SpudFiles

I want to build my very first airgun and I'm wondering which is best between a QEV and a sprinkler valve for the trigger mechanism. Is there a significant difference in speed and velocity. Also, where can I find a QEV in Canada?

Thank you

The main deciding factor I believe is cost and pressure. If you don't plan on going much higher than 125 psi than get a good sprinkler valve, if you are going high pressure go for the QEV. If you want performance, I am pretty sure the QEV has a faster opening time but I am not sure about the flow.

3/4" QEV is better performance-wise than a 1" sprinkler valve at equal pressures.

Thanks but where do you buy those QEVs?

ALIHISGREAT wrote:3/4" QEV is better performance-wise than a 1" sprinkler valve at equal pressures.

It is said it is better than even 2 sprinkler valves.

They have better flow+opening times

Since I don't know where to find a QEV and I already have a sprinkler valve at home, I might have to settle for the sprinkler valve with a blowgun.

1- I can't seem to be able to find anything bigger than ¾" to screw into my valve. Is there a big difference in performance between a ¾" valve and a 1" one?

2- I'm going to be using ABS for my air chamber. What would be the maximum pressure of a 2" or 3" capped ABS pipe? I really would like to reach 150 to 200 psi if possible.

I'm planning on using a ½" copper pipe to fire 3/8" steel slingshot ammo (with some sort of paper or cloth pouch to fill the air gap).

Thank you for the info.

I have this funny feeling that pressure rated ABS is about as common in Canada as in the USA.

By which I mean no suppliers have yet been found there.

Pressure rated PVC is more suitable than the unrated ABS any day of the week.

Actually pressure rated ABS is easy to come by. Even the ABS DWV around here has a pressure rating printed on the pipe.

I was actually checking this last night.

1 1/4" through 4" ABS (Foam core) has 320kpa (46.4psi) printed right on it.

This of course does NOT meet your stated pressure goal. Pressure rated PVC will most likely meet your goal (depending!).

However, 150-200psi is really pushing it with PVC IMO. For anything over 125psi, I would recommend metal.

A bigger safety margin will give you peace of mind.

Which is MUCH better than piece of mind!

That's my .02

Well, the ABS pipes I found are pretty thick. I'm sure they go way over 46 psi. Haven't seen any foam core. I'm talking about black thick ABS. It's at least 1/4 to 3/8" thick.

As for PVC, I can't find any where I live. Only flexible tubing or some valves.

I read that when PVC exploded it made more damage than ABS.

As for metal, could it be aluminum? It's lighter than steel.

qev's can be had from fastenal. They have stores in Canada.

http://www.fastenal.com/web/products.ex ... m_search=1


I wouldn't count on ABS holding together at 150 psi+.

Read the pipe. What does it say?

Irregardless of your feelings on the matter, IF it has a rating, it has one for a reason. You exceed that rating at your own risk.

Aluminum would be a much better option than ABS. You will have to give some thought as to how you're going to join it together though.

Epoxy (JB weld) should be fine.

Steel pipe and fittings of course, simply thread together, and will take more pressure than you would likely believe.

Edit:

Daisy brand 14mm marble slingshot ammo works well in 1/2" type M copper. The id of the pipe is .569" (very close to 9/16")

Recently, I was looking at an emergency device for marine use. It's a simple little can made with a really thin layer of aluminum and another of ABS. There's a horn on it to make a lot of noise. You may refill it as often as you like. It rates at 150 psi max!!! The can can be crushed with one hand!!! So when I look at 1/4 to 3/8" thick ABS pipes, I can't help but think it might withstand a lot more...

As anybody actually seen an ABS pipe explode under pressure at these pressures? Or it's only speculation?

I've looked over the QEVs on the Fastenal website. Unfortunately, maximum operating pressure of these valve don't exceed 150 psi. That's not enough. Or perhaps somebody else makes stronger ones..

acctually 'european' QEVs (and most likely 'fastenal' QEVs too) work well at much higher pressures...

even though they are rated to 150psi al-xg has used them at up to about 850 psi... many members, including me, have used QEVs at pressures exceding 500psi....

but you know... if you exceed the pressure rating you do it on your own risk

Since they don't sell these valves in hardware stores, I guess they'll be asking me a lot of questions. First one I always hear is: "What's it for?". I hate having to invent a story all the time. Same thing when I went for a sprinkler valve. I'm not going to say I want to build a gun!

When you mention the word "gun" here in Canada, everybody runs away or calls the cops!

airman wrote:

Gippeto wrote:qev's can be had from fastenal. They have stores in Canada.

http://www.fastenal.com/web/products.ex ... m_search=1


I wouldn't count on ABS holding together at 150 psi+.

Read the pipe. What does it say?

Irregardless of your feelings on the matter, IF it has a rating, it has one for a reason. You exceed that rating at your own risk.

Aluminum would be a much better option than ABS. You will have to give some thought as to how you're going to join it together though.

Epoxy (JB weld) should be fine.

Steel pipe and fittings of course, simply thread together, and will take more pressure than you would likely believe.

Edit:

Daisy brand 14mm marble slingshot ammo works well in 1/2" type M copper. The id of the pipe is .569" (very close to 9/16")

I've looked over the QEVs on the Fastenal website. Unfortunately, maximum operating pressure of these valve don't exceed 150 psi. That's not enough. Or perhaps somebody else makes stronger ones...

I took mine too 600 the other day....

airman wrote:Since they don't sell these valves in hardware stores, I guess they'll be asking me a lot of questions. First one I always hear is: "What's it for?". I hate having to invent a story all the time. Same thing when I went for a sprinkler valve. I'm not going to say I want to build a gun!

When you mention the word "gun" here in Canada, everybody runs away or calls the cops!

Who will be asking you questions? And never say 'gun'. First of all, in this context, 'gun' is not the correct term. 'Pneumatic Launcher' is more appropriate. Second, QEV's ARE sold in hardware stores. Fastenal is a hardware store.