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Atmospheric Propane Brazing Torch Experiments

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vtsteam:
This is an extension of a project started in the "Neat Stuff" board, an attempt to make a brazing torch that runs on propane and air in the home shop. Original topic is here:

http://madmodder.net/index.php/topic,8607

First few posts will re-post what's been done on the burner construction. And then new posts will be added.

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Toward a propane/free air brazing torch:

I tried a few things this morning before the rain started. I found a 20' 1/4" ID propane hose I had in storage  from a boat stove, UL rated at 350PSI. Thinking about using this for a brazing torch, but I wanted to attach it to an acetylene regulator and gauge and run at maybe 15 PSI. I want a steady regulated pressure. Unfortunately the ends were  M and  F compression fittings while the regulator was B type left hand thread.

Then I found an old cracked OxyAcet twin hose, no longer useful -- I was hanging on to it for no obvious reason. But of course I now realized the end connectors were still in fine shape, and there were 2 B type left hand connectors on the red hose -- oh boy!   :dremel:

I split the crimped ferrule with a Dremel tool, leaving the end swivel portion intact. As I thought, under the ferrule in the hose was a nice 1/4" hose barb end. So I figured I could mate that lefty B connector with hose barb to my 1/4" propane hose. but unfortunately I didn't have a small enough hose clamp to fit the hose. Actually I want two on this connection for security -- and they need to be the full round type. So couldn't go any further. Maybe I'll go to town and get clamps tomorrow.

Then I thought I'd try firing up my Harbor Freight weed burner and testing it as a brazing torch. It puts out massive heat.

http://www.harborfreight.com/propane-torch-91033.html

For the test, I took a piece of 3/8" plate and set a piece of 1/2" water pipe on it. I ground them both clean beforehand. I figured the torch could easily do the job, but after a couple minutes of heating -- even up to the point where the pipe was glowing red in daylight, I couldn't get the braze to flow on the plate -- not sure if it was a fluxing issue or a gas mixture issue. I hadn't used much flux in the joint and hadn't fluxed the rod. It was definitely hot enough to melt the brazing rod, but it stayed on the plate like a little worm. I'll have to repeat that again when the rain stops, with a flux coated rod.

But it was clear the flame was just too massive and spread out to be much good as a brazing torch. Very wasteful. I unscrewed the head, which measured a whopping 2-3/8" ID (!), and checked the bore of the jet, which was .060". Also huge.

I think I'd like to make a torch about 1/2" to 3/4" ID with a much more concentrated flame with a jet orifice somewhere around .040. Also, as I said, with an adjustable regulated propane supply. The weed burner is direct connected to the propane tank.

It does have a good handle, valve, wand, and trigger, so might make a good starter assembly for my brazing torch. But the head will need to be quite different.

vtsteam:
I got a little time today to work on a brazing burner. First I did quite a bit of web research on burners -- Reill, Oliver, T-Rex/hybrids, Gypsy Tinker's Mako, etc.

For starters I'm going to try a Mako type because of its simplicity, light weight, and narrow profile (useful for what is intended to be a hand torch), plus its reported good behavior and good turn down ratio.

I'll probably modify things along the way, and I'm keeping in mind features of the other burners I've looked at, which may come in.

Plus I like working with scrap electrical conduit and fence rail tube. Don't know why! In this case though, light weight and less restrictive porting with thinner walls are small advantages, maybe.

Anyway, here's a start:

I turned a scrap of Brass down to make it a tight sliding fit in 1/2" electrical conduit, with a shoulder, and drilled it 1/4" to fit a mig contact tip. Because the piece wasn't long enough to thread the gas connection end, I rummaged around in my old plumbing fittings box and found a compression to 3/8" pipe thread bushing. I sawed off the compression side, and faced it, leaving the hex shoulder and the pipe threads.

vtsteam:
Then I took them outside on the porch, set them on a firebrick, fluxed both parts and cut little strips of silver solder to put in the joint. I set one on top of the other with the solder sandwiched in between, heated with a handheld Mapp torch, and It was able to do the job. The pieces came together and the solder wet out very nicely.

vtsteam:
The silver brazed part:

vtsteam:
I cleaned up a piece of 1/2" conduit and fitted the end in. It was a tight sliding fit.

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