Mikey98118

I'm a fan of ribbon burners, BUT, how well they work depends on the builder, just the same as gun burners, and naturally aspirated single flame burners.

Cellular concrete blocks If you have a local source of lightweight insulating cellular concrete blocks, it can make a convenient structural choice for outer walls and subfloors so long as sufficient inner insulating layers separate them from the higher heats of forge interiors. However, you need to avoid the kind of cellular concrete that uses plastic based insulation in its formula; it will outgas toxic fumes. -----------------

Turn the heat up slowly and low, until the repairs are dry, dry, dry! Then rock and roll.

I am seeing yellow and white interiors, which is good. Tell us a little more about the cellular concrete outer slabs? I think you have something there

Casting your own form can also present the opportunity to create a longer funnel and/or a convex shape in the funnel wall; both of which will reduce back pressure against the fan. Be careful, or you will end up with a very in demand burner part $$$. Also, you would naturally have to present your burner to the casting group...

I have not changed my recommendation that the tip of the gas jet (whether a MIG tip or capillary tube) should be between 1/4" and 3/8" away from the mixing tube entrance; this is because this distance still constitutes the "sweet spot" for positioning.

Brick pile forges Brick pile forges have the advantage of being reshaped and resized, within the limit of their tops. If the top ends up larger than the rest of the forge, no harm is done; if it ends up to small it can be enlarged by cementing more brick around its borders. Additional burners can be included by use of a hole saw with carbide grit; so much for the good news. Use of hard clay firebricks will make for a cold forge and a large fuel bill. Foamed clay insulating bricks were never intended for use as a hot-face; they will rapidly crumble to rubble if used this way. K26 bricks are good to 2600 F, tuff mechanically, and able to withstand the rapid thermal cycling found in forges; They do need to have their hot-face sides sealed with a good high alumina castable refractory, such as Kast-O-lite 30, or with Metrikote.

Box Forges The size and shape of what I call box forges are usually limited to the builder’s choice of ceramic boards and backing bricks, although these parts can easily be cemented together; thus all such size restrictions are really due to a lack of knowledge or will. The burner or burners can be down-facing from the top of the forge or facing horizontally from the side of the forge and positioned near to its top. All parts on the top of the forge need to be cemented into a solid surface, to withstand the force of gravity. Ceramic boards on the side of the forge should be cemented together, but bricks on the side and bottom of the forge should be allowed to sit trapped in the forge structure, but be not cemented into a solid surface; this allows them to expand and contract during thermal cycling. The forge needs a rigid bottom plate to sit on; this may be metal or a double layer of cement board. A framework of angle iron is sufficient to hold the forge parts rigidly in place, although many people prefer sheet metal; if you choose sheet metal, remember to allow joints in its structure to allow movement; otherwise, it will be warped by the forge heat. You might also consider cement board trapped in angle iron, instead of sheet metal for the forge walls.

A third brick can be used as a convenient forge stand and as further insulation to keep the forge from overheating whatever surface it is placed on. One of the reasons foamed clay insulating bricks became the popular choice for these miniature forges is that nearly anything can be used to shape its surface; this is not true of K26 brick. You will need a grinder with grinding wheels meant for use on brick—not steel. The flame hole should be drilled toward the back end of the brick, to allow the flame to traverse the length of the forge before exiting out of the front exhaust exit.

Even this smallest of forges can benefit from a baffle wall in front of the exhaust opening. A simple hard clay firebrick with a center-hole drilled through it for the stock to be passed through will divert heated gas from the blacksmith and help to keep the forge hot.

The two-brick forge The smallest of brick forges is called the two-brick forge because most of them are built from two standard insulated firebricks that have been hollowed out, and a small hole drilled in the side of one of the bricks for a flame from a small air/propane torch to enter. The exhaust gas leaves out the front of the bricks, and the heating stock enters the forge through the same hole. I would suggest K26 brick instead; split bricks cemented together with Metrikote, and with their inside surfaces seal coated with it, and the side hole drilled with a hole saw incrusted with carbide grit. The Mag-Torch MT245C is an excellent propane torch with a low cost; it can be positioned at—not in—the hole opening, where it can induce the secondary air it needs, and avoid being overheated. Note that the MT245C has a weakness; its gas jet is only a few thousandths diameter, and easily gets plugged up from tars and waxes present in propane fuel gas keep a small glass container and solvent handy to soak it in, along with a compressed air container of the kind used to clean off computer parts, etc. to blow it clear of debris with.

High alumina kiln shelves will stand up better than anything else to flux; however, many people have a problem with whatever they use as the forge floor getting covered in flux; at this point, the smartest move you can make is to replace it. If you have a good pottery supply store handy, replacing the shelf is no problem; otherwise, using something that can be easily replaced can trump other factors. My K26 brick has lots of pretty large holes, which I plan to fill with something like refractory, or maybe Matrikote; you might consider using such a filler to help protect the brick against flux.

