Calculating flow and valve sizes

[Live1nce]

Hey guys, I used spudfiles quite a bit years ago, but lost my password to the account, so I just registered a new one. Now that I have some more time on my hands, I'm thinking of re-embarking on an old project. Well, I should say, continuing an old project. The reason this project is so challenging is because I will be using it for a paintball launcher, and therefore certain precautions must be adhered to for it to be safe. There are also many variables that require the cannon to be designed a certain way. Remember the ultimate goal is to make it look close to a real rocket launcher. http://www.science.co.il/arab-israeli-c ... 040511.jpg ( image is not really a real rocket launcher, but close enough to what i'm envisioning, just a smaller diameter)

Here is the dimensions and constraints of the cannon I will be modifying:

- Must be an inline system (similar to a coaxial, no bends, straight)
- Must be a 2"ID barrel so can also fire nerf rockets
- Must be a 2"ID chamber
- Complete, must not be much longer that 2'8" (give or take 1" maybe)
- Must be safe

I have made this design before, and then slid the entire assembly inside of 3" pvc. I used a on/off brass ball valve. What I want to upgrade or modify, is the valve. I want an electric ignition, and finding a solenoid that is small enough to even come close to fitting inside a 3" pipe with an inline system has been a headache. Now some of you might say... Why not just use a coaxial? Here are some good reasons I chose to avoid a coaxial for this project...

1. First and foremost, Having a 3" protective shield of PVC around the 2" chamber is necessary. Since this should resemble a shoulder fired rocket, the chamber will rest against the neck of the shooter. In-case of a rupture, chamber shrapnel will be contained (somewhat) inside of the 3" PVC shroud.
2. This launcher may end up being used in winter conditions, which will make the PVC brittle and even more risk of rupture, so safety is paramount in this project.
3. Launcher will be used in rough terrain and could possibly be dropped or smashed into a rock. The protective shroud comes in advantage here as well.
4. A coaxial would need a 3" chamber, to a 2" barrel to work properly. To put a protective shroud around this, You would need a 4" pipe. ( I have already made one like this, but it proved to be too cumbersome and heavy to lug around on your back all day)
5. I also find coaxial cannons to be more maintenance, and I want little maintenance.


I have recently taken a look at the GGDT tool (located here http://thehalls-in-bfe.com/GGDT/ ) and have been trying to calculate the Cv ( flow coefficient ) for a valve I can use. The problem is, I cant find a small valve for the project with a high enough Cv.... so here in lies my dilemma.

I have found some that are small enough valves, but the Cv is 4.6, hardly enough to move a nerf rocket out of the barrel!

Does anyone know of any small Valves with a low profile that will have a High Cv? What is an average Cv for a sprinkler valve? (I could get a valve slightly bigger than the 3" pvc, then just make a cutout into the 3" shroud where the sprinkler valve will poke through, but I don't really want to do this.

[Crna Legija]

A 1.5''-2'' sprinkler valve will be plenty for your needs, try find pressure rated abs for the chamber it is much safer then PVC because if it does rupture it only splits open not cracks and send shrapnel like PVC.

[ramses]

Mcmaster Carr gives valve CV. I'm very confident their 3/4" qev will fit in 3" pipe.

http://www.mcmaster.com/#exhaust-control-valves/=i3p3ox

[Live1nce]

A 1.5''-2'' sprinkler valve will be plenty for your needs, try find pressure rated abs for the chamber it is much safer then PVC because if it does rupture it only splits open not cracks and send shrapnel like PVC.

Thanks! I didn't know ABS only split.

Mcmaster Carr gives valve CV. I'm very confident their 3/4" qev will fit in 3" pipe.

http://www.mcmaster.com/#exhaust-control-valves/=i3p3ox

This looks like the perfect valve! But mcmaster only makes it with a 1/8" inlet and outlet. The Cv on the 2 valves I could use ranges from .10-.15
I don't think that is a high enough Cv to power a 2" bore size. The only other valve is the right angle valve, and that wouldn't fit inside the 3" pipe. Might as well go with a sprinkler valve then. How does an inline QEV (like the one in the link) work?

- Can it be set up for electronic ignition?
- Does it use pneumatic ignition like a modded sprinkler valve ?
- Is there an animation on how one off these inline QEV's work anywhere? I just did a brief search on google for "inline QEV animation" but i'm not getting any luck.

[POLAND_SPUD]

why don't you build a large spool/toolie valve ?

