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Old 12-07-2008, 10:08 PM #1
mrpurplehawk
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ideas for anti tank weapon

ok I am thinkin of making an Anti-tank weapon and I am completely lost, so does anyone want to help me get started like say some ideas on how to make it or is there any plans that I could get?

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Old 12-08-2008, 08:25 AM #2
bruno v
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Any plastic air chamber is dangerous don't use it!!!!

First I take no responsibility for what you are about to do.
I used a 1' X 2" aluminum pipe for the air chamber (rear) it needs to be thick enough to with stand 300psi and it needs to be tapped for the gauge, fill button and blow off valve I used a piece of aluminum pipe used for out riggers on a boat.
I threaded the back end and closed it with a black pipe cap (if you could it would be a lot lighter if you could close the end with a aluminum end and wield it. The black pipe cap is the heaviest part on my law.
On the pipe I tapped holes for the gauge, the adjustable blow off valve, and the fill button valve.

The front end of the pipe needs to have a 3/4" threaded hole. I had a friend of a friend do the wielding and I think he wielded a nut into the middle of an aluminum plug to give me a strong threaded end. (Do not try to use the reducers that are designed for aluminum pipe, you can't get them to seal properly).

I used a globe valve (rated 300psi) for the trigger you can get the globe valve, button valve and the adjustable blow off at Grainger and McMaster Carr they are catalogs and are on the web I forget where I got what but if your serious I will search and let you know the part numbers.

You need to use 2"X 3/4" pipe nipples to connect the trigger (globe valve) to the air chamber and the barrel.
To make the barrel I used 2" PVC pipe that is used for under ground electrical wires, it is flared on one end and you need the flare to make a tight seal for the breach loader. (I think I cut some of the flare off I have a 1 1/2" long flare)
My barrel is 19" from end to end. You need to get the pvc fittings to reduce the flare end of the barrel down to a 3/4" threaded hole. (Make sure you check out the reducer fittings, some plumping store clerks will give you more than you need and it will not look good).
Attach the barrel and air chamber to the trigger using the nipples.
I had to cut the lever of the globe valve so it would make it pass the end of the air chamber (don't make it too short it takes a good pull to pull the trigger when it is filled with air).
I tapped a 1/4" hole on the top and towards the front of the air chamber for the gauge.
About 2" back from the gauge hole I tapped another 1/4 " hole for the fill button. (If I were to do it over I would of tapped the fill button hole for a 3/8" fitting it would be stronger). You need brass nipples to attach the fill button and adjustable regulator to the air chamber.
I bought a cheap adjustable low-pressure vertical regulator and 1/4" adapter that you attach the reg to the in put of the fill button.
The reg's intake is off set 90 degrees, I attached a 1/4" adapter to the reg in-take and use a remote to fill the Law air chamber (I use a remote with my marker and because where the reg is attached to the air chamber it is not strong enough to hold an air bottle).
Next to the reg and near the back of the air chamber I tapped a hole for the blow off valve. (Put the blow off valve away from where your head will be).
I drilled a 2" hole with a hole drill about 2 1/2" in front of the flare for the breach loader. I then slid a 2" fernco (it is a rubber sleeve that is used to connect two pipes together you can buy it at any plumbing supply house) over the barrel. This will seal the hole after you load the rocket into the barrel. I also cut a 1/2" off a 2" pvc coupler and glued it to the barrel about 5 1/2" in front of the breach hole so the fernco will not slide off the barrel. You get 2 hose clamps with the fernco slide them over each end of the fernco and tighten them down just enough to prevent the air from escaping out the breach hole but not too tight, you want to be able to slide it forward to load the law.

Now trust me the way I designed this is for safety.

The adjustable blow off is good in the way it releases air, if you fill the air chamber too much, it does not pop, it releases the air slowly (saving air if you fill it to much). Also you may have to adjust it for the field’s specifications. I set the blow off for 275psi and I fill the air chamber to 250psi.
The fill button (rated too 300psi) is used to fill the air chamber when your ready to shoot it, this way you are not running around with the chamber charged, you can charge it when you need it.
The aluminum pipe is light and will not explode like PVC, it will just split if some thing goes wrong.
I used a cheap low-pressure reg (Tippman that I bought on line for about $20.00). I had to take one of the washers out of the reg to get it to adjust properly to 250psi. (The reg adjuster was not sensitive enough).
The most expensive part is the globe valve and the aluminum pipe.
Also don't paint the fernco it will not dry.
If you are serious about this I will take better pics of my Law and post them on the site that I posted above.
With very little practice you can shoot reload and fire again in about 6 seconds.
At 250psi this thing will shoot a nerf over 100' straight at a slight angle it will go a lot further. You also don't need to cut the wings of the nerf.
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Old 12-08-2008, 11:53 AM #3
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Used and constructed PROPERLY....PVC air chambers are far from dangerous.

