SpudFiles

First off, a big Thank You to the members of this site. Although, seeing some of the cannons you guys build makes me feel like I'll never get to a certain level. After seeing Lardas' First Hybrid I considered trying to get a job at a Machine Shop

Anyhow I started with a Cold Steel "Big Bore" blowgun. They are fun as-is, but I thought it could use more power.

The progression went like this:
1. Stock Blowgun
2. Hooked up to a paintball gun (not enough gas per shot to do anything effective with).
3. Taking the Metered Propane tube off my combustion gun and making chamber attached to a spring loaded ball valve. Shooting at well over 1,500 PSI (yes, reprimand me!).
4. Figuring out (thanks to the "Goons at Spudfiles"-D. Hall's words, not mine) that a QEV at 200 PSI would be more powerful and much more efficient than a ball valve.

Barrel: .625, 5 foot Blowgun
Chamber: approx 13 inches of .5 steel pipe
QEV: 1/4" in & Chamber, 3/8" into barrel
Trigger: Heavy duty blow gun
PSI gauge: 0-600
Gas hook up taken off a paintball gun. I have used HPA, CO2 and Nitrogen, with CO2 being the cheapest (I own a 20 lb bottle at $21 a fill)
and Nitrogen being ideal, but hard to get.

My goal is a 50/50 mix of power and accuracy. The shots I took from 25 yards (measured out and legit) were without any sights on the cannon. These are 2 3 gram darts and some marble/glass shot from 25 yards. Fired at 250 psi.

Since then I have added an empty laser sight mount, upside down as a ghost sight. I think it should work well because the QEV provides a concave top to center the sight.

I do have videos and am working on uploading them to YouTube.

DISCLAIMER: On the videos I refer to this as my "First Pneumonic Cannon". So, I know, but feel free to get your licks in. If anyone has a Pneumonic for remembering Pneumatic I'm all ears!

Questions:
How do I make this thing more powerful and more accurate?
Would a piston valve be an improvement or not really due to the barrel size?

While I love combustion cannons (I'll post my pics later), I love in the city and there is really no place to shoot such a beast (mine is a beast). I do have a silencer....

Hybrids are awesome, but there is something unappealing about the amount of time in between shots.

My next idea would be a pneuMATIC, autoMATIC that shoots slingshot ammo/buck shot- Who has already done this?

Again, I am a humble amateur amongst Demi-Gods! Thanks for reading.

Picture of ammo added. The cannon also shoots regular arrows.

Nice work for a first cannon, some very impressive penetration, kudos!

SweatNTeflon wrote:How do I make this thing more powerful and more accurate?
Would a piston valve be an improvement or not really due to the barrel size?

A QEV is essentially a piston valve, so if you have a go at making a home-made one it's unlikely you'll get better performance.

The easiest way to up the power is up the pressure, and try and reduce the pilot volume (area to which the blowgun is connected).

My next idea would be a pneuMATIC, autoMATIC that shoots slingshot ammo/buck shot- Who has already done this?

You can convert this current device to semi auto or full auto by changing a few parts around, have a look through this thread: http://www.spudfiles.com/forums/semi-au ... 23626.html

How did I know you'd comment first..... Cheers and thank you.

Now that I uploaded an avatar, I see that your's is not holding a "cannon", but a captive bolt gun as well?

Pilot volume: the only way I can see to reduce it is changing the female-female-male T from the 2" I have to a 1 3/8" OR changing the fittings to 1/8". What would you recommend? I'll run the numbers in GGDT and see what the results would be. I'd be a little concerned about 1/8" fittings breaking with normal wear and tear (not pneumatic functioning, just getting knocked around).

Upping the PSI, yes. I've shot it at 600, but I am just uncertain about running that much pressure through a QEV rated at 125. I have seen 150 rated QEV's, but nothing higher (unless you are talking oil drilling platform hardware). Any leads on a sturdier QEV?

GGDT is giving me the same velocity at (greatly) varying pilot volumes. What am I doing wrong?

Also, is there any issue in hooking up a 125 psi regulated CO2 tank, leaving the ball valve/fill open to achieve semi-auto mode? Perhaps a bit wasteful- but otherwise?

