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Existing cannon questions, what do you think about....

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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Existing cannon questions, what do you think about....

Unread postAuthor: williamfeldmann » Mon Sep 10, 2007 12:34 pm

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Here is my problem. This sucker has more than a little kick at 60 psi, I am 6 foot 2 and don't think I could hang on to it at 100 and above, my goal is 150.

I built this cannon for optimum performance. Yes the air is restriced coming out of the tank but only to 1 inch for the valve and then back to 2.5. The straight line design gives excellent air flow. My problem is sheer size. In order to fire this I hook the wye over my shoulder and have to reach out and hang onto the barrel to steady it. It's just unwieldy.

Here is what I want some thoughts on. Leave the tank and valve in the configuration they are in. Build a bend in after the valve to bring the barrel around for a modified over-under design, leaving the bend able to accept different barrels like this gun is now (anything that ends up in 1 inch male threaded fitting). Then making some sort of wood spacer to keep the barrel and tank in the same proximity.

Using the above mods, I could fire it while holding it if I wanted because the gun would be 3 feet shorter and I could build in a type of bipod system which when used with the pvc wye that is part of the tank will turn this into a tripod system. I have 4 feet of air line to my valve so no problem there.

Is building that bend into the system after the valve going affect my performance? Or should I build the bend in before the valve? Building it after the valve doesn't require me to glue it into the system so I could always unscrew the bend and still fire it bazooka style. Give opinions.

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Sorry for the hidious mspaint hackjob here but I need a better photo to take apart to get any better. Black lines are parts to be added.
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Unread postAuthor: spanerman » Mon Sep 10, 2007 12:38 pm

im pretty sure that some of the fittings arnt pressure rated........i wouldent go above 60psi..
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Unread postAuthor: williamfeldmann » Mon Sep 10, 2007 12:50 pm

spanerman

Every piece except the barrel and valve is pressure rated sch 40.

The barrel is 2.5 pvc conduit which I am pretty sure is cell core unless someone know better (it didn't have a pressure rating).

The tank stuff all came from my uncle who is a master plumber and works on systems for commercial buildings so all pipe is good stuff, not lowes cell core crap. Thanks for the worry though.
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Unread postAuthor: spanerman » Mon Sep 10, 2007 12:53 pm

hmm, im almost certain that you cant get Wyes pressure rated and the socket depth seems awful small...
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Unread postAuthor: williamfeldmann » Mon Sep 10, 2007 1:05 pm

You might be right, mcmaster doesn't even have a rating on their wyes. I know it is sch 40, I can still read it through the paint.

Anyone know if this thing is safe? I have already run shots of 75 psi through it and have left it pressurised sitting for around 10 minutes a couple of times.
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Unread postAuthor: Gepard » Mon Sep 10, 2007 1:16 pm

It's most likely to blow on firing/charging....can't remember which.......

I don't get why your asking about putting 2 bends and the effect it will have on performance hwile you have a single 1" valve....The valves are only something like 3/4" anyway so that's a massive choke on it....Make it under over type like in your pic but go with either a bigger valve, more valves or a new piston valve.
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Unread postAuthor: potatoflinger » Mon Sep 10, 2007 2:06 pm

The wye isn't pressure rated, it may be schedule 40, but it is still probably dwv, which refers to the socket depth. I wouldn't take the gun past 60 psi. It is a beautiful gun though.
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Unread postAuthor: meatballs » Mon Sep 10, 2007 2:07 pm

yeah if you want performance a piston is the way to go. you would get more power at lower pressures if you dont constrict the flow. consider that having a 2" valve allows 4x more flow at the same pressure. that means the projectile will reach higher velocities before leaving the barrel. with the constricted flow it works well until the projectile starts accellerating, cause as it gains speed some of the energy of the pressurized air is wasted forcing the air at high speed through the small opening, whereas with a larger valve more energy goes straight to the projectile.
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Unread postAuthor: MrCrowley » Mon Sep 10, 2007 4:09 pm

Looks like you have a tee and a wye in there, both aren't pressure rated.

Sch.40 is referred to as the thickness of the pipe but what you need to look out for is NSF-PW XXXPSI @73F. If it has that on the pipe it's all good to use.

Not sure about you but pressure rated pipe doesn't fit DWV fittings here, so your pipe may not be rated as well.

Very kick ass gun though, I like it alot.
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Unread postAuthor: williamfeldmann » Mon Sep 10, 2007 4:56 pm

The main 4 inch pipe that makes up the bulk of the tank is definitly pressure rated. It had pressure ratings printed on the side. I know the Tee and Wye both said Sch 40, as well as all bushings and reducers. The gun works well at 60-70 for what I wanted to do. In the future where do I find these types of junctions that are pressure rated?
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Unread postAuthor: veginator » Mon Sep 10, 2007 5:10 pm

sometimes i've have'nt seen NSF-PW on a pipe and it was still pressure rated just make sure that it says XXX psi.
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Unread postAuthor: MrCrowley » Mon Sep 10, 2007 5:16 pm

williamfeldmann wrote:The main 4 inch pipe that makes up the bulk of the tank is definitly pressure rated. It had pressure ratings printed on the side. I know the Tee and Wye both said Sch 40, as well as all bushings and reducers. The gun works well at 60-70 for what I wanted to do. In the future where do I find these types of junctions that are pressure rated?


60-70PSI should be safe, you can get pressure rated reducers but 99% of the time they are not. Bushings are the better and safer option. You can tell if its DWV by its thickness, its socket depth, markings on the pipe and they're usually a different shape and look different to pressure rated parts.

It's not worth looking for a pressure rated wye, it will be hard to find, just go with a normal tee. I hear HomeDepot and Lowes have some pressure rated parts, but aren't always reliable, best option is to go to a plumbing merchant that specialises in plumbing or some pool shop that make pools.

You can slo buy fittings and pipe of www.mcmaster.com
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Unread postAuthor: williamfeldmann » Mon Sep 10, 2007 5:21 pm

I used the wye simply because I was designing on the fly with parts on hand and the wye fit over my shoulder providing the bazooka style firing position. How deep are the sockets on pressure rated parts like these? These pieces accepted as much pipe as the rated cap and bushings lengthwise. Is it going to be cheaper to order from Mcmaster or to buy them at the local Plumb supply store?
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Unread postAuthor: MrCrowley » Mon Sep 10, 2007 5:39 pm

Try your local Plumb store first, it could save you some time and money on shipping, but just take a browse around McMaster first so you know what prices you are dealing with.
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