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I too has semi-auto

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: cannonmaster » Thu May 27, 2010 5:14 pm

looks like an awesom gun and i was wondering how many shots you can get off on one compression.
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Unread postAuthor: DinerKid » Thu May 27, 2010 8:21 pm

POLAND_SPUD wrote:yeah sorry I thought that I've seen these in clippard catalogue

17 bar is a lot (usually stuff form other companies is rated to 10bar max)


MJVO-3 valve is pretty much the best valve you can get... I've compared hundreds of data sheets and most 1/8" valves that I could find cost about 30-50 euro excluding shipping and taxes but clippard sells MJVO-3 for about 12$ not including taxes etc.

also check their QEVs - you can order them with male threads... it might not seems as much but it helps to reduce number of fittings and dead space to minimum


That is definitely a good price for what looks like a quality valve. It just seems a bit small. Is an 1/8" valve big enough to pilot a 1/2 QEV with good speed? How about a 3/4" QEV? Obviously a bigger pilot valve is always better, i am planning a new cannon with either a 1/2" or 3/4" QEV and if i could use the MJVO-3 and get it for a good price that would rock.

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Unread postAuthor: POLAND_SPUD » Thu May 27, 2010 8:36 pm

most 1/8" DCVs have good enough flow (250-300L/m) to pilot a 1/2" QEV...
1/8" QEV piloted by a 1/8" dcv can pilot a 3/4" QEV...

maybe the MJVO-3 can pilot a 3/4" QEV directly as it has better flow but I can't get them in Europe so... sorry I can't test it
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Unread postAuthor: Gun Freak » Thu May 27, 2010 8:37 pm

It wouldn't be worth piloting a QEV with a QEV. Try the DCV alone and you should be fine.
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Unread postAuthor: POLAND_SPUD » Thu May 27, 2010 9:11 pm

why not ? QEVs are normally used when you want to pilot large volumes with a small control valve.... maybe you are referring to costs but I got mine for about 1$ so I don't mind it
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Unread postAuthor: jor2daje » Thu May 27, 2010 10:49 pm

Ya piloting bigger qev's with smaller is a fine idea, if you look hard enough qevs are dirt cheap.
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Unread postAuthor: django » Fri May 28, 2010 2:48 am

I went out today and bought the MJVO-3 Poppet Valve and a "Clippard Air Cylinder "M-SSR-08-40( cost me $38.00 Aust, for the cylinder!!) its got 40mm stroke,12mm bore,Single acting but I might have problems in the air inlet for the cylinder is listed a Metric 5mm thread. I dont know how I'll be able to adapt from this size to a Brass Elbow that I'll be using on the gun like the set up in this thread???.

They didnt have a small QEV at the shop like I wanted so I'll have to order one in elsewhere,like one of these 1/4" jobs
http://www.bellpro.net/xcart_program/home.php?cat=268

I dont know how big an Air chamber I'll need on this gun,will be 6mm BB's,1/4" Qev,1/8" Poppet, barrel maybe at 1.5 foot long(350mm) I'm trying to keep the gun really small this time!. I have another question,ive had no dealings with Air Cylinders before but why doesnt the air cylinder actuate straight away when you apply air to it?!.I mean as per gun in this thread why doesnt that air cylinders rod fire outwards when you hook up the air?,does it only actuate when theres a pressure drop?...........
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Unread postAuthor: POLAND_SPUD » Fri May 28, 2010 5:26 am

you can buy push-to-connect fittings and calibrated tubing in almost every place selling pneumatic stuff... if you are lucky you might find some polyamide tubing rated very high... just get a 5mm fitting a lenght of tubing and another fitting to connect straight to the chamber
(but seriously buy some more if you can find some all metal ones)

or just buy some reduction nipples from 1/8" to 5mm (I don't know if you are aware of it and why you are asking but 5mm thread is quite widely used in pneuamatics)