Here is a good place to start learning about making air cannons.

http://www.spudfiles.com/spudtech_archive/


Here is a good place to learn WHY air does what it does when put under pressure, and how to safely contain it when building a LAW for paintball use.

http://www.doomlabs.com/


My LAW:

Last edited by voodoo27909 : 12-08-2008 at 12:03 PM.
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Old 12-08-2008, 11:56 AM #4
bruno v
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PVC is very dangerous as an air chamber if they fail they blow apart like a hand grenade metal will just split, and most fields and producers will not allow them.
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Old 12-08-2008, 12:09 PM #5
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...True that alot of field do not allow them. The honest truth is that every failure I have heard (and personally witnessed) were cause by human error, and not material failure. Paintball air tanks that we use on our markers are dangerous as well.....yet we accept the risks involved. Proper construction, prevention, and usage are key to anything being safe, and the PVC is rated for much more pressure than we are allowed to use in a game. It isnt the materials fault in documented failures to date.
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Old 12-08-2008, 06:07 PM #6
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Originally Posted by voodoo27909 View Post
...True that alot of field do not allow them. The honest truth is that every failure I have heard (and personally witnessed) were cause by human error, and not material failure. Paintball air tanks that we use on our markers are dangerous as well.....yet we accept the risks involved. Proper construction, prevention, and usage are key to anything being safe, and the PVC is rated for much more pressure than we are allowed to use in a game. It isnt the materials fault in documented failures to date.
....Human error Is the very reason I wont allow PVC air chambers at my field...Even if you have done all your research on Spudfiles as I have done in the past , pressure rated PVC pipe and fittings are not supposed to be used for compressed air applications per PVC manufacturer warnings about stress fracturing and the grenading effect caused by overpressurization.......Even if you build your launcher with a regulated air supply and safety pop-offs on your PVC chamber , This wont prevent your buddy from accidentally banging that air chamber on the back of your truck getting ready for the game...You wont even see the hairline crack in the PVC chamber but you will definitely hear and feel it when your launcher blows apart in your hands and a safety pop-off cant prevent this from happening.....I have seen 2 PVC launchers blow up in games the past 2 years and a third accidently fire when a blow gun pilot broke off a modded sprinkler valve....These launchers were all built correctlly per info you would get off Spudfiles but the accidents happened anyway.....If your going to build a launcher , spend the extra $50 for aluminum or steel air chamber and it will be MUCH safer for everybody.
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Old 12-09-2008, 01:42 AM #7
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...Any different from that same "Buddy" bumping a fiber wrapped "Pure Energy" compressed air tank on the back of the truck before a game? PVC is safe with the proper precautions. My chambers get changed out once a year (the whole UV ray arguement...etc). Does steel or Alum have different properties when they breech? Certainly. Are alum. tanks less likely to cause a shapnel related injury when that "Accident" happens? Most certainly, but I wouldnt go as far as to call PVC dangerous, unless it is the hands of some one who is unknowlegable in its care and use (and trust me...Im fully aware that those people are out there). There are TONS of players I see out on the fields that make me nervous that they are carrying 4500PSI compressed air on their markers! Accidents happen in any venue. Im not certain that one type of accident is any "safer" than another.

As far as alum chambers go...Im all for them as well if that is what some choose to construct with. What I DO have an issue with is converting fire extinguiser bottles over to LAW usage.
This is not safe (I understand people tap out the hole to fit 3/4 NP thread....), and it is not DOT legal either.

