SpudFiles

Posted: **Thu Jun 14, 2007 9:29 am**

jimmy101 wrote: Uh, joannaardway, I think you have your metals mixed up. Copper and aluminum oxides will both protect the un-oxidized metal below the oxide layer. Iron (and steel) oxide do not, they flake off, though a good stainless steel oxidizes and flakes very slowly.

Whoops. My mistake.

The point about steam locomotives still stands though - if those will last as long as they do, then a hybrid will last as least as long if properly maintained.

Posted: **Thu Jun 14, 2007 10:52 am**

Water vapour will hardly do anything to galvanized metal. You'd need to leave your gun in a moisture-rich environment for long periods of time before you see anything happen.

Posted: **Thu Jun 14, 2007 4:32 pm**

joannaardway wrote: The point about steam locomotives still stands though - if those will last as long as they do, then a hybrid will last as least as long if properly maintained.

Yes, but steam engines are well oiled, and I have even read about newer/restored ones having an epoxy coating applied. Where is Eric? Surely he can types us a book on the preventive maintenance of steam engines...

Posted: **Thu Jun 14, 2007 7:39 pm**

_Fnord wrote:Heh.. well, I was going to give my abs combustion a nice paintjob, but I guess I wont bother now.
I'll just post it the way it is sometime soon.

Were there any unusual variables (projectile type, low/high temp)
How many shots did you fire (total) before it failed?

Unrelated story: There's an abandon campsite about a mile away from my house in the middle of the woods. I was looking around there once and found a pvc combustion cannon hidden in the leaves. Aside from using primer, whoever built it was an idiot. The cb was something like .3:1, and half the fittings were dwv. Upon closer inspection of the vent plug, I found that it had exploded and someone had epoxied it back together.
I just left it there. Maybe someday the guy will return and attempt to shoot it again.

oxy acetlyne and remote firing sjould make a nice boom

Posted: **Thu Jun 14, 2007 8:10 pm**

Thats a bit insane to reapir a exploded cb? just get a new one and graft it into the old barrel. Ive had to do that once!!

Bubba

Posted: **Fri Jun 15, 2007 2:06 pm**

BC Pneumatics wrote:Yes, but steam engines are well oiled, and I have even read about newer/restored ones having an epoxy coating applied. Where is Eric? Surely he can types us a book on the preventive maintenance of steam engines...

The inside of the boiler certainly wouldn't be oiled, and that's where you've got all of your high pressure steam.
The newer ones might be epoxy coated, but they didn't have that back 100 years ago, and they didn't explode back then because of the lack of it.

I don't believe there is any undue risk to a steel hybrid - and certainly not more than a PVC one.
If anyone's really worried about it, then there are two suggestions:
1) Use a aluminium, or a suitable aluminium alloy.
2) Don't build a hybrid.

In the end, it's the choice of each individual builder what risks they're willing to take.

Posted: **Fri Jun 15, 2007 6:10 pm**

Perhaps you missed it Joanna, but I already mentioned that steel is certainly much safer than PVC or (rated) ABS.

Posted: **Fri Jun 15, 2007 9:50 pm**

Lol OMFG I never thought the day would come where Spudblaster would say don't use abs! I remember all the arguements about no abs is absolutely fine for a combustion! But I won't say I told you so.

Posted: **Fri Jun 15, 2007 11:07 pm**

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Posted: **Sat Jun 16, 2007 4:59 pm**

I dunno about you guys, but the only thing I can actually get is DWV ABS, so thats what I roll with (I can also get galvanized steel, but it's too narrow for a combustion). Getting pressure-rated PVC here is a major PITA, the guy there didn't know what a cap was...sigh...

Posted: **Sat Jun 16, 2007 7:54 pm**

ABS is a very unreliable material in the plumbing world. Because it is made with a cellular foam core, the molecules aren't as dense as PVC. Hence, ABS stands for Acrylonitrile Butadiene Styrene, note the STYRENE part. In fact, most codes now restrict the use of it.

Posted: **Sat Jun 16, 2007 7:57 pm**

@ nuclearspud-

try putting pvc into the sewer.

it is very durable and much stronger than pvc in the cold. it is also less brittle.

this cannon simply cracked, pvc would have exploded.

both have their advantages.

Posted: **Sat Jun 16, 2007 8:00 pm**

What do you mean put PVC in the sewer?

Merged:

PVC would not have exploded anyway. It has a way higher pressure rating and it is used in small sewer applications. Yes, i see how both have advantages, but I just think PVC has more.

Posted: **Sat Jun 16, 2007 9:08 pm**

...and some codes are restricting PVC, because cutting it produces PVC dust, which is hazardous.

ABS is also much more elastic than PVC, and that seems like a good thing since surviving combustion is mostly a matter of shock absorbtion.

Posted: **Sat Jun 16, 2007 9:28 pm**

In Australia ABS is only used for low pressure reticulation set ups! Thats why id never use it in a cannon at all plus it's tooooo small!
I agree with spudblaster theres not a hope in hell thats someone building a propane injected cannon out of it and living to tell the tail.

Bubba

SpudFiles

ABS cannon explosion