So, Frosty was saying the other day, that there are things missing from this thread. Naturally, I wondered what, and immediately box forges came to mind. Frosty and I have discussed brick pile forges on this forum, but not on this thread. To my mind, a brick pile forge has the advantage of being made of bricks, and therefore being as changeable as something built of Legos; both for shape and size. Whereas, the size and shape of what I call a box forge has practical limits tied to your choice of ceramic boards and backing bricks. Comments, disagreements, and/or questions?

neither the white nor the brown ceramic slabs look familiar. Could you name them for us? It would be pointless to attempt to discourage people from using bricks to build their forges; considering some of the newer bricks coming onto the marketplace, it also wouldn't be wise. What we are trying to do is encourage people to choose their bricks knowledgeably. Both brick pile forges and box forges that use ceramic boards and brick are only going to become more popular.

For old linear burners, with mild steel pipe reducers, which don't already have cross pipes; a small side hole can be used to hold a refrigeration tube to run fuel gas to the jet, and it can be held in place by tin or zinc-based solder and ordinary flux.

K26 brick is as insulating as soft firebrick, able to stand up against thermal cycling, and cheap to ship from eBay to your door. John, A 1" burner is about four times what you need. You can probably turn it down enough to work though.

The next change that mounting an impeller fan to a linear burner would need is a gas jet and gas tube that stays centered in the burner. So, for the first time in the last twenty years, I can truthfully say something positive for cross-pipes; this makes adding a "vortex devise" on an old linear burner more practical. Ben, Thank you for a question that forced me to think outside of the box

Unfortunately, that forge us lined with ceramic wool boards; as in lots of money! I don't expect you will get more than empty platitudes for your protests, but who knows. So, presuming you will have to help yourself; what know? Fortunately, there is a very good glue for all things made with ceramic fiber; and that is silicate based rigidizer; even more fortunately, that consists of fumed silica in water, which you can buy from eBay, with free shipping too So, about twenty bucks and some care will bring your forge back to life. BUT, do not forget to order Matricoat from Wayne, so as to protect that board from further bad news, and to save you a whole lot of money in wasted fuel, while it greatly extends the life of your board. Oh yes; you need that ceramic board sealed with the Matricoat to protect your lungs, anyway. There is a difference between silica and any other kind of glue; you need to let it dry, and then fire it before it will keep anything stuck together...

Well, okay; that is showing up my own druthers. From another person's point of view, a significant improvement in performance is worth some minor tinkering. It's my dog and I naturally want it to shine, but your question is quite legitimate; half a loaf is always worthwhile (curse it!)

These are venturi burners with some sort of vortex device. But if you meant to ask if the right fan could be mounted on a standard linear burner and act to form a powered vortex, the answer is yes. The next question that would come to mind is how well would that work? Mabe great maybe poor; to get it right you would need to follow this plan pretty closely, so why would completely rebuild a working burner that way?