At any rate, I respect field owners who do not allow PVC at their fields. Its their call to make, and I own LAW's which utalize alum. holding tanks as well for use at those fields, however I stand by my opinion that PVC can be just as safe as any other air tank out there in the right hands. How do we tell who is knowledgable...and who is not? We don't. On the other hand, I am no more confident of that guy over there filling that 4500 tank either. What we do is inherently dangerous no matter how you look at at....but I doubt that filling sched. 80 PVC to 100PSI air is any more dangerous than any other aspect of our sport. I completely respect every ones opinion on the subject, of course....these are simply my views and experiance on the subject.

Last edited by voodoo27909 : 12-09-2008 at 03:54 AM.
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Old 12-09-2008, 02:24 AM #8
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Old 12-09-2008, 02:50 PM #9
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Here's a good example of why NOT to use PVC for a chamber
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Old 12-09-2008, 04:36 PM #10
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This was a PVC chamber used to fill mortar rounds. It blew at a little over 100 psi. The shrapnel luckily was stopped by the walls of the bathtub, however pieces of PVC blew through the ceiling tiles above the tub. And no this was not me that blew this up, i just witnessed it.
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Old 12-10-2008, 12:40 AM #11
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Still dont get it.........I could come up with pictures all day showing blown Fiber wrapped air tanks. Are we going to ban everything we feel may cause an injury in paintball? What uproar would we cause if field owners decided to only allow steely tanks on markers because of the same arguement of "They are safer", or steel braided ASA lines (our nice plastic ones are made out of PVC by the way...) because the macro lines can inflict injuries when they blow and whip the heck out of someones wrist. Again...the toys we play with are inherently dangerous. Things happen.

By the way...is that a shreader valve drilled into the single wall side of that PVC tank? If it is, thats a BIG no no. Only drill into a double wall on the PVC tanks.

Would'nt a good bottom line to the entire issue be for field owners to require ALL compressed air tanks to carry a current hydro test before being allowed to be filled..regardless of the application, bought commercially or homemade, or pressure involved? It may sound silly, but in the name of safety..........It may very well stop alot of materials from being used.

This is a good conversation on the subject. I would like to see alot more input from scenario players.

Last edited by voodoo27909 : 12-10-2008 at 01:34 AM.
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Old 12-10-2008, 02:43 AM #12
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ok boys and girls lets stop and think for a sec its less what we fill with air and more how much we fill it air is not safe when compressed and then released in most cases.


i own 2 LAWS made by VooDoo and both are safe and work find both with blow off vales and regs this sport inst safe at all i mean come one were shooting each other with something thats going upwards of 200 mph


PVC is the best way to go
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Old 12-10-2008, 03:13 AM #13
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I wouldnt say "Best" way to go....but it is a safe alternative when handled properly by intelligent operators and builders. As EGOed pointed out, human error is a big concern to the field owners....and there is little evidence available to those checking the PVC launchers for safety that could expose a poorly constructed home made LAW, or abused home made LAW. About the best one could hope for is checking for obvious leaks, physical outward signs of damage and abuse, proper safety check devises (115psi pop-off valves, low scaled guages, arming valves to prevent airing up the air chamber until the shot is ready to be taken, a valve to shut off the firing valve to prevent accidental discharge, a shreader fill valve to pressure test the pop-off valve to insure its proper operation, a good low pressure regulator, proper construction materials and techniques, 100psi max fill...ETC). I completely understand the concerns raised, but honestly...the only way to dodge the whole "Who is liable" thing (which is REALLY what the field owners are getting at), is to ONLY allow commercially made, UN-ALTERED store bought launcers. If something goes wrong with one of these un-altered commercial launchers, everyone has an avenue to pursue for loss recovery should the need arise (God forbid).
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Old 12-10-2008, 06:21 PM #14
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The main reason PVC is not the best material for air chambers on a paintball field is the fact that the chemical properties which make up the PVC plastic change dramaticlly in temperatures colder than 60 degrees F.....The plastic becomes very brittle and much more suseptible to damage from impact at lower temps.....Many of our games are played in Spring and Fall with outside temps in the 40's so this is something to think about also if you are considering using PVC for your air chamber and you play in colder temps...I have built many cannons myself with PVC air chambers and never had one explode on me , just as Voodoo has , but I will always advise players to use metal or aluminum air chambers for an added measure of safety....Especially if you plan on using it in cooler temperatures.
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Old 12-10-2008, 08:42 PM #15
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Steel is the way to go

Go to home depot and buy a foot or so of 2 inch steel pipe. they will cut it from a larger peice. they will also thread the ends for free.

