Mikey98118

I did quite a bit of research along these lines for a book about crucibles; one of the three that the hacker destroyed. So before I forget the facts completely: (1) Untreated zirconium oxide changes its crystaline structure at about 1600 F as it passes beyond it, and again during cooling below it; this changes its size, crumbling any hard matrix it's part of. stabilized zirconium oxide used to cost twice what the plain oxide does; nowadays, it only costs about one-third more. And there are three different elements used as stabilizing agents. (2) You want to choose very fine zirconium oxide powder to make emissive coatings with, in order to get its famous heat repelling benefits. Also, really fine powder is colloidal, and so will spreads much better on a hot-face surfaces. (3) In the nineteen-sixties there were government sponsored tests made of zirconium coatings for heat shielding, and it was discovered that phosphoric acid was very useful for keeping zirconium particles "glued" to heating surfaces, because the first time its heated it polymerizes, and thereafter is sticky when heated, and vitreous when cold. Phosphoric acid also stays nicely suspended in water...now, I'm not suggesting that you can save tons of money and end up with a better product this way...you all should see that on your own. (4) Zirconium silicate is a man made material that's becoming ever more popular in castable refractory mixes, and as part of crucible formulas, because it doesn't break down under crystalline change or expose other materials in the matrix to physical stress, and the silica content is a standard binding ingredient in refractory formulas anyway. "What you describe about zirconia absorbing then re-radiating is the description of a reverberatory furnace. The liner get's hot and the stock is heated by radiated IR." Yes, but deliberately preserving and employing IR radiation should be a part of all forges and furnaces; this is why I keep harping on the use of exterior baffle plates on heating equipment. People think of heat loss from escaping combustion products through exhaust ports, which cannot be prevented, and fail utterly to see the equally great loss through radiated heat through those same ports, which is easily preventable!!!

Frosty has it right, But you can also use MIG tips the next size up, and insert capillary tube in them, in order to come up with the orifice you want without drilling, there are many ways to get around drilling in copper; all of them are better than drilling.

I liked the vinegar tip; it opens up whole new possibilities for using electrical conduit and fittings without exposure to zinc fumes

Isn't there also an SA knife makers guild? I believe they had a big conference/knife show in Los Vegas five or six years back.

The lack of a carbon = carbon bond looks like an exiting clue only until we consider hydrogen combustion, which is very hot without any carbon present at all, and should present the worst recombination example of all, but doesn't...unfortunately, the information posted on the Net is dependent on peoples' desire to post it; and that seldom is unselfish. On the other hand, once we leave the Net, information is a long way from free.

Frosty, To be fair, eight diameters always makes a good starting point during R&D, and most people would probably be perfectly happy with it as far as results go on most burners.

Kyle, The first problem with your burner is that you used a standard "T" pipe fitting instead of a Ward brand reducing "T"; you can order them from Larry Zoeller forge. The second problem is that you screwed a pipe fitting onto the burner, instead of building or buying a flared stainless steel flame nozzle; also available from Larry Zoeller Forge. Larry pioneered the popular modified side-arm burner. Make these simple changes and your burner should work fine. Kyle, Forge building questions are being debated elsewhere in these forums. If you don't want to read Gas Burners for Forges, Furnaces, & Kilns, then look under gas burners on youtube. In that section a guy shows a very creditable video on how to build a furnace from an old propane tank; his methods are a liittle different from mine, but I like them well enough.

Every naturally aspirated burner has a "turn down range; this consists of the amount of input pressure to the gas jet between the maximum jpressure, above which the flame blows clear off the burner, and the minimum input pressure, below which the flame becomes erratic and finally burns back into the mixing tube. These are pretty straight forward adjustments and easily gotten used to. But, most NA burners need to be choked back until they warm up; then the choke sleeve or choke plate can be opened all the way. This is such a basic problem that most of us forget it's a real surprise for newbies.

jcornell jcornell, I like your idea of a "home brew mix of zircopax and kaolin for a tough hard high IR "reflector" coating better than anything else I've heard. Zircopax is basically zirconium silicate (probably with a temporary binder ingredient added). The point of zirconium silicate instead of zirconium oxide is that it amounts to a form of stabilized zirconium (which is otherwise expensive) silicon is a common ingredient used to help bind (and vitrify) refractory mixtures together, and is fairly tough and heat resistant. Kaolin clay is another inexpensive tough heat resistant binder ingredient in refractory mixtures; together they should produce an ideal high emissivity coating and fiber sealant. What proportions do you use?

