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original Semi-auto idea

This area is for the discussion of BB or airsoft sub machine guns, and or other small arms such as pellets.
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original Semi-auto idea

Unread postAuthor: The Engineer » Fri Jan 23, 2009 1:23 am

I don't think I have posted this yet (if I have, please correct me). After taking a short break from spudding and then tinkering around a little bit, I have a few new ideas. This is one of them.

(check valve can be built or bought at Ace)
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Unread postAuthor: MrCrowley » Fri Jan 23, 2009 2:08 am

Essentially, everyone who has built a sprinkler valve cannon has done this. Aside from the hopper, which most people don't bother with.

The check valve isn't needed and restricts flow by the way.

But nice that you're thinking of ideas :)
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Unread postAuthor: sputnick » Fri Jan 23, 2009 7:27 am

Definitely been done, by a great many people.

At least you know it works :)
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Unread postAuthor: The Engineer » Sat Jan 24, 2009 1:42 am

Actually, I disagree with the check valve part. In my current cannon I use a 1/2inch barrel and the 'reset' valve air is strong enough to propel a 25gram shot about 2 feet (the shot even has 1/8inch space inside the barrel).
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Unread postAuthor: MrCrowley » Sat Jan 24, 2009 2:06 am

Try having the air input right next to the sprinkler or better yet, mounted on the sprinkler valve.

The check valve will limit flow unless you get like a 1" one, even then I wouldn't be sure. And they get pretty expensive that size, well atleast here they do.

Another thing would be to swap the spring for a stronger one, not sure what effect that would have on performance though. You could also make the equalization hole bigger, same thing for performance though. Someone should tests these things. :wink:
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Unread postAuthor: The Engineer » Sat Jan 24, 2009 9:42 am

Well thats what I'm looking at doing. After all, what's spudding if not that?

And yes I will use a 1", its only about $7.
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Unread postAuthor: MrCrowley » Sat Jan 24, 2009 11:53 am

With the check valve, are you hoping the burst of air that escapes through the sprinkler, isn't enough to open the check valve?
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Unread postAuthor: The Engineer » Sat Jan 24, 2009 12:55 pm

Basically, yes. As long as I replace the spring (as mentioned before) it shouldn't be a problem.
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Unread postAuthor: MrCrowley » Sat Jan 24, 2009 10:32 pm

Still think it'd be better to mod the valve with the ideas I put forward.
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Unread postAuthor: The Engineer » Sun Jan 25, 2009 12:53 am

You are probably right (as most on this site probably know more about pneumatics than I do), but to be honest I'm not exactly sure what your idea would accomplish....?
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Unread postAuthor: MrCrowley » Sun Jan 25, 2009 1:03 am

Enlarging the equalization hole would hopefully make the diaphragm seat quicker, meaning less air is expelling through the barrel.

Strengthening the spring hopefully would keep the diaphragm seated for longer when you are filling up the chamber. Since more force is on the diaphragm, it is kept down, and sealed, longer, allowing the pilot volume to fill as well. This also should help keep expelled air to a minimum.

There shouldn't be any negative side effects that would notice to these mods, though they may take some fine tuning. You can always try the check valve out first, if it doesn't work as well as planned, maybe try these mods.
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Last edited by MrCrowley on Sun Jan 25, 2009 4:51 pm, edited 1 time in total.
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Unread postAuthor: The Engineer » Sun Jan 25, 2009 1:31 pm

Aha, now I understand. Thanks, i will def. give those a shot if the check valve doesn't work. I'd love to try them, its simply a matter of time*effort. Thanks!
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Unread postAuthor: mike1010 » Mon Feb 02, 2009 7:14 am

you could just but a small like 1/4 ballvalve at the base of the barrel to vent the extra air and just close it before firing. easy cheap and small.
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Unread postAuthor: The Engineer » Sun Feb 08, 2009 10:38 pm

I could, except that this is supposed to be semi-automatic, and that would require more effort than simply pulling a 'trigger'.
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Unread postAuthor: iknowmy3tables » Fri Feb 13, 2009 3:39 pm

making a fill system for a semi auto should not be a problem, there are ways of doing this setup already, the loading setup is the only place that need new designs,
here one way to setup a sprinkler valve:
http://www.spudfiles.com/forums/true-semi-t156.html
that's one way to make the diaphragm reset quickly,

strengthening the spring would decrease performance because the spring tension hampers the diaphragm opening even if the effect is small.

the only method that doesn't hamper shooting performance is filling from the pilot, in fact this will allow you to remove the spring and increase shooting performance the best way to do this is to buy a QEV and a 3way valve. the downfall is that the fill rate may decrease which is just a problem on sprinkler valves, but you can improve it by increasing equalization flow which I did by cutting a flap in the diaphragm, adding a line with a check valve between the pilot and the chamber should increase flow enough that it won't be a problem, you can also see what I did with the deus ex machina
http://www.spudfiles.com/forums/deus-ex ... t7864.html
http://www.spudfiles.com/forums/deus-ex ... t8418.html
the valve used (http://www.spudfiles.com/forums/semi-blowgun-t6877.html) note that it's very weak and should be done if you can't or won't get a better 3way valve
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