Mikey98118

Another limitation in forge/furnace design is burner positioning. While the flame can be pointed in several ways in a forge, the flame in a casting furnace is aimed to impinge on the furnace wall as far forward as possible, without directly impinging on the crucible (since this promotes early crucible failure). If the flames in a forge were aimed this way, they would not burn for a long enough distance before impinging on work pieces, if the burner(s) should be pointed downward, toward the floor area. In these days of greatly improved refractories, it is better to aim them upward and slightly inward, to ensure the longest possible exhaust path in most forges; the exception being forges designed to create a hot spot, but there always are some limitations

I agree in principle. But, pushing the envelope is just sooo Mikey

Further details on C-c forges The main difference between a tube forge and a casting furnace is that the forge is positioned horizontally, and the furnace is vertical. With a little added work on its legs, and the addition of an emergency drain hole at the bottom to let liquid metal escape into a metal sand box (in case of crucible failure), a forge, with a locking hinged door, can be made to do both tasks well enough. One of the hard facts of equipment design is that there is no free lunch. Everything is a tradeoff. Being able to cast and forge in one piece of equipment must be paid for with some limitations on what can be done with the door and the floor, the larger the forge, the more serious these limitations become, but in a coffee-can forge/furnace the limitations are minor, because its capacity to heat work pieces for forging was minor to begin with.

Given propane for your fuel, or LPG (mostly propane/butane mixtures), and given a burner that is a good enough design to make a neutral flame: Then a 3/4" pipe size burner will heat a properly constructed 350 cubic inch forge (five-gallon cylinder) up to welding temperature. For every reduction in pipe size, divide the cubic inches in half. For every increase in pipe size, multiply the cubic inches by two. A mini-forge is two-gallon equivalent, so one 1/2" burner, or two 1/4" burners will more than do the trick. Nevertheless, I would advise you to use two 3/8" burners, and simply run them at lower fuel pressures. Naturally aspirated burners have long turn down ranges, so let them loaf along. So, why not choose 1/4" burners? Because 3/8 burners are a lot easier to construct; that's why!

Good forge designs have reached 2750 F, with an excellent burner. I believe 3000 F, when burning propane would be epic. However it only takes a good design to reach 3000 F, burning propylene.

Good, good. There is always plenty of room down at the deep end of the people's pool

Good!!! Most people are in such a hurry to build their first forge, that they have it half built before the realization sets in, that they didn't have a solid plan. And now they wish they had done this, and they wish they hadn't done that...it's kind of sad. You stated that you " have all the stainless sheets for the enclosure." I like that you chose stainless steel for your forge's enclosure (we usually just call that a "shell"). I hope that you are going to make that enclosure's shape worth the effort. As I recall, you were looking to build a min-forge (about two-gallon size). But, what shape? Box or tunnel forges are the simple choice, but oval shapes give you more usable area, which increases in importance as equipment. But, "D" shape forges share this same advantage with oval forges, and are a lot easier to build. Whacha think? Should read "...which increases in importance as equipment size shrinks."

Carbon fiber can withstand 3632 °F (2000 °C) in the absence of oxygen. So, carbon fiber could be a great way to strengthen refractory bodies, so long as both their inside and outside surfaces are carefully sealed.

