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Dual QEV Paintball LAW

Built a pneumatic cannon? Then post it here! This section is for completed, finished cannons that you have built. Please include pictures and information.
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Dual QEV Paintball LAW

Unread postAuthor: peeeto » Mon Jan 14, 2008 12:20 pm

Prototype Specs:

Barrel: 24" - 2"dia sch40 PVC
Primary Valve: 3/4" QEV
Secondary Valve: 1/4" QEV (pilots the Primary)
Secondary Pilot: blowgun (unmod)
Chamber: ~21" (effective) - 2"dia (sch40?) Galvanized Iron
Propellant: Compressed Air or CO2
Regulator: Palmers Stabilizer
Ammo: JCS F-69 Foam Rockets
Breach Load Sys: slide thru 2" conduit pipe holders, seals to partially tightened 2" Fernco.
Operating Pressures: planned 35-80 for testing
Typical Chrono Results: @ 50 psi - ~150 fps, @ 45 psi, ~140 fps

this prototype is my first gas gun. will be used for testing inorder to develop a lighter version for paintball scenario games. hopefully more gas efficient too...

after deciding to add the secondary QEV, i saw VAST improvement. even explored a little further by partially restricting the 14" QEV exhaust to simulate triggering by blowgun, and saw big velocity drop.

any tips anyone can give me on calibrating the GGDT parameters, lemme have em. i plan on charting the Velocity vs Pressure for different Barrel lengths, and then use those results to dial into the "true" Cv thru GGDT. i'll then use the resulting calibrated GGDT to design the final version.

NOTE So far, GGDT is suggesting a Cv of about 6 for the 3/4" QEV. less than the manuf's specs (~7.5), but greater than the only reference i've found reported by others here (reported ~1/2 the manuf's).

the nice thing about how fast the 1/4" QEV triggers is that the blowgun can be placed just about anywhere. same for the CO2 source (will be 9-oz CO2 tank) and the regulator. so i hope to end up with a comfortable result.

right now, i'm getting ~15 shots (150 fps) off 9-oz CO2.

p.s. although the proto does not, the final design _will_ have a safety ;). some other things that will be different are:
-NEW chamber will be 1-1/2" aluminum (12" pipe + 90d el =~14")
-NEW barrel will be 18"
-NEW GGDT predicts 140+ fps @ 75 psi
-the safety blowoff will be right off the Chamber;
-the CO2 supply will be thru much smaller dia. pipe;
-the trigger safety will be linked to the CO2 fill valve (fill will be turned off to fire to conserve gas).

thanks for taking a peek & your kind comments!

DQ-LAW(v0.3) vs Cabbage Patch Doll: http://www.youtube.com/profile?user=p333to
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Attachments
gas gun.v03.sm.jpg
current prototype for testing
Last edited by peeeto on Tue Jan 15, 2008 10:29 pm, edited 4 times in total.

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Unread postAuthor: ALIHISGREAT » Mon Jan 14, 2008 12:38 pm

ooh thats cool, what pressure do you use it at?
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Unread postAuthor: peeeto » Mon Jan 14, 2008 12:54 pm

right now, 50 psi (chrons ~145 fps, which is standard for paintball LAW). but the chamber's huge (~21" including the 90-degr el. the pipe part is only ~17").

the barrel is 24", and the rocket sits in ~3".

it's breach loaded.

will operate this prototype over a range to calibrate the GGDT model to settle on final design. since the final will be all plastic (xcept for valves & fittings), i'll keep pressures <90 psi, though likely much less (unless vastly improves gas efficiency, then i'll go nearer 90).
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Unread postAuthor: ALIHISGREAT » Mon Jan 14, 2008 1:13 pm

since the final will be all plastic


i would keep it lke it is because if you suddenly have the urge to destroy something you can upp the pressure to 200+psi
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Unread postAuthor: peeeto » Mon Jan 14, 2008 2:09 pm

ALIHISGREAT wrote:i would keep it lke it is because if you suddenly have the urge to destroy something you can upp the pressure to 200+psi


:lol: good idea, but i want a lightweight final design to carry around on the paintball field
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Unread postAuthor: ALIHISGREAT » Mon Jan 14, 2008 2:34 pm

peeeto wrote:
ALIHISGREAT wrote:i would keep it lke it is because if you suddenly have the urge to destroy something you can upp the pressure to 200+psi


:lol: good idea, but i want a lightweight final design to carry around on the paintball field


yeah i suppose, but make sure you have an expansion chamber so you don't freeze the pvc :)
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Unread postAuthor: peeeto » Mon Jan 14, 2008 2:38 pm

ALIHISGREAT wrote:yeah i suppose, but make sure you have an expansion chamber so you don't freeze the pvc :)


it uses a Palmers Stabilizer as regulator/expansion chamber.

the final version will be double-regulated by the Stabilizer and another Palmers Micro-Rock (the fine adjustment isn't very fine on the Stablizer, which i could remedy by purchasing the low pressure spring kit, but since i have the Micro-Rock, might as well use that for xtra safety).
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Unread postAuthor: PVC Arsenal 17 » Mon Jan 14, 2008 3:21 pm

peeeto wrote:
ALIHISGREAT wrote:i would keep it lke it is because if you suddenly have the urge to destroy something you can upp the pressure to 200+psi


:lol: good idea, but i want a lightweight final design to carry around on the paintball field


That's just what you want to avoid. Running around a paintball field with a pressurized tank made of plastic is like a bomb waiting to go off. Keep it metal. That way if you fall and bust your ass on a rock, at least you won't get perforated with shards of plastic.
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Unread postAuthor: daberno123 » Mon Jan 14, 2008 4:39 pm

How much does using the second QEV to pilot the first increase performance?

I ask because i might try it on my 1.5" ASCO

I agree with keeping it all metal for the sake of safety and it looks cooler and way more intimidating
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Unread postAuthor: dewey-1 » Mon Jan 14, 2008 4:53 pm

--
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Last edited by dewey-1 on Sun Apr 20, 2008 2:08 pm, edited 1 time in total.
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Unread postAuthor: daberno123 » Mon Jan 14, 2008 5:02 pm

So it wouldn't really help performance at all? Not even the slightest bit?
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Unread postAuthor: rna_duelers » Mon Jan 14, 2008 7:39 pm

Nice looking gun,with a lick of paint it will come up very nicely.I have to say that is one of the nicest looking paintball LAW systems I have seen.

And you used pink Thread tape!Which is good!

Perhaps you should copy and paste those specs/ideas from the other page and put it on here it would add a story to the picture and something for people to read while the look at it.
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Unread postAuthor: peeeto » Mon Jan 14, 2008 9:41 pm

ok - entered the specs.
thanks for the input!
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Unread postAuthor: potatoflinger » Mon Jan 14, 2008 9:46 pm

Awesome looking gun, I really like it! I do think you should keep the chamber metal, especially if you're going to be walking around with this thing.
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Unread postAuthor: Isomer » Mon Jan 14, 2008 10:05 pm

Very nice cannon. It will be quite a hefty gun to haul around on the paintball field with the metal chamber still attached. Also, it seems kinds pricey with the two QEVs.
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