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The True Power Of A Piston Valve

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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The True Power Of A Piston Valve

Unread postAuthor: MrCrowley » Sun Oct 21, 2007 10:31 pm

Well I was in the garage trying to rig up a new pilot setup for my SGA golfball cannon, which was leaking a bit.

So I finally found a good setup and just tinkered around trying to get it to work, I would worry about the huge pilot volume and uncomfortable triggering setup later, I just wanted it to work, leak and JB weld free.

I know what went wrong, the bumper on my piston wasn't enough to stop the piston flying into the back of the fitting, which tapers down on the inside to the threaded part of the fitting(threads on outside).

This happened at about 95psi by the way, blew my bloody ear drums out and a piece of PVC hit my check.

I was going to put some bolts in the fitting to stop this, but
a) didn't want to weaken the fitting(ironically)
b) didn't want to risk having any leaks
c) the piston could've cracked the whole tee if it had enough force on the bolts.
d) I just wanted to test it out, make sure it worked...

Boy did it work...
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Attachments
Setup.JPG
Pilot Setup - This was immediately after firing, I grabbed the camera and gathered the pieces.
Piston Stuck.JPG
Piston Stuck In Fitting - May not look it, but it was a tough one to get out, had to crack open the threads from the other fittings that were still stuck inside.
Carnage 2.JPG
Carnage
Carnage.JPG
Carnage
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Unread postAuthor: thespeedycicada » Sun Oct 21, 2007 10:36 pm

ohhhh no! is that the gun in your sticky? and how is your face?
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current projects: co-axial piston valve.Status DONE!
S.P.E.C.S update mk 1 construction begining in febuary all the maths for it are done plans are drawn up and parts are listed.
NEXT project:auto piston valve.
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Unread postAuthor: dapallox1 » Sun Oct 21, 2007 10:36 pm

Damn, that really sucks man. I had a pressure gauge (a really old one) exploded on me yesterday. Hit me in the cheek too... sucks. Hope you get it fixed. I really liked that gun.
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Current Project: 4" Tee Piston Valve
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Unread postAuthor: MrCrowley » Sun Oct 21, 2007 10:41 pm

Yeah it is the gun in my sticky. My face is fine, i'm kinda happy, the power I got from this thing with the sprinkler valve on instead of ball valve was AMAZING!

I'll get it fixed soon enough, i'll have my restricted drivers licence soon so I can get fittings when I want.
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Unread postAuthor: thespeedycicada » Sun Oct 21, 2007 10:47 pm

Scary stuff dude pvc scares the crap out of me in high power/stress applications.
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current projects: co-axial piston valve.Status DONE!
S.P.E.C.S update mk 1 construction begining in febuary all the maths for it are done plans are drawn up and parts are listed.
NEXT project:auto piston valve.
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Unread postAuthor: hi » Sun Oct 21, 2007 10:54 pm

i had that happen with a valve of mine. it too was a 2'' piston. i had peices of pvc all around me. now everytime i shoot a piston valve i have this little "what if" feeling in the pit of my stomach, but it sure doesnt stop me. :lol:

oddly enough the exploding piston is why i built my diaphragm gun. i figured a little peice of rubber wouldnt hurt me or the cannon.


good luck rebuilding it.
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"physics, gravity, and law enforcement are the only things that prevent me from operating at my full potential" - not sure, but i like the quote

you know you are not an engineer if you have to remind yourself "left loosy righty tighty"
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Unread postAuthor: CannonCreator » Sun Oct 21, 2007 10:55 pm

Ya dude that sucks, never seen that happen to a piston valve personally. Sorry about that man hope you get a new vavle on that cannon. And I have been wondering, Is that green paint spray or like a Lead paint?
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Spudding Is dangerous, I learned the hard way:
http://www.spudfiles.com/forums/my-eye- ... 15301.html

Guns. As They may Claim lives, they are lives. Our lives.

When Life gives you lemons, through them at somone.

