Mechanical timed close trigger-valve for an air(soft) gun - project

[Swatti]

Excuse me my poor English and total lack of knowledge of the matter. I may lack some correct terms and names.

Whatta heck is airsoft? Google it. Longer answer: kind of a sister-sport to more known "paintball"
While paintball is competitive sport, airsoft is more of "military simulation" and aims for realism... Or Rambo'ism.

Now, to the point. I need a valve for my project.
Skipping useless details, the idea is to shoot a 6mm plastic pellet using air. The weight of the bb is mere 0.2g
I have a HPA-bottle regulated down to 300psi and an adjustable regulator able go down to 10psi or so.

What I need is a valve to tie to the trigger.
Once pressed open, the valve needs to close soon after regardless of the button to open it being pressed. Aka: resetting itself.

It also needs to be mechanical. The entire gun is single shot hand-loaded "bolt-lock" so no fancy electrics or batteries for this.

Since the very low weight of the pellet the valve needs to stay open mere milliseconds but the amount of air it passes thru must be consistent.

Im not even sure what the actual name for such valve is so my searches have come empty.

 

[berkshire]

Go buy an airsoft pistol and reverse engineer it.
B.E.

You are judged not by what you know, but by what you can do.

 

[gerhardl]

Search for 'air gun trigger mechanism picture'

 

[Swatti]

I have fifteen years of experience upgrading and maintenance, even a small business doing tune-ups for airsoft guns.
If there was a system that worked here, I would have used it. There isn't.

Airsoft Pistols are eighter electric, motor driven piston. Gas-operated, using expanding gas like Co2 or single shot spring-loaded.

"airguns" are mostly spring-loaded or Co2 with spring-loaded hammer striking the valve for momentary open.

This is an entirely new system. This is combining different components from airsoft and partly paintball. Sadly there is no existing setup that has parts I need.

So please. Answer the question.

 

[gerhardl]

You are obviously very familiar with similar mechanisms. I have problems defining why this could not be adapted to your system, but can imagine that the combination of a consistent, repetitive defined volume/amount of air with (implied) constant pressure is the problem. This would be very difficult to keep constant with one single valve mechanism drawing from a larger volume.

Question/suggestion: What about a two-step combination?

Step 1. Presume the volume needed for a series of shots is in a main tank, large enough, or arranged/fed in such a way that the pressure is kept constant/large enough when drawing volumes for the shot series to not give significant variation. The mechanical bolt-loading action to be connected to a valve opening and closing to feed a small second tank, filling it for the amount for one single shot. Could be a spring-loaded push button valve.

Step 2. 'Standard' mechanical trigger-release of the volume in the single-shot tank.

Good luck!

 

[Swatti]

Secondary tank is only needed with Co2 setups to stabilize the pressure. Aka "expansion chamber"

With high pressure air it's simply not needed.

I just need a valve that shuts itself after its been opened. Can't be that hard?

 

[gerhardl]

Hello Swatti,

Please give air pressure (high???) and your best guess at free opening area. And yes, it could be simple, but others need to know as much as possible of all technical limitations. Milliseconds, 4 or 400? Amount of air? Etc? I will give it a try again with what I have at present

 

[gerhardl]

Below will give you an idea of what is available commercially. A lot of companies can supply similar valves. Even so-called 3/2 versions might be sensible to check.

http://www.parker.com/literature/Literature Files/IHD/MVsection.pdf

 

[Swatti]

Air pressure (Estimate) between 10 and 100 PSI - Adjustable via regulator, will determine power & velocity. I will use a choronograph to test and set the power according to our rules.

Valve needs to stay open only few milliseconds. Most important is the self-reset/automated close and consistant amount delivered.

 

[gerhardl]

Hello again, Swatti!

I believe that the valve you are searching for is not a common produced valve product. You would probably have to talk to producers with similar products, or invent one yourself. I also believe that even with a strong spring return action that 'a few milliseconds' could be a problem to obtain. Perhaps the real time needed is somewhat longer?

The nearest commercial I have found would be something like the link below, but I haven't checked the detailed information here, and price would probably be high compared with your total product cost target. Perhaps details about inner construction could help you?

http://www.fmctechnologies.com/en/FluidControl/Technologies/Invalco/MicroValves.aspx

 

[Swatti]

Is the "Few milliseconds" too long or too long?

Im willing to leave that out if i must.

MAIN PRIORITY is to get exactly the same amount of air thru each time the valve opens AND then auto-close, by nature it would have to auto-close on its own if the amount passing thru is limited.
By my estimate, increasing the pressure lets more air thru before the valve closes, thus letting me adjust it one way or the other.

Consistency. Its where it comes down to.

Price-wise im hoping to stay with made-in-china stuff UNTILL i find out what works, then im willing to invest a bit more on quality part. The budjet is fairly open, alltho it would seem silly to spend lots on single part when most of the gun is made from scrap, literaly.

 

[gerhardl]

Hello, Swatti!

OK. Consistency was what gave me the idea of two-stage release.

If you fill a smaller 'charging' chamber with consistent air pressure and releases all, you have moved your calibration from the timing and calibrating of the release valve. The loading of the charging chamber is un-depended of the later coming trigger action.

If you release all air the air in the charging chamber the amount and pressure will be constant, and you only need a release mechanism that is 'fast enough' and perhaps can be adopted from existing solutions.

Hope you find your solution, I do not think I can contribute with anything more than I already have done.

Good luck!

 

[berkshire]

Swatti

What I need is a valve to tie to the trigger.
Once pressed open, the valve needs to close soon after regardless of the button to open it being pressed. Aka: resetting itself.

I think the term you are looking for is " Pressurized Breach " . This system is used on some spear guns for Scuba diving.
A chamber is pre pressurized, then when the trigger is pulled, the pressure is released to the barrel by a second valve.
B.E.

You are judged not by what you know, but by what you can do.

 

[Swatti]

Is there a "pre-built" two-stage system or something like that "pressurized breach"

I was hoping to minimize the amount of components but I can adapt if need be.

 

[3DDave]

Seems like a fuel injector would work with a timing circuit to control the duration. Use a 555 one-shot circuit and a pot to control the duration.