SpudFiles

So I am currently working on a QEV cannon and while I wait for my 3-way valve to arrive I decided I would start working on a breech loading design. Hopefully I am posting this in the correct section. Anyways here are some pictures of what I have made. I know some of the parts are a little sloppy at the moment but it only took me about 5 minutes to make what I have. I am looking for advice so any tips or constructive criticism are greatly appreciated.

I still need to drill a hole on one of the end caps (pipe reducers) so a shaft can be attached to the "bolt?" so it can be moved back and fourth.

Here is a link with pictures to my QEV cannon
http://www.spudfiles.com/forums/qev-tri ... 21984.html


<a href="http://s1106.photobucket.com/albums/h37 ... 191330.jpg" target="_blank"><img src="http://i1106.photobucket.com/albums/h37 ... 191330.jpg" border="0" alt="Photobucket"></a>
Here is just a piece of 1/2 inch pvc to use as a "mock" barrel

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A 1/2 coupling which I have sanded down the inside so it will slide on the barrel. Also a hole was drilled into it to allow a marble to fit through.

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A couple of 1 inch to 1/2 inch adapters which have been cut down so the bolt will have room to slide when it is put together.

<a href="http://s1106.photobucket.com/albums/h37 ... 191401.jpg" target="_blank"><img src="http://i1106.photobucket.com/albums/h37 ... 191401.jpg" border="0" alt="Photobucket"></a>
Just an unmodified 1 inch to 1/2 inch tee

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Bolt placed on the barrel with holes aligned (sorry about the flash)

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Bolt on barrel with the barrel hole covered

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Assembled

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Closeup of the bolt closed

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Closeup of bolt open

That's a pretty clean looking breech.

Are you planning on using a magazine with it? It looks like it could take one without any modification.

Yeah I plan on just putting a piece of 1/2 inch PVC into the top of the tee

Back in the day, I built something very similar to this with a sliding cover bolt. I used a spring to ensure that it was closed when I wasn't pushing it back. Of course MINE failed miserably as I was young and stupid. That aside, this looks well built.

mlz3000, I think the breech is designed for use with a magazine, considering he bothered with a tee fitting instead of just a stand-alone slide.

I figured, but he didn't mention it.

Also, I misunderstood the design a bit . I thought that he had the tee there to facilitate a twist-only open method, rather than having to move it back and forth on the barrel.

Please forgive the sidetrack here...

Where are youse guys getting marbles that fit a 1/2" sch40 PVC pipe ?

I looked all over town for marbles. The only places I found them was at a craft store, for a gawdawful amount of dineros. And at a dollar store. Pretty good bargain there.

But the bargain went out the window when I got home.

The marbles are too big.

WT Huh ???

~~~

Edit to add to HoppinS10...

I am wondering why you didn't just use a 1/2" tee, in the first place ?

Hog it out to slide on your barrel, just like you did the original 1/2" fitting, and viola', you have the complete bolt in one swell foop.

Where are youse guys getting marbles that fit a 1/2" sch40 PVC pipe

Generally, you have to buy a bulk supply and then sieve them with a chunk of barrel material. Personally, I would just go to Mcmaster-carr and buy some steel balls. They seem to be a pretty consistent size.

Edit:

swell foop

Me oh my, that is one swell foop you have there.

Where are youse guys getting marbles that fit a 1/2" sch40 PVC pipe ?

I bought mine from a store called hobby lobby. They have all sorts of arts and crafts stuff they come in bags of about 100 for $2. Although they dont fit perfect in the barrel they are pretty close and work well. My cannon will fire through 1/2 inch pine at about 100 psi. They are pretty consistant in size from what I have seen so far. Im sure those steel balls that McMaster sells would be a better bet but the marbles were cheap and i can buy them locally.

I am wondering why you didn't just use a 1/2" tee, in the first place ?

Hog it out to slide on your barrel, just like you did the original 1/2" fitting, and viola', you have the complete bolt in one swell foop.

I was originally looking at using just a tee but didnt find it reliable enough to load 1 and only 1 marble into the barrel each time the trigger is pulled. I know there are some people who have built cannons with a "flap" in the tee that blows up to prevent a second marble from falling into the barrel but there is still some air that goes up into the magazine which would hinder performance. Also if I decided to make a sliding tee the magazine would move with the tee as it slid to open and close the breech. Hopefully I am making sense it has been a long day at work and my brain is fried.



Also forgot to mention that I have a spring loaded air cylinder that I plan to use to actuate the bolt. If all goes well when the trigger on the 3 way valve is pressed the gun will fire and also release the air from the cylinder which will bring the bolt into the open position so a marble will fall into the barrel. When the trigger is released, the cylinder will be pressurized and slide forward which will close the breach ready for the next shot. This is all in my head and havent actually attempted to make it work yet.

That sounds awesome!

You'll have to make sure that the breech stays open for long enough, or the marble might not fall in, but that sounds like a sweet design.