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The Gutmenduff Mk1.3

Built a pneumatic cannon? Then post it here! This section is for completed, finished cannons that you have built. Please include pictures and information.
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Unread postAuthor: VH_man » Mon Jan 05, 2009 8:38 pm

PVC Arsenal 17 wrote:A detent is a must. However if you make the breech slightly offset, the stack below the current shell will act as a detent.

Edit: I forgot to comment on your QEV. Your inlet to the barrel is located behind the breech. Is the bolt flow through? Or are you simply using the cylinder's rod (no close fit) and ignoring air lost out of the breech opening?


I didnt mention it very well, But the Bolt is Blow-through. I shall post a picture of it. I decided that as a nerf gun, Dead space wasnt really a worry.

That and the bolt/reciever seal is almost perfect. the Schedule 80 is lined with 17/32 brass, which fits my aluminum tube PERFECT.

Also, for your design, Why not simply have a QEV that gives a little "puff" of air to "blow" out the shell? It would be far more compact, and best of all, No moving parts :D
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Unread postAuthor: btrettel » Mon Jan 05, 2009 8:40 pm

That dead space isn't necessarily bad. I've noticed as I wrote my air gun simulation that some dead space between the valve and projectile is beneficial and helps efficiency. GGDT verified that it wasn't an error in my simulation. So don't think it's hurting performance. It could easily be improving your performance.
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Last edited by btrettel on Mon Jan 05, 2009 9:10 pm, edited 1 time in total.
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Unread postAuthor: PVC Arsenal 17 » Mon Jan 05, 2009 8:42 pm

Ah I see. Blow through is good. Wouldn't want too much of that air to leak out and diminish power & efficiency.

What size Al tube fits inside the 17/32 brass?

As for a QEV to blow the shells out, I could try it. But spring pressure might hold the shells too tight to be pushed out easily. If I had a vertical gravity fed mag it's quite possible. If I am able to do it, I absolutely will. The less moving parts the better.
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Unread postAuthor: btrettel » Mon Jan 05, 2009 8:47 pm

To fit in 17/32 brass a tube should have an OD of 0.5 inches. McMaster-Carr page 3613 shows the entire range of telescoping brass tubes so you can get an idea of what fits in what.
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Unread postAuthor: VH_man » Mon Jan 05, 2009 8:49 pm

Yea, its 1/2in Aluminum. Works great.

And if you dont mind, PVC arsenal, I am going to make an attempt at your shell design. Its just so simple I cant resist... Not to mention has such a "cool" factor.....

And it would be so compact too! gah. This is why I love and hate this site.
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Unread postAuthor: FishBoy » Mon Jan 05, 2009 9:49 pm

Very nice, it seems to cycle very smoothly. Are you planning on keeping the slide valve as the trigger (and btw, where did you get that?)? Haha with my ADD I would sit four hours just cycling that thing :D
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Unread postAuthor: Hailfire753 » Mon Jan 05, 2009 10:08 pm

Dang, I look forward to seeing your nifty new trigger setup... cause I'm using a similar design...
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Unread postAuthor: VH_man » Tue Jan 06, 2009 6:05 am

FishBoy wrote:Very nice, it seems to cycle very smoothly. Are you planning on keeping the slide valve as the trigger (and btw, where did you get that?)? Haha with my ADD I would sit four hours just cycling that thing :D


haha I do that....... Its very fun......
And i got the slide valve off mcmaster. just search for slide valve.

hailfire753 wrote:Dang, I look forward to seeing your nifty new trigger setup... cause I'm using a similar design...


its a normally closed 3 way valve attached to a special mechanism (a rod and spring) that keeps the valve depressed normally and releases the valve when the trigger is pulled.

also, you need a small QEV to pilot the 1/4in one. for this im using one of those mcmaster inline valves, of which you cant change where the exhaust goes.
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Unread postAuthor: john bunsenburner » Tue Jan 06, 2009 7:44 am

dumb noob question from me: what are single acting cylinders?

And great gun, try t get some one to film the nerf war, would be an awsome youtube vid! Oh and how about having multiple mags, it would be even more effective to gain en extra: holy **** he is gonna kick our ***es factor...dont you think?
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Unread postAuthor: btrettel » Tue Jan 06, 2009 8:28 am

The first result on Google for single acting cylinders has a good explanation and informative pictures: http://www.tpub.com/content/engine/1410 ... 05_156.htm

Single acting cylinders basically are the most common form of air cylinder out there. Single acting cylinders can only move in one direction. Double acting ones are the ones with holes on either end so they can be forced to move in either direction.

Edit: I actually have the document I linked to in PDF form. If I remember correctly it's some US Navy book on basic fluid power.
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Last edited by btrettel on Tue Jan 06, 2009 8:34 am, edited 1 time in total.
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Unread postAuthor: john bunsenburner » Tue Jan 06, 2009 8:30 am

ok, thanks, off i go to have a little readanything is better than writing an essay in FRENCH!!!
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Unread postAuthor: POLAND_SPUD » Tue Jan 06, 2009 8:38 am

nice gun....

I see there are more and more guns based on air cylinders... I am not quite happy that most of them fire nerfs but oh well... who cares it's still cool
:wink:

EDIT
how did you join the air cylinder with the bolt ?
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Unread postAuthor: Hailfire753 » Tue Jan 06, 2009 11:45 am

A qev piloted by another qev? I know the part you plan to use, but isnt it a little overkill?
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Unread postAuthor: VH_man » Tue Jan 06, 2009 6:22 pm

Hailfire753 wrote:A qev piloted by another qev? I know the part you plan to use, but isnt it a little overkill?


in order to pilot my 1/4in QEV with my 3 way valve, Yes I do need another QEV.
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Unread postAuthor: Hailfire753 » Tue Jan 06, 2009 10:37 pm

Low flow 3-way, then? Is it one of those custom made, push button ones mentioned in an earlier thread? Do you have a link?
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