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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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Unread postAuthor: Jimmy K » Sun Mar 27, 2011 8:42 am

Well, as a novice to bending PVC, the bends aren't coming out so well. I think I'm too impatient and that my flame is too hot (acetylene), so I bought a heat gun. Hopefully that will work a lot better. I got to bending 2" decently, so the next step is some 3" test runs and then the final stuff.

I also bought the trailer to which the cannon will be mounted. It's perfect- kinda low to the ground, wide, light, and very rigid. I just wired the lights up and will take it to be inspected and titled soon. I figured I should do it now before there is actually a cannon on it. The BMV might not like that.

I got a long stroke hydraulic cylinder for elevation too.. hopefully it will work. We'll see.
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Unread postAuthor: Technician1002 » Sun Mar 27, 2011 10:00 am

Keep trying. Use a large soft flame. The point heat source of acetylene is too concentrated. Heat gun, campstove, oven, propane torch, or heater is needed and lots of time.
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Unread postAuthor: Jimmy K » Mon Mar 28, 2011 9:35 am

I did a quick mock up of the cannon. The trailer to which it is going to be mounted is in one of the pictures on the left. The "sweeps" are not permanent.
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Unread postAuthor: Crna Legija » Mon Mar 28, 2011 9:56 am

looking good, but why didn't you put the ports on the same side of the tank. would have taken out 1 turn, still looks like it can do some dmg
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Last edited by Crna Legija on Mon Mar 28, 2011 10:09 am, edited 1 time in total.
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Unread postAuthor: Technician1002 » Mon Mar 28, 2011 9:59 am

With the PVC barrel, you could do an in barrel chrony shot to optimize the length of the barrel.

That thing is a beast..
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Unread postAuthor: Jimmy K » Mon Mar 28, 2011 11:01 am

-_- wrote:why didn't you put the ports on the same side of the tank


I was worried about the integrity of the welds of the pipe to the chamber, so I put the whole pipe through so that any forces outward would negate each other, rather than having two nipples facing in the same direction that do not have any backing. The pipe is weight bearing.

And Technician1002:
I will have to trim the barrel at least 3 feet to get it to mount to the trailer without hitting the truck.. so barrel optimization will probably be one of the last steps.
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Unread postAuthor: Jimmy K » Mon Mar 28, 2011 8:26 pm

Here is the complete valve and trigger assembly.
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Unread postAuthor: Gun Freak » Mon Mar 28, 2011 8:28 pm

Holy crap that's a monster.

I quote from VERA's thread:
dudeman508 wrote:
King_TaTer wrote: Any ideas on projectiles yet?


Small children :D :D :D
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Unread postAuthor: Zeus » Mon Mar 28, 2011 8:44 pm

Actually, D_Hall got into the muzzle at one pint for a photo, small children would require a sabot (discarding of course).

I wouldn't mind seeing a rather large dart being lauched from this, if it's light and the surface area at the back of the dart will be large (sabot?), impressive velocites could be achived.
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/sarcasm, /hyperbole
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Unread postAuthor: Fnord » Tue Mar 29, 2011 6:34 pm

You may need to make an internal coil-form to bend pvc that large without having it kink. Some thick bailing wire might work.
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Unread postAuthor: Jimmy K » Wed Mar 30, 2011 7:10 am

Here is the hydraulic hoist I am going to use (unless someone decides to use it for a dump trailer - my dad - before I get to it). It should work well.
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Unread postAuthor: mark.f » Wed Mar 30, 2011 8:03 am

Hmmm, just read you had an acetylene torch.

I would air on the side of caution when bending PVC for that purpose, since they will be fully pressurized for longer periods of time than if you had left the valves at the compressor and used the "sweeps" to connect to the barrel.

I would suggest that, whatever you do, you pressure test remotely. Sure, those pool guys use bent PVC in spa systems, but that's a longer radius bend, and at much lower pressures.

If you want to solve both the pressure rating problem, and how to keep your valves supported better, miter cut and weld some steel pipe into the shape you need.
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Unread postAuthor: Jimmy K » Sun Apr 10, 2011 10:24 am

I fired a horizontal test shot today at 20 psi. I lost the softball (3.82" diameter - almost a perfect fit) and scared the neighbor's horses.. not good.

I'm working on the mount to the trailer. My dad did indeed take the hydraulic lift for his trailer so I got a double acting cylinder instead. I also bought a compressor, generator, and some stabilizer jacks too (and somehow I'm still under budget). So basically it is done... it just needs to be put together.

Unfortunately, I don't think I'll be able to make a panning system. The only thrust bearings I could find that would support the weight of the cannon and hydraulics and withstand the recoil were very expensive and would require special maintenance.
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Last edited by Jimmy K on Sun Apr 17, 2011 7:30 pm, edited 1 time in total.
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Unread postAuthor: Technician1002 » Sun Apr 10, 2011 3:01 pm

Panning system is as close as the nearest scrap bicycle. With a torch the steering bearings work fine. If you have a scrap car, a wheel bearing assy from a front wheel works excellent. Visit a junk yard. Wheel bearings is not rocket science or expensive from a scrap yard. Wheels have the advantage of disk brakes. You can pan it and lock it.
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Unread postAuthor: mark.f » Sun Apr 10, 2011 4:08 pm

Technician1002 wrote:Wheels have the advantage of disk brakes. You can pan it and lock it.


Those humongous programmable electronic road signs use this exact same system to rotate the sign to the right viewing angle and lock it in place after towing to where you need it. A pin is also used for extra security.
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