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Directional Control Valves (3way valves and stuff like that)

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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Unread postAuthor: JDP12 » Mon Mar 29, 2010 1:31 pm

Wow thanks for this Poland-- its been very helpful
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Unread postAuthor: POLAND_SPUD » Mon Mar 29, 2010 3:18 pm

@Mrcrowley
Wonder if that is for a different type of actuator
in order to cut costs most of valves have the same main valve housing for all the different models... but they put different actuators on them...

and by 'actuators' I mean those small rectangular thingies on both end of the valve housing... (so these things are not only actuators like: air pilots, levers, buttons but also springs for spring return)
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Unread postAuthor: irisher » Mon Mar 29, 2010 3:55 pm

Well I just bought mine last night. (Direct acting 1/4"NPT) and I think this thread has been very helpful.
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Unread postAuthor: JDP12 » Mon Mar 29, 2010 3:59 pm

Quick question about mcmaster DCVs...

The following is how they describe it:

Choosing the Right Control Valve— Sending air pressure to the right place at the right time and then exhausting that pressure when it's no longer needed is a control valve's job. Here are two of the most common styles of control valves:
Two-Pressure-Output (4 Way) Valves— With two pressure output ports, you can use these valves to control a double-acting cylinder, which requires pressure to extend and retract the cylinder rod.
Single-Pressure-Output (3 Way) Valves— With a single pressure output port, you can use these valves to control a single-acting cylinder, which requires pressure to extend the cylinder rod while an internal spring retracts the cylinder rod.
To Operate Control Valves— Use pedals, knobs, and levers to manually operate your control valves. Use rollers and electric solenoids to operate control valves in your automated systems. Electric solenoids will allow automation with computers and programmable logic controllers (PLCs).
Air Flow and Coefficient of Volume (Cv )— Coefficient of volume is a measurement that indicates how much air flow a control valve can provide to your cylinder or component. The higher the Cv value, the higher the air flow rate. Looking at valves with the same port size, but different Cv values and not sure which one to choose? Select the one with the higher Cv value because low air flow can slow down your entire system.


Sorry, just not understanding their explanation very well.[/quote]
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Unread postAuthor: POLAND_SPUD » Mon Mar 29, 2010 4:09 pm

4 way valves are similar to 5 way valves... 5 way valves are like two stacked 3 way valves... so you can use them to fill/vent two outputs at the same time... when one port is pressurised the other one is vented

the only difference is that 5 way valves have two exhausts while 4 way valves have only one

it's explained in one of the links on the 1st page (the one with animations)

5 and 4 way valves might be useful if you want to control a double acting cylinder... also if you want to use a double acting cylinder to build a gun using the same design as the semiauto
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Unread postAuthor: MrCrowley » Mon Mar 29, 2010 4:44 pm

in order to cut costs most of valves have the same main valve housing for all the different models... but they put different actuators on them...

and by 'actuators' I mean those small rectangular thingies on both end of the valve housing... (so these things are not only actuators like: air pilots, levers, buttons but also springs for spring return)

Yeah I thought so. I'm thinking I can use the threads to srew in a bolt of some sort that I can use to trigger the spool instead of the push-button.

I'll have to test it out first, I only have one 1/8" male fitting in my box of fittings haha so I probably can't test it for a few days (already put air through it and triggered it, but I mean test it on a gun).
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Unread postAuthor: POLAND_SPUD » Mon Mar 29, 2010 5:17 pm

heh yeah at first it's difficult to find fittings for these things, as most of them are 1/8". It might be a good idea to inquire sellers if they have some fittings for them

Yeah I thought so
this can be quite useful (assuming you have stuff from one manufacturer as these things are not standardized) you can buy one manual 3 way valve and one air actuated bistable 5 way valve... as a result you can mod a 3 way valve into air actuated valve, 5 way valve into manually actuated valve and so on.......

@MrCrowley
These things are quite comfortable when mounted on a gun. Have a look on the semiauto MKIII and the design I used there.

You might also remove just the roller itself and leave the lever as it is, or replace it with a different lever
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Unread postAuthor: JDP12 » Mon Mar 29, 2010 5:38 pm

thanks poland, i was misunderstanding something. Got it now.
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Unread postAuthor: MrCrowley » Sun Apr 04, 2010 12:06 am

Image
Found my camera, by the way :P

I have a trigger from some spark-igniter gun thingy that I'm planning on using to trigger this. The bolt is temporary but could be permanent. Just there to demonstrate how I can make my own push button for it. Will probably paint the flat metal piece black at some stage.
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Unread postAuthor: POLAND_SPUD » Sun Apr 04, 2010 12:23 am

you could have used a simple bolt you know.. that would make it easier to attach some sort of a lever to it

but I guess it looks good... lol what are you using now, duracell's batteries ?
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Unread postAuthor: jackssmirkingrevenge » Wed Apr 14, 2010 5:47 am

I ordered these, still want to make a decent semi :) not sure how well they will take 400-800 psi but I sure as hell intend to find out :)
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Unread postAuthor: POLAND_SPUD » Wed Apr 14, 2010 6:27 am

they are toggle valves so they stay in the last position... a spring return version would be a better choice for a trigger...

what size are they ? probably 5mm thread I guess, which means that their flow might be a bit low (good enough for piloting 1/8" and 1/4" QEVs)

not sure how well they will take 400-800 psi
it depends mostly on their construction... since they are direct acting there is a greater chance that they will...
now the question is whether they are spool or poppet valves? I am guessing they are spool valves which mean that they might handle it well

I guess you could have chosen better but we'll see... I like the way they look and how compact they are
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Unread postAuthor: jackssmirkingrevenge » Wed Apr 14, 2010 7:59 am

POLAND_SPUD wrote:they are toggle valves so they stay in the last position... a spring return version would be a better choice for a trigger...


Making a spring return would be extremely easy so no worries there.

what size are they ? probably 5mm thread I guess, which means that their flow might be a bit low (good enough for piloting 1/8" and 1/4" QEVs)


No idea but if I make a HPA semi it will be for 0.22"-0.25" calibre so good enough for my purposes, if I could pilot a 1" piston with a schrader these should be even better.

I guess you could have chosen better but we'll see... I like the way they look and how compact they are.


They're about 6 euros a piece including postage and I'll have four to play with so worth a try in any case :) I'll keep you all posted.
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Unread postAuthor: jackssmirkingrevenge » Thu Apr 29, 2010 3:21 pm

Package arrived today, basically a spool valve - the balanced construction means it should be quite happy with high pressures. Feed is through the port in the side, and depending on the toggle position, it either dumps through the back or leaks through the front bast the toggle itself, meaning some porting will have to be drilled to make it a decent pilot, but it looks like it's up to the job. Now for a prototype...
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Unread postAuthor: POLAND_SPUD » Thu Apr 29, 2010 4:57 pm

cool.. If you think of it it isn't much different from MRR's push-button valve...

well basically it looks the same (two o-rings)... the only thing he has to change is to rearrange the valve housing...
and voila a homemade DCV
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