brass brazing with a large propane torch

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.
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 on www.backyardmetalcasting.com did not. A venturi was fabricated with an inlet taper down to about 3/8" within 1/2" and out to full diameter within 3 1/2". This venturi did not work well at all. It made the flame very rich, looking like it had almost no air. Furthermore, propane leaked out of the holes which were supplied to draw in air, and was easily ignited. This created an unpleasant odor, as well as a safety hazard.
Several 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 www.backyardmetalcasting.com has an e-mail button, it is discouraged to send e-mail to Lionel Oliver, since he is understandably very busy. Has anyone noted any success with these large torches for brazing? They certainly do have the potential do generate a lot of heat, since it only took several minutes to empty a partially filled disposable cooking propane cylinder, although to no real use.
Thanks, Eric
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The trouble with any kind of air/gas torch is that 80% of the air that is flowing through it is nitrogen, which is purely parasitic from a heat standpoint. It has to be raised up to the exhaust gas temperature, which robs the flame of energy, and it does not contribute to combustion at all.
This is the primary reason why oxy-fuel torches are so much better suited to brazing or silver soldering. If you try it once you will *never* ever go back. The only other suggestions I could possibly give are to a) preheat the items in a charcoal grill, and b) be sure to surround them with firebrick when doing the brazing so that some of the heat of the flame is contained.
But seriously, borrow an oxyacetlyene rig and try it.
Jim
================================================= please reply to: JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com =================================================
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On 3 Nov 2003 16:15:50 -0800, snipped-for-privacy@my-deja.com (Eric Chang) wrote:

How much brazing do you plan on doing?
Just a few items? Rent an acetylene torch.
Lots of brazing? Buy an acetylene torch.
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Technically, brazing brass is welding, since the parent metal and the filler rod are the same. If you ever do get it up to temperature, you will be creating a seam of brass on brass, fuzed, not wetted.
How about using Mapp gas. I have never used it, but I know it produces a much higher flame temperature than propane. The next step after that is Prestolite, which is air/acetylene--should be hot enough to melt brass.
But, I agree with the others. If you can get your hands on oxy/acetylene, your troubles will be over.
Have you considered silver solder? It makes very strong joints on brass if the fit-up is good.
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On Tue, 04 Nov 2003 03:35:11 GMT, "Leo Lichtman"

Looking at the "small" propane torches, and even Mapp, the high turbulence torches make more heat with Propane than a standard torch does with Mapp . The problem is, it's not the AMOUNT of heat produced that counts, it's the temperature of the flame. The high swirl Propane torch may produve 4 times as many BTUs as the regular Mapp torch, and still be several hundred degrees cooler. Brazing, and welding, require high temperature in a concentrated area. High enough to melt the subject metal - whether it be Silver Solder, Spelter (for brazing) or steel in the case of welding.
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(Eric Chang)

Hi John. I am not planning to do much brazing. I actually only have two very small and cheap items to fix, and both repairs are non-challenging. If it came to pure practicality, there are other high value activities to work on like plumbing (yuck!). Really, I want to develop a tool and a methodology, rather than just get the job done. I know this sounds kind of silly, but since my career got sidetracked at an early age, I have been building tools for a living. It is actually highly rewarding, and I am not interested in any other career paths now.
Thanks, Eric
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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 Website @ http://webpages.charter.net/dawill/tmoranwms
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...

Hi Tim. Thank you for confirming my suspicions. The flame really does look too rich. This may be the only problem. So, if I go with a smaller jet hole, things should work better. Or, I can use one of the more tried and true designs, such as the Ron Reil EZ Burner. He does not mention it on his web page, but google says that he has brazed very large items with his burners. My little prototype will not even melt brass held in the middle of the flame. One of the www pages he links to says that a good burner flame will melt a cast aluminum washing machine transmission in open air, and is hard to stand even 6 feet away from.
...

AHA! I am using a .035" tip. Your first hand information is really valuable.
...