Buy 2 pipe end caps $5?, some jb weld $4, a "pop off valve" $5(125 or 150 psi) and a psi gauge $10

Also determine what you are using for a valve and buy the correct sized "Pipe nipple" 3/4 x 3, or 1" x 3 ect.

Drill a hole so the nipple fits into one end of the pipe cap. drill holes for for the pop off valve and gauge where you want them.

Jb weld the nipple,gauge,and pop off valve in place.

then rig up your valve to your new air chamber
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Old 12-11-2008, 12:49 AM #16
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Wait a second...I definately DO NOT agree to JB weld being used to secure fittings, valves, or gauges in any material used for pressurized air. You're joking...right?
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Old 12-11-2008, 05:23 AM #17
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PVC is not the best way to go, its just the cheapest way to go. I have been at an away game where a PVC chamber blew, sending one guy to the hospital... Bad reg and no relief valve. One heck of a boom. Granted it could have been a whole lot safer with a blow off valve. I'm not saying Voodoo's stuff is a ticking time bomb, but there are other options.

The field I play wont allow PVC air chambers anymore. Due to two incidents in the states to the North and South of us with PVC chambers blowing and people getting hurt.

There are other options out there where you dont really need to go PVC. Our field actually started using old CO2 tanks for pressure chambers. Our field engineer uses the small kitchen fire extinguisher bodies for his pressure chambers.
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Old 12-11-2008, 08:50 AM #18
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The thing to use as an air chamber is aluminum pipe it is lighter than the PVC air chamber shown in the pics above.
Using steel is cheaper but very heavy, the steel cap I have on the end of my LAW is the heaviest part of the LAW.
The only problem with aluminum is you need to have the end that the trigger screws into welded. the reducers for aluminum ends suck.
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Old 12-13-2008, 09:40 PM #19
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Pass on the PVC
Also, the pipe you buy at the hardware store is a overkill. Use tubing and weld all your caps, fittings, etc. use a section of tubing cut open and flattened out as your end caps. When you get away from using caps, couplers, tee's and all the other related threaded pipe connectors, the result will be the same wieght as PVC without all the shrapnel.
I'm also not too crazy about the thinwall Al fire extinguisher bottles as they were never made to cycle that many times and aluminum is very sensitive to metal fatigue.... I'd still take thinwall Al over PVC.
And just for thought; PVC does not show up on Xray; so they'll be poking and digging a while to find all the pieces.

It's not really an issue of will PVC hold the pressure; it's an issue of what happens when it fails.

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Old 12-14-2008, 10:02 AM #20
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Originally Posted by Naked Rampage View Post
It's not really an issue of will PVC hold the pressure; it's an issue of what happens when it fails.


....now THAT statement Im perfectly fine with. Also, as I already pointed out, it is HIGHLY illegal (Federal law) to toy around with fire extinguisher bottles. They can not be converted legally, nor refilled by un qualified persons, especially if that refill involves it being used for anything other than its intended use. What does everyone think about requiring LAW air tanks to be governed (enforced by the paintball community) by the same hydro laws that our marker air tanks fall under???
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Old 12-14-2008, 01:04 PM #21
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....Also, as I already pointed out, it is HIGHLY illegal (Federal law) to toy around with fire extinguisher bottles.What does everyone think about requiring LAW air tanks to be governed (enforced by the paintball community) by the same hydro laws that our marker air tanks fall under???
If ya poke around a bit, I think you'll find that applies to transportation of refilled bottles. An empty bottle is not refilled and therefore OK by DOT.

on hydro of non-standard tanks-
About the only thing that could be done there is the same procedure for air pigs (fat little air tanks with a short hose for tires and stuff); when built, they are stamped with a "discard after XX-XXXX"
It usually reflects a length of time that water could accumulate and rust out the inside of the tank. When using steel tanks & CO2, it's not an issue. My tank is stainless so no problem inside or out.
Most people don't keep the same launcher long enough for anything to happen.
The real players build a cannon and use it long enough to get good, then say "screw this walking crap" and build a tank!... after that, it's a refit and improvement every couple of years or sooner.....I have not played the Grand Finale with the same main gun in the past 6 years. I've been through 3 tanks and 1 major refit in that time as well.
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