New QEV Rifle

Show us your pneumatic spud gun! Discuss pneumatic (compressed gas) powered potato guns and related accessories. Valve types, actuation, pipe, materials, fittings, compressors, safety, gas choices, and more.
nz_cannons
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Tue Oct 23, 2007 1:28 am

After building my first gun around my newly purchased QEV and whatever parts I had lying around I set out to construct something a little better.

My main focus was to reposition the main chamber and decrease the pilot volume, as well as relocating the exhaust valve.

I went to the store and purchased the components I needed, surprisingly the stainless steel fittings (very nice IMO) were about the same price as the brass, so I decided to use them.

I only used a brass end cap because it was easier to drill through, and I don't think there were stainless steel screw in barbs. The stainless steel, as well as not rusting, is also a lot harder, which means the threads will take a bit more abuse then the brass would.

I'm not sure exactly what type of tube I used, but it's high spec and can easily hold a lot of pressure, as well as looking pretty mean.

The schrader valve I got for free from a tyre/wheel place. I couldn't find a fitting that it screwed into so I just drilled a hole in the cap and used the nuts it came with to hold it in place, it seals ok, no obvious leaking.

The barrel is the same one as on my last one, rather thin walled aluminum tubing. The wall thickness is only 1mm which I think is a little too thin, I would like something a little heavier.
I had to use the same method of attaching the QEV to the barrel as last time because I couldn't think of a solution at the time, it's all good though. Its reasonably strong and doesn't leak.

The ball valve is really smooth to open and close although it still puts off my aim when firing the thing.

I usually take it up to around 170-180 psi using my air compressor. I think the only thing limiting it is where the tube is pushed on to the barbs.
Although they would probably hold to a lot higher pressure, the air compressor has a similar setup using that type of tube and barbs, so if the gun doesn't go then that will (or the crappy tyre filling device will, I go off the scale on it's built in pressure gauge).

Specs:

-The barrel is 1m long with a 10mm internal diameter (0.4 inch)
-The chamber is the same as the last one, about 400ml I would guess.
-QEV is 3/8 inch variety

Pros

-The QEV works a lot better with a small pilot volume, it goes off with a bang and you feel the recoil.
-It's compact.
-Reasonably powerful for it's size I guess.
-Can take high pressures. (High for what I'm using)
-Triggers well, using a ball valve seems to work nicely.

Cons

-Difficult to aim without a stock to keep it steady.
-Moving the ball valve puts my aim off.
-No safety, can be accidently set off when removing the filling thing from the schrader.
-Has to be muzzle loaded.

I will eventually come up with something that rectifys these problems.

Now some pictures.
Attachments
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The filling system.
The filling system.
This is the only way I could think of at the moment for attaching the ball valve to the gun. It works ok and doesn't move around at all.
This is the only way I could think of at the moment for attaching the ball valve to the gun. It works ok and doesn't move around at all.
trigger.jpg (37.7 KiB) Viewed 5630 times
Shot along the barrel. Quite easy to hold I reckon.
Shot along the barrel. Quite easy to hold I reckon.
hold.jpg (34.61 KiB) Viewed 5630 times
These are my standard ammunition. They are 50mm nails pushed through a tyre valve cap. <br /><br />The valve caps are a perfect fit for my 10mm barrel (although some need a wee trim).<br /><br />After the nail is pushed in I fill the caps with hot glue. <br />These work extremely well, they fly nice and straight and can easily be mass produced.<br />I'm working on how to make them even better but that will come another time.
These are my standard ammunition. They are 50mm nails pushed through a tyre valve cap.

The valve caps are a perfect fit for my 10mm barrel (although some need a wee trim).

