this, you should really consider modding it to work without the electric component. It gets rid of the hassle of batteries and wires, but more importantly drastically increases performance.

Edited by Ivan S, 28 March 2013 - 12:57 AM.

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#24 Arvex

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Posted 30 March 2013 - 12:09 PM

That air intake valve is what I'm looking for (at least for the prototype), didn't know what it was called.


Ivan, there's already going to be a 12V battery strapped to it for the air pump(s), might as well use an electric air release system for a little more consistency. However, I might look into those if it looks like the air flow rate could be an issue (probably won't be.) It looks like I'll only need to put about 40-65 PSI on the projectile for not even a whole second.

I just sent Draconis a PM to ask about the mass and dimensions of the Draconis missile so I could build it to fire those. I'm going to use a Titan missile for my prototype/testing rig in the meantime.
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#25 Arvex

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Posted 13 June 2013 - 09:37 PM

I know we aren't supposed to double post, but I think there is enough of a time gap that people are no longer looking for updates on edits so I need to post an actual reply to get this back on the first page. If a mod or admin wants to smack me for it; I deserved it.

I managed to assemble the air cannon a while ago, but wasn't able to test it because the 12V outlet on my car was broken. After I resolved that, I charged it up and dry fired it a few times earlier today and let it sit with air in it for a moment to see if it was leaking. It has no problem holding 60 PSI and releases it plenty quick enough through the temporary valve.

Posted Image
Prototype, fully assembled. It's assembled with a two part orange PVC solvent and purple primer. All threaded portions have teflon tape applied.

All that remains now is to assemble the ammo for it then the shell/carrying components and battery. However, a recent real life issue might make purchasing materials for the shell difficult, so that's on hold. I have everything for making the ammo now and plan to start assembling the prototypes this weekend.

EDIT: Once I get the ammo assembled and arrange for a battery, I'll make an actual video of it firing.

EDIT2: Charge times were a little slow, but it was a cheap pump so I'm not surprised. Going to look at getting better pumps or upgrading the motor before I get all of the parts to add a second pump because that changes the shape of it cannon significantly and would involve using parts I don't even know exist.

EDIT3: Just completed the first test fire with the prototype ammo. Everything seems to work, but the firing range was horrible. My only thought is that maybe it's because I'm not opening the valve fast enough and it's leaking out and pushing the shot off the pipe before it's fully opened?

Additionally, the cheap air pump gets very hot... Burned myself a little when I tried to pick it up. I stopped my test firing when I thought I saw smoke or steam shooting out of the pipe on the last shot.

EDIT4: Drained my car battery pretty quickly during that test run. Maybe the air pump approach isn't going to work as well as I initially hoped.

Edited by Arvex, 17 June 2013 - 01:20 PM.

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