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#1 bjack

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Posted 18 July 2007 - 10:28 PM

I've been working on a semi-automatic gun and everything has been going well except for my valve. I have a perfectly air tight tank that can hold up to 70 PSI from 25 - 30 pumps from a bicycle pump. I originally tried to use Dr. Nerf's valve design, but I've found it almost impossible to get the seals airtight. Does anybody have any ideas as how in just one pull of a trigger i could release the air from a firing tank and keep any more air from flooding the firing tank while the trigger is being depressed?

And while im asking, any ideas for a trigger activated breech?
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#2 newby

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Posted 18 July 2007 - 10:51 PM

As for your valve problem, I've heard of people putting bladders on their at2ks and just using the standard at2k valve. the trick for that set up is to depress the trigger quickly and then let up. You could also use a couple of ball valves in succession (leaving the one closest to the barrel closed and the other open to let in air. then closing the back valve and open the front valve to release air). My last possible recommendation is to use a hose valve.

-at2k valve
-double ball valve,
-double or single hose valve


On to your trigger activated breech, I'd suggest using the turret assembly from a DTG or Maverick.

-NEWB
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#3 bjack

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Posted 19 July 2007 - 12:15 AM

Oh thanks, I actually didn't even think of using a turret design like that. And yeah maybe I'll go out and buy an AT2K and try that too. Thanks.

If anyone else has ideas I'm still open to suggestions.
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#4 Prometheus

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Posted 19 July 2007 - 06:59 AM

As for your valve problem, I've heard of people putting bladders on their at2ks and just using the standard at2k valve. the trick for that set up is to depress the trigger quickly and then let up. You could also use a couple of ball valves in succession (leaving the one closest to the barrel closed and the other open to let in air. then closing the back valve and open the front valve to release air). My last possible recommendation is to use a hose valve.

-at2k valve
-double ball valve,
-double or single hose valve


On to your trigger activated breech, I'd suggest using the turret assembly from a DTG or Maverick.

-NEWB


How is that semi-auto? oh, that`s right, it`s not. You need some form of breech actuation that will reload a round after you have pulled the trigger. So, pull, fire, reload. All in one fluid motion. Look at CaptainSlug`s ABP for reference.
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#5 Dr Nerf

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Posted 19 July 2007 - 10:59 AM

I originally tried to use Dr. Nerf's valve design, but I've found it almost impossible to get the seals airtight.

I encountered similar problems at first but solved this problem by remeasuring and getting the right size O-rings. Originally, I bought and used the wrong size O-rings. I would also recommend using more O-rings than I used. Each set in mine had 2; however each set in yours may have 3 if the center divider is removed. I also replaced the O-rings in mine at least on other time since I built it because the system requires maintenance. Lubricated and with the right size O-rings, the system is a great semi-auto valve. Admittedly, I think the seals would perform better if they were not O-rings, but that was what I had to work with at the time.
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#6 Doom

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Posted 20 July 2007 - 08:33 AM

bjack, the difficulty in getting a seal is why I redesigned the valve to use different materials. I'm still working on constructing it due to problems getting the seal right before the trigger to seal perfectly. Apparently, a 1 inch diameter seal does not work in a 1.003 inch diameter pipe! If you want to use a vastly improved Dr. Nerf style valve, wait for my Nerf gun to be completed.
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#7 bjack

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Posted 20 July 2007 - 01:26 PM

When do you plan on having yours finished?
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#8 newby

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Posted 20 July 2007 - 02:12 PM

On to your trigger activated breech, I'd suggest using the turret assembly from a DTG or Maverick.


Hey Prometheus, if you rigged an at2k valve to a DTG with a bladder, you would be able to shoot ten rounds without re-priming your gun, but I guess you're right.

True definition of 'semi-automatic': "A weapon which automatically reloads after each shot, but requires a trigger pull for every shot." ~http://www.tea-and-medals.co.uk/glossary.htm

So technically, it wouldn't be semi-automatic, but you would get the same basic result by having a turret, and it would take a lot less time to get right.

~NEWB
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#9 Doom

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Posted 22 July 2007 - 06:10 AM

When do you plan on having yours finished?


There is no planned time at the moment. I'm just doing it in my spare time. The earliest I can say is in a week and the latest I can say is never. I will try to finish it before the end of August if push comes to shove. I planned on making this Nerf gun for quite some time actually. Take a look at my posts... this idea goes back to last year. I was hoping someone would pick it up, but it doesn't seem that anyone can read a good idea and build from it.

Anyway, I also was hoping to have a trigger activated breech, but timing becomes an issue. Gas-blowback could work too, but I'd lose some power and it would be hard to make. I think trigger activated is the way to go and I should link it to the trigger moving forward. Just if you wanted a head start on that part.
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#10 bjack

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Posted 22 July 2007 - 09:16 PM

Yeah thats actually what I've been designing for the breech but I'm still working on the specifics, all i really need is to figure out this valve.
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