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Help with 'rocket launcher' design

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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Help with 'rocket launcher' design

Unread postAuthor: Marlowe » Mon Oct 27, 2008 9:09 pm

Hey! I'm a paintball player in the North Carolina Triangle area, and my friends and I may be making a team soon. Well, our rocket launcher recently broke, and I've been trying to make a better one for when we get a sponsor. I've had some experience with very simple pneumatics before (read:ballvalves). So, i checked out your wiki, saw some plans and some pictures, and now i think I've got an idea of what to do. My real question now is, "Will It Work?" If you could help me out here, that'd be great. I just want to know what could make it more efficient, smaller, more paintball accesable, etc... I'm going to put it in a shell to make it look better, probably a bullpup sort of thing. For those of you who don't know, thats when the trigger is in front of the ammo feed and firing mechanism. Speaking of ammo feed, do you think that mine seems prety good? It's an alright breech loading system, with a low profile for getting rid of gear shots. I had rigged up a little example using some spare tubing and some of my little brother's KNEX, and it seemed to work alright. I'm still trying to think of ways to make it better, so if you could help out on that too I'd apreciate it. I'm really trying to get rid of thepressure chamber, but would that raise the PSI too much? Thanks for your attention, hope you can help!
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These are the plans I would really like help with.
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Unread postAuthor: rp181 » Mon Oct 27, 2008 9:33 pm

I dont see any reason why it wouldnt work, but you may encounter problems with breach loading and higher pressure, though personally i've never done a breach loader. The airhose dosnt matter as long as its rated to the proper pressure. The steel braided hosing might be easier to work with.
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Unread postAuthor: psycix » Wed Oct 29, 2008 5:49 pm

Beware when using long hoses.
The longer your hose, the more pilot volume you have, the slower your valve opens.
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Unread postAuthor: Marlowe » Thu Oct 30, 2008 8:11 pm

Ok, so I'll use some short (thank you psycix) steel braided hosing (thank you rp181), probably from tippman products. But do I still need the so called "pressure chamber" (please see drawing for details), or can i connect the air supply directly to the sprinkler valve? This would be ideal, as I am constantly looking for a smaller version of this thing. Thanks for the advice guys, anyone have anything else to contribute?
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Unread postAuthor: grumpy » Thu Oct 30, 2008 8:29 pm

you do know that a sprinkler valve is only rated to 150 psi, and the smaller the pressure chamber the more pressure you will have to use.
and yes you will need some sort of pressure chamber.
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Unread postAuthor: judgment_arms » Fri Oct 31, 2008 10:37 am

Marlowe!
sorry I didn't find your thread sooner.

you told me you were building a tank gun, I thought you meant a main gun for a tank, not an AT weapon. :?


sprinkler valves don't lend themselves well to man-portable, compact, cannon.
they require long barrels and a large pressure chamber volume.


you going to want a good piston valve, preferably a chamber-valve like the ones used by Biged and myself, or the valve used in Clide's golf ball semi.

chamber-vlaves (also known as inline valves) are compact and powerful, being no bigger than a pressure chamber but with the speed and flow of a piston valve.
depending on the pipe used, they're also capable of running at a high pressure


another thing to consider is burst disk cartridges of similar design to what Davidvaini has come up with.


understandably, building such valves might be a little to complex.
one might try using two sprinkler valves, the improved flow might allow for shorter overall chamber and barrel length.


by far though, best thing would be to get a good 1.5-2 inch QEV, I'm getting +250fps off of a 13inch by 1.5inch chamber and using a 7inch barrel, which allows me to just stuff a NERF right into the end of the barrel making it incredibly quick to reload.
not to mention loud enough to leave your ears ringing. :D
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Unread postAuthor: Marlowe » Mon Nov 03, 2008 10:41 pm

Thanks a lot for the advice guys! I'm getting really excited about this thing, and trust me when this is done I'll be coming to you for more help with other launcher designs. So, taking into account everyone's advice (and being stupid in Spudtech and not wanting to make complex things), I have the revised edition of my plans. Anything else you want to help me out on with the design would be greatly appreciated. I didn't really label anything on the bottom half of the plans, but I'm really tired after wrestling practice and really must get to bed. Please note that if I didn't mention it in the upper diagram, I didn't change it. Thanks again.
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Unread postAuthor: psycix » Tue Nov 04, 2008 1:58 pm

Looks good.
Only comment is that I would use a piston valve instead.
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Unread postAuthor: Marlowe » Wed Nov 05, 2008 8:49 pm

I would, but I'm almost entirely new to pneumatic gun designs, and I just want a good little try at it for right now. Later on, I might go ahead and make a piston based gun. If no one else has any more comments, I'll start on construction next weekend, give some completed pictures. Also, if anyone has a preferred way of making handles you would like to pass on to me, I'd really appreciate it.
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Unread postAuthor: psycix » Fri Nov 07, 2008 3:16 pm

My first pneumatic was also a piston valved one. If you do enough research you can always skip a few steps in your spudding "career."
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Unread postAuthor: Marlowe » Fri Nov 07, 2008 8:00 pm

Well, alright, I guess you got me. But if I could perhaps get a better explanation of how a Piston valve works, I would be much obliged. The wiki was very confusing, I couldn't make heads or tales of it. Maybe draw a little diagram in Paint to help me out, give me some advice on building materials, if that isn't too much to ask. Also, the Piston goes with the sprinkler valve, correct?
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Unread postAuthor: keep_it_real » Fri Nov 07, 2008 8:26 pm

Check this out if you haven't seen itPiston Valves

People often use a sprinkler valve to pilot their piston valve. It's kind of overkill unless you have a big pilot area but since it does release air so fast, it means your piston doesn't have to seal quite as well. This also allows you to have a blowgun as a trigger. If you're using this as a tank, you wouldn't want a ball valve pilot because that would sacrifice accuracy.
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Unread postAuthor: judgment_arms » Fri Nov 07, 2008 8:55 pm

Piston valves are overkill on a paintball anti-armor weapon.

the main problem I've had is the tendency to shred the NERF, on the other hand I've got NO dead volume and the air hammer is... well air alone generates noticeable recoil...:roll:


I'd recommend staying with sprinklers for simplicity's sake, on top of that pistons tend to be a bit bulky.
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Unread postAuthor: Marlowe » Fri Nov 07, 2008 10:29 pm

Thanks for the advice yall', and so quickly too. So, I guess this launcher stays how it is (sans piston) due to it's shredding of NERF rockets. But, that piston page helped out a lot, and I was planning on fixing up a nice little co-ax pistol when I finally understood how to make them. Needless to say, I shall come to you guys for help with that one too, I never trust myself with these things. So, I guess thats the verdict, the launcher remains how it was in the second plans (sans piston). But now, it brings me to another question. When I'm done building it (probably in about two-three weeks), how should I paint it. Digi or Macropattern? Angular or Round? I leave it to you to decide!!!
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Unread postAuthor: judgment_arms » Fri Nov 07, 2008 10:56 pm

solid OD/solid black/solid any color.

Camo doesn't work.

if you must use Camo go with tiger stripe.
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