Got it, thanks Tim!!
Eric ...
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http://www.riel1.net
This guy has a lot of burner designs, they are meant for forges. For open-air heating I don't know how they'll do, they're meant for use in a highly insulated forge box. My opinion is that, if you want to get the job done, go rent/buy an oxy-acetylene rig. If your aim is to make burners, go full speed ahead. What's your time worth?
Stan
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A couple of thoughts. One is that the original designer was likely using a larger refillable propane tank. There is less restriction coming out of the tank and at high flows he probably had higher pressure at the orifice. If you are going to do much of this I would buy a 20 lb tank. Propane bought by the gallon is much cheaper than by the small tank. You can also buy an adapter from Harbor Freight to refill the small bottles from the larger tank.
You could also use a small sqirrel cage blower to blow air in that hole in the back. You can control the pressure by a rotating bit of sheet metal added to restrict the input.
I have made several torches similar to that one, but have not tried to use them for brazing.
You can also buy a brazing rod called Sil-Fos. It is mostly copper with a little silver and some phosphorous. It works well for copper and copper alloys. The AWS spec isBCuP-5. Any welding supply shop should have it and maybe plumbing supply houses. I have used it with a small propane torch on things that are not too big. And as someone else said some insulating fire brick around and under your work will help a lot.
Where are you located?
Dan
snipped-for-privacy@my-deja.com (Eric Chang) wrote in message

Contrary to the

Has anyone noted any success with these

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snipped-for-privacy@krl.org (Dan Caster) wrote in message

Hi Dan. You are correct. I do have trouble with freezing, if the burner is being run for too long. I would like to get some more promising results before buying a white elephant (or Blue Rhino, as it may be).

This also sounds promising. I did try blowing with my breath in the back of the tube. This was very effective. The flame became louder and bluer, and quite a bit hotter. It was able to melt the brass, and even stick it to the steel. From this very limited set of experiments, I am sure that these torches will be able to do brass brazing of mild steel.

I hear that this is good for working with copper tubing. It melts at somewhat lower of a temperature. I would like to try it in the future.

Bay Area, California.
Thanks for your comments, Dan.
Eric

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Do they allow using Propane for bar-be-que in the Bay area?
You ought to be able to find a better deal than Blue Rhino. Propane in Washington State is about $1.50 / gallon at the feed store. Check at RV places.
Dan
snipped-for-privacy@my-deja.com (Eric Chang) wrote in message

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On 3 Nov 2003 16:15:50 -0800, snipped-for-privacy@my-deja.com (Eric Chang) wrote:

(snip)
Oxy-acetylene will give you better control, but for large work these self-aspirated propane burners work very well at much lower initial cost and fuel cost. I built a Reil burner that is one hell of a blowtorch. Orifice was #56 drill, runs on 20 PSI propane. Flame is all blue and of quite short length-to-diameter ratio. Not recommended for repair of frames for eyeglasses but very good for brazing angleiron or cannonballs. These torches absolutely will melt aluminum and brass.
Notes: the 1:12 taper is very important, and you do need a higher-pressure (20 PSI or so) propane regulator.
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Don Foreman ( snipped-for-privacy@goldengate.net) wrote: : Oxy-acetylene will give you better control, but for large work these : self-aspirated propane burners work very well at much lower initial : cost and fuel cost. I built a Reil burner that is one hell of a : blowtorch. Orifice was #56 drill, runs on 20 PSI propane. Flame is : all blue and of quite short length-to-diameter ratio. Not : recommended for repair of frames for eyeglasses but very good for : brazing angleiron or cannonballs. These torches absolutely will melt : aluminum and brass.
: Notes: the 1:12 taper is very important, and you do need a : higher-pressure (20 PSI or so) propane regulator.
Hi Don. Thanks for the informative reply. This is very useful information. At least I know that these burners can potentially work. I rebuilt the burner with construction that looked more like the Reil design. This used a bell type reducer with no side air holes and a 1:12 tapered nozzle. This worked much better, and there was a loud blue flame. This flame, however, was not hot enough to get a small piece of sheet steel red hot or to melt a small piece of brass brazing rod. But it looked like the pictures on the web pages. The flare did get red hot for much of its length. I will try tuning it per the instructions on the www page, knowing that it should work.
Thanks, Eric
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