Nice cannon. I like how you used the casting protrusions at the top of the QEV as the rear sights. If you like jack's work, you can also implement an adjustable one pretty simply as well.

As far as the pilot volume goes, GGDT assumes one-way flow past or through the piston... that is, the valve will pilot with ANYTHING. QEV's 'cup piston' works as a one-way valve, so you should be able to pilot it with anything, although there will be a delay in piloting and a slightly slower opening time, as there will be more air behind the piston slowing it and a smaller orifice for that air to exit. A larger pilot with less pilot volume ensures as little delay between the pilot and piston opening as possible, as well as keeping pressure behind the piston from rising as it moves backwards.

nice cannon. I too have a cold steel blowgun. Their lots of fun. Is that the blowgun barrel hooked up to the qev?

SweatNTeflon wrote:Now that I uploaded an avatar, I see that your's is not holding a "cannon", but a captive bolt gun as well?

same movie

I'd be a little concerned about 1/8" fittings breaking with normal wear and tear (not pneumatic functioning, just getting knocked around).

As long as they're not made of paper I wouldn't be too concerned.

Upping the PSI, yes. I've shot it at 600, but I am just uncertain about running that much pressure through a QEV rated at 125. I have seen 150 rated QEV's, but nothing higher (unless you are talking oil drilling platform hardware). Any leads on a sturdier QEV?

QEVs with metal bodies can usually take several times their rated pressuRe without flying apart. The usual weak point is the piston or diaphragm. I would take the valve apart, and see what can be done, either beefing the existing parts up or replacing them with something more hard wearing.

SweatNTeflon wrote:Also, is there any issue in hooking up a 125 psi regulated CO2 tank, leaving the ball valve/fill open to achieve semi-auto mode? Perhaps a bit wasteful- but otherwise?

replace the blowgun and ball valve with a Three way valve, see the link in my previous response - not wasteful at all, as the feed from the main tank is automatically cut when the valve is in the 'fire' position.

replace the blowgun and ball valve with a Three way valve, see the link in my previous response - not wasteful at all, as the feed from the main tank is automatically cut when the valve is in the 'fire' position.

Mod the QEV instead.
Poke a tiny hole through the diaphram between the valveseat and the outer rim. stay away from the center..this is what seals the valve..

This mod will make the pilot repressurise after the blowgun is shut, really fast I might add.
If the valve doesn't have a core-spring to aod the diaphram put in a small spring that will push the valve shut..

The blowgun can now be hooked up directly to the pilot port and the valve will pop open and reshut at every triggerpull.
You won't need to fill from the back...so

Put that large tank under the barrel as your reservoir/chamber.
You won't need a secondary chamber anymore.

Brain,

I see a couple issues with that.

Firstly, I am not willing to open up the QEV until it fails. So far it has held up very well even at 600 PSI (see damage pics of 100 grain projectile through both sides of a steel tank). When it does fail I will certainly open it up and perhaps make the adjustments you've suggested.

The second issue is that "the big tank" I have hooked up is a HPA Paintball tank capable of holding 4000 PSI. It does have a regulator on it, but I am unsure of what that is set on and I don't think it can be adjusted low enough to work with a (modified- I am assuming by poking a small hole in the diaphragm that I am indeed weakening the valve, yes?) QEV. Even using unregulated CO2 might be pushing it?

The other issue with semi-auto is that (due to my lacking machining/technical skills) the only ammo I'd be able to use is something like marbles/ball bearings fed through a simple T fitting. Ideally I would construct a semi-auto with a clip that would feed in the 3 gram black-and-orange darts. But again, the issue with this is that I just don't have the technical skill-set to do this easily.

All that being said, I really like your idea and will probably try to implement it in the future, but with a regulator between the tank and the QEV.

Thanks for your guidance. Please let me know if I am missing anything or have't understood correctly.

Here are the damage pics of a 100 grain field tip fired through a disposable helium tank. At 600 PSI they go through both walls. As I am unsure of wall thickness, I will shoot at measured steel sheets next time

Very nice damage Brian's advice is sound but if you want to stick with standard parts a three way valve is your ideal solution for semi auto.

I am assuming by poking a small hole in the diaphragm that I am indeed weakening the valve, yes?)

not if done correctly.
the hole should be tiny and perfectly round to avoid tearing.
And yes...you'd need a regulator and you would still need to hook it up to a firing reservoir.

