SpudFiles

mega_swordman wrote:I have another question. This test is simply testing the effects of PVC shrapnel after a pressure related explosion. Is there a possibility that the shrapnel will react differently when the pipe ruptures when a large shock is induced (i.e. dropped while pressurized).

That is a very good option. One that would definitely be accounted for, since most accidents occur when the launcher is dropped. As far as the reaction of the fragments, chances are they will not act any differently, as the fragments are unpredictable to begin with.

Something else that should be tested would be the force of the shock wave presented by the rupturing. In my experience, this is the part that does the most harm. Ex: Have you ever been to a fireworks show and felt the "boom" in your chest? That is the shock from the explosion.

Incidentally I'd wonder if the very large air blast wouldn't rip through the cardboard just by itself

It might damage you hearing a little but in practice the air blast would have no significant physical effect, so the screens would have to be secured well in place.

Is there a possibility that the shrapnel will react differently when the pipe ruptures when a large shock is induced (i.e. dropped while pressurized).

Interesting observation, this would actually allow you to make the pipe fail at below its normal bursting pressure - you could test this by having a weight over the chamber in a tube held by a pin - pull out the pin from a distance, weight falls and *whoomph*

It took 1,029 psi to bust the pipe, i beleave the pipe was 10' long. All it did was crack and blow water. If i remember correctly

Did he use water to pressurise the pipe? Water pressure and air pressure produce very different failures, which is why fluid is normally used for pressure testing.

jackssmirkingrevenge wrote:

Incidentally I'd wonder if the very large air blast wouldn't rip through the cardboard just by itself

It might damage you hearing a little but in practice the air blast would have no significant physical effect, so the screens would have to be secured well in place.

Enclosed all round, I'd say the air would try to blow out the sides, especially if a fragment ripped it, providing a weak point. Could easily affect the results.

This is why I suggested a perimeter screen, I figured the open top would be sufficient to negate the blast effects.

Something else that should be tested would be the force of the shock wave presented by the rupturing. In my experience, this is the part that does the most harm. Ex: Have you ever been to a fireworks show and felt the "boom" in your chest? That is the shock from the explosion

I think one would be more at risk from the fragments, certainly in this case. If you look at military explosive devices, only thermobaric warheads or very large explosive charges rely on the blast effect only. Some grenades for example come with a separate fragmentation cup that soldiers using them at close quarters can remove in order to reduce risk to themselves.

How much PSI do you think the pipe will handle? I can do it but my max psi is gonna be 150, do you think thats enough?

I don't have any data regarding the burst pressure of DWV tubing - I would think however that a small length of large diameter tube would fail well before 150 psi.

If a sharp frag hits you in the eye, it won't matter if it's going 30 fps or 300 fps, you will still have a serious injury.


Someone did blowup a couple guns made with dwv fittings a while back (anyone remember blowing up "Van Halens Guitar"?;)

They both burst at about 200psi if I remember right. The main problem with testing DWV pipe is that there may be flaws in one piece while another will hold the same as an NSF-pw rating.

Quite an interesting plan. With my high pressure pump, I could try this out, although the exact failure pressure concerns me. I'm not sure that it would fail within the realms of typical pressures, I imagine most failures are either due to abuse or fatigue. A failure at 100 psi caused by dropping something will be very different to one caused by a static 300 psi.

So resorting to shocks like dropping large weights on things might be necessary to initiate fracture to get realistic results.
But a worst case scenario could be created with pressures near to the static failure pressure, combined with a shock.

An important observation would be damage to soft tissue, as a lot of people fire their launchers while against their torsos, and that's a major concern to worry about.

PS: What is it with youtube? It's taking ages to load, even on a very fast connection. These days I tend to just download the videos with Real Player, then delete them after I'm done, because that's so much faster.

EDIT: Woo, I got me enough spudbux fer a signature now.

If your comment about flying shards of PVC was directed at me, I am planning on testing this in a large area with a long length, close to 75 ft of hose in between me and the pipe. I could also be inside a building if I so please. I think I will be fine, and if your still worried I will even throw on some safety goggles.

If a sharp frag hits you in the eye, it won't matter if it's going 30 fps or 300 fps, you will still have a serious injury.

Fair comment, but the same goes for low velocity airsoft projectiles that are otherwise safe to fire at a human target.

So resorting to shocks like dropping large weights on things might be necessary to initiate fracture to get realistic results.
But a worst case scenario could be created with pressures near to the static failure pressure, combined with a shock.

Another alternative would be shooting the said chamber with an airgun or similar - I seem to recall seeing a test online where someone attempted to destroy a PVC chamber by overpressurising it but it failed to rupture so he resorted to shooting it with a rimfire rifle.

An important observation would be damage to soft tissue, as a lot of people fire their launchers while against their torsos, and that's a major concern to worry about.

Hence this suggestion: What you could do is first see how many layers of cardboard a PVC fragment from the exploding chamber would penetrate. Take the same fragment and load it with a sabot in a pneumatic cannon, and alter the pressure until it penetrates the same number of layers as it did in the fragmentation test. You can then fire it at ballistics gel using the same pressure.

I am planning on testing this in a large area with a long length, close to 75 ft of hose in between me and the pipe.

Awaiting the results with bated breath, stay safe

Ok so my plan as of now is to use a 10 inch by 4 inch piece of sewage pipe, its the thin wall stuff so that may need to be redone, and I am trying to minimize the amount of heavy shrapnel so I am going to plumb my air line directly into a cap. All goes well, I will slowly increase pressure till the max on my CO2, which is 150 psi. Hopefully it will go boom

sounds good, some ear protection is probably in order

If ShowNoMercy's test fails, I could always test with my nitrogen setup. That can reach 500 psi really quickly even in a big chamber, but I'm not too keen on wasting excessive amounts of gas in one test.

I believe something similar has been tried, what I would need is a high pressure source and a inflation system that I didn't have to hold while inflating

Don't use a manual pump.

Not unless you've got a long hose (even more knackering) and good ear protection. Somehow really loud surprise bangs seem even worse if you've been heaving away at a pump nervously waiting for it to blow.