SpudFiles

What I want to show you here is a pneumatic timer circuit... the circuit is basically a DCV (direction control valve; often refereed to as a 3 way / 5 way valve or a spool / poppet valve) that switches automatically from one position to the other...

The circuit has all the basic advantages that DCVs have when used as a piloting valve for QEVs. The most important is of course the fact that they cut off air supply when piloting the gun.
Additionally, it can be made fully adjustable - with the use of flow restriction valves (needle valve) (or by increasing the volume in between the timer valve and the needle valve)

The circuit can be fitted in place of any DCV used to pilot QEV/piston gun in a matter of seconds and it allows to achieve fully automatic fire. Of course it can be used for other stuff as well: to cycle a single or double acting air cylinder or to build an automatic meter on a combustion gun


I've ordered one of these

Technically, it's a time delay valve... it switches after an adjustable time delay once there is pneumatic signal at their pilot port (so it's a pneumatically actuated valve - you send air to its 'pilot' port to switch it)

if you need more detail it's a monostable valve with spring return... air enters through one port and then through a needle valve to a small volume chamber (which is used to slow down the cycle) and then acts directly on the spool/poppet and once a given pressure is reached it switches it... as soon as the air in it's pilot side is vented spring return switches it back to the previous position

READ THE COMMENT -> the valve I mentioned in the above paragraph didn't work... because it didn't work the way it should - that is, it was a normally closed valve but it should be a normally open valve (or one that can be both a NO or NC valve). I should have made sure it's a NO valve but I didn't - and it turned out it can't be converted to be used as a NO valve

Time delay valves are normally used when there is a need for a given time delay between the signal sent to it and the actuation of the valve (in this particular model you can adjust it between 0-10 seconds)

However, I want to use this valve to build a pneumatic timer circuit that switches the valve from one position to the other automatically in a loop.

In other words, when air is supplied to the circuit it flows through the valve and then via a T supplies both the QEV/piston valve/whatever-you-want-to attach-to-it and the piloting port on the valve itself...

after an adjustable time delay the valve will switch - and vent both the QEV/piston valve/whatever-you-want-to attach-to-it and its piloting port... once the piloting port is vented the spool/poppet returns back to its starting position and the whole cycle starts from the very beginning


there are ready made valves that offer the same function as I want to achieve with this circuit. You can also build a similar circuit with just a pneumatically actuated valve (but then you need to add a flow restricting valve to it)

Pneumatically actuated valve is a valve that switches thx to air supplied to its pilot port. Pressure acts on the side of the spool and exerts force on it that actuates/switches it. That's exactly the second valve I used to test this idea and it worked. Note that these valves are generally cheaper and easier to find than delay valves


there is one additional advantage of this design from the point of view of a spudder, apart form the fact that it offers advantages of DCVs on QEV/piston valves and allows to achieve full auto.

The whole system can be controlled/triggered by a simple two way two position valve (a blowgun, small manually actuated DCV, ball valve) that does not have to be close to the QEV and the timer circuit. Normally you would have to have the piloting valve close to the QEV/piston valve in order to reduce dead space and pilot them fast. Here the circuit is mounted directly on the QEV but it's controlled by opening the valve that supplies air to the circuit... so as a result the triggering valve can be placed anywhere on the gun (or even away from it)

EDIT
ohh dammit
it hasn't arrived yet, since there is no way that the design won't work (as it's used in pneumatics all the time) I'll update it once I get the part... sorry I don't feel like writing it all over again

EDIT
I've got it today... it does work as a delay valve but so far I couldn't get it to cycle properly...

