Forges 101

[Mikey98118]

Saving up heat

People are looking to maximize fuel efficiency in their heating equipment. Naturally aspirated burners have large turn-down ranges. So, it would seem that a wide selection of burner sizes isn’t needed. But heat management is about more than how well fuel burns.

    The reason flames, whenever possible, are aimed on a tangent, is to cause their combustion gasses to swirl around equipment interiors; creating a longer distance from flame tip to exhaust opening. A longer exhaust path increases the amount of "hang time” for combustion energy to be deposited on internal surfaces. That seems obvious, doesn't it?

    What isn't so clear is that the heat gain isn't added by hot gases blowing a few inches farther at high velocity; it’s due to the ongoing drop in velocity over that added distance. Combustion gases begin to slow as soon as they leave the flame envelope, but the blast from a small flame decelerates much faster than that from a large flame.

    The smaller flames of two 1/2" burners will use the same amount of fuel as a single 3/4” burner, but will drop velocity much faster in a five-gallon propane cylinder forge or casting furnace, greatly increasing efficiency; because they can burn faster/hotter without creating a wasteful tongue of fire out the exhaust port.

    What about people who want to build a two-gallon forge or furnace from a non-refillable helium or Freon cylinder? They will need two 3/8" burners to do the same trick. Someone who wants to forge hand tools or cast jewelry in a one-gallon paint-can or three Lb. coffee-can will want two 1/4" burners to run their equipment with maximum efficiency; a 1/4" burner is also ideal for a miniature brick forge, or tomato can jewelry furnace, which so many people attempt to run from a store-bought propane torch; without making the necessary modifications.

    Do multiple flame burners (ex. Ribbon burners) take deceleration even further? Yes, they sure do; unfortunately, ribbon burners themselves tend to be large. Over time, compact ribbon burners will be perfected, but first there must be a lot more interest in doing so; there isn’t much, because ribbon burners provide the most advantage when heating large equipment.

    In the meantime  Joppa Glass seems to be the only source of small multi-hole burner heads.

[Mikey98118]

Is welding needed?

I see the lack of welding skills and/or equipment frequently listed as the main objection to building forges. It is understandable that, do to the increase in low cost wire feed welding machines, amateurs consider them some kind of magic key to home brewed steel work; they are quite right. But when considering what is needed to build good gas forges, this technology is mostly irrelevant, because good forges are screwed or riveted together. Heating equipment changes dimensions with every change of temperature, and welds restrict movement. Can good equipment be,at least partially welded together? Yes, and some is partially welded together, by professionals, who know what they are doing. But no welding is needed to make a good home built forge.

 

[SinDoc]

Due to my shaky hands, I make pretty bad beads for welds. If I was building a propane forge, I think I would probably use bolts to hold it together since at some point the refractory will need replaced.

But seriously, my welds are AWFUL looking 

[Mikey98118]

I welded for half a century. At one point I was a multi certified mirror weldor in the shipyards. At seventy-five-five I;m probably no better a weldor than some twenty something kid. Anyone with the will can learn to fly high. But age or circumstance grounds every pilot, sooner or later

[pnut]

I think a lot of people forget that you can screw together or rivet most things if you don't have a welder. It's not going to solve every problem but for forge bodies, frames, and stands it works fine. 

Pnut

[Ted Ewert]

I have to agree with everything Mikey has shared in this thread. Pig headed individuals like myself generally learn the hard way, but I've come to the same conclusions so wisely laid forth here. 

I've built a number of gas forges and each one is smaller than the last. My latest is a 5 tube ribbon type design and I have already removed one of the tubes. My fuel consumption is probably 80 percent less than that of my original designes, and I can easily get to welding temp.

"Forge" is a bit of a misnomer. High temperature gas oven is a closer description. Heat retention is everything. I have 2" of wool and an inch of kast o lite. The doors are 2" kast o lite. 

Note on kast o lite. I recently recasted the lining of my oven. It's already falling apart. I did not use the stainless needles this time and I think that's the cause. It has cracked lengthwise in two places and the floor is crumbling. I tried using a liner this time and it all fell off.

Structurally kast o lite is garbage. It needs some reinforcement to stay together. I'm going to try putting some course stainless screen inside the tube and the floor next time. 