I liked both viewpoints; especially as hot-face coatings are an important subject for me at present. I'm still chewing on the information. And I can almost see Charlotte wondering why I'd feel hesitant on this subject. Well, it ain't so straightforward as running a hard coating over rigidized ceramic blanket after all, because of stabilized zirconium oxide powder, and of zirconium silicate. It turns out that so called infrared "reflector" coatings are actually high emissivity coatings. The way a product liike ITC-100 actually works is that the zirconium content is highly absorbent of radiant energy, which it then re-radiates it in all directions. With a thin coating (under two millimeters) there is a net gain in heat absorption, along with a net gain in heat radiation, and thus it is used on some exterior crucible surfaces. But, with thicker layers (five millimeters and up) the net effect is re-radiation along with very efficient insulation from heat gain, and so these are used on interior equipment surfaces to boost "reflection" of radiant energy from equipment hot-faces. Confusing isn't it? A very thin coating of zirconium on the outside of a crucible increases heat transfer through its wall, but a thicker coating on equipment walls acts as a highly efficient heat "reflector." So, why would anyone use something this expensive for heat "reflection" instead of an extra layer of insulation? Partly because elevated radiant energy levels within heating equipment do heating work, and passive insulation does not, and partly because every bit of heat turned back at the surface layer of the hot-face, helps to spare the wall material from exposure to elevated heat levels, which is very important for products like ceramic fiber blanket and board. But the kicker is that the efficiency of insulating products falls off at elevated temperatures, while the efficiency of emissivity coatings increases at higher heat levels. Zirconium silicate is used as an ingredient in refractories for this very purpose. And so we see that comparatively thin refractory layers that are rich in it can do an almighty lot to increase both the efficiency and the life expectancy of a forge. Whew, them's hard sayins! 1

From the very beginning I did all my testing out in the open air, because I found that any naturally aspirated burner that works well in open air only works all the better after being placed in a forge or furnace. So, discovering the ability of these burners to be used as heating torches was a by product of testing procedures. During the years since publication canister mounted air/propane torches have improved immensely, but they still can't compete with a properly built and tuned homemade burner.

Okay, If we are talking about tapered mixing tubes, then I would think that 12:1 ratio might be more useful than 8 diameters, but on straight tube or pipe, a rule of thumb consisting of x many diameters for mixing tube length will end up variable according to mixture feed speed, internal pressure, and whether or not internal vanes are installed. So, exactly how many diameters of length are optimal is going to change for every burner design. Fourteen diameters are needed on my vortex burners only to deliberately provide more friction so as to slow down swirl in the exiting flame. But installing internal vanes in order to shorten mixing tube length would add another layer of complexity, which I don't want to introduce to "the discussion" at this stage of the game.

Charlotte, You stated that "MAPP's real strength was in forehand horizontal welding." I can only picture forward flame welding in the horizontal position as appropriate for for either a root pass, or multiple bead finish passes; when I wanted good single bead shape on a finish pass I welded back hand. Give with the details; us ex welders wanna know!

You've probably already read up some about brick pile forges on these forums; they are an especially good option for people who don't have any firm ideas on what shape or size they want their gas forge to be. On the other hand they aren't exactly cheap to build. Also, if you want the forge to be portable, than a light steel shell is pretty much essential. One of the handiest things to use for the forge shell on a knife maker's forge is a two gallon non refillable refrigerant cylinder, because its wall thickness is ideal, giving the maximum strength to weight ratio you could desire for that size of tunnel forge. A five gallon (twenty pound) LPG (propane or butane) cylinder is the most commonly used item for tunnel (cylindrical shaped) forges, but a five gallon paint can will do just fine. Don't use a popcorn can; their wall thickness is too thin. And don't let anyone kid you that a certain minimum strength in the shell isn't needed; it is. You will probably be suspending a high alumina kiln shelf from that shell, and bolting legs to it, along with a pipe to hold the burner. It also needs to be strong enough to prevent damage to insulating fire brick and/or rigidized ceramic fiber blanket and brittle hot-face coatings. If you choose to use a five gallon paint can there will even be room to install an outer layer of perllite glued together with water glass, which is also both rigid and delicate, just like rigidized ceramic blanket (but a LOT cheaper).

Frosty's evaluation is dead on the money, and I encourage you to make that flare.

