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Pilot line pressure???

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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Pilot line pressure???

Unread postAuthor: ImHUGEnJAPAN » Mon Jul 28, 2008 5:58 pm

I recently added a pilot line to my cannon so I could move the trigger to a more comfortable position. This might be a stupid question but, here it goes.

When you pressurize the air chamber does the pilot line on a modded sprinkler valve hold the same pressure as what you put in the air chamber?

I used rubber tubing that is rated for 55 psi (it's what they had). I fill the chamber to 80 psi. Does this have the potential to end badly? The only I can think of is that the cannon will fire accidentally if the pilot line fails.

That could definately be bad.

I have shot this about three times (using extreme caution to test it) and on the third time I noticed a small leak. I just don't want this to be "it's not a matter of IF but WHEN" scenario.

I'm prbably going to get some higher rated tubing after I finish painting it just to be on the safe side.
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Unread postAuthor: POLAND_SPUD » Mon Jul 28, 2008 6:09 pm

that's a very unfortunate situtation... ok let say that there is a 95% chance that it won't fail.... but's what if it does ? use the pilot valve without a line and get a pressure rated one

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I think you knew the answer to this question before you asked
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Unread postAuthor: ImHUGEnJAPAN » Mon Jul 28, 2008 6:43 pm

POLAND_SPUD wrote:that's a very unfortunate situtation... ok let say that there is a 95% chance that it won't fail.... but's what if it does ? use the pilot valve without a line and get a pressure rated one

EDIT
I think you knew the answer to this question before you asked


THat's what I thought.

Thanks

It's just a matter of replacing a 4" piece of hose so it's no big deal.
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Unread postAuthor: Mr.Sandman » Mon Jul 28, 2008 8:14 pm

ImHUGEnJAPAN wrote:
POLAND_SPUD wrote:that's a very unfortunate situtation... ok let say that there is a 95% chance that it won't fail.... but's what if it does ? use the pilot valve without a line and get a pressure rated one

EDIT
I think you knew the answer to this question before you asked


THat's what I thought.

Thanks

It's just a matter of replacing a 4" piece of hose so it's no big deal.


wouldnt the pilot line just inflate like a balloon and pop? that actually sounds pretty fun to me, like a rubber firecraker
:D :D :twisted:
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Unread postAuthor: ImHUGEnJAPAN » Mon Jul 28, 2008 9:37 pm

Mr.Sandman wrote:
ImHUGEnJAPAN wrote:
POLAND_SPUD wrote:that's a very unfortunate situtation... ok let say that there is a 95% chance that it won't fail.... but's what if it does ? use the pilot valve without a line and get a pressure rated one

EDIT
I think you knew the answer to this question before you asked


THat's what I thought.

Thanks

It's just a matter of replacing a 4" piece of hose so it's no big deal.


wouldnt the pilot line just inflate like a balloon and pop? that actually sounds pretty fun to me, like a rubber firecraker
:D :D :twisted:




LOL...I thought the same thing when I bought it or it would just split. It hasn't yet. That's why I was wondering how much pressure the pilot line actual holds when you pressurize the air chamber. Doesn't It have to be the equal or the valve would open.
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Unread postAuthor: Mr.Sandman » Mon Jul 28, 2008 9:45 pm

i quess most of the pressure rarings are far below their fail pressure( for liability reasons probably). also to answer your question yes if the pressure isnt equal inside the sprinkler valve diaphragm it will open.

edit: just a quick question do you live in japan? yeah i know it is a pretty dumb off topic question but i kinda want to know. i think ill start a topic on the race of people on spudfiles
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Unread postAuthor: psycix » Tue Jul 29, 2008 8:10 am

When you are taking a hose above its rating it will probably get inflated on weak points (as near the connection to the hose barbs) and pop.
The danger, however, is not that the hose pops, but its the gun that gets pilotted. Watch out for that.
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Unread postAuthor: ImHUGEnJAPAN » Tue Jul 29, 2008 8:21 am

Mr.Sandman wrote:i quess most of the pressure rarings are far below their fail pressure( for liability reasons probably). also to answer your question yes if the pressure isnt equal inside the sprinkler valve diaphragm it will open.

edit: just a quick question do you live in japan? yeah i know it is a pretty dumb off topic question but i kinda want to know. i think ill start a topic on the race of people on spudfiles


Actually I live in Indiana. Don't worry your not the first one to ask. I get it all the time. I just used my xbox live tag. I'm 30 and still play video games....hehehe, My wife calls me her third son...lol. I think I'll always be just a big kid. Pixels, paintballs, or potato's I love shooting them all!!!
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Unread postAuthor: ImHUGEnJAPAN » Tue Jul 29, 2008 8:23 am

psycix wrote:When you are taking a hose above its rating it will probably get inflated on weak points (as near the connection to the hose barbs) and pop.
The danger, however, is not that the hose pops, but its the gun that gets pilotted. Watch out for that.


Im going to change the pilot line. I got a six foot section of tube for $2 so I'm not that concerned about scraping it.
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Unread postAuthor: Hotwired » Tue Jul 29, 2008 9:10 am

You really do not want any concerns about your pilot lines.

Almost all piloted valves on this site use negative action, that is they dump air to move a piston. So anything that can cause that air to be released randomly is very bad.

Solars cannon is the only one I know of that uses a positive action - allowing air into a normally unpressurised pilot line which goes to a piston face to force open the valve.

Positive action piloting is inherently safer but also a lot more work to do.
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Unread postAuthor: Ragnarok » Tue Jul 29, 2008 10:18 am

Hotwired wrote:Positive action piloting is inherently safer but also a lot more work to do.

Still, the problem with negative acting can be dealt with.

Even total pilot rupture or the piston catastrophically failing couldn't trigger HEAL if the main safety was on. I have done that a few times, trying to fire it with the main safety on, usually (although not exclusively) by mistake. What happens a very solid thud, followed by confusion, and finally, a feeling of slight sheepishness when the muppet holding the cannon realises what's happened.
On the bright side, I've not yet had an accidental triggering of any of my cannons (touch wood) - 'cos I've made them so that at least two things would have to fail almost simultaneously for any unintentional firings.

To contribute to the topic more usefully, your pilot line should be up to the job. I'll be honest, most things can survive a lot more than their rating (they have to, it's a safety factor kinda thing) but it's not normally something I'd advocate doing if there is any alternative... despite doing it myself occasionally...
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Unread postAuthor: Mr.Sandman » Tue Jul 29, 2008 10:53 am

darnit ragnarok why are you always right :roll: :D 8)
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Unread postAuthor: Ragnarok » Tue Jul 29, 2008 11:38 am

Mr.Sandman wrote:darnit ragnarok why are you always right.

A patented combination of wit, luck and intuition... not to mention a tricked out Delorean to allow me to cover my arse and correct myself when I do make a mistake. :D
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Unread postAuthor: psycix » Wed Jul 30, 2008 12:20 pm

Ragnarok wrote:
Mr.Sandman wrote:darnit ragnarok why are you always right.

A patented combination of wit, luck and intuition... not to mention a tricked out Delorean to allow me to cover my arse and correct myself when I do make a mistake. :D

Ah, so with a bit of tweaking your spuds can impact before they're fired... :D
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