EDIT ( 4.12.2009 )
I added comments (in darkred it's hard to miss it) that should help to avoid the problems I encountered
I also corrected the diagram and updated its comment

Looks promising. You should post a build log as you go.

today I got the valve but so far I couldn't get it to cycle properly...
the valve works perfectly as a delay valve (so for example I can use it to extent the air cylinder after 0 - 10 second after supplying air to the valve; there is also one port that can be used to expand the chamber and thus get even longer delay)...

as you can see the valve is really large and it has a really interesting design (I've dissembled the valve to find out what the problem is and out of curiosity)
of course there are smaller delay valves out there - for example clippard's PV-1 (p. 165 in their catalogue... it's like.. hmm 4-5 times as small as the one I have).

now... why it doesn't work the way it should...
the circuit doesn't work because the valve stops in between one position and the other... maybe I'll just say what happens....

air is supplied to port R (see pics) and it flows both to the pilot port and to the part I want to pressurise (I've tested it both on a QEV gun and an air cylinder).... after a set time delay the valve almost switches... some air leaks through both ports (A and P)

any ideas why does it happen? and how to fix it?



also, isn't it that air should be always supplied to port marked as P ?

I think that might be a problem as air source acts on the bottom side of the spool when it is supplied via port R

well anyway if you have any ideas why it doesn't work I would appreciated if you post them...

I am 100% sure that a timer circuit can be built with two such valves but obviously I would preffer to get it to work with just one valve as having to use two increases costs, size and complexity...
sure... weight wouldn't be such a big deal if I had PV-1 but I can't get them in poland

Well here's a good idea I forgot about! I'm very interested in what you're working on. Unfortunately I don't have much time to say more than this right now. I'll resurface more active in a few weeks.

Maybe it only cycles with enough pressure differential. Shouldn't one port vent to atmosphere or something?

it works!!! muhahahahaha!!

today I was trying to get this thing the circuit to work when this arrived...

well I bought it just in case the circuit won't work with just one valve... as you can see it's just a 3 way air piloted valve (not a proper time delay valve as it doesn't have an inbuilt flow restricting orifice/needle valve; also as yo u can see it's pretty old - it was produced in early 1990's in poland)

well guess what.. it does work with it.. no need to add more valves
.. I quickly built the circuit with it and supplied air to it... and it works!! at first the cycle time was way to high (sounded like 30 - 50hz to me)... unfortunately, I don't have a needle valve so instead I used 15m of 4X2mm poly amide tubing to cause air restriction and now I get about 1.5hz cycle... so this thing is fully adjustable

my guess is that BOSCH 0820215003 valve didn't work the way it should because its construction can only accept air via port 'P'

I'll add a video ASAP

sorry but for some reason it takes ages for me to upload even smallest video files on youtube... so I had to sped up some parts of it and I reduced quality

[youtube][/youtube]

here you can see the valve filling and venting an aircylinder... of course, I've tested it with a QEV gun as well... I used the longer lenght of tubing to casue flow restricion to bring ROF down...

sorry as I've mentioned eariler I don't have a needle valve (for some unknown reason I couldn't find ones for 4mm OD tubing)



IDK if you are aware of it but IMO opinion it's a great step forward... the circuit does work with just one air piloted valve and it's adjustable...


let me compare this circuit with the pop off design that's thought to be the only way to achieve full auto with a QEV gun...
so, from my perspective and according to my knowledge the circuit has the following advantages over the pop-off design:

-saves air
-it is fully adjustable
-it can be almost as compact as the pop-off valve
-its price is comparable to that of a pop-off valve (air piloted valves are common - quite often they are cheaper than comparable manually actuated valves)
-it isn't much more complicated - you need just aneed the valve itself, a couple of fittings and a 2 way valve (so for example a blowgun) to trigger it
-the circuit and the valve itself can be used without a QEV... of course you'll probably need at least a 1/4" ported valve to get an acceptable performance with bbs but I've seen quite a lot of 3/8" or even 1/2" air piloted valves sold for a couple of bucks


any comments, ideas, questions ?

So I no longer have the monopoly on jackhammers then

Sweet, so we'll be seeing a proper auto from you soon?

I'm jealous. Really.

You should stick "Full-auto QEV gun" in the title and the views of this thread will increase exponentially.

