I've flipped through many of the threads here regarding oxy/acetylene torches, so I thought I'd share my current (rather oddball) setup. I have about 4 decades of 'blue wrench' experience and up until about 8 years ago, I was pretty much a satisfied O/A user. But all that changed when I needed a refill and was astounded at the cost - not to mention that my aging back isn't as capable as it once was at lugging 60+ pounds of bottles around. This had to change,... and change it did.
First take a quick gander at the image below, and you'll see NO oxygen bottle. In its place, is an medical oxygen concentrator (on wheels, no less). A nifty, 50 pound machine that sucks-in ambient air, separates the undesirables, then pumps out 97% pure oxygen at about 9 PSI @ up to 5 LPM. Not quite enough pressure to feed a model 300 Victor cutting attachment, but more than enough to fillet braze a chunk of 1/4" thick mild steel.
My forte is HPVs, or human powered vehicles. I also dabble in metal art. Suffice to say, most of my projects are considered 'light gage', so brazing with LFB along with a variety of Harris silver (mostly 45, 45t and 56) has been my primary tool for most of these projects.
So just how does this system compare with O/A?...
Well, O/P is not without its quirks, that's for sure. It's a little fussy to light, especially in a breeze, and you need to make sure you apply an adequate coating of quality flux to prevent premature charing. It is also extremely challenging to weld with, which I might add, has nothing to do with flame temperature since O/P produces a flame temp in the neighborhood of about 5000°f (O/A is bit higher at around 5700°f). Steel melts, depending on the alloy, around 2500-2750°F. That said, the system accomplishes nearly every task I ask of it. If I absolutely need to weld, I use my MIG.
The concentrator shown below is my second, it was used (about 3500 hrs), didn't function (it needed a $25 HEPA filter), and I paid $25 for it. They are rather expensive new, but on the used market I frequently see them selling for well below $300... or about the same price as a set of full O/A bottles. The propane bottle is an unmolested, 20 pound (5 gal) BBQ bottle. So far, I'm averaging about 15 HPV frames and about a dozen art projects per fill - last refill 8 months ago was $11.60.
I use a victor model 710 (dual stage) acetylene regulator, but most any, externally adjustable acetylene regulator will suffice and even screw-on the LPG bottle if it has the standard CGA 510 fitting (or frequently called a POL fitting). The fuel hose must be "T" rated, as opposed to the more common "R" rated acetylene hose. I use the smaller 3/16". Just cut-off the fitting on one end of the oxygen hose and slide it on the barbed, tapered fitting on the concentrator. I have since tweaked the concentrator's internal regulator to a more suitable 6 PSI - I typically run my fuel reg between 4-6 PSI.
My torch is a Victor J-28 (my third since my first J-27 in early '70), so I have a sizable stock of J series tips. Speaking of tips, the setup functions noticeably better if you purchase a suitable alt fuel tips. Oddly enough, I'm using a UN-J acetylene mixer with alt fuel tips. Acetylene tips will work in a pinch, but lighting the torch becomes more difficult and adjustments are much more sensitive.
Produced by a single, 15 second pass on a rusty 1/4" thick sample using a Victor #4 tip.
Art samples using the same torch with different tip
