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PCP building blog

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: wyz2285 » Mon Mar 12, 2012 11:35 am

I use nylon as valve body, I don´t think it´s a solid platform for shear screws.
Update diagram: the seal has the same area as the counter piston housing, will it work?
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CpTn_lAw wrote::D "yay, me wanna make big multishot pnoob with 1000 psi foot pump compressor using diamond as main material. Do you think wet bread make good sealant? " :D
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Unread postAuthor: Gippeto » Mon Mar 12, 2012 1:25 pm

You need to pay attention to the surface area upon which the pressure is acting...calculate the forces on the spool and compare them with the strength of the spring...is it gonna close?

I'm assuming your drawing is no longer to scale. :wink:

Nylon is a very poor choice for a material to be used thusly in a pcp... (Delrin/Acetal at a minimum) what pressure were you thinking about running it at??

Give serious thought to how you're going to secure the valve...it coming out like a bullet is a scenario you NEED to avoid. If you mention epoxy again...I'm outa here. :lol:

One suggestion would be to copy the design of the Crosman 160/QB78...place a steel ring behind the valve..(valve stem would be extended through this piece). With the valve making good contact and the piece secured to the tube appropriately, it'll take the load. Then one smallish screw to keep the valve itself indexed and yer good to go.

Piece I'm talking about is Prt#0200

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Unread postAuthor: wyz2285 » Mon Mar 12, 2012 1:44 pm

Well I'm going secure the valve exactly the same way as I am doing now, take a look at the latest video I posted, it's working very well for now.
My drawing it's still in scale :roll: well I will see if I can find a tube really slightly bigger than the spool housing, 1mm ID bigger...
Nylon is the only material I can get, and for now the only material I can work with my drill press.
I'm hoping I can use a soleniod to open this thing...
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CpTn_lAw wrote::D "yay, me wanna make big multishot pnoob with 1000 psi foot pump compressor using diamond as main material. Do you think wet bread make good sealant? " :D
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Unread postAuthor: qwerty » Mon Mar 12, 2012 1:46 pm

Haven't been around for a while, got back into the gun "phase" after watching air rifle hutning videos.
Anyway, enough about me, looks awesome wyz can't wait to see it finished.

I might even have to attempt one myself, still got the ol' shocky. :)
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Unread postAuthor: wyz2285 » Wed Mar 14, 2012 10:46 am

So IF I´m able to make the counter balanced hammer valve working, I´d like to make it a semi, or even full automatic, by using the solenoid to operate the valve.
The solenoid in normal conditions isn´t strong enough(12v DC), but I use a 250v 80uf capacitor to activate it, it gives a really strong, instant pull, just as a hammer :wink: .
So, dear dewey-1, can you make me a circuit(hopefully not to complicate) that allows semi/full auto? without adjusting the fire rate, but uses a capacitor(anybody knows how big it should be? I think 64v 1000uf) to power the solenoid instead of 12v DC? Like this video shows, thank you very much :)
[youtube]http://www.youtube.com/watch?v=eki5MrZ3KR8[/youtube]
If full auto it´s too difficult, I´m fine with semi :)
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CpTn_lAw wrote::D "yay, me wanna make big multishot pnoob with 1000 psi foot pump compressor using diamond as main material. Do you think wet bread make good sealant? " :D
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Unread postAuthor: Brian the brain » Wed Mar 14, 2012 3:08 pm

Update diagram: the seal has the same area as the counter piston housing, will it work?


Yes.

Oh and..
The surface areas are not equal.
One seals on the inside of the tube, the other on the face of it.
That tiny difference would make it just right.
You need a tiny difference to get a perfect seal and to make it snap shut after a burst.


I'm sorry if I was somehow unclear about how my version works but it seems you have accidentally copied the basic design.

I say go for it!!
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Oh my friggin god stop being so awesome, that thing is pure kick ass. Most innovative and creative pneumatic that the files have ever come by!

Can't ask for a better compliment!!
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Unread postAuthor: wyz2285 » Wed Mar 14, 2012 5:15 pm

One seals on the inside of the tube, the other on the face of it.
That tiny difference would make it just right.

Thank you sir! :D
So the area differential will be between the tube's OD and ID right?
I´m going to make it :P
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Last edited by wyz2285 on Thu Mar 15, 2012 3:27 pm, edited 1 time in total.
CpTn_lAw wrote::D "yay, me wanna make big multishot pnoob with 1000 psi foot pump compressor using diamond as main material. Do you think wet bread make good sealant? " :D
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Unread postAuthor: Brian the brain » Thu Mar 15, 2012 2:40 pm

Depending on the wall thickness of the tube ofcourse.
You would need about 1-2 mm difference in diameters.

get to work!!
:D
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Gun Freak wrote:
Oh my friggin god stop being so awesome, that thing is pure kick ass. Most innovative and creative pneumatic that the files have ever come by!

Can't ask for a better compliment!!
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Unread postAuthor: wyz2285 » Thu Mar 15, 2012 3:27 pm

The ID is 10.3mm, OD is 11.7mm
The difference is 1.4mm, area differential would be 19.3mm2, I hope it´s ok :)
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CpTn_lAw wrote::D "yay, me wanna make big multishot pnoob with 1000 psi foot pump compressor using diamond as main material. Do you think wet bread make good sealant? " :D
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Unread postAuthor: Goats spudz » Fri Mar 16, 2012 4:27 pm

Will this work for 1000psi ?
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Unread postAuthor: wyz2285 » Fri Mar 16, 2012 5:15 pm

For me it will, but as Gippeto said, the o-rings will be blow out and worn out very quickly.
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CpTn_lAw wrote::D "yay, me wanna make big multishot pnoob with 1000 psi foot pump compressor using diamond as main material. Do you think wet bread make good sealant? " :D
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Unread postAuthor: Goats spudz » Fri Mar 16, 2012 6:25 pm

wyz2285 wrote:For me it will, but as Gippeto said, the o-rings will be blow out and worn out very quickly.
so a normal hammer valve with a nylon seal would be better?
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there would be an o-ring around the thick stem
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Unread postAuthor: Crna Legija » Fri Mar 16, 2012 6:45 pm

Goats spudz wrote:Will this work for 1000psi ?


That wont work at all theirs a O-ring between the valve port and barrel port and the valve stem would get blown out.
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Unread postAuthor: dahakka » Mon Mar 19, 2012 8:37 am

Image

Image


Image

when i use 0.1gr bb , power is good
but when i use 1gr steel bb , ...
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... terrible :( :( :(
Image

any idea?
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Unread postAuthor: wyz2285 » Mon Mar 19, 2012 9:07 am

E=1/2mv2
as steel bbs are a lot heavier than airsoft bb, you lost a lot velocity, and didn't compensate the increased energy you got by increase the weight.
But where did you got that big bag of steel bbs?
The gun looks good, polish it and paint.
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CpTn_lAw wrote::D "yay, me wanna make big multishot pnoob with 1000 psi foot pump compressor using diamond as main material. Do you think wet bread make good sealant? " :D
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