Mounting burner ports: Typically, a burner port (entrance) consists of a short steel tube or pipe with about 1/4” larger inside diameter than the burner’s flame retention nozzle’s outside diameter. This allows enough space to aim the burner somewhat within the portal. The burner is held in position and aimed with two rows of thumbscrews; each row has three equidistant screws. One of the advantages of these screws is that they can hold a pipe or tube in place within the portal, and resting exactly where the flame is intended to impinge, while the portal opening is being ground into an oblong shape (to allow the tube to be aimed at a desired angle). This method ends up with a very close fit between tube and shell opening, to promote easy silver brazing of the port’s tube to the equipment shell. You are building a burner, so why not employ it to help you construct its forge? Alternatively, you can drill and mount a burner port in the shell with three bent flat bars and some pop rivets, or self-drilling screws. Bracketing parts together can end up looking tacky if you do not manage to keep the shell opening tolerances close. Employing screwed brackets can be a be a minor pain, if the burner’s port tube is positioned at an angle. Welding equipment parts, such as burner ports unto a steel shell, takes a wire feed machine and a learning curve. Some people are reworded with distortion in the shell, because of welding contraction; it only takes a little time to learn to run a wire feed welder, and somewhat more to bridge gaps with one; but it takes a lot more time to learn where and how much to weld without creating distortion. Neither brazing, or silver brazing makes that problem. Hard brazing requires an oxy/fuel torch, or an air/fuel torch, propylene fuel, and a lot of skill, Silver brazing can be done with an air/fuel torch, propane, and close attention to setup, but most silver brazing alloys won’t bridge gaps very easily. However, some silver soldering alloys do bridge gaps. Silver brazing by hand torch benefits from a lower temperature filler with broad melting range such as Ufhauser silver braze filler A-54N (54% silver/ ) that has a broad elastic range (250 °F), and bridges minor gaps; it can be considered a capping alloy, but if heated too slowly it can suffer from liquation (where the alloy separates into solid and liquid zones); it will melt between 1325 °F (dark red) and 1575 °F (bright red). The high temperature portion will melt only above the normal brazing temperature afterward. For this reason, alloy A-54N should be heated rapidly through its melting range. If you are joining a thin shell from a tin can to a thicker tube, keep the flame mostly on the tube. This filler alloy has a good color match to steel. Reasonable care with a sanding drum or grinding stone in a die grinder or electric rotary tool, will easily produce a sufficiently close-fit in the joint between a burner portal tube and the forge shell opening. If you’re silver brazing on stainless steel, burn polypropylene fuel gas (if you employ an air/fuel torch), and a high temperature black flux. Car mufflers are zinc coated, and silver brazing parts to this kind of forge shell will ensure lots of damage to the plating. Stay Brite silver solder may be employed afterward, if you don’t want to paint the forge shell. Most zinc-based soldering alloys are zinc-tin-lead (avoid these), zinc-tin-copper (excellent), or zinc-cadmium (use fume rated respirator with these and follow all safety guidelines to the letter). Note: The main ingredient in zinc flux is zinc chloride (follow safety guidelines on container); it is the only ingredient in many of them; it tends to “tin” the surface of steel, rather than just cleaning it. If steel is freshly cleaned and power buffed with stainless steel wire wheels, it can be zinc soldered without flux, but why do things the hard way? Zinc’s melting point is 787 °F; comfortably below its boiling point (1665 °F). Zinc fumes are easily seen and smelled; avoid them. Unlike lead fumes, it takes a heavier dose of zinc vapors to cause fume fever. Unlike lead, the body can tolerate a little zinc, but keep your dose tiny; none is best. No metal fumes are good for your lungs. Caution: Metals give off toxic fumes upon reaching their boiling points. Using zinc coated sheet metal or parts (such as car mufflers) is okay if you're careful about doing it. The boiling temperature of zinc (the point at which it makes fumes) is 1665 °F (bright red heat). Your forge shell should not get higher than one-fourth that temperature. But you do need to be careful to keep the shell well away from the edge of the exhaust openings, by not making the openings in ceramic fiber, kiln shelf, or cast refractory even with, or even near the shell. Zinc coated flame retention nozzles or mixing tubes are out. There is no reason at all to avoid zinc coated reducer fittings on a burner’s air openings. In other words, keep zinc away from part surfaces that may become incandescent (above 1200 °F or 649 °C). Note: Preheat temperatures should be kept down to 600 °F (315 °C on zinc coated surfaces, such as car mufflers, to avoid damage to the existing coating on their surfaces, and to keep scale formation down on the steel; “tinning” the bare steel with a zinc chloride-based flux will help with this. Remove all residual flux with hot water and a clean rag after soldering. Larry Zoeller (of Larry Zoeller Forge) is credited for first mounting schedule #40 pipe to a forge shell with conduit locking rings; he calls it a “burner holder assembly.” If you’re looking for fast and easy, he sells them for $25 and shipping from his website. Their main limitation is that they can only be positioned at right angles. The burner port’s tube should be completely external to the forge shell; it should not extend inside the forge further than is needed to secure a locking ring. A washer should be provided to slide up and down the burner’s mixing tube above the portal, so that it can limit how much secondary air the burner flame can induce through the gap between the burner’s mixing tube and the portal wall. A nut can be silver brazed onto the washer, so that a thumbscrew can keep it positioned at the right distance away from the portal edge; limiting secondary air into the forge to only what is needed for complete combustion, without lowering internal temperatures needlessly. To consider air introduced from the burner opening as no different than air from other openings is a sad mistake, since those other openings don’t have flames inducing air into the equipment.

Air Chokes are a burner’s secondary control For several years there were two very good reasons for adding chokes on burners; the first being to prevent chimney effects from overheating burners after shutdown, and the second was to vary flame characteristics. As gas burners have grown more intense, using chokes to alter flame characteristics has diminished; the technique still works, but is less appealing than it was in the past. Burner chokes greatly diminish chimney effects from traveling up through the burner after shutdown, but might require a secondary control mechanism (such as a moving washer on the burner's mixing tube), to stop it from overheating from air rising between the burner and its portal; this is especially true of burners with electrical fans. This washer can also serve to control excess secondary air induction, created by the flame, from lowering forge temperatures, while the burner is running. Caution: Never trust an external washer to stop flames from backing up from the forge interior, and overheating the burner; this is the equivalent of using a bandage, when a wound needs stitches. The flame is pushing into the burner portal because of back pressure in the forge. You need to address the problem BEFORE YOU BURN DOWN YOUR SHOP! You may simply need to enlarge the exhaust opening in your forge, or you may have too large, and/or too many, or even too weak burners, mounted in your forge.

What size burners, and what size furnace?