I cast the tube (liner) in a mold I made. I then insert it into the preinsulated shell and pack any gaps with wool. Then I poor a level floor. 

Before I insert the tube I install a few stainless quarter inch bolts where the floor is going to be, to anchor the floor. Kast o lite will not stick to cured kast o lite. Kast o lite can be drilled with a masonry bit, but don't use a hammer drill. Go slow and gentle and it works fine. Oh, and make sure your piece is well supported before drilling. I made a wooden cradle to support the tube.

One last thing... take heed of Mikey's wisdom. 

 

 

 

[Frosty]

8 minutes ago, Ted Ewert said:

Structurally kast o lite is garbage.

Then you're using it incorrectly. How long at 100% humidity did you allow it to cure? If you're casting the flame face anyway why cast the flat floor individually as a separate piece? Did you not realize a significantly thicker section WILL have a greater change in volume during thermal cycling? 

Why didn't you cast a D shape liner? 

The liner in my daily user forge is 1/2" of kastolite floor with 3/8" walls and roof, supported on 2 layers of rigidized 1", 8lb. Kaowool. It's been scraped, banged and generally abused for a few years now and is not in need of repair.

When it comes to heat you can flux small welds by rubbing the join in the puddles of molten flux that live on the forge floor.

If your experiences say: it's "garbage," my experiences say it's operator error.

Frosty The Lucky.

[Mikey98118]

My favorite answer to problems is...wait for it...avoidance

Some high alumina refractories or better than others, and some builders are are more careful than others. But none of us can match the care and exactness that goes into high alumina kiln furniture; that's why I use it. So, if at first you don't succeed, cheat baby, cheat

[Frosty]

[Ted Ewert]

As I said, I used a mold and mixed the refractory according to the manufacturers instructions. I led it sit in the mold for a few days before removing it. The mold is a tube shape, and to add a floor to the mold causes problems getting it apart after curing. This, among other reasons, is why I chose to add the floor afterwards. 

I have used this method in the past with no problems. I also use my forge daily which causes a lot of wear and tear, not to mention thermal cycling. The cracking is not a big concern because the tube is supported by the insulation. In fact, the cracking may be due to the tube being packed too tightly, not allowing for adequate expansion. Nevertheless, the edge of the floor is starting to wear away where the flame stream hits it. I can only attribute that to a material failure / design flaw.

The only other thing I can think of is that this Kast-o-lite is not brand new. Its been in a tightly sealed container for a little over a year. This may be part of the problem.

On the other hand, the doors are holding up just fine. Those were also cast out of the same material.

I only used the Kast o lite because I already had it, and I knew I could drill out the holes for the gas tubes. Next time I'll cast the holes in, and possibly the floor, and I'm going to use some reinforcement.

Kast o lite is generally a good refractory material, but it has its limitations. Obviously I have exceeded those limitations and will have to account for them if I used it again.

One last note. I have casted  many similar tubes in the past using portland cement as a base adhesive. This was for another experimental project I was undertaking, but it caused me to become quite familiar with the mixing, casting and curing process of mortars. I can't rule out pilot error, but this is not new to me either. 

[Buzzkill]

1 hour ago, Ted Ewert said:

Structurally kast o lite is garbage.

This has not been my experience.  I did have a couple crumbly castings, but I'm fairly sure why now. On one of the failed castings I used half a dry sonotube without buttering the surface before casting and I just let it cure/dry in open air.   It was a bit crumbly especially around the edges. The last one I cast using half a sonotube is still in use in a D shaped forge after a couple years.  It has some cracks across from the burner, but it has not crumbled or shown other signs of imminent failure.  On this one I wet the surface of the sonotube before applying the kastolite mix, and when done I covered it with a wet towel.  I added water to the wet towel several times over the next couple days before letting the surface air dry.  I removed the tube by burning it out.  After firing briefly several times in gradually increasing duration and temperature I coated the flame face with Matrikote.  I can't say this is the perfect way to handle the material, but it has worked fairly well for me.

Nothing else in my forge supports this inner shell of kastolite.  The two straight edges rest on the forge floor, and the casting supports itself, the two layers of superwool, and the sheet metal "wrap" over the top of the whole thing.  In addition it gets bumped and scraped occasionally as stock is being placed in or removed from the forge.

