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MIKE (HP Marble Gun)

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: far_cry » Mon Jun 01, 2009 8:30 pm

VH_man wrote:
starman wrote:Whew, you were precariously close to the edge of what looks like a homemade sandwiched plywood platform. Probably wasn't the safest shot of the year...result was impressive however.


actually, its an old rotting peice of wood. i have shot clean through it with this gun before....... so........ its actually QUITE safe. that and the cannon is.... like..... 4 feet long.

that and the camera was a good 20 feet away. it was just zoomed in.

as for penetration, im waiting for my bloody Mcmaster order to come in with the 0-600 psi guage so i can get my lead slug moving at speeds i want :D. it was "out for delivery" at 2:45 thismorning and it still hasnt arived at 4:00 in the afternoon.......


i am sorry for kicking an old topic
but , did you get your gauge "11 month later"
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Unread postAuthor: rikukiakuchiki777 » Tue Jun 02, 2009 4:26 am

Sorry to be a noob, but how does the O-ring piston valve work? I've looked at the 'piston valves explained visually' but they all have equilisation holes and whatnot. If the O-ring seals the pilot area, how does the hpa get into the chamber?
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Unread postAuthor: jackssmirkingrevenge » Tue Jun 02, 2009 4:54 am

rikukiakuchiki777 wrote:If the O-ring seals the pilot area, how does the hpa get into the chamber?


This is because the o-ring is "floating" at it only seals in one direction, a bit like these pump heads:

Image

The grooves cut in front of the o-ring allow the air to flow one way ("down" if we're looking at the above photo) but behind the o-ring there's a solid unbroken steel washer that makes a perfect seal and therefore air cannot flow "up".
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Unread postAuthor: jmadden91 » Tue Jun 02, 2009 4:59 am

Mate that helps me a lot. I think i will have to make one of the above pictured pistons. My wooden one is not up to the job. Thanks JSR

Edit: Is the one used in the original gun floating though? It looks like a number of thin layers of rubber rather than an o ring (for the sealing face at least)

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Last edited by jmadden91 on Tue Jun 02, 2009 5:56 am, edited 1 time in total.
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Unread postAuthor: VH_man » Tue Jun 02, 2009 5:55 am

far_cry:

Yes, Ill admit to it, I used my shock pump without a gauge. I went by how much the hose increased in diameter. Worked well enough... Seeing as the hose increases in diameter after a mere 200 PSI...
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Unread postAuthor: spot » Tue Jun 02, 2009 10:38 am

Is the one used in the original gun floating though? It looks like a number of thin layers of rubber rather than an o ring (for the sealing face at least)
The O-ring on the piston is not floating. You can see that because the o-ring doesn't have any space to move. The thing you are talking abouth though is the sealing face. The right "rubber piece" is the o-ring, and the several rubber pieces to the left is the sealing face. If you don't know what a sealing face is, I suggest you to look it up in the wiki. (It's the part of the piston that seals against the barrel on a barrel sealing piston).
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Unread postAuthor: jmadden91 » Tue Jun 02, 2009 8:16 pm

I know what a sealing face is mate.

Where is the equalization on his piston then? Surely if that o ring is fixed the air couldn't get through? Unless there is just a hole or something not visible in the pic
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Unread postAuthor: rikukiakuchiki777 » Tue Jun 02, 2009 11:20 pm

jmadden91 wrote:Where is the equalization on his piston then? Surely if that o ring is fixed the air couldn't get through? Unless there is just a hole or something not visible in the pic


My thoughts exactly. Is there an equilisation hole inside the piston?
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Unread postAuthor: spot » Tue Jun 02, 2009 11:45 pm

Sorry, I was confused about you saying "It looks like a number of thin layers of rubber". I don't know wheree the equalization is, maybe the o-ring doesn't seal 100%? Because a hole or something would make the o-ring useless... And I doubt there's a check-valve hidden in the piston
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Unread postAuthor: jmadden91 » Wed Jun 03, 2009 12:30 am

yeh sorry mate i was talking about the sealing face originally. I was way off haha
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