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piston gun probloms

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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piston gun probloms

Unread postAuthor: turbohacker » Wed Feb 21, 2007 1:02 am

I just completed my second attempt at a piston gun, it consists of a two foot section of three inch with a one and a half foot long two inch barrel inside it (barrel sealer) the piston is two washers welded to a bolt with some rubber on one side. My problem is that it seals and will hold pressure but when I acuate the modified one inch sprinkler valve it only lets the air out of the back of the piston. I do know that air makes it through my pilot hole because i actuated the piston by sticking a broom handle down the barrel and it fired, any suggestions would be extremely appreciated :D
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Unread postAuthor: noname » Wed Feb 21, 2007 1:09 am

Problems:
You pilot valve isn't big enough (it is, a modified sprinkler is pretty much the best pilot for large piston valves)
Your piston has too much friction
Your piston is a bad fit.


Don't expect great results, there isn't very much space between 3" and 2" PVC, I wouldn't expect it to be very strong.
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Unread postAuthor: chaos » Wed Feb 21, 2007 1:18 am

pics would help a little i have kindof the same problem but a little different,if i fill it up from behind the piston it seals and everyhing works good however if i fill it from the chamber the air goes striaght out the barrel so i was wondering why this is because i have it spring loaded? anyway a agre with noname
Problems:
You pilot valve isn't big enough (it is, a modified sprinkler is pretty much the best pilot for large piston valves)
Your piston has too much friction
Your piston is a bad fit.


Don't expect great results, there isn't very much space between 3" and 2" PVC, I wouldn't expect it to be very strong.


peace
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Unread postAuthor: killagorrila99 » Wed Feb 21, 2007 1:38 am

Mould one out of hot glue, Use 4mm thick neoprene, use half a tennis ball as a bumper, fill from behind the piston and use a 1.5 inch ball valve as a vent. Lube the piston up with silicon spray and theres no reason why it shouldnt work.
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Unread postAuthor: MrCrowley » Wed Feb 21, 2007 1:53 am

A sprinkler would be better then a 1.5" ball valve.
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Unread postAuthor: chaos » Wed Feb 21, 2007 3:41 am

hey killa is there any way to fill a piston gun from the chamber i need to find out?

peace?
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Unread postAuthor: MrCrowley » Wed Feb 21, 2007 4:20 am

You need a spring on the back of the piston.
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Unread postAuthor: killagorrila99 » Wed Feb 21, 2007 5:50 am

MrCrowley wrote:A sprinkler would be better then a 1.5" ball valve.

Well, If ya wanna get technical...
A sprinkler may open faster, but A 1.5 ball valve would have a larger opening, Rather than a 9/16 hole. So both would be fine... Technically.
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Unread postAuthor: jrrdw » Wed Feb 21, 2007 6:00 am

Your piston could be getting cocked side ways, two warshers isn't very thick for a guideing surface. Pilot hole mite be to big, doe's the air take time to escape? or woosh out all at once? Your piston could just be getting stuck, can you get access to it? Look inside the slideing surface for scores, that well tell you if it's getting stuck.
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Unread postAuthor: turbohacker » Wed Feb 21, 2007 8:05 pm

thank you for your help,
I do know that the pison slides well.
I fill it from behind the piston and the piston itself is a very good seal, which is why i drilled pilot holes
Any other ideas :?: :glasses3:
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Unread postAuthor: chaos » Sat Feb 24, 2007 7:59 pm

umm too many pilot holes you only need one very small one,just an idea.

peace
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Unread postAuthor: schmanman » Sat Feb 24, 2007 8:04 pm

chaos wrote:umm too many pilot holes you only need one very small one,just an idea.

peace


umm, apparently, you dont really know what you're talking about, no offense.

the larger the pilot valve/hole in the back of the valve, the better.
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Unread postAuthor: chaos » Sat Feb 24, 2007 8:22 pm

oh crap my bad im still asleep i thought equalization holes.i know what im talking about just had a "brain dead" moment, so yer what about your equalization hole on your piston?maybe its to big.
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