Semi-auto airsoft gun - pneumatic cylinder as air chamber

[piotrekwyso]

Hi! I am Piotr and this is my first post on SpudFiles.
I am building semi-auto magazine-fed airsoft rifle with hop-up. I have recently came up with an idea of using pneumatic cylinder for reloading and as an air chamber.
I have question, whether will it work good or not? and what is recommended air chamber volume. I am using 10 bar air supply and 6mm BBs.

Here are some videos that may help you understand what I mean:
(Around 4:15)

[jackssmirkingrevenge]

Welcome to the forum!

What is it with Poland and pneumatic cylinders...

http://www.spudfiles.com/pneumatic-cann ... 20259.html

what is recommended air chamber volume

GGDT is the best tool available to determine such parameters. I suggest you download it and don't hesitate to inquire on the forum if you need help using it.

I have question, whether will it work good or not?

Assuming the "Trigger valve" is a three-way valve that cuts off the air supply and simultaneously vents the QEV pilot chamber, it should work well.

How are you actuating the cylinder? It would be interesting if you could tie the cylinder with the pilot volume, for example the pilot pressure keeps the cylinder in the "closed" position, so that venting the pilot simultaneously opens the QEV while also opening the bolt. The trick would be timing it so that the bolt is not open before the BB has left the barrel...

[piotrekwyso]

Well It may be not quite visible on my drawing, but bolt is open and cylinder is retracted (no pressure) the other end of cylinder is sealed, so it acts as natural spring retracting cylinder. When it is connected to air supply, it will extend pushing qev and nozzle with bb into barrel and nozzle will be pushed into bucking sealing bb ready to shot.

I do not worry about cylinder retracting too soon, because from what i have calculated, bb will exit the barrel in around 0,03 s (550-600 fps estimated). I will maybe put some spring physically retarding bolt opening.

Many thanks for advice and reccomending me this program. As soon as I get home, I will try to calculate this volume, if it happens to be too small, I will have to redesign a little bit my model.

I will make an update around tuesday when all my parts are shipped

[jackssmirkingrevenge]

Well It may be not quite visible on my drawing, but bolt is open and cylinder is retracted (no pressure) the other end of cylinder is sealed, so it acts as natural spring retracting cylinder. When it is connected to air supply, it will extend pushing qev and nozzle with bb into barrel and nozzle will be pushed into bucking sealing bb ready to shot.

Ahhh I understand it now, the air cylinder is also the firing chamber! It was your post title and I didn't catch that, apologies!

That's very clever, given the relative weight of the chamber assembly vis a vis the BB I think it will be out of the barrel long before the nozzle disengages the bucking.

[piotrekwyso]

This project hasn't died yet!
So I've got all the parts and I've succesfully built my makeshift-hpa-engine which, to my suprise, works quite well.
I've got pretty consistent 300-350 fps at around 4 bar. I haven't checked max fps at 10 bar yet, but I'm doing it tomorrow and I am quite sure it will exceed estimated 600 fps.



The thing with pneumatic cylinder acting as a chamber and bolt at the same time worked ad seals well, even at full-auto.


I want it to have select-fire so I've bought 3/2 NO 12V DC solenoid. I plan to use it as my pilot valve and it would be activated via a microcontroller of some sort. I've seen other select fire projects using Arduino nano, but it provides only 5V output. Should I use some transistors or something? I can do the programming needed, but I don't know a thing about electronics so can somebody help me with all that electronics stuff?
Thanks in advance.

[jackssmirkingrevenge]

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Looking good!

I want it to have select-fire so I've bought 3/2 NO 12V DC solenoid. I plan to use it as my pilot valve and it would be activated via a microcontroller of some sort.

For full auto you could achieve it with a simple 555 Timer, an arduino seems like an unnecessary complication.