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Blow forward Breech Concept Redesign

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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Blow forward Breech Concept Redesign

Unread postAuthor: thedeathofall » Wed Feb 11, 2009 9:50 pm

Okay, so I really like Jack's original blow-forward design, even if he doesn't, but it has a few flaws.

First of all, very few people are as in love with epoxy as JSR. :roll: I personally stay very far away from the stuff. So to redesign it, it needs the plugs and piston to be made out of something else... PVC rod. 1 inch PVC rod It makes a perfect piston in a 60 cc syringe without having to be filed ore sanded. McMaster is full of the stuff. I have personally ordered it several times.

Secondly, If the power needs to be increased/decreased, the plugs need to be removable, which again means no epoxy... Instead, the plugs will be held in place with screws, but to be airtight, I will add a few o-rings to the mix.

Lastly, the design he made uses two holes in one of the plugs. One for a rod, and another for the air. This makes it hard to add the o-ring and is well, kind of ugly. If the rod was simply a tube with epoxy on the end, it would do the same thing right? Well if we add holes in the side of the tube, air can flow through right? So if you look at the paint diagrams i made, you can see that by boring a hole in the plug for the tube, and a bigger hole halfway through for the air inlet (like a 1/8 inch nipple) you can do the same thing, only neater and more appealing.:wink:

Image

Image


Hope you all enjoy
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Unread postAuthor: roboman » Wed Feb 11, 2009 10:19 pm

That should work... only way to find out is to build it! Do you intend to make a prototype?
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Unread postAuthor: thedeathofall » Wed Feb 11, 2009 10:24 pm

Working on it right now.. I just happen to lack a few things. O-rings, a certain size aluminum tube, and a steady drilling hand. :wink:
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Unread postAuthor: roboman » Wed Feb 11, 2009 10:30 pm

You should invest in a good drill press. It allows you to make your holes MUCH straighter.
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Unread postAuthor: thedeathofall » Wed Feb 11, 2009 10:54 pm

Ya I know. I have thought about it before, but never really needed it. Now with all this precise drilling, I am feeling like an idiot for not having one. :?
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Unread postAuthor: jackssmirkingrevenge » Thu Feb 12, 2009 12:51 am

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Unread postAuthor: inonickname » Thu Feb 12, 2009 2:52 am

Cool, might hook up something similar to my paladin blowback tee design... Would make the mag design easier.
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Unread postAuthor: thedeathofall » Thu Feb 12, 2009 11:37 am

Okay, okay, you got me on that one Jack. I seriously haven't seen the thread, but you did get it made. Would you mind telling me how it performs compared to the original version?

_______
EDIT

After reading the thread you posted, I came to the conclusion that my design is different. I use a compression spring the same way as in the original concept. I simply use a different rod.

While I like the idea of you second version Jack, I see the actual idea slightly harder to control. I have always had a knack for breaking those types of springs. :roll: They just don't like to stay together.

Essentially my design is the exact same as yours from the third page

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Unread postAuthor: jackssmirkingrevenge » Sat Feb 14, 2009 4:28 am

thedeathofall wrote:Essentially my design is the exact same as yours from the third page


... which is essentially clide's design from his GB semi launcher. Now build it and make it work ;)
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Unread postAuthor: thedeathofall » Sat Feb 14, 2009 10:45 pm

Yes SIR! Right away SIR!
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Unread postAuthor: littlebro05 » Sun Feb 15, 2009 1:34 am

Oh yeah, looks good.

But out of curiosity when you firing this thing, how air efficient do you think this would be? Would reducing the volume of air to push the piston increase efficiency but decrease performance dramatically or not by much? And when you call it "semi-automatic" does this mean each time you pull the trigger on the blowgun you have to let go when the bb is fired to let the piston reset to it's original position? (sorry abit obvious but just making sure).
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Unread postAuthor: thedeathofall » Sat Feb 21, 2009 1:10 pm

@littlebro

While i am still working on this, I have instead decided to base a few guns around a different design. (closer to what Jack said) This is because it is simpler and more air efficient. however, because it uses less air, there wont be as much build up and it will probably have less power. I will simply have to test it and see.

Decreasing the volume of air, will indeed decrease performance, but i don't know how.

Yes, by semi automatic i do mean that you have to release the trigger to reseat the piston. If you hold the trigger, the air pushes the piston forward and rushes by it, holding it in the forward position.
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