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Atmospheric Propane Brazing Torch Experiments

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vtsteam:
Then I drilled for tapping for a #6 set screw right through both the outer casing and the brass fitting. The set screw will allow adjusting the position the MIG tip in the brass fitting, as well as lock the outer casing to the steel tube shell.

vtsteam:
I tapped the burner base and installed a .030" mig tip.  I also milled two 3/8" x 1" air ports lengthwise on the barrel. That's different than a Mako burner which as radially milled ports, so I wasn't sure what to expect for performance. I guessed that the open area was roughly equal to that in the Mako design. The slots are similar to the Hybrid burners like the T-rex, but those feature a much larger barrel and venturi, and the nozzle orifice is forward of the slots.

vtsteam:
I connected the propane hose to the tank and regulator hose barb using 2 new proper size hose clamps, and connected the other end to a gas ball valve and then to the burner base.

Here's the complete assembly (minus a burner flare):

vtsteam:
I tried a lot of experiments today with the new burner.

I tried it with and without a flare, with different amounts of flare in the flare (!) with different mig tip positions, and lengths, and with and without the three 1/4" holes in the end of the main barrel, which appear on the Mako design. Pressures ranged from 2 to 15 PSI.

To summarize, the burner definitely requires a flare in free air, and the flare should be flared. The tip position was best with this design placed far forward near the end of the air slots. That is different than the Mako design which positions the orifice in the middle of the air slots. But, of course those slots run radially, not axially.

The burner worked very well, though I think the flare needs more flare currently to increase stability at the higher pressure end of the range, and in wind (It was very blustery today -- not actually a good day for testing).

It puts out a lot of heat, but it is diffuse heat compared to a hand held torch, which really focuses a flame. For that reason, it never was able to do more than soften brazing rod rather than really fuse it to base metal despite the fact that it was producing lots of heat and flame. I'm sure it would be a fine burner in a forge or foundry where insulation could allow a rapid temperature rise, radiant wall heating, and contain  the flame.

But in open air playing against metal it was just too big a flame to reach good brazing temperature. I'd rate this burner as a success as a massive and efficient heat source, but a failure as a hand held brazing torch.

Focusing an atmospheric flame is something I want to find out about.

Here's the burner with flare and forward orifice location:

vtsteam:
Here's a picture of the flame at 5 PSI nearly fully open throttle:

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