Of course there could be some variance from one batch of the material to another, but in my experience it has good structural strength the way I cast it last.  YMMV

[Frosty]

What's difficult about making a D shaped form? It's seriously easy, cut a piece of board with a length minus the thickness of the sonotube wall and staple it inside the sonotube and cut away the tube. Wrap it in saran wrap or wax paper. 

Strip it from the casting either by slitting and pealing it in pieces. 

The recommended method of making this for is by rolling the Kastolite between stops, say 1/2" or 3/8" square stock to form a uniform thickness then wrap it around the form. According to the blog entries by folks using Kastolite ad other products. Rolling it on a piece of burlap or canvas allows you to lift and wrap it tightly without cracks or prolonging cure time.

Once set you need to strip it and cure it in 100% humidity. I've had good luck with 24hrs but usually cure it 36-48. 

I've used needles and other reinforcements in other refractories but haven't needed any with Kastolite. There is already refractory fiber "rebar" in the mix. 

I don't sell the stuff and am sure there are better products available. I haven't looked recently, I still have probably 30 lbs. sealed in a bucket. What made me start using it was the recommendation from the guys at the place I buy my refractories and price. 

Without a kiln wash a propane flame impinging directly on Kastolite will degrade it over time, burning propane is VERY chemically active. Commercial propane furnaces are carefully designed to combustion is complete before the flame can touch the liner. Same for oil fired furnaces but less so.

Plistex 900 is impermeable so super heated propane combustion byproducts can't penetrate the liner. It's also darned chemical and mechanical erosion resistant.

No, nothing's perfect, we all have to work within

Frosty The Lucky.

 

[Ted Ewert]

I'll try your suggestions next time. I may try and salvage this build with some of that plistex you mentioned. The other stuff I used just flaked off.

[Mikey98118]

PListex is pretty good stuff, and very economical.

[Ted Ewert]

Ordered some, thanks for the suggestion. 

[Frosty]

Remember to butter the liner before applying the plistex. Mix the plistex to a consistency like thin latex paint and apply it in thin coats.  Allow it to dry between coats and apply a number of coats.

Sure it takes longer but kiln washed applied in thick coats tend to flake in the rapid thermal cycling a propane subjects it to.

Frosty The Lucky.

[Mikey98118]

Caution: Nearly all of the torch-heads rated for MAP gas (propylene) have the same warning about not turning the torch down too far, because they will overheat; this is despite their flame tubes being several times longer than nine times their diameters, which is all that is needed for adequate mixing of fuel gas with air. The long flame tubes are simply another safety measure; this makes sense, once you realize that the incoming air is mixed with fuel gas that has been greatly cooled down by expansion from its liquid state.

    When that flame tube is placed in a super-heated environment, like a forge or casting furnace, overheating problems increase; it’s something to keep in mind before cutting back your burner to save fuel. It’s better to use smaller burners running full blast than larger burners that need to be cut back.

    Why should this problem show up with burners placed in heating equipment? With lower the gas pressure, less super-cooled gas/air mixture is going through the burner at any given time. But the heat retaining layers of insulation surrounding that burner will rapidly accumulate high temperatures, regardless of how low the burner is turned down. So, it becomes important to keep the refrigeration effect from the incoming fuel/air mixture also turned up on high. It should go without saying that you must never install a small burner deeper into heating equipment than the length of its flame retention nozzle. Leave the flame tube, or mixing tube, out in the open air.

 

[Mikey98118]

Below is a tool description that I have deleted from my book notes, as the tool was a marginal choice at its previously low price, but amounts to a bad joke at its present boated pandemic price of $60. I personally believe that the present price gouging that is going on can't last very long, and anyone who allows himself to be victimized by it will low more than money; self respect will be the major loss.

The Shop4Omni electric die grinder is sold in the same price range as low-end rotary tools; it is almost as comfortable to grip as a DeWalt, and while nowhere near as tough, it is serviceable if you handle it carefully. Why carefully? This is one of several reduced-power long shaft die grinders on the market; its spindle is contained in a neck extension of the plastic body, rather than in the usual bolt-on cast aluminum housing. The stronger metal extension is intended to protect long spindles from bending during kickback, which can be severe in any kind of medium to high-power grinder.  A more serious complaint is that it won’t accept ¼” accessories. You’ll have to shop around for the slightly smaller 6-millimeter shank equivalents, or buy a Makita 763625-8-1/4 Collet Cone to replace its original collet with.

