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
The burner is made out of 3/4" steel tubing with a 1:12 flare at the end. There is a crosswise 1/4" copper tube (the original prototype by L. Oliver used steel pipe). One end of this tube is sealed, and a
0.04" orifice is drilled in the tubing. This sprays gas down the tube. Six 3/8" holes are drilled downwind of the orifice, three on the top and three on the bottom; and two were drilled on the sides, even though the text said that they are not necessary. The site also said that there was no need to leave the main burner tube open on the back end, but it was left open anyway, since that is how the prototype was made.When it was done, it lit OK, but it did not work. The main problem was that it did not seem to get hot enough. It produced a huge long flame, which was yellowish at the extremeties, indicating that the mixture was too rich. It was barely able to raise the target (about
3"x1/2" of 18 ga steel tubing) up to red heat, and this was insufficient to more than soften the brass rod. It was enough to burn most of the flux off, due to the large flame. Contrary to the original designer's experience, the torch was very sensitive to plugging the tube in the back. The flame became even richer. From some more investigations with google, it seemed that this kind of burner requires a venturi. It is odd that the one onSeveral posts recommended the use of a tweco contact tip as an air orifice. This was difficult to retrofit, due to the design of the upwind burner, since the rear of the burner tube is not really accessible. Being a little wiser from previous experiences, I did not want to do anything really permanent without more careful investigation, so the tip was just clamped in the propane hose with some twisted steel wire, and stuffed in the back of the burner tube. This worked a little better, but the miserable makeshift venturi was really interfering with the airflow. The venturi was removed, and the flame looked more reasonable with a shorter inner blue cone, but it still had some yellow indicating richness.
There are alternate burner designs, perhaps more well tried, which use venturi's made out of pipe reducers. Would these designs be more recommended? The lionel Oliver design is appealing due to its simplicity, but if it is difficult to get it to work, perhaps some investigation should be made into the EZ-burner type of design, which has the air inlet in the back. The tweco tip can still be used. Although
Thanks, Eric