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Homemade At2k Tank

A Work in Progress

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#1 roboman

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Posted 13 June 2010 - 04:10 PM

I have come to love my two AT2Ks dearly, but, unfortunately, they are becoming harder and harder to find. Well, I have a lathe, so I thought to myself, "Why not build my own?" After 1 hour of CAD, $20 of aluminum, and about 5 hours of machining, I had a prototype. Unfortunately, this valve had issues sealing properly, because I didn't get the tank body perfectly aligned with the back, so the "plug" didn't seat correctly. I found that if I pushed the stem in until it clicked, I got a nearly perfect seal. This is not good, though, since I don't want to have to manually re-seat the plug after every shot.

Now, I'm rebuilding the tank, and this time, I'm going to cut threads into the two halves, once I make an internal threading tool. This way, If I screw it up again, I'll have a better chance of fixing it. I'll post images of the CAD model and drawings, once I revise them.

For now, here is a picture of the completed, screwed up tank, as well as the new, revised design.

Anyone have ideas as to how I could improve the seal?

Posted Image

Edited by roboman, 13 June 2010 - 05:25 PM.

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#2 Blue

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Posted 13 June 2010 - 04:14 PM

Do you have the O-ring setup in that little nub part sticking out the back of the tank? That is what makes the seals in 2k's, and it looks like all you have is a chunk of metal.
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#3 JATDO

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Posted 13 June 2010 - 04:32 PM

This is very very cool. How heavy are these?
And if you do perfect these, and if you're willing to sell them, how much would they cost?

Good luck getting them to work. :)
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#4 roboman

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Posted 13 June 2010 - 04:37 PM

Do you have the O-ring setup in that little nub part sticking out the back of the tank? That is what makes the seals in 2k's, and it looks like all you have is a chunk of metal.


Yeah, the O-ring is sandwiched between two aluminum plugs. Once I get the CAD drawings posted, you'll be able to see it better.

This is very very cool. How heavy are these?
And if you do perfect these, and if you're willing to sell them, how much would they cost?

Good luck getting them to work. biggrin.gif


They're not much heavier than a normal valve. Remember, they're hollow, and have an .060" wall.

Yes, I'd definitely be willing to sell them, although I haven't decided on a price yet.

EDIT: Pictures!

Posted Image
Exploded.

Posted Image
Another view.

Posted Image
Just in case anyone wants to make one.

Posted Image
A rendering of the completed valve.

Notice how, in the "real life" version, I omitted the nub where the tubing would normally connect. This is because I don't have a mill. Yet. :)

Also, in the CAD model, I omitted the spring. I didn't want to model one. Any small spring that's a little under 1" long will work. I think the one I used came from a printer.

All of the CAD was done in Autodesk Inventor 2011.

Edited by roboman, 13 June 2010 - 05:26 PM.

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#5 JATDO

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Posted 13 June 2010 - 05:07 PM

Do you think you could make the front hole on the tank into a coupler? That way you could just put a barrel on it.
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#6 roboman

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Posted 13 June 2010 - 05:12 PM

Do you think you could make the front hole on the tank into a coupler? That way you could just put a barrel on it.


Yes, I could do just about anything to the front. Right now, it's tapped for 1/8" NPT pipe fittings, because I like them. With the current setup, one could attach a 1/8" brass nipple in between the tank and a barrel. Of course, the barrel would have to have a plug that is already drilled and tapped for 1/8" NPT fittings, but that's easy. :)

Also, the OD of the protrusion is .527", meaning that PETG could, in theory, press-fit onto it. I don't have any, so I haven't tried.

Those of you at the last SCUN war saw what I did with some 1" HDPE and Mcmaster aluminum.

Edited by roboman, 14 June 2010 - 12:40 AM.

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#7 Lt Stefan

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Posted 13 June 2010 - 05:30 PM

This is very cool. I have a couple of questions for you.

1.Could you post a parts list of everything you used?
2.Did you use aluminum bar or aluminum tube?
3.Aside from getting your ideas on "paper," how does the CAD model help you actually machine the parts? Unless it's a CNC lathe, of course. Is it?
4.What are you using to thread the two halves?
5.Why did you decide to use the same dimensions of an at2k tank and not, for example, make it larger and more powerful but just using the same valve design?

Edited by Lt. Stefan, 13 June 2010 - 05:32 PM.

