SpudFiles

For my entertainment this summer I am thinking I might build a qev marble gun that I won't spend a whole afternoon pumping up like my other one.
I can't afford metal pipe, nor do I have the tools or experience to solder it. So I was wondering if it would be ok on the pvc threads if I connected them to a qev or a safety valve. I know that unscrewing it is bad for the threads so I was just wondering about leaving it there.

Thanks,
Salty

It'll be fine. Where'd you hear that unscrewing was bad for the threads?

they are all npt threads so it would be fine.

noname wrote:It'll be fine. Where'd you hear that unscrewing was bad for the threads?

Someone was saying how the metal chews up the pvc threads, I can't remember who or where it was.

Well, since it won't explode in my face, I'd say production chances are going up

It was probably in the launcher failure log, where my piston valve failed because the metal bushing "bit" too tightly into the PVC female adapter.

Darnit I just ran into a problem. When I looked around McMaster for qev's I got these funky-looking solenoids, and when I looked at home depot's web site I got trash can storage.

Does anyone know a) where on McMaster (or preferably home depot or other local store) I can get a qev and B) what a good size is for a 3'' chamber and a 1/2'' barrel.

On the mcmaster QEV section, go to the top of the page, and you will see 3 or 4 different pages. Click the last one. This will bring you to the right qev section. the largest qev they have is 3/4 inch.

edit: the page is 941

A 3/4" QEV is $20 on McMaster, part number 6646K23.
Be sure to bookmark that page. I've been there about 10 times and it still took me 10 minutes to find it.
You can also search Exhaust Control Valves, and then scroll down a ways.

even if its a 1/2'' barrel, still get a 3/4'' QEV, ou will get slightly better proformance.

Ok, I was searching around while I was designing it to find out where it was filled from etc. and I realized that it was piloted and filled through the same hole. I don't have an air compressor so I came up with this idea; attach a tee to the qev and have a schraeder and a ball valve on the tee.




EDIT: Another thing I was wondering was what size of pipe or coupling do I need for a ghetto breech on 1/2'' pipe? (I'm planning to O-ring it)

http://www.spudfiles.com/forums/fish-ki ... t8838.html

'tis all good...

I actually used a brass bushing on one of my cannons, threaded into a plastic 1/2 in. elbow. i was looking at it a week after I had finished it, and the plastic elbow had cracked! Long story short, the bushing "killed the plastic threads on my gun.

Whoah...it's been under my nose this whole time. I hope you don't mind if I copy your valve setup.

I was also planning to make a barrel support tee thing, but I'm gonna keep my ghetto breech idea.

Flying_Salt wrote: EDIT: Another thing I was wondering was what size of pipe or coupling do I need for a ghetto breech on 1/2'' pipe? (I'm planning to O-ring it)

1/2" coupling... Come on Salty, use that thing on your shoulders [/i]

Flying_Salt wrote:Whoah...it's been under my nose this whole time. I hope you don't mind if I copy your valve setup.

I was also planning to make a barrel support tee thing, but I'm gonna keep my ghetto breech idea.

Go for it. My breech idea really only works with .40 blowgun barrels because the quick disconnects fit right over them. Whatever you come up with, good luck!

rmich732 wrote:

Flying_Salt wrote: EDIT: Another thing I was wondering was what size of pipe or coupling do I need for a ghetto breech on 1/2'' pipe? (I'm planning to O-ring it)

1/2" coupling... Come on Salty, use that thing on your shoulders [/i]

hehe... it happens.

Check out this page: http://www.flexpvc.com/cart/agora.cgi?p ... VC-Couples

Somewhere on there are extra long couplings. They might work better if you decide to make a longer breech.