sweet pneumatic video

[rna_duelers]

Pressure rated pipe all the way.Just because it lasted all those tests doesn't mean the next time you use it in a pressured environment its not going to explode.It's like trusting your life on a land mine that has a 80kg pressure pad and you weigh 75kg...Are you still going to step on the mine?

There is a reason they have pressure rated Pipes and non pressure rated pipes,one is for pressure the other is not.And if you love ABS so much get some pressure rated ABS pipe and then you can have the best of both world.

[super spuder]

stop arguing, no one wants to read all this crap, post usefull stuff or dont post at all, i am just tired of all this bla bla bla, what make you so sure presure rated pipe is not going to fail ????????????? i used ABS to make a pneumatic cannon and i am not going to take it apart just because som guy told me it is not safe.

[rna_duelers]

well pressure rated pipe has a 3X burst pressure rating...So SCH80 2" rated to 400 odd PSI bursts at 1200PSI.Although ntohing is ever 100% safe but there is a HUGE differecne between 1200-PSI and a 0-PSI burst rating.

[SpudBlaster15]

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[rna_duelers]

Ever looked at the wall thickness of pressure rated and non pressure rated?Pressure rated ABS pipe in 3/4 size has a wall thickness of 3.92mm,that is as probably as thick as wall as on your 3" ABS non pressure rated pipe.I'm not attacking ABS as a pipe just the non pressure rated kind being used in pressure situation.

[MrCrowley]

What is the difference between pressure rated and non pressure rated pipe? Exactly as the name implies. One type is tested, the other is not. Otherwise, they are virtually identical.

I can't agree with you there, the two pipes are completely different in how they are made and our thick they are and even their shape and socket depth is different as you already know.

And thats just PVC, with ABS if its cell core its not even structurally the same, as you know its got air bubbles in it like foam.

[Solar]

HEre is a good pro and con on spudtech.

http://www.spudtech.com/content.asp?id=14

[jrrdw]

Any pipe can burst at any given time, no manufacture is perfect, nothing man made is perfect. I have not yet experianced pipe failure, and hope not to, but i'm sure i will at some point in time.
How long have you had the cannon in the video Super Spudder? You said about 30 shots now? Ever try long distance shots at a target? I ask a lot of questions don't i? Are we there yet?

[super spuder]

to answer your long list of questions, i have had this cannon in peices for a verry long time, trying to get something that will work as the piston. I just recently got it togather 9 days ago, and i fired it for the first time about 6 days ago. i have not done any distance shots because i dont feel like hauling a target out in the feild, all i have done for distance is fired it at about a 45' angle, and the inside of the golf ball went right out of sight really quickly. For anyone that still doubts the 750 fps, if it was only going 350 fps ,do you really think it could go through 1/2 inch press board? sorry if anything i spelled wrong, spell check no worky

[SpudBlaster15]

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[clide]

I am severely annoyed by individuals who automatically believe that because ABS is unrated, it is unsafe to use. I have pressurized 3" DWV ABS to 120psi at -25*C, and left it for 12 hours with no failure. I have ignited a stoichiometric propane/oxygen mixture inside a closed ABS chamber, once without failure, the 2nd time it split lengthwise with no shrapnel production. Stoichiometric propane/air has no effect on a closed ABS chamber. It is safe to use.

Low temperature makes the pipe stronger, but more brittle. And you are still using a limited sample as a basis for your conclusion that ABS is always safe. I am fairly confident I could take a piece of PVC and pressurize it to 1000 psi without it blowing up, does that mean it is safe to do? Nope.

What is the difference between pressure rated and non pressure rated pipe? Exactly as the name implies. One type is tested, the other is not. Otherwise, they are virtually identical.

Sch 40 DWV pipe and Sch 40 pressure rated pipe are visually identical, the only physical difference being in the fittings, and possibly better quality control standards. Still, it is only 100psi, which any DWV pipe (aside from cellular core) should be able to handle safely.

I doubt any of the individuals attacking DWV ABS have even tested it in a pressure situation. If you did so, you would realize just how paranoid you are acting.

I think you completely fail to grasp the idea of what makes something safe. Do you think it was just a marketing decision by the piping companies to mark the ABS as DWV? No, it was a decision by highly trained engineers. If it was safe to use for pressure then it would be marked that way. Could you explain to me why they would decide to mark a pipe as DWV when it would be safe to use for pressure applications? Because I can't think of a reason.

if it was only going 350 fps ,do you really think it could go through 1/2 inch press board?

Yep, 350 fps to go through a 1/2" board sounds about right.

[joannaardway]

In a choice between rated pipe at £10 a foot, and unrated pipe at £2 a foot, even if someone swore blind that they were equally safe, I would go pressure rated, because then the company is giving their word that it's safe.

ABS itself is not the death trap - in fact, if it does go wrong, then it's much safer. (Unless a rupture occurs in a piston pilot volume, which is very likely to trigger the cannon when you really don't want it to).
But, I would really rather my cannons didn't go wrong in the first place. Rating is essential to get that confidence.

At the moment, I use copper pipes, rated to about 40 bar (580 psi), with a burst pressure of up to 2000 psi (depending on the bore).
Copper can be used at any temperature up to about 100 *C and down to about -50 *C, tears rather than shattering, can be bent to most shapes, isn't damaged by solvents and all the joints can be removed and undone if you make a mistake.
Even if I use 300 psi, that's a 2:1 safety ratio over the already generous 3:1 on the pipe already, with safe failure if it should happen to go wrong.

So, let's all use copper because it's so safe and versatile - and if you don't I'll swear at you and call you an idiot.

Got the point yet?
Whatever material we choose is our own choice. We can recommend what people do, but we can't tell anyone what they must use. We can suggest against using the wrong glues and cell core pipe, and petition for primer use, but not much more.

I think it's time to stop this petty squabbling over pipe types. I and most UK people use copper, Spudblaster and Super spuder use ABS, n00bs use unrated and DWV parts, and many others use rated PVC.

Each to their own. In short:
Rated PVC = unlikely to fail, but nasty if it does.
Unrated PVC = a bit like standing on a big mountain in a thunderstorm waving a lighting conductor about and carrying an earthed wire.
Unrated ABS pipe = more likely to fail than rated PVC, but much safer if it does.
Rated ABS pipe = rare, but unlikely to fail, and safe if it does.
Copper = costly, but exceptionally unlikely to fail, and very safe if it does.
Steel = costly, rare and heavy. Less likely to fail than anything else, but if it did, I wouldn't want to be within a 1/4 mile of there.

I think that's all that needs to be said about construction materials.

@ Super spuder - if that is firing at 750 fps, then I'm a monkey's aunt. 750 fps is exceptionally fast, and I have never seen it done in a cannon using anything other than light ammo and pretty high pressures.
350 is pretty likely though - that would be about 250 joules (with a whole golf ball), and I've made big messes of 1" thick MDF board with half that (but smaller projectiles)

[super spuder]

well i must have still dome something wrong. can someone post the actuall GGDT page with the numbers filled out, and i can check if it is right, cause i am using the old GGDT on the srpead sheet.

[joannaardway]

That's probably not GGDT (the GGDT spreadsheets aren't available, and haven't been for years) - that's going to be the spudtech calculator, which is accepted as hopelessly optimistic and inaccurate.

[super spuder]

yea, your right, that is what it is well, can someone still post the GGDT results up so i can see them?