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Backpressure Problem

PAS with jet and mysterious problem

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#1 louiec3

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Posted 15 December 2009 - 10:30 PM

I finished a PAS with an Airtech jet squadron integration, but...
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I'm having problems with the back pressure system (like the hornet, big salvo, and blastfire)
I can pump it up all the way with NO leaks at all, but when I push the blast button in all the air from the system escapes around the button, and when a barrel does fire it is delayed for about a second and not much air comes out.

The blast button was a problem in the stock gun because there was no spring pushing it up but I can get it to seal by pointing the gun vertically.
Also when I sake the gun/tanks I can hear the valve parts moving back and forward.
Before I did this integration the system would equalize the tanks after each shot, and the blast button leaked like a sieve.

Any help would be appreciated.

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That tubing goes to the pump.
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The tanks are connected like that on both sides. I had to drill a hole in front of the tank to make them work because the stock tubing was the weirdest size.

And because I know you all like videos.

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#2 cheesypiza001

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Posted 15 December 2009 - 10:41 PM

I have had this problem before. You can't have your thumb too close to the trigger otherwise the air does not have enough room to escape. Try glueing a tack (the kind seen here) on the valve.

EDIT: By the way, I forgot to tell you that your gun looks sweet.

Edited by cheesypiza001, 15 December 2009 - 10:41 PM.

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#3 TantumBull

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Posted 15 December 2009 - 10:51 PM

You need one pilot valve per back pressure valve, or a bunch in a row combined into one valve (ie SMDTG trigger). One trigger valve will very rarely trigger more than one valve at a time. Maybe look in to Y tubing fittings, but I doubt it'll do much.
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#4 Blue

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Posted 15 December 2009 - 11:45 PM

Tantum, would a hornet trigger replacement somehow solve the problem?
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#5 TantumBull

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Posted 16 December 2009 - 12:54 AM

Tantum, would a hornet trigger replacement somehow solve the problem?

If you could somehow get that working, yes. Unfortunately that trigger system relies on the shell of the hornet and uses a ratchet system. It would probably be pretty hard to replicate that set up outside of a hornet shell. I would pursue Bob's ideas over this.

Also, forgot to say, that gun looks freakin awesome. Really great work. Unfortunately if I used it during a round I would probably end up pretending to fly it around for the duration of the round. :lol:
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#6 Zorns Lemma

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Posted 16 December 2009 - 02:55 AM

You don't need exactly 1 release valve per dump valve (else how would the blast buttons on Hornets and Blastfires work) but each dump valve needs to be independent of the others when interacting with the trigger. It's not quite the right analogy, but if you were comparing this to an electrical system, you wan parallel wiring rather than series wiring.

So, replace all that random tee crap and directly feed all the tubing into the trigger, drilling 1/4" holes and using lots of superglue and goop.

It's not a pretty solution, but it's pretty much the only one that will work the way you want, because a tree of 1/8" ID vinyl tubing is not going to permit the fast airflow needed for all 4 of those poppets to fire (see what Bob said).
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#7 louiec3

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Posted 16 December 2009 - 07:46 AM

OK I think I'll do what Zorn said. Thanks everyone I'll let you know if it works.
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