SpudFiles

This is directed at the 3 way valve makers, Do you think a homemade 1/2 DCV would have enough power itself to propel a .25g airsoft bb at say..... 500fps? I mean no piston valve at all just the 3 way itself at a pressure of 200psi?

TBH i don't have any experience with 3 way valves and semi auto so i was just wondering.

Hope you can help.

I don't see why you would use a 3 way for that, you would ether have air constantly flow to atmosphere and when you trigger it would go to your barrel or the other way around. All you need is a two way valve like a blow gun or even better a pressure washer handle. And yes you could get 500fps with a long enough barrel.

edit: Wait, If you put a small tank on your 3 way then it would work, i dont think you would get 500fps tho.

if you make the 3 way big enough you can get that kind of velocity if you can push it open fast enough. this would also require a larger tank.

the much better option would be to put a qev or piston valve on it. more power and less air used

it is very difficult to say whether or not it will give you 500 fps. This is because in an ideal world with zero valve opening time and 200 psi, you would get over 500 fps.

The problem is that all valves that I know of other than burst disks take time to open and allow maximum flow. this causes the projectile to start moving in the barrel before the pressure reaches its maximum, which means your projectile isn't accelerating at your desired rate for the whole barrel travel, giving you a lower velocity when the bb exits the barrel. if your valve is dependent on the speed of your trigger pull then the velocity will most likely be very inconsistent and possibly quite poor depending on the quality and size of the valve and its vents.

My suggestion would be to use your homemade 3-way valve with a quick exhaust valve, information on this is readily available. My other suggestion would be this: http://www.spudfiles.com/forums/valvele ... 21143.html

qwerty wrote:I mean no piston valve at all just the 3 way itself at a pressure of 200psi?

That would be using the 3 way valve as a piston valve.

If you want to build a 3 way as a main valve you have to do some changes in the design.

For example, this is a design of a repeating 3 way valve that I have in mind at the moment.



Actually you can't call it "3 way" anymore but it is based on the same internals as the homemade ones, with one little change. To make it a repeating valve the surface area in the middle is smaller than the areas left and right.

What happens...
1. In closed position the surface areas left and right are balanced and the middle is open to fill the chamber.
2. The valve is opened by a strong spring, the middle closes to cut the air supply from the fill chamber, the valve fires. Now the chamber is emptied and the valve is out of balance due to the area differential of the left and the middle part -> the valve resets.

I don't see why you would use a 3 way for that, you would ether have air constantly flow to atmosphere and when you trigger it would go to your barrel or the other way around. All you need is a two way valve like a blow gun or even better a pressure washer handle. And yes you could get 500fps with a long enough barrel.

I would use MRR's design though, i'm not to fussed about power but i just want semi auto.

Thanks guys for your thoughts anyway.

Do you think a homemade 1/2 DCV would have enough power itself to propel a .25g airsoft bb at say..... 500fps?

If I were you I'd just buy a 1/4" indirect acting 3 way valve and use it as the main valve. Why indirect acing ?? well because they have a small inbuilt valve that pilots the main spool/poppet... thx to that fact its opening time is pretty fast


P is where you attach the air source, A is the chamebr and Ex A (R) is where you attach the barrel

add an airsoft hop-up unit and voila ! you've got a semi... if the valve is a solenoid valve you might as well add a time relay and now you've got a full auto/semi auto gun with adjustable ROF

Now that would be perfect but i would never find a retailer of one of those in the UK.

I am sure someone from the UK can find a better shop, but have a look here http://www.pneu-store.co.uk/index.php?o ... 8&Itemid=2

also it might be a good idea to check ebay
http://cgi.ebay.co.uk/Festo-Air-Pneumat ... ltDomain_3 (It's probably 1/8", 1/4" would be better)
http://cgi.ebay.co.uk/Pneumatic-Valve-S ... ltDomain_3 (not what you should be looking for but it's pretty cheap )

http://cgi.ebay.co.uk/Pneumatic-Single- ... ltDomain_3 (it's 5 way but it will do)

Hmm they look Fine to use but look at the price! those would cost me 1 1/2 months of pocket money to buy it

Ideally i would like Clippards 1/8 MJV-3. I found an American site selling it for $12 which seems reasonable but i don't know how much the shipping ect. would add up too.

I am sure you can find something cheap on ebay

lol look what I found -> http://cgi.ebay.co.uk/Powerstar4-Air-am ... ltDomain_3

I bought my all of my DCVs, incluning the 3/2 solenoid valves, from the UK, ebay mainly. I think I got both of them for £12 inc postage. And I've seen them go for even less.

Ok Ebay it is, but do you guys have any ideas on what i should actually type in?
I've tried "directional control valve" "3 way valve" "3 way solenoid"

But these haven't come up with any decent results.

EDIT: could someone explain the difference between indirect and direct acting is?

what I should actually type in

try 'solenoid valve'

it's in the sticky I posted on them...
anyway, I already explained it in this thread... the indirect acting valve has a small inbuilt piloting valve that switches (pilots) the main spool/poppet

in the direct acting valves the actuator are mechanically linked with the spool or poppet... so in other words the spool will only move as fast as you can press the button, lever, the armature moves etc.

I found that direct acting valves handle high pressures better then indirect acting valves (of course if we are talking about stuff rated to 10bar max... there are probably some high pressure indirect acting valves). On the other hand, indirect acting valves switch faster and their flow is usually higher (most high flow solenoid valves are indirect acting valves.... becasue it takes less power to actuate a small pilot valve first than to move the whole spool)


Damn, everything has already been explained at least a hundred of times. You could have used google to check that....
Anyway I guess I should follow this guy's advice
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