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#8 Foam Ninja

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Posted 13 June 2010 - 05:39 PM

Wait you said you have to keep reseting the pin. Can't you just slap a spring in there to make it reset itself?
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#9 roboman

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Posted 13 June 2010 - 05:41 PM

This is very cool. I have a couple of questions for you.

1.Could you post a parts list of everything you used?
2.Did you use aluminum bar or aluminum tube?
3.Aside from getting your ideas on "paper," how does the CAD model help you actually machine the parts? Unless it's a CNC lathe, of course. Is it?
4.What are you using to thread the two halves?
5.Why did you decide to use the same dimensions of an at2k tank and not, for example, make it larger and more powerful but just using the same valve design?


1. The parts list is on the drawing.

I used 1 3/8" 6061-T6 aluminum bar stock, 5/8" 6061-T6 aluminum bar stock, a random spring from a printer, a modified hose barb, some 1/8" music wire, a 1/4" OD x 1/8" ID O-ring, another O-ring that I can't remember the dimensions of, and some J-B Weld. The need for epoxy, or any other adhesives should be eliminated in the final revision of the tank.

2.I used round aluminum bar stock.

3. I need working drawings when I machine things. They help me keep track of measurements. I wish I had a CNC lathe. My school has two, and I am allowed to use them, but at the moment, I'm on summer vacation.

4.I am planning on using a single-point threading tool to cut the threads. I still need to make the internal threading tool. For the 1/8" NPT threads, I used a pipe tap.

5. I wanted a drop-in replacement of the AT2K tank, mostly so my tanks would be war-legal. I don't have an AT3K, or else I would've made one of those, too.

Wait you said you have to keep resetting the pin. Can't you just slap a spring in there to make it reset itself?


I did. As previously stated, I accidentally offset the back cap of the tank, when I was gluing it. Thus, the pin and plug do not perfectly line up with the sealing face.

Now, I'm thinking about using a sink washer in place of the O-rings on the plug, since it wouldn't require the two halves to be perfectly straight.

Edited by roboman, 13 June 2010 - 05:56 PM.

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#10 Lt Stefan

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Posted 13 June 2010 - 05:54 PM

3. I need working drawings when I machine things. They help me keep track of measurements. I wish I had a CNC lathe. My school has two, and I am allowed to use them, but at the moment, I'm on summer vacation.

4.I am planning on using a single-point threading tool to cut the threads. I still need to make the internal threading tool. For the 1/8" NPT threads, I used a pipe tap.


3. So if these need to be machined to such exact specifications, do you think anyone with a lathe can make one or do you need to have a lo of experience?

4. That means if I wanted to make on of these, I would need to make a homemade tap as well?
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#11 roboman

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Posted 13 June 2010 - 06:01 PM

3. I need working drawings when I machine things. They help me keep track of measurements. I wish I had a CNC lathe. My school has two, and I am allowed to use them, but at the moment, I'm on summer vacation.

4.I am planning on using a single-point threading tool to cut the threads. I still need to make the internal threading tool. For the 1/8" NPT threads, I used a pipe tap.


3. So if these need to be machined to such exact specifications, do you think anyone with a lathe can make one or do you need to have a lo of experience?

4. That means if I wanted to make on of these, I would need to make a homemade tap as well?


3. I've only had my lathe for a year, and I only recently acquired proper tooling for it. This is definitely not difficult to make, as long as you know how to operate a lathe.

4. This is a single-point threading tool. I'm going to make my own, on my school's CNC mill. As you can see, it is not a tap. You would need a tap if you desired to have pipe threads on the "business end" of the tank, like I do. Also, you can do away with the threads entirely, and simply J-B Weld the two pieces together. That's what I did the first time, and it worked. The threads simply give you the ability to make adjustments and service the tank, if needed.

Do you have/have access to a lathe?

Edited by roboman, 13 June 2010 - 11:08 PM.

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#12 Lt Stefan

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Posted 13 June 2010 - 06:14 PM

I donít but I will by the end of the summer. It doesnít have to be an expensive metal lathe right? Will a simple wood lathe work?
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#13 roboman

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Posted 13 June 2010 - 06:22 PM

I donít but I will by the end of the summer. It doesnít have to be an expensive metal lathe right? Will a simple wood lathe work?


NO. I have an 8x12 from Harbor Freight. A wood lathe has a weak motor, and is in no way, shape, or form meant for cutting anything other than wood. You will kill/seriously injure yourself if you try to cut metal on a wood lathe.