The only project in my sights over the next few weeks is a Nerf gun... will I go with full auto? I don't know yet, but this is awfully compelling.

the first real test will probably be carried out when I finish my semiauto MKIII... I am still waiting for the machined T to arrive ( and no I don't mind waiting so long - actually, I've had quite a lot of things consuming a lot of my time for the past few months so for me it's even better)... I'll jsut have to unscrew teh manually actuated valve and replace it with this valve/circuit

It has been proved that DCVs can be used to achieve semi-auto with a QEV gun. It also has been proved that full-auto QEV guns can be built with a DCV as a filling&piloting valve controlled by a timer. However, back then I used an electronic timer so that resulted in increased complexity.
Naturally, building a fully pneumatic timer circuit/system was the next step...

well I must say that I expected this thing to work (but on Monday, when the valve I ordered failed to cycle I really regretted that fact that I wrote 'there is no way that the design won't work' )

so... to sum it up, the thing works as expected with a qev gun (I'll add a video soon) and it's fairly simple to build and implement it...

but the biggest problem in building a semi or full-auto gun is reliable feeding... the previous versions of my semiauto suffered feeding problem caused only by my own poor building skills... the design was sound

on the other hand, performance problems were caused by the improper choice of valves (both the main valve - 1/2"QEV for 16mm barrel; and a DCV that couldn't handle high pressures due to inherent characteristics of its contructon), ammo and, partly, also my poor building skills

I really hope I'll manage to finally finish my semiauto project as I am pretty much tired of it (as it's 2 or 3 years old)

and I hope you'll find this thread and idea useful... lol I've just noticed that I tend to write looooooong boring responses when I am tired... I wonder if BTB will edit small font?

POLAND_SPUD wrote:but the biggest problem in building a semi or full-auto gun is reliable feeding...

Don't we know it :-/ well, let's face it, spring loaded stick mags as used in the caselman would seem to work well enough...

[youtube][/youtube]

sorry but I didn't have time to post it yesterday
as you can see ROF is affected by chamber size but it was expected so there is no need to comment on that...

what you can't see is that ROF is also affected by varying the dlow of air into the circuit...
the video was taken in my house and air was provided from my fridge compressor via 10m lenght of 4X2 polyamide tubing which restricts flow a lot but when I tested the same setup connected to a regular airhose that offers much higher flow the ROF was much higher

in other words, if you reduce flow of air to the circuit you can bring ROF down... the best part is that single shots are possible...

with a blowgun as the triggering valve you could probably have a trigger system similar to the one used on steyr AUG....
trigger pulled half-way -> single shot
trigger pulled all the way -> full auto at the highest ROF


lol now I hate myself for not having one of those cheap flow restricting fittings

Awsome..

every now and then a very good idea comes along and this surely revives the full auto quest!

That's a very promising mechanism!

I had some time today so I quickly put this thing together...

[youtube][/youtube]

just to clarify:
this valve is a 5 way valve so it's bigger than it should be and there are way more tubing&fittings there than you really need... also the pressure used here was probably around 50 psi (lol that was shot at 4AM in my basement so you can guess why)

notice that the valve isn't even directly attached to the pilot side of the QEV.. instead there is a couple of cm of tubing between it and it's attached to the 3 way valve that's already on the gun


also I realized that I wrote way too much text in this thread which made it seem more complicated than it really is
so just to summarize.... this whole design comes down to:

1. get an air actuated 3 way valve and attach it to the pilot side of the QEV
2. get a needle valve and connect it with the piloting port of the 3 way valve
3. join the chamber side of your gun with the needle valve (which is already attached to the 3 way valve

ohh BTW I just put a 1/8" QEV on the piloting side of the MKIII and all I can say is... damn this works the way it should and helps a lot

also I found a way to attach the cam directly to the gun... lol pneumatic version of the land warrior...
hmm I wonder how would it work at longer ranges?