Charles, quoting an article. passes on the author's statement that "...the distance the flame travels before hitting an obstruction matters, too close to the floor/wall and the fuel is not completely consumed. " I don't find this to be so; in fact, once the forge interior becomes yellow hot any decent burner design should put out flames that are completely consumed, obstruction or no. What does commonly go wrong when sufficient distance isn't provided, is that any super-heated oxygen molecules escaping the primary flame envelope will cause a lot of scaling on work surfaces before they are consumed in secondary combustion within the forge. The simple solution for such a problem is running a reducing flame; of course, that can lead to other complications...best to design both forge and burner as well as you can, and only employ educing flames when they are the best option for the job you're doing :-) Tunnel forges normally have down facing burners set at about a twenty degree angle to promote swirl, instead of top dead center, which is also found, but is far less common. Nearly every gas forge has a kiln shelf or hard fire brick floor that the burner is aimed toward in order to spare ceramic fiber insulation from direct flame impingement. But what would happen if each burner were facing upward at a twenty degree angle against a cast refractory flame impingement ring, so that there was loads of distance before it hit the work? This would also end the so called "chimney effect and greatly reduce interference from back pressure through buoyancy. Shall we discuss this possibility? I plan to use it in my next portable forge.

I used MAPP in the shipyards for years; it was superior to anything else for torch cutting, heat bending, and silver brazing. I listened to both sides of the debate among welders as to whether it was good for flame welding carbon steel for years, but my interest was low because my employers were the ones paying out big bucks for acetylene on special pipe welds. After the shipyards closed, I spent another sixteen years working in small boiler shops and ship repair projects for the fishing fleet; both kinds of employer mostly used oxyacetylene. By the time I was personally concerned about the efficiency and cost of supplies, MAPP gas was a memory. However, propylene gas could be purchased for only a third more cost than propane from welding supply dealers, if you bought your own D.O.T. approved cylinder, and while both fuel gases were way cheaper than acetylene, they also both use three to four times as much oxygen in the flame. Now, oxygen in many places is reasonably priced, but Seattle isn't one of them. If you're an industrial customer, its cheap here. If you're a hobbyist or small business owner, get ready to be sheared...

I can only agree with Charlotte. My three favorite examples of corporate bonehead thinking are a little yellow 150 amp gasoline powered welding machine that could be lifted by one person and had a true hundred percent duty cycle. The manufacturer was bought out by Lincoln and shut down, so it wouldn't compete with their 150 amp piece of junk welding machine. There used to be a rubber welding gasket sold which wrapped completely around welding helmet light filters, covering their edges on three sides; it totally prevented light leaks, cost two bucks, and lasted for years. The manufacturer was bought out and production shut down; thereafter we all got to replace our one dollar (but you needed one on each side of the filter) oil impregnated paper gaskets about twice a year, and light leaks were a constant problem. Finally, a well known manufacturer of auto-darken welding helmets came out with a model that had a green LED light just above its lens. When the auto-darkening filter was in rest state, it was the equivalent of a #4 green light filter, and the LED would provide just enough green light, which the filter did not interfere with to allow the operator to change position before starting another weld. The flaw in this system was that they forgot about weld berries, which over time would destroy the LED. Rather than provide a protective clear plastic filter for the LED, incorporate it into the auto-darken filter (where it would have been protected) or sell quick installing replacement lights (after all LEDs are cheap), the company discontinued the helmet! So, if you want a high production capacity helmet for short welds, you must build your own. When I was a working stiff, all this stuff just made me grin; after all, work was dog eat dog, and everything bad only tended to cripple my competition, while I did workarounds. The working man's world is still dog eat dog, but I'm out of it; so don't mind teaching "them as listens."

Frosty, I only took one metal shop class, and the only ting offered was sheet metal. This wasn't from lack of interest, and I did get to work summers, weekends, and holidays in my father's ornamental iron works from age twelve (mostly loved it), meeting old timer weldors and construction boomers; picking up a lot of general knowledge from them and from dad. Outside of sheet metal shop in junior high, all the shop classes offered in my school system at the high school level were electronic or automotive classes. I hope shop classes have improved in southern California over the last fifty years, but somehow doubt it. Blacksmithing, brazing, and welding would be excellent subjects for teenage boys to be exposed to. Trouble is they are expensive classes to run, as compared to baloney subjects that only cost for the light bill, and a teacher's salary. None of that hurt me, since all my education except simple math and writing skills was learned outside the school system (I learned to read before age five, along with my sister and brother; first from holding contests reading billboards and comic books, and later at the town library) Post grade school, everything I learned was in spite of school; not at it.

I just knew if I could get Frosty to talk about brick pile forges something good would come up, and sure enough someone responded to his comment about painting the bricks with kiln wash with a better finish coating. Mentally, I hugged that idea to me and ran around in gleeful circles with it. Obvious; yes, but all good ideas are obvious...after someone else points them out! This little detail would make all the difference in how long insulating fire bricks last, and would create a tough enough surface that ITC 100 could be painted on one face to further increase efficiency.

