Mk IV QEV Popoff. Updated 22 Feb

[SubsonicSpud]

Well guys I decided to muck around with psycix QEV pop off design, and made a slightly ghetto test weapon. It is a 1/4 qev hooked up to a 8bar pop off with may dodgy barrel and magazine attatchment. The barrel and mag are some carbon fibre tube I had lying around which i quickly machined up a tee block for out of acetal. The tubes are just a press fit in the block, with the aid of some tape

Here are some pics






And a damage video

[youtube][/youtube]

Considering it was leaking like a sieve and poping at about 7bar I am pretty happy with the results.

I will be making a proper version of this with a much higher pop off pressure, hopefully around 15 -20 bar. I will make a proper tee feed for the magazine with spring loaded ball stop, which should stop the double feeding.

[jrrdw]

Cool! Nice looking at that. I embeded the video for you, that way it stays on spudfiles instead of youtube servers kicking it out after time.

[Brian the brain]

Nice!
I hope you too see the potential of a hopper instead of a magtube...


I like the materials you used to build this.Clean and simple.Love the squared QEV!

Am I hearing correctly that the first two or three shots cycle faster?

[SubsonicSpud]

Cool! Nice looking at that. I embeded the video for you, that way it stays on spudfiles instead of youtube servers kicking it out after time.

Thanks for that. I was not sure how to embed the video


BTB, it probably did cycle a little faster at first. I was firing and regulating the flow by tuning on the shutoff valve on the air tank. It was not at its full ROF

SubsonicSpud

[psycix]

Very nice!
What kind of QEV is that?

What does the interior of the T piece look like? (Where your barrel and mag attach)
I'll upload my video in a few days. Full auto is lots of fun.

[SubsonicSpud]

Very nice!
What kind of QEV is that?

What does the interior of the T piece look like? (Where your barrel and mag attach)
I'll upload my video in a few days. Full auto is lots of fun.

Thanks for the idea in the first place psycix :thumbleft:

It is a QEV used for Pneumatic ram process systems. They seem to be the only type easily available in Australia. It is the same as a normal QEV except the body is just a block of machined aluminium, lots of beef on them to tap mounting holes too, and they look very tidy. The Tee piece is just a block with a hole through for the barrel, then another drilled at approximately right angles to it. The barrel has a semi-circular cut out in the top of it which matches a cutout in the base of the mag tube as in this picture



I was getting a lot of double feeds with the mag, but that can be expected when there is no stop for the ammo, It actually works really well at about 10RPS any slower then that seems to let a couple of doubles got through. I will make a more refined Tee tomorrow with a stopper and will crank up the pop off valve pressure. I'll shoot it through the crony and see what sort of results I can get. I intend to stick with this calibre too, as it is the most economical size to buy sinkers in.

By the way, can't wait to see you're brbrbrbrbrbrbrbrbrbrbraat gun in full rage It scares me what these things will do at 30bar

SubsonicSpud

[jackssmirkingrevenge]

Sweet try shimming the spring to increase the pop-off pressure.

[SubsonicSpud]

Sweet try shimming the spring to increase the pop-off pressure.

Yep thats what I was intending to do, plus I also realised the top of the pop off can also be screwed down about another 1/4" onto the spring 8)

[SubsonicSpud]

Well I have re-designed the Tee a little bit, and made it out of acrylic. feeds a lot more reliably now and is transparent so you can tell if it is loaded or if there is a jam in the system. I also adjusted the popoff so it is now firing at about 12bar, and boy dose that crank up the noise 8)

I shot it through the crony and I was getting around 270fps out of 3gram lead sinkers. The pop of valve can still be adjusted up to about 25bar so there is still a lot more power to be had

Here is the new video



And a few pictures



a close up of the new Tee



All I have to do now is make a proper trigger and incorporate a needle valve into it to make the ROF fully adjustable. I may also run the Mag and chamber parallel to the barrel and have it spring fed so I can hold more rounds and have a neater look.

SubsonicSpud

[Technician1002]

Well I have re-designed the Tee a little bit, and made it out of acrylic.

SubsonicSpud

Nice job.
May I recommend polycarbonate instead of acrylic? It doesn't craze and crack as badly. It's just harder to solvent weld, but since your part isn't welded, it should work.

[SubsonicSpud]

Well I have re-designed the Tee a little bit, and made it out of acrylic.

SubsonicSpud

Nice job.
May I recommend polycarbonate instead of acrylic? It doesn't craze and crack as badly. It's just harder to solvent weld, but since your part isn't welded, it should work.

Yeah I know what you mean, acrylic is a pain to work with, but it is what I had laying around. I also made the mistake of using a nice sharp drill bit on it ,which dug in and took a few chips out of the holes I was drilling

[jackssmirkingrevenge]

Very nice and that's already almost 8 ft/lbs you're getting, very healthy I would suggest adding an o-ring or detent to the mag though to improve reliability.

Also, videos from closer to the target appreciated

What calibre is the barrel?

[SubsonicSpud]

Very nice and that's already almost 8 ft/lbs you're getting, very healthy I would suggest adding an o-ring or detent to the mag though to improve reliability.

Also, videos from closer to the target appreciated

What calibre is the barrel?

Thanks JSR, and I'm hoping I can get a lot more out of it yet too . As for a detent in the mag, I sort of forgot to include that when I was making the Tee. What I think I will do is drill a narrow hole up into the barrel from the bottom of the tee, just infront of where the ammo sits. I'll have a small rod of rubber to fit in the hole and hold it up in place with a screw behind it. The small rod of rubber would protrude up into the barrel half a mm or so, just enough to stop the ammo rolling out.

The calibre of the barrel is 8mm, unfortunately the sinkers I am using are about 6.5 -7mm so they are not the best fit.

I was going to get a few more videos of some destruction but I ran out of ammo I'll get more ammo tomorrow and start shredding some stuff, Hmm I wonder if I can find any toy diggers around

[jackssmirkingrevenge]

What I think I will do is drill a narrow hole up into the barrel from the bottom of the tee, just infront of where the ammo sits. I'll have a small rod of rubber to fit in the hole and hold it up in place with a screw behind it. The small rod of rubber would protrude up into the barrel half a mm or so, just enough to stop the ammo rolling out.:

That should work nicely and you can adjust the strength by screwing in or out, great idea

The calibre of the barrel is 8mm, unfortunately the sinkers I am using are about 6.5 -7mm so they are not the best fit.

Holy Etruscan snoods, that is a massive source of inefficiency (and also a source of double feeds if your magazine tube is also 8mm) - I had once calculated that using a 4.5mm barrel instead of a 5mm barrel for 4.5mm lead BBs resulted in a 33% increase in muzzle energy, so you're losing a lot of power there! You can get ball bearings in 8mm, that would be perfect ammunition for this

Diggers are evil and should be punished!

[SubsonicSpud]

Holy Etruscan snoods, that is a massive source of inefficiency (and also a source of double feeds if your magazine tube is also 8mm) - I had once calculated that using a 4.5mm barrel instead of a 5mm barrel for 4.5mm lead BBs resulted in a 33% increase in muzzle energy, so you're losing a lot of power there! You can get ball bearings in 8mm, that would be perfect ammunition for this

Yeah I know I'm losing a fair bit of power, as for the Tee, it has been drilled to match the sinkers, so it feeds ok. I can never find a good source of BB to use as ammo unfortunately, I will just try and find a barrel to match the ammo, or even sleeve it with some thin walled plastic tube. The only other economical source of ammo I can think of is arts and crafts beads Gees I wish Australia has Airsoft.