I mean as per gun in this thread why doesnt that air cylinders rod fire outwards when you hook up the air?,does it only actuate when theres a pressure drop?
I don't quite get it what you are saying... :?
the single acting air cylinder retracts when the gun fires... that's how it works... once you depress the button lever teh chamebr is filled with air and so is the air cylinder
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Unread postAuthor: django » Fri May 28, 2010 5:33 am

DUH-OH,I'm sorry for some reason I was thinking the Air Cylinder's rod was retracted at rest then when fired the rod shoots forwards :oops:
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Unread postAuthor: killerbanjo » Tue Jan 04, 2011 3:02 pm

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Unread postAuthor: django » Thu Jan 20, 2011 9:00 am

Still trying to find a suitable sized block of Aluminium to make the feeder block to make a gun similar to this.

I was going to have the end of the air cylinders actuating rod stop JUST BEFORE the air inlet not over it= will the BB fall into the air inlet if I do this?.Im trying to maximise flow,I would think the bb will be expelled past the air inlet from the Air cylinders rod flying forwards so fast??.

Im going to try put a seal of some sort at the end of the Air cylinder rod too so it shuts off air going to the mag.
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Unread postAuthor: POLAND_SPUD » Thu Jan 20, 2011 9:30 am

actuating rod stop JUST BEFORE the air inlet not over it
Sure, it works that way - just make sure there is something that keeps the BB from rolling back

ohh and BTW... you don't need a machined block... you can use two Ts instead

Just measure the distance the bolt has to travel from the mag to the air inlet and you know what air cylinder you need (stroke in mm)
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Unread postAuthor: Gaderelguitarist » Thu Jan 20, 2011 11:53 am

Django, I feel as though it would me more efficient to have the bolt hold the bb just slightly in front of the inlet hole, not directly over it, but not completely in front of it. This eliminates the falling in problem, as well as increasing the rear portion of the bb the air will act upon, rather than having to hit it from the bottom.

Also, don't listen to Poland. If you can machine an aluminum piece to hide all your gibblets, then go for it. Two tees, schmoo shcmees. :lol:
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Unread postAuthor: django » Fri Jan 21, 2011 5:07 am

Gaderelguitarist wrote:Django, I feel as though it would me more efficient to have the bolt hold the bb just slightly in front of the inlet hole, not directly over it, but not completely in front of it. This eliminates the falling in problem, as well as increasing the rear portion of the bb the air will act upon, rather than having to hit it from the bottom.

Also, don't listen to Poland. If you can machine an aluminum piece to hide all your gibblets, then go for it. Two tees, schmoo shcmees. :lol:



Yeh I see what you mean about the air hitting the bottom of the BB, the Air Cylinder im using is really small the whole thing is only 140mm long,15mm wide,bore stroke is 40mm and the threaded rod on the cylinder is only 3mm thick so I cant drill air holes in it like the original gun in this thread.

So trying to figure out my best option to stop the bbs dropping and get good enough flow. if I do make it so the Air cylinder's rod hold's the bb slightly infront of the air inlet as you suggest I think it will really hold back flow as I cant drill holes in that rod( too small)

What if I drill the air inlet hole 5mm or so and have the Air cylinders rod stop just before the air inlet,then the bb cant fall in there but yes will be a bit flow restrictive too :roll: . or I could grind the end of the threaded rod a bit thinner and do it your way but it will make the rod's end weak......
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Unread postAuthor: POLAND_SPUD » Fri Jan 21, 2011 5:54 am

the air cylinder extends so fast that ammo is shot into the barrel...
so as long as you have there something that keeps it in place it should stay be ok

so I cant drill air holes in it like the original gun in this thread
you've got a threaded rod - it is threaded for a reason - you can attach something to it

If you really insist on using the air cylinder to keep ammo in place just build a bolt that screws on the rod and that's it (put a thin needle on the tip or something)
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Last edited by POLAND_SPUD on Fri Jan 21, 2011 6:10 am, edited 1 time in total.
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