Old is the new Pneu. Project/Design 56K beware

[Foughtwolf]

Hi all- Im still new here so I dont have much to stand on, so lt me introduce myself in a more full manner as an lead in to the below project.

My name is Landon Collins, otherwise known by my online handle Foughtwolf, and among other things I have a passion for design. Over the last couple of years through the use of Google Sketchup(Because I am too poor to get Solid Works currently and took to Sketchup like a duck to water.) Ive begun working on a number of different designs, primarily revolving around paintball and real steel- both of these when combined have actually proven quite useful for my current project depicted below in its infancy.

The Goal: to create a electro pneumatic airsoft rifle; This is not new territory Im aware, Polarstar beat me by a few years but I find their price outrageous- but thats just my personal opinion on the matter. The true goal however is simple, design and produce or market a design that tips the scale at half that of the Polarstar Fusion engine.
Impossible? Far from it. Easy? Now thats the million dollar question.

Lets start; Heres a mess of parts I imported from past projects and ongoing ones, mostly real steel stuff pulled off my pet project the Liberty Rifle.

Depicted: A mess of parts.

But whats that wee little box down to the right hand side? Lets take a closer look shall we?

Oh, its an AEG cylinder and nozzle of some kind-right?

Now Im just confused, whats that thing running down the center?
Allow me to show you.

Thats...helpful?
Let me cut the whole thing in half

Better?
Maybe- I see lots of o-rings and a spring?

Yes, now lets delve right into it and give you all a good explanation as to just what you are seeing and how it functions. Lets remove the o-rings and spring briefly to clear up some of the clutter, and add a dollop of paint so we can identify each part.

Thats better: Here we have the bolt,chamber, and guide rod.
Please note that because the spring return is very new the chamber hasnt been stretched enough to allow for the compressed spring, just an oversite for now as i determine if I wish to keep a spring return or go for a different solenoid setup like I had planned originally but cut for the simplicity of a spring.

Above we see the bolt has been forced forward to the end of its travel by the solenoid impulse of air (either from a dump chamber or the solenoid itself if there is enough volume and pressure for the relatively small object airsoft gunsfire, im not great at that kind of math.) and the ingress of air has filled the rear of the chamber, forcing it forward past the inner seals on the guide rod, at which time it vents down the hollow bolt and propels the BB down the barrel. When the air pressure behind the bolt has lowered enough for the spring to overcome it, it will be pushed backwards once more into its resting position, ready for the next impulse from the solenoid to fire again.

Now do bear in mind this project has only been going on for the past month at best and only taken priority in the last week or so. The reason I show it is because I want the input of players who have more experience than I. Community participation has always been key in all my designs because I find that there are always those with more knowledge out there who are willing to help.

[j man 3]

how are you going to set up the timing?  (How long the bolt will be open per PSI of air form the solenoid?)

[Foughtwolf]

Well in the above design its a little limited in dwell time because its not completely controlled by the solenoid and air- theres the spring that will eventually overcome it. Its not that bad though as FASOR(Froward Air:Spring On Return) has been around a long time and its usually not an issue.

That being said I realized that given the small size, it would be rather hard to use a spring light enough for such a small amount of air to overcome and still reliably return the bolt to the rearward position. Right now Ive added a dedicated dump chamber behind the bolt with a tail on the bolt that seals it until the impulse from the solenoid pushes the bolt forward- allowing the seal between chambers to be opened and let the chamber empty down the bolt. Im kind of resticted on how large i can make the chambers currently because I dont have a gearbox to measure at the moment- something I intend to remedy soon enough.

[Blue1]

where are you getting your pressurized air from? a hpa tank or the solenoid? the reason I am asking is generally air actuated solenoids use very small amounts of air. You need the volume of air coming out of the nozzle to at least match the volume of air inside the barrel otherwise you will get bb's that roll out or jamb. Also with the bolt pushing that far forward you will need to set the barrel forward more if you are to use standard aeg mags otherwise the bolt will hit the hop up nub. Sorry if I am re stating something that you have already thought of but the description left me wondering.

[Foughtwolf]

No no, you didnt repeat anything nor would I mind if you did! The whole reason I posted this so early was to get input from those more knowledgeable than myself.

I need to update the photos but since I havent I'll just tell you, I rebuilt it into two separate chambers, a dump chamber for volume sits behind the main one, with a sealed tail on the bolt keeping the pressure back. When the solenoid impulse dumps air into the rear of the bolt chamber it pushes the whole bolt forward, the dump chamber seal disengages and dumps its volume out down the spine of the bolt, firing the BB.

As for hopup interference, I dont think it would be an issue, at the most it moves about .300 back and forth overall, and the whole thing could simply be set back somewhat in order to allow for any of those issues.

My only current worry is how small everything is, Im not entirely certain that the bolt would be able to withstand the forces its put under for extended periods due to the design and its small size. im thinking I might redesign it or perhaps make it larger overall once I have a gearbox I can measure out and mock up for size reference.