But with you just starting out I suggest JSR's approach.
For now.

My next idea would be a pneuMATIC, autoMATIC that shoots slingshot ammo/buck shot- Who has already done this?

You'll need to look into the Tee-mag thing if you want to realise that goal.
I suggest using the piston type QEV for that build.The piston type should stand up to normal abuse with the mod.

After pouring over this site I feel "outgunned" in every sense of the word. The quality of some of these cannons is at a level I'll probably never achieve. Granted I have no desire to build some of the cannons that DYI and Lars build. However, I'd love to be able to put together something like Gippeto did with his 3000 PSI monster-big-bore gun. Wow. To do this (besides gaining the scientific knowledge) I would need to learn CAD and some metal fabrication, yes? OR have somebody do that work for me I suppose.

Any recommendations on this? Seems like the reasonable route would be learning CAD and then taking the designs to a fabricator. That is considering I am not rich nor am I in any field related to metal working.

I digress....

GGDT says a 200 fps increase in my design if I swap the 1/4"(pilot)-1/4"(chamber)-3/8" (barrel) QEV out for a 3/4" (all three). Seems like the most bang for the buck. Thoughts?

Damage pics of an 18 G steel rod projectile hitting a cement block. It didn't go through it (like a 12 gauge would), but it did break it.... Not as reliable as testing through standardized metal sheets, but I was still happy with it.

Why don't more people use the Big Bore Blowguns as barrels? http://www.coldsteel.com/Big-Bore-Blowguns.aspx
It seems like a good idea considering it comes with ready-made ammo & sabots.

Has anybody made a .50 cal pneumatic from a muzzle loading off-the-shelf barrel? I was thinking of that. You'd get a rifled barrel and .50 cal projectiles are cheap and abundant here is the States.

BTB or JSR- could you provide a link to a thread about modifying a QEV for semi-auto (poking a hole in the diaphragm), please?

A bit off topic- I'll be moving to Japan in August. Airguns that "fire metal" projectiles are illegal, but I was wondering if anyone on SF has lived or is living there??

SweatNTeflon wrote:Any recommendations on this? Seems like the reasonable route would be learning CAD and then taking the designs to a fabricator. That is considering I am not rich nor am I in any field related to metal working.

Learning CAD legally is pretty pricey, and quite challenging. Getting parts made is also not exactly cheap, properly made parts for something like Gipetto's launcher will probably cost you the equivalent of a good small lathe. Not trying to put you off, just a heads up. If you want to build on a budget, you might want to get knowledgable with eBay and high strength epoxy

GGDT says a 200 fps increase in my design if I swap the 1/4"(pilot)-1/4"(chamber)-3/8" (barrel) QEV out for a 3/4" (all three). Seems like the most bang for the buck. Thoughts?

Moar valve = moar powah

Has anybody made a .50 cal pneumatic from a muzzle loading off-the-shelf barrel? I was thinking of that. You'd get a rifled barrel and .50 cal projectiles are cheap and abundant here is the States.

http://www.spudfiles.com/forums/400-psi ... 23422.html

BTB or JSR- could you provide a link to a thread about modifying a QEV for semi-auto (poking a hole in the diaphragm), please?

Errrrr... It's just poking a hole, take the valve apart and take some pictures

A bit off topic- I'll be moving to Japan in August. Airguns that "fire metal" projectiles are illegal, but I was wondering if anyone on SF has lived or is living there??

Oddly enough I don't remember any Japanese members on the forum.

New stats

3/4 QEV piloted by old 1/4 QEV, piloted by blowgun.
Chamber up by almost 5 fold to just under 12 cubic inches.

Same barrel (60 inch .625).

Shots using CO2 at 400.

I have tested both QEV valves to 600 PSI with the older, smaller chamber. Unfortunately I can't get past 400 PSI with the current chamber and my paintball CO2 tank. Getting HPA is on my list to do.

I suck at computers, sorry. Here is the link to videos on YouTube.

42g dart shot at 3, 16 gauge plates of steel at 400 PSI:
[youtube][/youtube]

3 gram plastic dart shot at 3/4' plywood:
[youtube][/youtube]

Good stuff, impressive penetration and nice to see those sparks flying