    This grinder only generates 230 watts from its brushed motor, versus DeWalt’s 504 watts. A disadvantage? Not for burner construction; an RTX-6 rotary tool generates ten more watts, but at 30,000 RPM; this tool’s maximum RPM is 25,000; meaning it generates more torque from those watts. You end up trading convenient ergonomics for more torque, and the use of sturdier mandrels. Which tool will suit you best, mainly depends on how much heating equipment, tables, and stands you wish to build; after completing your burner.

    While the Shop4Omni is definitely a two-handed tool, you don’t want to mount a handle on it, because its power switch is located on the tool’s rear (back) face; thus, inviting disaster should you attempt to turn it off, by shifting the grip of one hand, while the other is temporarily dangling the tool from a handle; that’s just a very bad idea. Of course, you could first shift the grip of your other hand from the handle, to the tool’s neck, but you only have to forget to do that one time, for big trouble to strike—so just don’t go there. Part of the general advice about cutting techniques; to stop the disc before removing it from the kerf, can’t be safely applied with this grinder, because of where its power switch is located. You knew there had to be reasons why this tool was so cheap, right? The price is the only reason this tool is listed here; it has received some bad reviews; read and consider them before buying. Yes, I have one. No, it hasn’t died, but the whole point of customer reviews is to hear from hundreds of owners, instead of relying on one person’s present experience.

   

[Mikey98118]

110-220V rating: Imported tools that are advertised as 110-220V are actually higher voltage equipment that was designed for sale in Europe and Asia, with 110V electrical cords mounted for the US, Canadian, and Mexican markets; when plugged into 110V outlets here, they are already running at half of their designed voltage. Small wonder that they rapidly start overheating when you use their speed controls. The only question left is whether the control circuit or motor will fail first.

    Nothing prevents you from changing their plugs back for use in a 220V outlet in your garage, should you run across the occasional tool that is worth this effort. The imported 280-watt 3” angle grinders qualified, but they are getting hard to find, and are now seriously overpriced. Most of such equipment is third rate junk, but not always. Sometimes, good 220V equipment is sold as 110V’220V by third rate suppliers.

       

[Mikey98118]

Elecric Die grinders are at the other end of the power curve from rotary tools; I don’t advise their use to everyone, or for every job; their sheer power can make them dangerous in weak or inattentive hands; that said, if you’re looking for more cutting and grinding power on pipe, angles, and equipment shells, or faster help in cleaning up burrs, weld spatter, or rust from curved surfaces, even the weaker variety will totally beat out rotary tools—for power; not for control.

    I don’t believe that anything comes close to a DeWalt 1-1/2” extended shaft electric die grinder for daily use in a steel shop, which doesn’t make them the best choice for part time home use, or for building heating equipment. You need to decide how much power you want in your hands, before choosing a tool. Too much power can be far worse than too little. No one ever ends up in the emergency ward because their tools are too weak.

 

The VOTOER 480W Rotary Tool is actually a full-power compact electric die-grinder that can be used as a micro drill; it’s called a rotary tool because it can run rotary accessories (3/32” and 1/8” shanks), but it has twice the power of the Shop4Omni die grinder, and three times the power of an average rotary tool; it has a keyed chuck that varies from .6mm (0.024”) to 6.5mm (1/4” plus 0.006”).; this not only mounts ¼” shanks for more rigid cutting mandrels, but all the drill sizes you will need. Variable speed adjustment is from 5,000 to 32,000 RPM. This tool should run at about 20,000 RPM at the mid-range setting on a router speed controller; it has the lowest minimum speed rating of any rotary tool or die grinder in this text, for micro drilling. The large air vents provide good cooling; they face forward, to help exhaust air blow dust away from the tool’s rear air entrances.   

    Some serious accessories that can help build your burner are included with the one offered on Amazon.com, along with a spare set of brushes. Tool length is 11” and body diameter is just under 2-1/4”; it should be comfortable to hold, as a two-handed tool, even in small hands. Don’t attempt to run it one-handed—or any other tool with this much power.

