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Safety check...

Post about things you have launched or thought about launching. Also post about various materials used for building cannons. No posts about explosive projectiles!
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Safety check...

Unread postAuthor: sco77 » Mon Aug 01, 2011 5:59 pm

This is my first gun that I made which was originally made to only goto 200PSI, but I was thinking about converting (gauge) to 300PSI, I know it can goto 300+ PSI but also know that some parts of it are not rated over 150PSI so my real safety concern is how likely is a catastrophic failure at 300PSI and what would the likely debris potential be?

I would really like to piece together some of these pipes and fittings and pressure to 300+ PSI and shoot different parts of it from a distance with a rifle and record the results of how well it holds up under catastrophic failure.
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Unread postAuthor: Gun Freak » Mon Aug 01, 2011 6:02 pm

Dude... you could put 400 psi in that and smash it with a sledge hammer and it wouldn't fail.
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Unread postAuthor: Technician1002 » Mon Aug 01, 2011 6:06 pm

The all metal construction will do fine for external safety. The most likely point of failure is the piston inside the QEV so any failure parts would eject from the barrel. Safety concerns is in a failure is an accidental discharge. Assume it can go off unexpectedly when it is being filled and keep it pointed in a safe direction downrange when filling.
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Unread postAuthor: saefroch » Mon Aug 01, 2011 8:19 pm

Those metal parts will probably hold 2,000psi, but that would decimate the seals. Most schedule 40 metal fittings are rated to 150psi, but that's a load of crap, they're good to much higher.

Shooting it with a rifle won't properly simulate failure, but go right ahead :). In my opinion though, unless you have a large-calibre sniper rifle with armour-piercing rounds dead on, it won't do anything. Because of the curvature of the pipes, projectiles will ricochet off and just scratch.
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Unread postAuthor: Moonbogg » Mon Aug 01, 2011 11:54 pm

If you shoot it under pressure, it may crack or have a hole punched in it and the pressure will escape. I don't see it failing in any catastrophic way. You may consider pressure testing the cannon by doing hydro testing. That may ease your mind, but don't destroy the thing! Use it! I know my next cannon project will by hydro tested before use.
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Unread postAuthor: Technician1002 » Tue Aug 02, 2011 12:09 am

It is possible to shatter the galvanized cast iron elbows if shot. They are not soft iron. Other than the cast iron parts, it is not fragile.
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Unread postAuthor: Daltonultra » Tue Aug 02, 2011 2:12 am

I do beg to differ that it would take large-caliber AP rounds to harm pipe like that. I know for a fact that my Mosin-Nagant, firing standard-issue military surplus 7.62x54R, will easily penetrate. So will .30-06, .308, 7.62 NATO, and pretty much any standard-issue military rifle round. And I'm not talking about armor-piercing rounds, just conventional steel-core rounds.

I personally measured 3/8" penetration into a steel tank-cap using 7.62x54R. And even a glancing shot can splash a lot of metal away. I have target frames that will show that clearly enough...
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Unread postAuthor: Mr.Tallahassee » Tue Aug 02, 2011 2:23 am

I don't think a rifle round will do much to cause catastrophic failure. The best way to test failure is hydro testing.

That gun will more than easily hold 400PSI. Although I would have used a street elbow to attach the barrel to minimize dead space as well as make the gun slightly more compact. Great gun though!
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Unread postAuthor: saefroch » Tue Aug 02, 2011 8:51 am

Daltonultra wrote:I personally measured 3/8" penetration into a steel tank-cap using 7.62x54R. And even a glancing shot can splash a lot of metal away. I have target frames that will show that clearly enough...
Were you were shooting at a flat surface of this tank cap?
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Unread postAuthor: Gippeto » Tue Aug 02, 2011 9:33 am

@ the OP... 300psi seems pretty safe IMO.

Factual data may inspire more than blatant conjecture though...so I leave you with this parting read.

http://www.spudfiles.com/forums/the-fai ... 15393.html
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Unread postAuthor: jhalek90 » Tue Aug 02, 2011 8:50 pm

That qev should be fine at 300 psi. If you want to be safe, don't load any ammo, keep the barrel away from anything important, and fill to 300psi. If you hear any hissing out the barrel, your qev is about to blow.


I have used 1/4" qev of the same style all the way to 600psi.
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Unread postAuthor: jhalek90 » Tue Aug 02, 2011 8:51 pm

That qev should be fine at 300 psi. If you want to be safe, don't load any ammo, keep the barrel away from anything important, and fill to 300psi. If you hear any hissing out the barrel, your qev is about to blow.


I have used 1/4" qev of the same style all the way to 600psi.
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