After the nail is pushed in I fill the caps with hot glue.
These work extremely well, they fly nice and straight and can easily be mass produced.
I'm working on how to make them even better but that will come another time.
I shot a dart through the 3 bottles of water and it still embeded itself quite far into the wood. This was from about 4-5m. I also did one with 6 filled bottles with results about the same ( dart was sticking out about 15mm more).
I shot a dart through the 3 bottles of water and it still embeded itself quite far into the wood. This was from about 4-5m. I also did one with 6 filled bottles with results about the same ( dart was sticking out about 15mm more).
Thickness of wood compared to length of nail in dart.
Thickness of wood compared to length of nail in dart.
Close up of nail in wood after going through bottles.
Close up of nail in wood after going through bottles.
This pic shows the darts that have gone right through a solid plank of wood, about 30mm thick, the small ones allmost come right out the other side.
This pic shows the darts that have gone right through a solid plank of wood, about 30mm thick, the small ones allmost come right out the other side.
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Tue Oct 23, 2007 1:38 am

Fuckin awesome bro :D :D
Loving the damage. My only suggestion would be a different actuator for the pilot, like a blow gun. Nice ammo BTW.
Very insane work- i love it :twisted:
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experament-u2
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Tue Oct 23, 2007 1:54 am

looks sick chap
nice work on the darts to and maby add a handle so the ball valve becomes just a trigger so you stay on target.
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MrCrowley
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Tue Oct 23, 2007 1:55 am

Great work mate, we have the only QEV guns in NZ probably :P

What is your chamber from?
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jackssmirkingrevenge
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Tue Oct 23, 2007 1:59 am

pilot...volume...too...big.... must resist...commenting... gah!

*ahem*

looking good :D
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battlemonkey
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Tue Oct 23, 2007 2:37 am

How far away from the plank are u shooting?5meters or did you sneak up on it and fire at point blank
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Tue Oct 23, 2007 2:43 am

jackssmirkingrevenge wrote:pilot...volume...too...big.... must resist...commenting... gah!

*ahem*

looking good :D
Glad someone else noticed, and was rude enough not to comment on it! :lol: :lol:
America, the greatest gangster of all time. With 200 million odd foot soldiers at it's whim and call.
When you fill your car with refined oil remember that it has been paid for with blood and guts, some from your own countrymen, most not.
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MrCrowley
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Tue Oct 23, 2007 2:57 am

battlemonkey wrote:How far away from the plank are u shooting?5meters or did you sneak up on it and fire at point blank
He said 4-5m.
nz_cannons
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Tue Oct 23, 2007 3:08 am

Cheers, um, yeah was about 4-5meters away, they still rip through it. The bottle is a CO2 gas cylinder from an old sodastream machine.

I don't get it, how could the pilot volume be too big? Seems about as small as I can get without just connecting the ballvalve straight to the tee. I wanted the tube so I could position the ballvalve where I liked.
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battlemonkey
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Tue Oct 23, 2007 3:14 am

i kinow what you mean, a cannon has to feel right when you fire it otherwise its really hard to aim
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MrCrowley
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Tue Oct 23, 2007 3:15 am

1) With JSR, the pilot volume is never too small

2) You could shorten the hose a bit, it has some slack in it.
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Tue Oct 23, 2007 3:22 am

Or use smaller id hose with appropriate fittings.
America, the greatest gangster of all time. With 200 million odd foot soldiers at it's whim and call.
When you fill your car with refined oil remember that it has been paid for with blood and guts, some from your own countrymen, most not.
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battlemonkey
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Tue Oct 23, 2007 3:29 am

about the tubing i would hose clamp it on as over 100 psi when it comes off the metal it travels at speed. happened to me at 160psi when filling fire extingusher
nz_cannons
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Tue Oct 23, 2007 3:35 am

Yeah am a bit worried about that happening, tube coming off and slicing into my arm or something.

Might have to upgrade to copper tubing and proper fittings eh.
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battlemonkey
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Tue Oct 23, 2007 3:40 am

is it plastic. if so just put a screw tightening hose clamp on there. seemed to work for me :wink:
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