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Why do this?

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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Why do this?

Unread postAuthor: elitesniper » Mon Nov 19, 2007 9:57 pm

Um sorry for this newby question but why do u have to tap in a gauge where the pvc is twice as thick?
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Unread postAuthor: mopherman » Mon Nov 19, 2007 10:00 pm

It just gives the threads more thickness to grip to. It helps with leaks and prevents failiers
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Unread postAuthor: sjog » Mon Nov 19, 2007 10:33 pm

when morpher says failures he means flyers you know the gauge flying get it ? lots'o pressure get it? oh ya duct tape will fix it no epoxy it
that 'ill do it then ya can get the coveted award GHETTO wheeee
don't even bother to tap it , a lot of kids find some jackass way to just
spin it in epoxy again!
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Unread postAuthor: Ragnarok » Mon Nov 19, 2007 10:34 pm

The far more important point is that holes in a material are weak points, stresses form around the edges, which will reduce service life, and safety.

Doubling the thickness, even if the threads can't grip the whole way through, halves the stress around the holes, and that reduces the effects of all kinds of nasty engineering gremlins.
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Unread postAuthor: bluerussetboy » Mon Nov 19, 2007 10:34 pm

does anyone have any type of scientific evidence of this? do pvc manufacturers advise this? is there a manufacturer recommended thickness for the addition of gauges or other peripherals? is this just the spudfiles accepted norm? who/where did your information come from?
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Unread postAuthor: sjog » Mon Nov 19, 2007 10:57 pm

vast experience of spudfilers blue boy
not many threads catching on radius 1/4 " thick 3 maybe 4
bump/jar the gauge tear out the threads, no visable damage
then the gauge flys at 100-600 fps wear your first basemens glove it's bigger the question is what do I protect my face or my balls, or some where in the middle? hmm.. let me think a minute...
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Unread postAuthor: Ragnarok » Mon Nov 19, 2007 11:01 pm

PVC manufacturers do not recommend it one way or the other because they think that no-one is going to be half witted enough to drill holes in a bit of pipe to install a pressure gauge.
They don't design their products for nutters like us to make such nonsense from.

However, I am a student engineer, I can get that same information from anywhere. At the here and now, within arms reach of my laptop, I have a book called "Structures" by J.E. Gordon which deals with such things. His other book "The new science of strong materials" is also very good reading on the subject matter.

There is no exact passage on drilling holes into PVC, but it does talk about strain "lines" around "flaws", and how cracks can propagate from there. I'm too lazy to type the passage now, and I expect I'll be having a 36-hour day before I get any sleep, so it will have to wait.
There is also an interesting section on why pipe will tear along it's length rather than a circumference.

They're both good books, hard to come by, but well worth the read if you're a geeky engineer like me.

Aside from solid proof, it's being recommended to you by people who, contrary to appearance on occasion, do know what they're talking about. It is generally recommended by spudfiles users, and there is good science behind that.
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Unread postAuthor: elitesniper » Mon Nov 19, 2007 11:03 pm

lol Kinda hard on the boy isnt it? :? hey i secured my gauge with a nut from the inside is that ok? but its on one layer of pvc (secured by a nut on the bottom)
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Unread postAuthor: MrCrowley » Mon Nov 19, 2007 11:05 pm

bluerussetboy wrote:does anyone have any type of scientific evidence of this? do pvc manufacturers advise this? is there a manufacturer recommended thickness for the addition of gauges or other peripherals? is this just the spudfiles accepted norm? who/where did your information come from?


Well apart from common sense, there's no reason it shouldn't work and why it would be worse then single layer tapping. Also PVC manufactures don't even recommend using PVC pipe with compressed air.

Don't let that put you off, it's because if it explodes there's going to be a lot more shrapnel at high speeds piercing your skin then if it was filled with high pressure water.
So it's a legal reason they don't recommend compressed air and PVC pipe, not because they pipe can't take it.

But if it's pressure rated to a decent amount, and you don't give it a reason to fail it should be fine.

They probably recommend threading it into a threaded tee, I doubt they would recommend tapping at all.
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Unread postAuthor: elitesniper » Mon Nov 19, 2007 11:08 pm

Haha I doubt they even recommend to make compressed air guns that fire a couple hundred fps:D Lol but im only doing around 60-100 psi and my pipe is rated 450 so I should be safe :D, right?
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Unread postAuthor: MrCrowley » Mon Nov 19, 2007 11:09 pm

elitesniper wrote:lol Kinda hard on the boy isnt it? :? hey i secured my gauge with a nut from the inside is that ok? but its on one layer of pvc (secured by a nut on the bottom)


Well it wont fly out in hit you in the head, but it still risks a fracture, if you're using it at pressures under 150psi it should be fine.
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Unread postAuthor: ShowNoMercy » Mon Nov 19, 2007 11:09 pm

If you do it right you should not have a problem, stop worrying so much. If it fails, it fails learn from it and move on.
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Unread postAuthor: elitesniper » Mon Nov 19, 2007 11:12 pm

But I look at the gauge when im pumping so Im kinda worried lol. It might pop my eye out , and i enjoy seeing :?
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Unread postAuthor: ShowNoMercy » Mon Nov 19, 2007 11:14 pm

You sir, need some balls. If you are really that worried, drill the hole and get some tubing and use some right angle pieces to get the gauge facing you but if the tap fails it shoots it elsewhere. Comprende?
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Unread postAuthor: sjog » Mon Nov 19, 2007 11:15 pm

Ragnarok strain ,flaws and that stuff. good reason to use a tap properly

elitesniper you got the right idea and oh ya I was a little hard on the Beeve
I just got the question authority vibe. I'm not the auth. either!

Authority = Wiki , research
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