Frosty, I first encountered this as the nine diameters rule of thumb (in Ron's pages?), and through experimentation found that with my jet-ejector design it could be as few as eight diameters and as much as ten. With the shorter lengths producing a more powerful swirling flame and the longer lengths producing smoother flames (which are more desirable for brazing work). My vortex burners require fourteen diameters for a smooth flame. It seems likely that length to diameter ratios change according to burner design, and the "industry standard" is a little shaky, yes?

Remember that we are talking about braze welding; not silver braze "sweating." I've even braze welded with one of the burners in my first book (and wrote a short chapter on how to do so), and also remember that I stated "being able to do a thing doesn't mean we can do it well." Pinpoint heating is the key to professional grade braze welding, and that depends on a super hot flame. Some braze welding is even done with the arc from a TIG machine. Braze welding also used to be done with both twin carbon arc and single carbon arc "flames" for the same reason. MAPP gas isn't produced anymore; it has been replaced with propylene fuel gas since 2008; weather or not it could successfully be used for steel welding was a subject under debate. On the one hand a friend of mine used it for welding steel tubing. On the other hand It was not used for any certification tests, which suggests to me that it wasn't quite "up to snuff." If I were going to flame weld steel without employing acetylene, I would use a twin carbon arc, to supply the excess carbon from its flame, which can otherwise only be supplied by acetylene, for it is claimed that the carbon content transferred to steel from an oxyacetylene flame is the reason MAPP gas wasn't supposed to be used. I don't personally know whether or not the flame's carbon content was the actual reason, as claimed, that MAPP was no good for welding steel, or it was an urban myth. Back when I had ready acsess to the tools and materials to make these tests I was too busy making a living instead :-)

rjs, Nothing but a TIG welder comes close to an oxyacetylene torch, and I never liked using TIG all that much. Twin carbon arcs didn't just fade away; they were quietly done away with by their own manufacturers back in the sixties; that was when weldors who had been using less than safe eye protection started showing up for eye surgery do to collective damage over the course of their careers; it was during that period that safety regulations on helmet filters were tighetened up considerably. Many old filter designs were removed from the market, and twin carbon arcs made by mainstream American manufacturers were quietly "dissapered" at the same time.l Why you ask? Because carbon arcs put out more UV than any other arc source, and companies like Forney were shaking in their boots for fear of potential law suites. For those of you who don't go back that far, a liberal revolution was going on in America back then. Today auto-darkening helmet filters have "come a long way baby" and can easily handle the increased risk from this tool. But, in the meantime, the American Welding Society has leaned on Uncle Sappy to get absurd safety standards put in place for carbon arc heating/welding. How do I know this? Because, at the same time carbon arc gouging, (an important industrial process $$$), which puts out exactly the same amount of UV for amps used has much lower requirements. I wrote to the department involved, and they answered that they "were just following AWS recommendations; on querying them, I was referred to their "safety standards commitee," and eventually to the single individual who wrote the recommendation. I asked for his justification, and never heard back from him. For those who don't know it, many welding experts have membership in the AWS (I suspect, in order to receive their magazine, which is excellent), but it is manufacturers and big time distributors who run it. There is a lot of money to be made selling TIG machines and supplies, and very little money to be made selling twin carbon arc torches, so even though the generation who might have sued over eye damage is long dead, it's still all about money. Isn't 'democracy' wonderful? "Truth, justice, and the almighty buck."

rjs, They claim it can be used for brazing; by this we assume they mean hard brazing. What the American Welding Society terms braze welding and the Brits call spelter brazing. We assume this meaning because silver brazing uses much lower temperatures that can alredy be achieved by any air-propane torch. Since their claimed temperature of 4172 F is within hard brazing range, technically speaking it should be able to do so. But here's the catch: just because we can do a thing doesn't mean we can do it well. An oxy-propane flame is about 4800 degrees and it doesn't do braze welding well. You want at least an oxy-propylene flame (5200 F), and oxyacetylene is better (5800 F). We have all experienced the frustration of trying to overreach with a poor tool. If you want to braze weld and don't have an oxyacetylene torch set, I would recommend using a twin carbon arc instead.

Charlotte, Then I'm glad you didn't see my book first; there is a place for every decent burner design; the more the merrier. Now, all we need to do is lure you out of your reluctance to discuss yours :-) And yes, I do appreciate your unwillingness to spread knowledge that may lead the careless into trouble. But, you can share the incites on combustion heating that you've collected over time. And I will be "siting in the front row" with my ears ready to be filled.