Introduction to Vortex Burners Craftsmen have constructed forced-air gas burners for decades; typically employing squirrel cage blowers. But powering air swirl, instead of air push at a burner’s air intake radically changes output performance. Why? Because the more forceful the output of a burner is the more its output must somehow be broken back in the flame nozzle, to keep the flame from being blown clear off the burner’s end; that’s pretty counterproductive. While flame nozzles can be used to ease the problem, reducing the problem at its source gives far better control. Unfortunately, the idea of pushing input air is so entrenched that the other popular terms for powered burners are “forced-air, and fan-blown” Standard forced-air burners still have a place, notably on multi-flame burner heads, but are awkward on compact heating equipment. To begin with, let’s clarify just what is meant by the term vortex burner; technically it’s any burner that swirls the fuel/air mixture at some point; so technically, nearly every stable fuel/air burner would qualify—even some Bunsen burners. Often, the term vortex burner is granted to those that swirl the flames they make. But, causing a flame to swirl happens way too late in the mixing process to provide more than minimal benefits; applied this way the title is complete hype. Forcing an air stream directly at the funnel wall of a linear burner will create a weak vortical flow, but at the cost of also increasing the air/gas mixture pressure through the passage. The special fans on “”V” burners, are used to power up an otherwise passive vortex by creating lateral spin—not forward push—at the funnel entrance; thus, all the energy is spent strengthening vortical flow down the funnel transit, which then increases incoming air flow, while dropping incoming air pressure, by speeding up the gas/air mixture’s forward velocity and spin rate, all the way through the burner to the flame nozzle, where mixture pressure behind the flame is reduced still further. Positive pressure in the burner’s gas/air mixture severely limits how much a flame can be strengthened. So powering up vortical flow, instead of pushing the air, results in much larger and faster flames than are attainable with a standard forced air burner. Every part of a Vortex burner is designed either to enhance, or benefit from, the principles of vortical flow; so the name is actually relevant—not just something that sounds impressive. Once you construct an air/fuel burner that can produce a neutral compact flame (near to total combustion in the primary wave front) from LPG fuels and air, it would seem that it’s the most you're ever going to achieve. So, if the safety cautions to follow make you nervous, why would you go on to build this kind of burner? The truth is that performance involves more than complete and compact combustion. Further improvements can still be made, like: Much greater flame variance (turn-down range); more powerful flames from smaller burners; and the ability to simply change out flame nozzle diameters on a single burner, rather than switching between two or three separate burner sizes; all of these advantages are very much missing in most other fuel/air burners, including high performance jet-ejector tube types (mine). Vortex burners are quieter than other turbulent flame burners because of more thorough air/fuel mixing. I believe they come as close to the murmer of linear flames as turbulent flames can. Note: flame noise is generated by flame variance from millisecond to millisecond during combustion; such variance is mainly the product of imperfect fuel/air mixing; improved mixing results in increased flame stability, and therefore a reduction in flame noise. These burners provide the same stable performance on the smallest burner you can construct. This enables miniature burner sizes (1/4” and under) with turn-down ranges, from a perfect flame, to be increased by an order of magnitude. When it comes to jumbo size burners (1-1/2” and larger) that extra flame stability happens to be very comforting; if you’ve ever run one of those monsters, than you know just how desirable a smoother flame is. Four aspects of vortical flow, which make it a dynamic “motor” for burners: (1) Fluid movement through a restriction (ex. a funnel) will always create a vortex. (2) The forward motion (linear velocity) of a vortex tends to reach about one-half its rotational speed (angular velocity). (3) When a fluid (liquid, gas, or plasma) is forced to spiral through a circular reducing passage ( such as a funnel), rotational speed increases the smaller the restriction gets, because, in a vortex, angular velocity (spin rate) increases the closer a spinning fluid is forced to its center of axis; the opposite result of spinning a solid. Thus forward motion is also quite rapid at the funnel’s small opening. (4) BUT, fluid pressure drops at the same time; an ideal situation for fuel/air mixing, high feed rate, and especially for maintaining a very low pressure feed into a burner’s mixing tube and flame nozzle areas. So, if air pressure from an ordinary axial fan, or squirrel cage fan, will contribute to vortical flow, when run through a funnel, why insist on impeller blades? Direct air flow from an ordinary fan has to be turned almost ninety degrees before it makes a positive contribution to air flow in a restricted shape like a funnel, losing a lot of its kinetic energy in that motion, and it increases incoming air pressure at the same time; impeller blades fling most of their air against the funnel wall close to parallel with it, contributing much more energy to vortical flow, without raising air pressure at all. In fact, since the air is first slung toward the tips of the blades a low-pressure central area is created at the fan, forming a vortex right at the funnel opening, which only increases in power as it travels down the funnel, instead of gradually forming in the funnel. Placing a pressurized gas stream just before the mixing tube entrance (near the funnel’s small end) adds air induction, while minimally increasing flow pressure; this synergistic “double motor” effect constitutes a peerless way to feed an air/fuel gas mixture into a gas burner’s mixing tube. A vortex burner employs a modified cone or bell shape, on which an axial fan is mounted; because they are also gas-jet powered (air induced), they will run in both powered and naturally aspirated modes, although not with as much output, without the fan running. But the unique difference in a vortex burner, is that its fan features impeller blades, which are designed to create air swirl, rather than air push, so that they enhance vortical flow somewhat, even without being spun. It is all but impossible to establish a stable flame on your burner without swirling the air and fuel gas into a somewhat homogenous mixture, as they travel through the burner’s mixing tube. Any burner providing a stream of gaseous fuel before the entrance to a cylindrical opening (the mixing tube) will induce air entrainment (via Bernoulli’s principle), a funnel behind the gas stream will also provide swirl to the air entering the mixing tube. All linear burners, unlike jet-ejector designs, need some type of constricting form mounted at the air entrance, to create air swirl for sufficient mingling of air and fuel gas.

This is not a rule, but a preference; The difference being that, if there is a good reason to permanently attach the mixing tube to a reducer fitting, then a long centering rod allows that to work out okay, although reducer and mixing tube must then be aligned perfectly before brazing or welding the joint; afterward, its inner surface must be power sanded to ensure good airflow; this aggravation becomes an actual impediment to progress when funnels are used as air scoops. As for theory; I will cut and past it shortly.

Coyoteman, A forge made from a five-gallon propane cylinder is a BIG forge; it only needs one central 3/4" burner, although some people use two 1/2" burners, spaced so that the forge has three equal spaces, with a burner at either side of the middle space. A "knife makers" forge made from a non-refillable helium or Freon cylinder is what we usually recommend for a first forge; it only needs one 1/2" burner. Box forges made from brick can be any size with any amount of burners.

Well said, Wayne. Newbies need to be reminded of common sense over and over.

With an adjustable regulator, you don't need a needle valve (although it is still nice). On the other hand, a needle valve cannot replace the safety of a regulator.