SpudFiles

Man, I will not throw away my DWV ABS cannon.

You are talking about advanced combustion? Are we talking propane combustion? Oh that's a whole other story then, and it explains why the ABS failed.

And anyways, any cannon I shoot, I do not hold it in my arm. I get back to a safe distance with remote wiring.

SpudBlaster15 wrote: _Fnord: This was a routine shot, the last of about 100 in the launcher's lifetime. BTW, that story is hilarious.

spudthug wrote:for the last time he said that it was his first shot god damnit!@!@!@!@

Umm I think not.

Really I have spoken to people all over. That have dealt with ABS and PVC on a regular basis. They have always said that they would pick ABS over PVC any day. Why you ask? I will tell.

ABS tends to fail more readily but when it fails it tends to split down the side and not shrapnel.

PVC tends to fail less but when it fails you better not be right next to it unless you want to mimic that dart board that has been used for 20 some years.

it would be nice to see someone do some tests with a pressure gauge attatched to the chambers of a combustion (with different fuels) and a pneumatic. if this has been done already i cant find it.

Spuddin wrote:it would be nice to see someone do some tests with a pressure gauge attatched to the chambers of a combustion (with different fuels) and a pneumatic. if this has been done already i cant find it.

Utterly useless. You get a pressure spike, so the meter would peak so rapidly, that you'd never be able to read it.

We can estimate the chamber pressures, or use other methods of measurement (it was done with a piezo sensor by someone - I forget who), but a pressure gauge won't do the job.

Back to general talk: I agree with Hotwired, we need to sort out our horrible mess up of terms. DWV (not that DWV is an ideal term either. We should say unrated, because a fair amount of pipe marked DWV is actually rated to obscenely high pressures) ABS needs to be seperated from rated ABS.

DWV/Unrated anything is potentially dangerous. Cell core is even worse.

Rated anything will probably hold together until the cows come home, fall asleep, wake up, eat something, then go away, get lost and finally getting hit by a train - as long as it was properly constructed.

If I could get it easily, then all of my cannons would be either rated ABS, or metal (anyone of copper, aluminium or steel). I wouldn't even touch PVC pipe, because of the nasty effects in failure states.

So, this is a petition for people to start using unambigous terms when talking about pipe types...

actually, you can make a rather ghetto peak pressure guage by taking a normal guage, say 0-100, and attache a check valve to it. thatway when is peaks the air is forced past and retained. im not sure about any shrinkage in the hot gas tho....

Again, practically useless.

The pressure comes almost totally from the hot gases, so when that heat is lost, which will happen very fast, then the gauge will zero again, with no recorded result.

well, my uncle was telling me about a pressure gauge that has two needles, one is for peak pressure, and the other is for what the pressure is now

A-98 you have a good idea about using a check valve if nobody can find a peak pressure gauge, i just happen to have a small check valve that i will look into riggin up pal. thx. btw it might not be useful to some but maybe useful to others im sure, thats why we are here

That is only useful, though, if you can confirm that the checkvalve opened. I think that using a pressure gauge with a piece of pencil lead on the needle would be a cheap way to find what pressure it has reached.

The only peak pressure gauges I have seen (like the ones sandman mentioned) were for water pressure, but I never looked very hard.
Also, the pressure isn't the only thing that causes pipes to fail, the VoD, etc, makes a large difference.

Well mate its good to hear your ok!
But alas I think you have just sparked a PVC ABS debate again!!

Bubba

No, I don't foresee this one turning into a PVC vs. ABS debate. I really think this one will just turn into a debate about how to best use ABS safely. Besides, there's no need to debate, everyone knows PVC is better.....

JK, don't kill me.

Yeah there got to be a way of figuring it out and putting it on here so every one can be like ok and take it for gospel. So that faules like this dont happen a frequlenty!

Bubba

Lorem ipsum dolor sit amet, consectetur adipiscing elit. Cras nec placerat erat. Vivamus dapibus egestas nunc, at eleifend neque. Suspendisse potenti. Sed dictum lacus eu nisl pretium vehicula. Ut faucibus hendrerit nisi. Integer ultricies orci eu ultrices malesuada. Fusce id mauris risus. Suspendisse finibus ligula et nisl rutrum efficitur. Vestibulum posuere erat pellentesque ornare venenatis. Integer commodo fermentum tortor in pharetra. Proin scelerisque consectetur posuere. Vestibulum molestie augue ac nibh feugiat scelerisque. Sed aliquet a nunc in mattis.

Steel imposes more limitations, mostly from cost and weight, but there is one more problem.
Combustion, by definition, produces CO2 and H2O. Steel cannons would be susceptible to rusting, even if galvanized. Of course, stainless is outside the price range of most spudders.
I am a tad surprised we don't see more work with aluminum. Maybe becasue it is hard to weld, and a bit expensive/ 'exotic' in the forms we use.