Go with something like this: Look! It's on sale!

There are plenty of improvements and upgrades out there for it. I didn't know this when I went out and bought mine, which doesn't have a knob to control speed. However, the motor is beastly, and the lathe itself is nearly indestructible. Here is is: The price seems to have gone up...

Little Machine Shop is absolutely amazing for small, imported lathes and mills. I've spent about $250 on tooling since I got my lathe. Be careful, it's addictive!

Also, Mini-Lathe.com is an excellent source of information on these machines.
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#14 Lt Stefan

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Posted 13 June 2010 - 06:27 PM

Thanks for the help. Seems like I will have to spend more money than I want, but I guess it will be worth it.

On a side note, how do you know if you are staying within the tolerances? Do you stop every few minutes to measure?
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#15 roboman

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Posted 13 June 2010 - 06:30 PM

Thanks for the help. Seems like I will have to spend more money than I want, but I guess it will be worth it.

On a side note, how do you know if you are staying within the tolerances? Do you stop every few minutes to measure?


When I'm turning something, I'll usually do a few "roughing" passes, then stop, measure it, and figure out how much I need to take off for the final "finishing" pass.

Trust me, your lathe will become your favorite tool in your shop.
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#16 SonReeceSonJensen

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Posted 13 June 2010 - 07:57 PM

Put me down for two and a Titan sized one. You know, as soon as you get the processed streamlined.

Good work, you could make up the cost of the tools in no time.
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#17 roboman

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Posted 13 June 2010 - 08:20 PM

Put me down for two and a Titan sized one. You know, as soon as you get the processed streamlined.

Good work, you could make up the cost of the tools in no time.


You'd have to get me the dimensions of a titan tank. Once you do, and I get the design perfected, I'd be glad to make them.
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#18 k9turrent

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Posted 13 June 2010 - 10:43 PM

When I first read the title, I was actually expecting some crappy pvc tank, but this is rather pleasant.

If I get a chance to, I will see if I can use my college's CNC lathe to make a perfect metal to Derlin/metal seal.
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That's about it. And thanks Angela who helped me with these pictures.. It looks huge in her hands.


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#19 roboman

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Posted 13 June 2010 - 10:48 PM

When I first read the title, I was actually expecting some crappy pvc tank, but this is rather pleasant.

If I get a chance to, I will see if I can use my college's CNC lathe to make a perfect metal to Derlin/metal seal.


I'm thinking about using a faucet washer. Faucet Washer

If you want, I'll send you the CAD files, assuming you use Autodesk Inventor or AutoCAD.

I'm thinking about making a whole writeup, if anyone is interested. This can be made entirely with a lathe and drill press.

Edited by roboman, 13 June 2010 - 11:42 PM.

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#20 roboman

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Posted 13 June 2010 - 11:46 PM

I definitely recommend the faucet (cone) washers. You can actually screw them down to your trigger rod. The largest I have been able to find are almost .75" across. I'm not sure nerfing ever needs a blast valve bigger than that anyway. But they tend to be a pretty hard rubber, so I generally have had to shape the seat they fit into pretty carefully


I can easily chamfer the inside of the sealing face, so the washer conforms to it. Are they threaded internally?
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#21 MindWarrior

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Posted 14 June 2010 - 12:04 AM

Very, Very nice. Now machine an at2k turret for this.
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#22 roboman

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Posted 14 June 2010 - 12:06 AM

Very, Very nice. Now machine an at2k turret for this.


I intend to, once I get enough money for a milling machine and rotary table (~$1000).
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#23 roboman

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Posted 14 June 2010 - 12:09 AM

Some similar types are threaded internally, but the ones I have found have been more hemispherical than conical, and pretty small. I've always just put a round head machine screw through them, just as they're used in faucet valves.


Makes sense. I'll just modify the "plug" so it has a flat back, and is tapped to accept whatever size screw happens to fit the washers.

Thanks for the help!
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#24 street slick

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Posted 14 June 2010 - 11:18 AM

I personally think these will be popular and people will buy them, and if you go through with the 2k turret you will be rich!
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#25 MindWarrior

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Posted 14 June 2010 - 11:36 AM

The turret, I suspect would be far more expensive to pruduce, like 30$~ at least, I suspect. Would there be any failsafe to prevent over pressure to be war legal?
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