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Semi Auto QDV Airgun

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Semi Auto QDV Airgun

Unread postAuthor: ByeBye » Sat Nov 27, 2010 5:44 pm

Image
This is just a pneumatic, but loading, firing and refilling is done in one stroke.

Charged:
Image
Firing:
Image

EDIT: I forgot to draw a spring in front of the bolt:
Image
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Unread postAuthor: Ragnarok » Sat Nov 27, 2010 6:47 pm

I can't see how this counts as a QDV. The valve is only moved manually, and doesn't have a pneumatic "kick" to open the valve.

It also looks like it'd be a pig to get all of those seals to work.
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Unread postAuthor: jackssmirkingrevenge » Sat Nov 27, 2010 6:55 pm

Yes, I've obviously tried something vaguely similar :)

Image
Image

Mr. Ragnarok makes some valid points though, there are easier and more efficient ways to achieve a semi...
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Unread postAuthor: ByeBye » Sat Nov 27, 2010 6:55 pm

Ragnarok wrote:I can't see how this counts as a QDV.

This is the piston of the QDV
Image
Here you can see the air pushing the piston back when is fires.Image

@ JSR, I still see some difference in operation xP
(btw, what do you use to draw those diagrams?)
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Last edited by ByeBye on Sat Nov 27, 2010 7:04 pm, edited 1 time in total.

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Unread postAuthor: saefroch » Sat Nov 27, 2010 7:03 pm

I'm almost dead sure this isn't a QDV.

I concur with Ragnarok, it'd be a real PITA to get those seals to line up. I think you'd have to relate (and with great precision) the spring constant for the two different springs to the location of the holes.

Not only that, but the opening speed of this valve would be incredibly slow. If you don't push the big cylinder forward hard enough it'd probably just fart, because as soon as the valve opens the pressure introduced into the barrel forces the firing mechanism back and tries to shut the seals. By comparison, as soon as a QDV is triggered, the airflow forces the valve open faster, not slower.

And also a side note, if I take your diagram literally, there's a very good chance that it would simply dump the magazine out the barrel if you bumped it even the slightest. There's nothing keeping the top BB from slipping down the barrel.

Aside from all of that I do LOVE the concept. This has inspired me to work on a design I've left lying around for far too long.

I'd actually just take all the springs off and operate the center cylinder manually through a sealed rod out the back of the rest of the valve. That'd let pneumatic forces take over, instead of being constantly restrained by the springs.
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Unread postAuthor: ByeBye » Sat Nov 27, 2010 7:11 pm

So... Ready for the trashbin.
Thx for the replies and saving me a lot of time and money building something that won't work :D
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Unread postAuthor: Ragnarok » Sat Nov 27, 2010 7:12 pm

ByeBye wrote:This is the piston of the QDV

Ah... the positioning of the arrow implied something different (air flowing through, rather than that being a plug/cap), but seeing that - yeah, I guess that counts.
My comments on the seals still stand though, and as Jack said, still rather complex for what it's actually trying to do.

What's your plan for stopping it kicking back violently on firing?
If the chamber and valve have been pushed forwards, the recoil kick is going to be directed into just them... and whatever pushed them forwards.

That said, pulling them forward with a spring (so the user's hand is not directly implicated) would help that. Heck, get the combination right with that and you could go full auto.

btw, what do you use to draw those diagrams?

Jack's diagrams, as far as I know, are often just scanned drawings that get some colour in Paint.
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Unread postAuthor: saefroch » Sat Nov 27, 2010 7:14 pm

Drawing up alternate design for you, ByeBye. Your concept will work, I think.
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Last edited by saefroch on Sat Nov 27, 2010 7:56 pm, edited 4 times in total.
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Unread postAuthor: ByeBye » Sat Nov 27, 2010 7:19 pm

Ragnarok wrote:
ByeBye wrote:This is the piston of the QDV

What's your plan for stopping it kicking back violently on firing?

I was thinking about a piece of rubber in the spring..

Ragnarok wrote:That said, pulling them forward with a spring (so the user's hand is not directly implicated) would help that.

What? sry, it's 1:15 AM here :P
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Unread postAuthor: jackssmirkingrevenge » Sat Nov 27, 2010 7:33 pm

Ragnarok wrote:Jack's diagrams, as far as I know, are often just scanned drawings that get some colour in Paint.


Precisely how the above were made, however these days I prefer to use paint directly.

I've whittled down your design a little (and it comes out somewhat similar to the electric drive design, though crucually with a larger diameter bolt which means it would achieve blowback) this would work and would be much simpler to implement.
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Unread postAuthor: saefroch » Sat Nov 27, 2010 7:50 pm

JSR: Wouldn't that design have a tendency to shut as soon as the valve opens? Isn't there a net force moving the piston to the right as soon as the ports align?
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Unread postAuthor: Gun Freak » Sat Nov 27, 2010 7:53 pm

It looks pretty ballanced to me, putting a spring in front should be enough...
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Unread postAuthor: jackssmirkingrevenge » Sat Nov 27, 2010 7:56 pm

saefroch wrote:JSR: Wouldn't that design have a tendency to shut as soon as the valve opens? Isn't there a net force moving the piston to the right as soon as the ports align?


That's the idea, the air pressure would fire the projectile and reset the bolt at the same time, there's the potential for full auto with a bit of fiddling ;)
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Unread postAuthor: saefroch » Sat Nov 27, 2010 7:56 pm

Would this be a semi-auto QDV then?
Image

jackssmirkingrevenge wrote:That's the idea, the air pressure would fire the projectile and reset the bolt at the same time, there's the potential for full auto with a bit of fiddling
Isn't there then a good possibility less than all of the air inside the piston would be used to propel the projectile? Certainly a good full-auto design, but wouldn't it be decidedly lacking for semi-auto?
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Unread postAuthor: ByeBye » Mon Nov 29, 2010 1:22 pm

How about this?
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