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A place to ask general spud cannon related questions.
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Unread postAuthor: jackssmirkingrevenge » Mon Nov 28, 2011 5:42 pm

Pilot volume affects performance. Larger pilot volume means the pilot area empties more slowly for a given pilot valve, so the piston opens more slowly.

Piston leakage affects performance to the extent that the launcher might not even fire.
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Unread postAuthor: sharpshooter11000 » Mon Nov 28, 2011 5:48 pm

It doesn't need amazing performance, it's only going to be firing airsoft bbs in a big cloud. I've increased the piston diameter to 52.8 leaving a 0.1mm gap, is that better? Should the valve work now?
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Unread postAuthor: jackssmirkingrevenge » Mon Nov 28, 2011 5:56 pm

sharpshooter11000 wrote:Should the valve work now?


If your pilot valve has a greater flow than the equivalent of a 4.5mm diameter pipe, yes.

It's a fairly large diameter piston, so even a small gap in diameter translates as a lot of area.

A smaller piston gives you more margin for error if your pilot valve is small.
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Unread postAuthor: sharpshooter11000 » Mon Nov 28, 2011 6:08 pm

Hmmm... Maybe I should look for a bigger valve.
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Unread postAuthor: jackssmirkingrevenge » Tue Nov 29, 2011 12:10 am

sharpshooter11000 wrote:Hmmm... Maybe I should look for a bigger valve.


... or optimise your piston.

For example, 2" diameter piston piloted by a schrader, with the benefit of an o-ring seal. The tricky bit is making it a floating o-ring to allow air to flow from the pilot to the chamber (assuming you're filling from the pilot) but not vice versa, that or having separate fill valves for pilot and chamber.
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Unread postAuthor: Crna Legija » Tue Nov 29, 2011 12:48 am

idk why it posted i went back
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Unread postAuthor: stoj » Tue Nov 29, 2011 3:17 am

Question: Is it possible to set up the system as shown? By this I mean look at the placement of the schrader valves (this just makes the construction process slightly easier, whereas if not possible, i'll just use a 4way junction between the slide and air tank.)[/img][/b]
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Unread postAuthor: Crna Legija » Tue Nov 29, 2011 4:23 am

Not will a stander QEV you will need to put a small hole 1mm or less i would say and a weak spring behind the piston then it will work.
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Unread postAuthor: wyz2285 » Fri Dec 02, 2011 9:31 am

Hi I have a small question about diaphragm valves, how fast can they go from close->open ->close again? Because I'm going to buy one and I will control the valve with a timer circuit. In the fastest ROF the valve has to open and close 10 times per second. I found that solenoid 3-ways are capable to do that, but is a diaphragm valve can do that too?
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Unread postAuthor: jackssmirkingrevenge » Fri Dec 02, 2011 10:23 am

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Unread postAuthor: wyz2285 » Fri Dec 02, 2011 11:37 am

Yes that's the valve i'm thinking about, but the information i need isn't there :roll:
Damn :evil: 2.5mm orifice is terrible :evil:
So now I'm very unsure about witch way to go, 1/4qev+12v 3way or this valve :? with qev I will get much more power looks like, but not very air-economic, the pilot air is probably all lost :( with the solenoid valve I will save some pilot air but 2.5mm orifice is really really lame :x with only 10bar the power will be a joke :evil:
The 3way: http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... 0765257895
qev: http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... 0904190999
But even the 3-way is fast enough, is the qev fast enough to close too?
I think my best chance would be use a 3-way as firing valve :roll: so I tried to find a decent flow 3-way and this is what I found: http://www.ebay.com/itm/PT-3-8-Air-Inle ... 3cbe7b631b, it's 3/8 with decent orifice but it says 3way 2position on the title but in the describetion it says 2position 5way :? anybody help?
I found a lot 1/8 ones, but the orifice are only 1.5mm :( .
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Unread postAuthor: jackssmirkingrevenge » Sat Dec 03, 2011 8:25 am

wyz2285 wrote:But even the 3-way is fast enough, is the qev fast enough to close too?


Look at my pop-off piloted QEV cycling ;)

I tried to find a decent flow 3-way and this is what I found: http://www.ebay.com/itm/PT-3-8-Air-Inle ... 3cbe7b631b, it's 3/8 with decent orifice but it says 3way 2position on the title but in the describetion it says 2position 5way :? anybody help?


Could it be that it's 3 way 2 position with 5 ports?
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Unread postAuthor: Goats spudz » Sat Dec 03, 2011 11:24 am

What would be the best .22 bore barrel for my air gun as my brass one bent quite easily, im thinking this http://www.ebay.co.uk/itm/Carbon-Fiber-Tube-8mm-x-1meter-1mm-Wall-OD8mm-ID-6mm-/330647839436?pt=UK_Crafts_Other_Crafts_EH&hash=item4cfc25a2cc#ht_500wt_1287

also if it was like 6mm id and 20mm od that would be cool
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Unread postAuthor: POLAND_SPUD » Sat Dec 03, 2011 11:29 am

Could it be that it's 3 way 2 position with 5 ports?

nope it's a 5 way valve
5 way = 5 ports


Though don't worry you can still use it as a 3 way valve (though you'd have to block of port B and it will waste some air trapped in the valve and exhaust it through the exhaust of port B)

If you think of it a 5 way valve is essentially two 3 way valves that switch at the same time (one to closed the other to open position and the other way round) and have one common port
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Last edited by POLAND_SPUD on Sun Dec 04, 2011 8:10 am, edited 1 time in total.
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Unread postAuthor: wyz2285 » Sat Dec 03, 2011 5:48 pm

Thanks Poland
I have made my decision, 1/4 qev + 1/8 3-way, as the 3-ways I can found only holds 8 bar :(
Jack does your full auto reaches a 600 rpm? Because in the fastest ROF I can choose from the chip is 10 Hz(10 Rps).
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