Live, Breathe, Eat, Paintball
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Unread postAuthor: LikimysCrotchus5 » Sun Oct 21, 2007 11:11 pm

Well good for you :D your new pilot system works, a little too well :lol: But whatever just fix it up, then she's ready to go, and start the whole process over again :D. Well good luck with that. Have fun and safe spuddin, plz :D

P.S. Is that heavy duty deoderent? You must have some stinky pits then :D
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Unread postAuthor: jackssmirkingrevenge » Sun Oct 21, 2007 11:25 pm

ouch, glad you weren't seriously hurt.

As a matter of interest, is your bumper that section on the rear of the piston? And how much travel did it have to accelerate enough to do that kind of damage? A bit more that 0.375" methinks ;p
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Unread postAuthor: MrCrowley » Sun Oct 21, 2007 11:28 pm

It's heavy duty foot spray, not mine, just found it in our house :P

The paint, is just your everyday camo green spray paint, we don't get kyrlon fusion here.

I've had part of this guns chamber blow up before, ever since then I hate using PVC at over 100psi, I wont be scared of pistons because I know exactly what went wrong and how to fix it.

jackssmirkingrevenge wrote:ouch, glad you weren't seriously hurt.

As a matter of interest, is your bumper that section on the rear of the piston? And how much travel did it have to accelerate enough to do that kind of damage? A bit more that 0.375" methinks ;p


Yeah, that black part is the bumper, it's softer then it looks. And when I put this new pilot setup in I forgot that this bumper was probably only good for my old setup, where the piston(with bumper) slammed into four bolts.

With this setup it slams into a the tapered fitting, which I forgot all about, the piston travel would be about 2.5" :roll:
I know, I know, but like I said in my OP, I just wanted to get it to work, then I would start minimizing my massive pilot volume.

You don't want to even see what I have after that PVC threaded fitting, there is a 1" tee and a sprinkler valve with a 4" long nipple on it, It's all I had for the time being.
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Unread postAuthor: jackssmirkingrevenge » Sun Oct 21, 2007 11:41 pm

:shock:

You pilot volume was over 10 times larger than it should have been :?: :!: :?: :!: :?: :!:

Oh the humanity!

tsk tsk, you should have know better ;)

I guess it's a cultural choice.

European perspective: make pilot volume as small as possible so it can be triggered with something with as little flow as a schrader.

American persepctive: make pilot volume as big as the chamber, who cares, then fit the biggest, baddest ass pilot valve you can afford.

I despair sometimes :roll: :D :D :D
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Unread postAuthor: MrCrowley » Sun Oct 21, 2007 11:56 pm

Haha good thing i'm not American then :wink:

All I can say, was it was a temporary setup which was going to change once I had the right fittings.

By the way the 1/4 of the barrels diameter = piston travel only applies to co-axials according to clide, he said give it a bit more in barrel sealers.

With my old setup is was just over an inch, but this was merely a temporary test setup, trust me I would've minimised dead space as much as possible before presenting it to you JSR :P
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Unread postAuthor: ammosmoke » Mon Oct 22, 2007 1:22 am

I take offense to that!

JK, but really, we aren't, I least I'm not like that. Isn't it funny what stereotypes do? I mean seriously. Man, and we don't even want to get into Euro vs American car arguments!!!!! THOSE ARE THE WORST!!! Anyways.. stop beating on Americans already.... Maybe we'll do the same.

I don't beat on other countries.....
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Unread postAuthor: MrCrowley » Mon Oct 22, 2007 2:08 am

Just thought i'd mention the fittings that 'failed' were bought in America :shock:

Just kidding. I still got the recipet, wonder if they accept international returns :D
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Unread postAuthor: jrrdw » Mon Oct 22, 2007 5:50 am

ammosmoke wrote:I take offense to that!

JK, but really, we aren't, I least I'm not like that. Isn't it funny what stereotypes do? I mean seriously. Man, and we don't even want to get into Euro vs American car arguments!!!!! THOSE ARE THE WORST!!! Anyways.. stop beating on Americans already.... Maybe we'll do the same.

I don't beat on other countries.....


^Ditto^
What country invented PVC?
I'd like to know.
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