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| skyjive |
 Posted: 08/21/2008 22:56 PM Post subject: Sprinkler vs. QEV |
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Specialist
Joined: 26 May 2008
Posts: 44
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I'm working on a .5" copper gun that I plan to run of CO2 at about 120 psi. I have at my disposal a modded sprinkler (1") from BCARMS and a 3/4" QEV from mcmaster. My options are essentially
1) Use the sprinkler, which would work fine
2) Use the QEV with the sprinkler as a pilot valve
Would the QEV have significantly better flow/ opening time when piloted by the sprinkler as opposed to simply using the sprinkler as the primary valve? |
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| jackssmirkingrevenge |
| Posted: 08/21/2008 22:59 PM Post subject: |
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space monkey
Joined: 15 Mar 2007
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| For a half inch calibre, I'd go with the QEV and a blowgun pilot. |
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| brogdenlaxmiddie |
| Posted: 08/21/2008 23:02 PM Post subject: |
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Colonel
Joined: 22 Jul 2007
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| I very much agree with JSR, no need to have super piloting in a small launcher like that. |
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| skyjive |
| Posted: 08/21/2008 23:13 PM Post subject: |
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| Yeah that's what I thought at first, but the gun was pathetically underpowered at 200 psi with a QEV/blowgun and I think it wasn't piloting fast enough. So I don't want to take any chances with the pilot setup being inadequate. I of course realize its overkill, but as long as I have the sprinkler I might as well use it, right? I mean, there's not a point at which increasing pilot valve size actually hurts, there's just a point at which it doesn't really help either. |
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| jackssmirkingrevenge |
| Posted: 08/21/2008 23:22 PM Post subject: |
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space monkey
Joined: 15 Mar 2007
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| skyjive wrote: | | the gun was pathetically underpowered at 200 psi with a QEV/blowgun and I think it wasn't piloting fast enough. |
What's your chamber size and barrel length? Could it be that your expectations of power were unrealistic? |
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| skyjive |
| Posted: 08/21/2008 23:34 PM Post subject: |
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Joined: 26 May 2008
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| 200 psi, chamber size ~30 in3 barrel length 68". As a baseline test I compared it to a PVC gun at 60 psi with 55 in3 and the same barrel caliber and length and it was far weaker, so I concluded there must be a valve problem. |
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| frankrede |
| Posted: 08/22/2008 0:15 AM Post subject: |
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Sangheili
Joined: 20 Jul 2006
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That makes no sense, A working QEV will outpower a sprinkler easily.
You obviously were having some problems in your setup.
Did you have your air input running while you tried to pilot it?
Lets see a pic of your QEV |
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| Pilgrimman |
| Posted: 08/22/2008 1:49 AM Post subject: |
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Lieutenant Colonel
Joined: 28 Jun 2007
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It could be that, but I notice with my cannons that a bigger chamber always helps. Of course, that may just be an increase in PERCEIVED power from the extra noise... Bottom line, it makes no sense that a QEV is underperforming  |
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| psycix |
| Posted: 08/22/2008 7:33 AM Post subject: |
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Major General
Joined: 25 Jun 2007
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A QEV is always more powerful then a sprinkler of the same size.
Do not use a 1" sprinkler to pilot a QEV, it will give excessive pilot volume.
If you want optimal results for your QEV, use another QEV to pilot it 
Pilot valves are more about opening time then flow. |
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| jonnyboy |
| Posted: 08/22/2008 8:15 AM Post subject: |
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Sergeant Major
Joined: 26 May 2008
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| A qev is better. By the way if your running co2 with a copper gun why not pump up the pressure? |
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| skyjive |
| Posted: 08/22/2008 10:50 AM Post subject: |
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@ jonnyboy: Since the QE apparently wasn't working, I took the target pressure down to 120 so I could use a sprinkler valve
So I guess I should give a QEV/blowgun setup another shot, its possible that my pilot volume was too large since I had to have some 3/4" fittings on the pilot side of the valve in order to plumb in the quick change adapter for the 12g cartridges. Is it possible to fill a QEV setup from the chamber side instead? This would reduce pilot volume by allowing only the blowgun on the pilot side of the QEV. |
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| POLAND_SPUD |
| Posted: 08/22/2008 11:04 AM Post subject: |
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Brigadier General
Joined: 13 Oct 2007
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3/4" is a lot for a blowgun...
wait a second.... have you diconected the CO2 source (or closed it's flow) before piloting ?? |
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| skyjive |
| Posted: 08/22/2008 13:31 PM Post subject: |
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The gun fills off 12g cartridges, the whole cartridge is dumped into th chamber so there should not be any pressure higher than chamber pressure coming from the cartridge once its finished dumping into the chamber. So I don't think that's the problem, although I do leave it attached and don't unscrew it before firing.
If 3/4" is too much for a blowgun to pilot efficiently (which I suspect is true), then what kind of pilot valve would be more appropriate? |
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| brogdenlaxmiddie |
| Posted: 08/22/2008 13:43 PM Post subject: |
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Colonel
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| ramses |
| Posted: 08/22/2008 13:59 PM Post subject: |
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You can't fill from the chamber with a qev. 
Keep in mind that unless there is a valve closed between the pilot volume and the co2 cartridge, the CO2 cartridge becomes part of the pilot volume.
You could see if Modding the blowgun helps. |
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