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Will a pneumatic cylinder keep up?

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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Will a pneumatic cylinder keep up?

Unread postAuthor: inonickname » Thu Jul 16, 2009 4:12 am

I've finally decided on the configuration for my nerf rifle.

Open bolt, magazine fed (no carts), QEV actuated, 400 psi op. pressure, switchable between semi and full automatic, pneumatic cylinder to close the bolt.

My plan is to use a pneumatic cylinder to close the bolt before the qev actuates. I'd like to be able to use the pilot gas from the QEV to actuate the cylinder. The problem is, it needs to move over a range of 2" to seal the breech before the valve actuates. I feel that this wont work because the qev will probably fire before the cylinder has closed the breech.

Any thoughts? Is there a way to force the cylinder to close before the qev can open? I can make a blowforward bolt, though I'd rather not.
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Unread postAuthor: POLAND_SPUD » Thu Jul 16, 2009 5:32 am

I don't think it will have enough time to close... on my semiauto the bolt starts to open when I vent the QEV... the cylinder doesn't have enough time to open before all the air form the chamber is out...



I like the idea to use a pneumatic cylinder but I don't think you already know how it is going to work

why does it have to close when the gun fires ?
you could use the same design as I used on my semi auto

a 3way valve is all you need... basically, it's a closed bolt design:
the gun reloads ammo when the chamber is being filled and it is held shut when you pilot the QEV

what pilot valve do you plan to use ?



now this doesn't have anything to do with this thread...

I've been thinking of combining the valve on the marshmallow gun with an aircylinder... the idea is quite simple: instead of opening the valve manually an air cylinder does it... the air cylinder is hooked up to the chamber and there is a small valve in between (for example a blowgun)...

when the valve is opened the air cylinder retracts and opens the piston valve...
the cylinder is vented as the gun fires because it's hooked up with the chamber (and because the shot takes only tens of miliseconds when the valve is still open)...
a strong spring returns the piston back to the closed postion...

the piston of the marshmallow valve could be joined directly with the bolt/loading mechanism

so what do you think of it ??
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Unread postAuthor: spot » Thu Jul 16, 2009 5:35 am

What's wrong with a closed bolt system? That way you won't waste any gas actuating your cilinder ;).
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Unread postAuthor: inonickname » Thu Jul 16, 2009 5:39 am

Edit: @ spot, I changed my mind to a closed bolt system which will work better. The original idea was to recycle exhaust gas, but this will work so much better. And anyway, closed bolt is much cooler.

Uhh duuhh, I feel like a retard now.

I thought of a closed bolt but not in such a simple way.

Fill chamber, pressure overcomes spring which closes bolt, fire, chamber is empty, spring re opens bolt, round chambers, fill, bolt closes.

^ That's it..

In fact, that's perfectly suited seen as it will have a constant air source through a quick disconnect. It might be less compatible with a pop off automatic system but meh..

Thanks for the input. About your gun, could you provide a link?

Going to mill a magazine next week, and pick up some telescoping tube and round foam next time I'm in perth
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Unread postAuthor: POLAND_SPUD » Thu Jul 16, 2009 5:49 am

http://www.spudfiles.com/forums/i-has-s ... 16872.html

the gun is a bit more complex because I decided to use a 5way valve that I had at hand (so it wastes some air just for operation of the cylinder)

I must say it eveoled quite a lot but I am still working on it though..

the previous version worked but the flow-through bolt chocked the flow so it wasn't as powerful as it could have been... now I am working on an improved version and I am close to finishing it it (if I move my lazy ass to my basement to finish it :D )
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Unread postAuthor: 30cal man » Thu Jul 16, 2009 9:55 am

let me know if this works i built a qev gun a while back and i had an idea simulair to this but a little more complex and when i assembled it the chamber was too big and didnt completly empty which inturn did not allow the air cylinder to move anyhow oh and by the way to get a increased responce time for your air cylinder place a qev on it clipperd and bimba both sell them as well as www.airsoldier.com if you go to air soldier anyone email the guy before you order it says that somehwere on the site i did that and i got all that i orderd fast good luck looking forward to results
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Unread postAuthor: POLAND_SPUD » Sat Jul 18, 2009 10:41 pm

uhmmm I've found one of these -> http://www.zorin.pl/okno_produkt.php?pr ... 2=&d3=&SA=

you might ask 'wtf is that?!"
well it's a 'thingy'.... it has an inbuilt 5 way valve... when pressure is present at port 'x' the valve automatically switches from one position to the other with an adjustable delay...

you could use it to make sure that the air cylinder moves a fraction of second before the QEV fires...


of course there is no point in incorporating this because it increases complexity and anyway a closed bolt design is simply superior

however, you can use one of these -> http://www.zorin.pl/okno_zalacznik.php?nr=3459 to turn the design I used into a full auto gun without using any electronics

or this -> http://www.zorin.pl/okno_zalacznik.php?nr=3351 but it will only work if you don't see any point in using a double acting pneumatic cylinder (it's just a 3way valve that switches from one position to the other with a delay of 0.2 seconds)


lol I just wanted to share it with you... out of the things I provided links to the last one seems as the most useful one... both for you and for others
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