propane and oxygen

sandman · Sat Apr 07, 2007 12:51 pm

i think he means when they mix

super spuder · Sat Apr 07, 2007 12:56 pm

yea that is probly what he ment. sorry

super spuder · Sat Apr 07, 2007 1:32 pm

so i am just wondering. does anyone have or know someone that has a propane and oxygen potatoe cannon. if so how big is the cannon? and what is the performance like?

willarddaniels · Sat Apr 07, 2007 10:16 pm

I'll let you know when it is done... I am building one now but I will not fire it until I get a digital gauge in order to read the peak pressures. Without that, it is just blind experimentation. Blind experimentation = death. ..or at least lots of damage to property and/or cannon.

super spuder · Sat Apr 07, 2007 10:22 pm

lol yea. good luck with it. what is it made out of? metal or sch 80/or higher

willarddaniels · Sat Apr 07, 2007 10:42 pm

Metal sch 80. Threaded fittings, then welded - except the union which is the weak link. Also using a secondary casing around the chamber and union ... just in case.
This won't be done for many months... I need to budget the rest of the pieces, including extra unions.

hi · Sat Apr 07, 2007 11:20 pm

i was thinking of making a pistol using oxygen. i would use M copper pipe, the sleeve that in a bunch off couplers, then sleeve that in sch 80 steel. the chamber would be 1'' and about 6'' long. would that be safe, or am i an idiot? the union would be sch 80 steel and so would the barrel.

edit- this is just an idea, i havent bought any thing yet, and if i make it, it wont be for a few weeks.

super spuder · Sun Apr 08, 2007 4:10 pm

sounds cool. i think you would be safe with is sleeved in sch 80 steel. it can hold alot of presure

VRietscha · Mon Apr 09, 2007 9:50 am

I would think that just 1.5x or 2x combustion with air accounting for 1 shot and pure O2 accounting for the other shot of oxydizer shouldn't be too bad. I would definitely say to make a remote detonation wiring setup. What kind of actual pressures do people get on their gun?? Has anyone tried a one-way valve and a guage to get an actual reading or even a car compression tester?

boilingleadbath · Mon Apr 09, 2007 1:30 pm

I don't know as much about combustion as I'd like to know, but my understanding is that, so long as the combustion flamefront is subsonic...
1) You don't form a proper shockwave
2) The magnitude of the 'acoustic wave' is fairly minor, probably even at our flamefront velocities insignificant.

So, so long as it doesn't detonate, you arn't dealing with much more stress than the gaseq pressures would suggest.

(and, if I'm "he", I did NOT mean when the gasses mix. Very few propellants are hypergolic. Rather, I meant that when the gasses are ignited, they begin to burn normally and take a goodly amount of time before they transition from deflagration to detonation.

heavymetalsarge · Thu Apr 12, 2007 9:04 am

generally any flammable gaseous hydrocarbon with oxygen in the confines of a spud gun will detonate, the same should be with the presence of compressed oxygen should produce more efficient detonation thus louder bang and a farther spud launch.

PS. super spuder u said u were Canadian, so where are u from

jimmy101 · Thu Apr 12, 2007 1:23 pm

heavymetalsarge wrote:generally any flammable gaseous hydrocarbon with oxygen in the confines of a spud gun will detonate, the same should be with the presence of compressed oxygen should produce more efficient detonation thus louder bang and a farther spud launch.

Damn...

No, a flammable hydrocarbon with oxygen will not detonate. Even in pure oxygen it is extremely unlikely that it will detonate.

Spud guns are deflagration devices not detonation devices. Deflagration simply means the fuel burns relatively quickly.

Modern rifles, cannons etc. are also deflagration devices, the powder burns, it does not detonate.

boilingleadbath · Thu Apr 12, 2007 5:28 pm

Woah...
So, I was looking for hard numbers to, you know, shut these people up...

<a href="http://thermal.mech.saitama-u.ac.jp/fil ... F">This</a> doesn't confirm my former statements; rather, it shows that DDT occurs within 7" in a 4" tube!

Meanwhile, <a href="http://www.gexcon.com/index.php?src=han ... 2b">gexcon </a>shows propane/air transitioning in about 11 meters in a 4" pipe.

This massive decrease in required distance is backed up by <a href="http://www.galcit.caltech.edu/EDL/publi ... f">This</a> paper too...

heavymetalsarge · Fri Apr 13, 2007 8:43 am

jimmy101 wrote:
heavymetalsarge wrote:generally any flammable gaseous hydrocarbon with oxygen in the confines of a spud gun will detonate, the same should be with the presence of compressed oxygen should produce more efficient detonation thus louder bang and a farther spud launch.
Damn...

No, a flammable hydrocarbon with oxygen will not detonate. Even in pure oxygen it is extremely unlikely that it will detonate.

Spud guns are deflagration devices not detonation devices. Deflagration simply means the fuel burns relatively quickly.

Modern rifles, cannons etc. are also deflagration devices, the powder burns, it does not detonate.

i am sorry when i meant detonate i meant rapidly burn producing a detonation like experience

jimmy101 · Fri Apr 13, 2007 10:24 am

Heavymetalsarge:

Sorry, didn't mean to rag on ya.

The word you were looking for is "explode". An explosion can be a deflagration of detonation event. Someone on spudtech had a signature along the lines of;
"an explosion can be defined as a loud noise followed by objects being rapidly displace from where they were"

So, a spud gun produces a "rapid defalgration causing an explosion like experience".

Spuders generally try to stay away from detonation events. People aren't real sure that pressure rated sch40 PVC will handle the higher pressure and shock produced by a detonation event.