"Eric Chang" wrote in message
om...
Hi. I read a post on google that said that it was possible to do
brass brazing with a large propane torch. The typical Home Depot
variety don't have enough heat output to get the metal up to
temperature. So, I bought some Bernzomatic brass brazing rods, and
looked up a simple design (www.backyardmetalcasting.com). There is a
design called "upwind burner" which I thought would be big enough.

I never really got the idea behind it. Apparently his model worked
quite nicely, but personally I don't see how it could possibly draw
in enough air. Maybe his jet hole drill was much smaller than he
thought.

A bit of EMT tubing is certainly a convienient and tempting burner
tube, and I managed to make one work very nice. My construction
requires brazing using yet another burner, but you could use welding,
rivets or other hardware, etc. instead. Even soft solder will work
if you use enough of it!
Anywho, I took a 6" piece of 3/4" dia. (I think it's listed as 1/2",
go figure) conduit, brazed a flare to one end (a 3x1" sheet of steel
bent in a cylinder and skewed to get the taper) and a bit of steel
rod to the other. This rod is bent, to mount the jet tube to. The
jet tube consists of 1/4" copper tubing with the gas attachment of
your choice at one end (I use 1/4" flare, you might use compression
fittings instead, whatever), and at the other, a .023" tweeco tip.
The thread on the tip is 1/4-20, so if you care you can drill and tap
a bit of steel, such that the 1/4" tubing slides in one end and the
tip screws in the other. Mind that this will not seal well, and all
needs to be soldered/silver soldered/brazed in place (copper will
accept brass filler well, just don't overheat it excessively).
Anyway, once you get the tip attached to the supply tube, braze/silver
solder it onto the offset rod you attached to the EMT earlier.

The end of the tip should be between 1/8 and 1/2" from the rim of the
EMT, and centered in it, shooting straight down its length. No venturi
necessary. Approxamately speaking, farther the tip is from the end of
the tube, the leaner the mixture is. Since that brazed-on rod isn't
very adjustable, I recommend using some thin sheet steel flaps, or just
masking tape so you can fine-tune the mixture.

Or grab some various bits of pipe, venturi-like bits for the pipes, some
sort of crude flares for them, and a jet/gas supply tube with an adequate
diameter hole in it, and have at it!

Oh, and for reference, a #57 drill (.04"-ish I think) is best fitted
to a 1" pipe (that is, with extra lean-ness headroom to choke it down
to neutral).

I gotta go to the bathroom so I can't proofread this big post....

Tim

--
"That's for the courts to decide." - Homer Simpson
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