BTW, it is quite common for the super-heated steam, which is generated while the refractory is heat curing, to snuff burner flames. If you drilled a weep hole in the bottom of your forge shell, it would spit and drip water until the cure is nearly done; that would give you a visual cue of just how much steam is being generated, for a while.

I only suffered through bad copies with my name on them for the first five years, or so. After that, people started picking and choosing through my design principles, to make their own individual burners; this is exactly what I was shooting for

I have been trying to produce some of them. Alas, it takes a lot of study, before we are able to pronounce a few tiny little "facts." That study makes us see how inaccurate our "facts"are, and how limited. Thus, the more we learn, the less we know. Fortunately, myriads faced this problem before us, and we won't be the last. Misery does love company

Being right is becoming so much more complicated; the more I learn the further away right gets. Soon it will require plane trips to come close.

I mostly like your choices, but the MIG contact tips look like they are positioned off center to the mixing tube; you will probably need to bend them into better alignment at some point. I assume that the brick you are employing as a forge floor, is of the semi-insulating variety, and won't be to much of a heat sink...

So what limits do I foresee on the usefulness of fan-induced burners? First of all, they should prove unworkable on ribbon burners, because such burners have plenum chambers, rather than flame retention nozzles. The greater potential pressure drop in a plenum chamber probably needs increased mixture flow pressure; a reduction in its pressure would only invite back fires into the mixing tube. I do expect small 12V fans to begin being employed on ribbon burners, but they should be squirrel cage fans, which increase the pressure of the burner's gas/air mixture. I do not see fan-induced vortex burners ever become popular on small burner sizes (3/8" and less), because the whole point of these burners is control of small spaces; thus, supercharging them to get more flame is pointless. So, we see the usefulness of fan-induced burners, while real,, is itself limited No one shoe fits all. So, what advantage do I think a little 12V squirel cage fan could possibly add to a naturally aspirated ribbon burner? Some increased pressure in the gas/air mixture, might be just what is needed to get better control of the flames, for complete combustion in a single flame envelope--or not; but if it works, it would be worthwhile.

On one hand, strong or weak is all too often in the eye of the beholder. When it comes to our own equipment, that eye may be too fond to be trusted On the other hand, we could compare naturally aspirated equipment to bicycles. Fat tires replaced by narrow, three speeds replaced with 15, steel tube frames replaced by...well, you get the idea. Then one day a motorcycle zooms by, and what we think about fast or slow, changes forever. Fans with impeller blades is the equivalent of a gasoline engine; much will change...but much will not No shoe size fits all.

The 3/4" Mr Volcano burner came today; it has all stainless steel parts on the burner. The ball valve is cast brass and well made. The mixing tube's inside diameter is 0.834" and the distance between the forward edge of the two air openings is 6.75" for eight times the tube's inside diameter. I would rather see nine diameters, but eight will work. I think they should double the width of the two ribs, to strengthen them. As to value for price; I don't see how they make any money on these burners Will post again, after I run the burner.

I've been thinking about this stuff for so long, that I lose track of what all I have discussed, and what I merely intended to AFB; so what do you think about adding fins at the entrance to your burners? I like you to be generally confused

You are right, Frosty. I need to go back and make things clear. Vortex burners with moving impeller blades at their air entrances (ex. funnel openings), as you get from installation of modern axial computer fans, create two differences from other linear burners, whether naturally aspirated, or fan-blown (blades that push air forward): The first, and desired difference, is that those impeller blades swirl the incoming air around inside the funnel structure, creating much stronger vortex motion; creating fast swirl, with forward motion of about one-half the high velocity around its axis. But unlike any other method of increasing mixture flow speed, the air in that mixture is reduced in pressure. The second thing that happens is that the low pressure area at the funnel entrance can suck fuel gas back into the fan, where it ignites, if you aren't careful to prevent that from occurring, by careful design. This high-speed low-pressure gas/air mixture is then dumped into the flame retention nozzle at the far end of the mixing tube. When the fan speed is turned up to maximum, and the fuel gas pressure is turned up to match the greatly increased air flow, a second larger diameter flame retention nozzle is needed to handle this increased flow. Thus fan-induced burner output; not fan-blown, or naturally aspirated burners, can be rated by largest flame retention nozzle diameter. No other burner can be rated that way, because no other burner can be turned up anywhere near this high, without blowing its flame out.

I was not discussing gun burners per say. Nearly all gun burners use fans to push air into the burner; this causes the gas/air mixture flow to increase in both speed and pressure. The pressure increase severely limits how much flow the burner's flame retention nozzle can handle; it is largely self-defeating; or if you prefer it self-limiting. This is why I call call vortex burners with moving impeller blades, which reduce mixture flow pressure to be fan-induced--not fan blown. A reduced pressure mixture flow, is much easier for flame retention nozzles to control.

That is why I wanted one; to see for sure how hot it burners, and how well made it is.

Took my own advice, and ordered one through Amazon.com; it should arrive tomorrow.

If someone tried to build this well proven burner, it would probably cost as much money as they are asking for it. I have been hoping Mr. Volcano would market their burner