SpudFiles

Hello all! I have decided to start making my own airgun( .177 or .22 lead pellets probably), and will be a PCP design. Bu I have been having trouble finding anything on valves to use, it seems most of the people on here use QEV valves, but I have herd of others like the hammer valve and spool valve. Could anyone explain the pros and cons of using the different setups of valves? I could really use some help!

It depends on what you want and what resources you have available in terms of technical ability, facilities and budget.

What sort of performance do you expect? Semi automatic or single shot? What are you using as a pressure source?

I want to be shooting around 700-850 fps and with decent hitting power, multi shot is desired and will depend on how big and long of a tube I use for my chamber, I don't know if I am going to fill from a bulk source or use a hand pump, but I would like to be able to shoot at least five rounds or more. I don't know any equations that I can plug thease numbers into and get my psi I need. And that also brings me to what the topic of this post was, valves. I don't know a lot about them or which one I should use. I know for multi shot, that's usaly a balanced hammer valve or a QEV piloted by it, correct?

Southclaw wrote:I want to be shooting around 700-850 fps and with decent hitting power, multi shot is desired and will depend on how big and long of a tube I use for my chamber, I don't know if I am going to fill from a bulk source or use a hand pump, but I would like to be able to shoot at least five rounds or more.

I would go for 0.22" and look at pressures or at least 400 psi. A Ninja paintball tank would make a nice chamber, by simply removing shims you can regulate the output to around 450 psi.

I don't know any equations that I can plug thease numbers into and get my psi I need.

GGDT is a wonderful resource to tap into: http://www.thehalls-in-bfe.com/GGDT/

And that also brings me to what the topic of this post was, valves. I don't know a lot about them or which one I should use. I know for multi shot, that's usaly a balanced hammer valve or a QEV piloted by it, correct?

A hammer valve is a relatively complex undertaking. The best one I've seen made without the benefit of machine tools was this: http://www.spudfiles.com/how-to-databas ... 23202.html

A QEV and slide valve setup on the other hand can be put together using off-the-shelf parts: http://www.spudfiles.com/how-to-databas ... 23626.html

The above from a short barrel and only 120 psi managed to push a 16 grain 0.22" lead pellet to 355 fps, upping the pressure to the 400 psi range and using a longer barrel would give you the performance you seek.

Is that why soo many people use the QEV valve? Because it can be made easy with off the shelf parts? Which one provides better consistency, and performance?

Now I'm not opposed to it, just wondering.but why is it that lots of people suggest the QEV? What makes it better? Dose it give better performance or something? If I want multi shot then I need to use a hammer valve correct? I have access to lathes and a milling machine, but I was just wondering what the performance difference was between the different valves. And if I wanted to have say, a twenty shot capability, I have to make the chamber larger, or can I increase pressure? Or both? I thought it was more volume. But just wanted to check.

A QEV is definitely a cheaply available off-the-shelf item, and since most spudguns tend to have larger calibres than your average commercial airgun, an exhaust valve is infinitely more practical than a hammer valve forl arge bores.

Hammer valves open very quickly, however they tend to have poor flow compared to exhaust valves and usually involve a lot of dead space. One of their positive attributes is that they are self regulating to some extent - with less pressure in the barrel, they offer less resistance to the hammer and let out more air.

In terms of consistency, hammer valves tend to have a "sweet spot". Have a look at this thread: http://www.spudfiles.com/pneumatic-cann ... 24571.html

In either case, a regulated air supply is a good idea.

With access to machine tools, a commercial design can be replicated with relative ease. Or purchased, for less than $300

Again it depends on what you want to achieve.

As you can propaly tell, I'm new here, are there any other sites like this that I can get any info from? I'd really like to learn more about how airguns work and the building process, it looks like I need to learn a lot more until I can make my own gun.

Check out the 'Spudtech Archive' button at the top of the page. You can't post anything there but from my understanding it was the very 1st spudgun forum, plenty of info there as well. There are others but they are very basic.

IMO, you are at the best and biggest spudgun database in the world.

If you want to build a "proper" PCP with the use of adequate machine tools, that would be equivalent to a store bought item, there are other forums you can consult.

Here's a good place to start: http://airgundevelopment.com/