American Chopper episode got even more reckless

He probably wouldn't have heard him anyway, just high pitched ringing. : )

Can't be. The red line at my acetylen bottle's pressure regulator is at

8 bar (116psi).

No, it can disintegrate without O. And if it is getting into contact with copper, it will ignite earlier. Brass up to 60% (IIRC) copper is OK.

Nick

I hope not. I got about 250 psi in my tank right now. :)

Yes, no oxygen, no fire.

No. It doesn't combust as normally understood (fuel plus oxygen combining) at high pressure. What's actually happening is a breakdown of the bonds between the atoms of the acetylene molecules into simpler compounds with lower bond energy, releasing the energy of the previous bonding scheme as heat in one massive dump. The proper term is "deflagration". Any fire that results is due to the heat of the breakdown getting combustion started on whatever acet molecules are left as oxygen comes into the mix after the balloon breaks from the initial pressure jump of the deflagration.

Yes. You can even get it without squeezing the balloon. First-day demo in high school welding shop involved the teacher loading two calibrated "color-change" balloons - They started out dark green, and as their calibrated pressure was reached, went almost clear - in the back lot from a remote-shutoff hose run from the acet manifold. First one maxed out at 12 pounds, and went "pop" in standard, fairly unimpressive balloon fashion just before it was totally clear. Second one was rated for 20 pounds, and erupted into a suitably impressive fireball as it was just reaching "almost transparent".

No. As mentioned, it's not combustion as normally understood (fuel plus oxygen combining), but a breakdown of the bonds between the atoms of the acetylene molecules. It'll happen just the same regardless of presence or absence of oxygen.

Dave, you might want to review some basic gas welding books...

Incorrect, Dave.

See my other post for more detail. In summary: Pure acetylene at 15-ish pounds doesn't "burn", a process which does indeed require oxygen. Instead, it "deflagrates", a process of chemical breakdown that has no need whatsoever for oxygen to be present in order to happen. (presence of oxygen may in fact inhibit deflagration in some cases) The only commonality between the two processes is that they both generate a lot of heat.

(Something capable of deflagration doesn't even need to be "flammable" as the term is generally used - It might be something you can't light by putting a torch to it, but it's still possible for deflagration to happen, resulting in an explosion)

Cool site Walt. I took mine down as it was a total joke. (Front-page) Any chance you are the same guy as in "Wally's Speed Shop"?-- Very cool toys and I like the old Yamaha, Brings back some memories.

All the best,

Rob

Fraser Competition Engines Chicago, IL.

Done properly it can be a fun blast. At one shop I worked at we had He for filling attention getting balloons and an OA set in the shop. So, with me in ear plugs, gloves and full face shield I filled several balloons with OA while another person filled several balloons with He. With all of them tied together a fuse was fashioned from a strip of paper. Fuse lit,the air burst balloons were released and went to about 150 feet before the OA went off, it was a beautiful thing. Car alarms went off for blocks, people came out of their shops and looked around for the "whatever the hell" made that noise. That was the first and last time we did that. But it was a great blast. I know, I'm sick.

That's me! If you're refering to the yamaha trail bike i agree... very fun! I googled your page and saw it was down, if you need some help getting her up again, drop me an email, i'd be glad to help.

walt (wally) wallyatwallys-speed-shopdotcom (u know how to fix that)

NOT to play with acetylene balloons.

Kick ass! Yea, that Yamaha was one of the first bikes we had as kids. Left a lot of knee-cap and elbow meat on the ground. Could beat that bike all day long and it would just ask for more. They don't make them like that anymore. I also had an old CB350 we put the engine into a go-kart in High school. (My brother and I) Just turned all the pipes over the top, lost the airbox and made a dual acting cable shifter and clutch pedal. The most insane cart I ever owned! I'll drop you a line on the Web-stuff as soon as that part is ready for the photographer and video clips of the dyno's in action. I'm almost ready to start. I need to get the shop in sorts and have the two dyno's up and running before I advertise. One drive on and one engine dyno. Got a lot of work in front of me. Plus wiring and the CNC is a headache in itself. (And the P&H overhead gantry crane is shot presently. Can't wait to get that bill....Ouch!) Hey. I will buy one of your shirts (I sort of wear the underdog clothes at the track to support the little guy like myself.) Can you E-mail me the order link and paypal account to snipped-for-privacy@robfraser.net I'll even have it in a photo on the web page. I'll send you some of my decals and whatever I can scrounge up. New shirts are on the "to-do" list. Going with the bowling shirts this time. Just send me the address in that E-mail off line.

Thanks for the offer of help. I need it!

Rob "wallster" wrote in message news:bK-dnQ-TXsZ251DenZ2dnUVZ snipped-for-privacy@adelphia.com...

Lung cancer.

Thanks for clearing it up.... That sucks even worse.

Rob

Fraser Competition Engines Chicago, IL.

The instructor in my first gas welding class was giving the orientation lecture in a gymnasium- sized shop. We were gathered around a steel assembly table. While giving us the standard safety lecture he was fiddling with a Styrofoam coffee cup. He poked a hole with a pencil and set it top down. A bit later he lit his torch, adjusted for a nice neutral flame, and then wiped the flame out. He held the flowing gas to the pencil hole and then relit the torch. He said, "Now, listen!" and held the torch to the hole. Fortunately, I had no class immediately after, because it was several hours before I could hear clearly again.

A more graphic demonstration of the extreme explosive power and brisance of a perfect oxy-acetylene mix would be hard to imagine. That was the sharpest CRACK I have ever heard, and I have been within 50' of a lightning strike that converted the top six feet of a telephone pole to toothpicks.

-- --Pete "Peter W. Meek"

I read your other post. Thanks, very informative. But, I have a question. If acetylene "defagrates" at around 15 psi, how do they get it into my tank at 250 psi or more?

I am sure someone will correct me if I'm wrong, but I think that is the reason for the acetone and matrix in acetylene tanks. It helps to stabilize the acetylene and prevent(or at least limit) this problem.

JW

OK, I've done a little research (very little)

This is what I've found from

Deflagration is a process of subsonic combustion that usually propagates through thermal conductivity (hot burning material heats the next layer of cold material and ignites it). Deflagration is different from detonation which is supersonic and propagates through shock compression

The best I can tell, deflagration IS combustion. Combustion REQUIRES an oxidizer of some sort.

If I'm still wrong, please point me to a site where I can learn more.

The neutral flame is so important to the db level. What's that? I can't hear you.... Tom