FYI, the full acetylene bottles I've used consistently showed 250 psi @ approx. 70f. IIRC, pure propane is closer to 110 psi @ 70f.

I average about 15 bike builds per 20 pound (5 gal) bottle. In reality, the refills are limited to about 4.5 gallons in the new bottles @ $2.10 per gal.. From the same 20 lb bottle, I also do metal art - perhaps 4 or 5 pieces @ 30 minutes torch-time each. The OC draws 5 amps @ 115 vac.

You are correct, my memory failed me.
Been a while since I had a fresh bottle.

"Acetylene is no more dangerous than any other fuel gas and less dangerous than many."

It is a bit like saying which is more dangerous driving head on into a pick-up on your bike or an eighteen wheeler. Any gas needs to be learned, and it needs to be handled properly. If you do everything right, you are OK either way.

What bothers me about acet is that it has a bunch of sneaky features. It doesn't like the tanks laid on side; you can't operate the pressure over 14 psi; drop something on the hose and it may blow up etc... Of course if one knows all the bad stuff one just doesn't do any of it. But it does concern me how many of these rigs are out there in ignorant hands (not talking bike builder here). You can do all three of those things and not blow yourself up with propane.

The other thing is liability. I just bet that if you blow yourself off the block with acet used in your home shop/garage there isn't an insurance company in the world coming to that party. Commercial use is a different thing.

You can also transport propane bottles (that you got at the corner 7/11, rather than the welding supply shop three counties over) in your trunk and no one will bat an eye.

I thought I'd give an update on this thread. Me and a friend set up a shop with propane and an oxygen concentrator following the advice here. Works pretty well!

First we had some trouble brass-brazing a crown, but we later realized the oxy supply was bottoming out due to a faulty check valve on the torch handle. With that out of the way we did obtain a loud and big flame, so we tried unbrazing the crown. As some of you may know, that takes a LOT of heat. Well it didn't work, but it got HOT!

http://bikeforums.net/attachment.php...hmentid=146767

Unbrazing a silver-brazed practice crown was a piece-o'-cake, however. Here it is as it just sled down the steerer.

http://bikeforums.net/attachment.php...hmentid=146768

So thank to PaPa for the idea, it's a sweet set-up. Looking forward for more brazing practice! The concentrator seems to give a slightly pulsating oxy pressure now, we'll look into it.

That`s pretty cool! You used acetylene of propane?

We're using a BBQ propane tank for the fuel. The idea is to have the gases easily available

http://bikeforums.net/attachment.php...hmentid=146772

Cool. Could be one of those deals where less is more orifice wise. or not...

Also, keep in mind when trying to un-braze, that you need lots of diffuse heat. Try an atmospheric propane hearth or, just add heat with a propane torch, not the main place of Oxy since diffuse is the deal. Check out Rheil burners, Hybrid burners, etc... Just using propane you could reduce a frame to a puddle in a propane furnace, so the heat is there.

Tuz, Glad to see some results. Questions;

1. What nozzle are you typically using during assembly? (not disassembly)
2. Did you perform any oxy line pressure checks yet? (ideally during use).
3. Are you still around 2-2.5 LPM? (looks higher in the pics)
4. Have you had a chance to experiment with the UNN-J mixer yet? (not that I expect any improvement, rather I'm curious if your results differ from mine)

While the maximum neutral flame temperature of O/A is slightly higher than O/P, propane actual produces much higher BTU;

Propane produces approx. 2500 BTU per Cu. Ft., while acetylene is closer to 1500 BTU per Cu. Ft.

And as I mentioned elsewhere, once on the torch, position the small, blue inner cone further away from the joint (or area being heated), unlike O/A.

For 'unbrazing', I use a twin flame attachment similer to the one below (pictured is Uniweld's, but its a type 17 so should fit your J-28 (mine is a Victor, but I couldn't find it in there new catalog??). This gizmo allows you to heat two sides of the joint at once - (I bent the tubes on mine so the tips are aimed at each other):

http://uniweld.com/Larger_View/Type17TFT_lg.jpg

Hey PaPa, thanks for the tips again.
1. We used a #4 TEN tip
2. we haven't checked the pressure yet. I'll remove the low-P gauge from my oxy reg and put it in line once I get the proper connector
3. I think we where at ~4LPM in the pic as we wanted the biggest flame possible to do the unbrazing
4. We haven't tested the UNN-J yet! I will, and also test that acet rosebud tip (TEP #00) and TEN #2 tip

And I may try unbrazing the test crown again, this time with an auxilliary mapp/air torch