[Live1nce]

why don't you build a large spool/toolie valve ?

Never heard of this valve. I am researching it right now.

[Technician1002]

For spool valve check my SIG. Common name for mine is QDV when at rest is balanced and unbalanced when triggered, the chamber pressure blows it open.

Toolie is a barrel sealing piston where the valve is extended between the seat and pilot with a rod to span the chamber.
Thread on Toolie showing the long piston.
http://www.spudfiles.com/forums/help-wi ... 24141.html

Piston valves have a higher CV than a similar size diaphragm valve due to the reduced edges and bends internal to the valve.

[Live1nce]

Seems Like this would work great, but how much maintenance and time does it take to build one? I want to be able to crank this thing out quickly and keep maintenance to a minimum. So far, Your QDV valve seems to be the best option, but I would still like to try and make it easier, with an industrial type valve.



Does anyone know anything about these valves?
http://nbltbh.com/en/products.php?tid=2&page=1

I'm not even sure if they are inline valves or not.

[POLAND_SPUD]

these are cartridge valve... don't know what they are ? google them

plus it seems they are for hydraulics... and chinease


A spool valve wouldn't require a much maintance - if designed properly

[dewey-1]

A 1 inch sprinkler valve is probably your most reasonable option for your stated requirements. A modified sprinkler valve will give the best performance compared to solenoid actuated. The old standby Orbit 57101.

http://www.menards.com/main/plumbing/wa ... c-8670.htm

http://www.spudfiles.com/forums/apg-2-a ... 22390.html

[Live1nce]

these are cartridge valve... don't know what they are ? google them

A spool valve wouldn't require a much maintance - if designed properly

My google skills aren't too hot. But I try. Is there any links on here that discuss how to make a reliable spool valve? There is a machine shop down the street, so I can make custom parts if that is needed.

A 1 inch sprinkler valve is probably your most reasonable option for your stated requirements. A modified sprinkler valve will give the best performance compared to solenoid actuated. The old standby Orbit 57101.

http://www.menards.com/main/plumbing/wa ... c-8670.htm

http://www.spudfiles.com/forums/apg-2-a ... 22390.html

Last resort I will go with a basic sprinkler valve, but I like the challenge of trying something unique and different. I'm sure you understand, trying something new is the fun of it! I was looking at that canon in the link too earlier. Seems like a cool design! Might end up doing something similar myself

[POLAND_SPUD]

a cartridge valve is a valve that is screwed into a special manifold... it won't work without it as it isn't complete at all
in other words - it isn't useful for you

plus they're for hydraulics so their flow sucks



I am pretty sure others can come up with the right design for a spool valve...

[MrCrowley]

Yeah, I bought one but haven't found a use for it.

[ramses]

http://www.mcmaster.com/#exhaust-control-valves/=i3p3ox

This looks like the perfect valve! But mcmaster only makes it with a 1/8" inlet and outlet. The Cv on the 2 valves I could use ranges from .10-.15
I don't think that is a high enough Cv to power a 2" bore size. The only other valve is the right angle valve, and that wouldn't fit inside the 3" pipe. Might as well go with a sprinkler valve then. [/quote]

Crap, it's bigger than I remember it.

The inline valves work by having the vent ports around the outside. You cannot connect the barrel to them; they're just pin holes.

The problem with trying to use an inline is that you have 3 ports you need to fit on 2 ends of a cylinder.

At this point, I would recommend using some sort of spring actuated ball valve with a shortened handle and a fairly big torsion spring held by a sear.

[Live1nce]

Ok guys, so I picked up a small solenoid valve off ebay for this project. I couldn't get any of my questions about the valve answered by the seller, so I just figured i'd take a gamble and pick it up anyways. Wasn't like it was going to break the bank or anything.

http://www.ebay.com/itm/110697685734?ss ... _739wt_952

It just arrived and just as I figured, the port under the seal is 3/8's of an inch. My guess is it will be too low of a Cv for a 2" cannon.

- Is my assumption correct?
- Can I make it work with a higher PSI? (the valve can handle 120)

I would like to know if any of you have had experience with a port size this small while using a 2" barrel. If there's no way it will work, then i won't bother wasting the fittings on this valve. I'll just order something bigger.

(I want to at least put my shot out to about 130' without having to lob it too much)


I don't know if i'm using GGDT right, but this is a rough estimate, and possibly completely inaccurate. But remember I don't need this cannon shooting to fast. I don't want to hurt anyone, and possible ammunition may be water balloons.