    The electrical switch is a rocker type, and located at its bottom, near the rear of its motor housing (not on its back face), so it will greatly benefit from the addition of a safety handle (mounted on its chuck housing). Do a careful job mounting the safety handle and it can support an acrylic guard too. Cut the guard from a thick plastic water glass, combined with a sheet metal handle. Inward facing set screws near the bottom of the glass are used to trap the whole assembly on the grinder. Multiple set screws, facing upward on the bottom of the glass, can secure a sheet metal safety handle to the clear guard.

     It is also worthwhile to sand down the rear section of the plastic body, where it forms a collar around the rocker switch. No doubt the collar is meant to keep the switch from being accidentally turned on, if the tool is laid down on table clutter, but it interferes with smooth handling. If the plastic collar’s height gradually slopes away, starting from the center of the switch, and increasing toward the rear (its “off” side), the collar can still mostly serve its function, but there will be far less interference to quick stops, using your third or fourth finger. You are marginally increasing the risk of accidentally turning the tool on, for added speed in emergency stops, with reduced risk of jarring a running tool, at a critical moment. Altering the tool will void its warranty; run your tool for a while, to make sure it isn’t a lemon, before touching that collar.

    The Votoer 480 puts out a lot of torque; you will constantly be tempted to turn down its power for cutting work, so just order a fan or router speed controller right up front, to protect your investment.

    The reason this tool escapes inclusion in the “problem child” category is partly good ergonomics, and its ability to easily accept safety features, combined with low cost for what it is. To be honest, its overall handiness is the biggest factor. With a speed controller set at 50% during cutting, this die grinder becomes a powerful rotary tool, or mid-range die grinder; not too overpowered for surface cutting work, if you don’t “drift off.” While running the Votoer at full power for grinding, sanding, and brushing, keep a strict watch on what you’re doing, just as you would with any other high-power equipment. Do not cut with the tool at full power, or with a diamond coated steel disc mounted (with or without a handle installed). Unlike a resin bonded disc, steel discs cannot be destroyed during kickback, releasing the tool before it gets dangerously flung about.

Warning: Do not mount a steel circular saw blade on this or any other electric die grinder. A teethed circular blade will kickback, and will be flung about, and then will become highly dangerous; they are more than nasty enough on low power rotary tools; mounting one on a medium or high-power die grinder is insane!

There are only 56 customer reviews of the product (at this writing); they are better than average. The tool appears to be well built, and the asking price is high enough not to put it in the category of probable junk; to be frank, I wouldn’t have taken a chance on it, if it weren’t an exceptionally promising design, which is capable of doing the whole variety of tasks you may want done, better than any other single electrical tool. My tool is smooth running, with plenty of torque; its chuck has no runout.

Note: There is a similar drill/grinder (it’s red) that is rated 110V/220V; its sellers boast it has 240 watts, which is no more than the little Black and Decker rotary tool; this is not the worst news about them; their online customer reviews paint a picture of fall- apart junk. I can’t say for sure because I never received mine; the drop shipper kept my money, and refused to even answer the complaint I sent him. It was “Caveat emptor” all over the place!

    There is now a black and gray colored version of probably this same ‘tool’ being offered by some of the same people who push the red one; one site shows them side by side, as though something this obvious will fool everyone, because we’re so dumb!

About keyed chucks: Ever wonder why so many drill presses in steel shops have keyless chucks? No, it isn’t because the keys get lost; it’s due to the moron factor. Some gorilla uses a hammer to tighten the original keyed chuck, instead of using the key to tighten it gradually, by using all three holes in turn: 1, 2, 3, 1, 2, 3…until the bit is tight. Just a little bit of such pounding will destroy any keyed chuck. Then the owner replaces it with a keyless chuck—because it’s too inconvenient to fire all the shop’s gorillas. And so, second rate keyless chucks have become popular, and chaos wins another victory.

    BTW, new chucks of either kind, need tender loving care; oil them and baby them over sticking spots until they wear in a little bit; just as you would carefully wear in the motor of a new car.

What about famous name brand die grinders? Well, Dewalt's grinder is a day's pay, and the compact grinders with famous names are a week's pay.

[Mikey98118]

 

Compact electric die grinders, and cutoff tools:

Power tools evolve in response to market forces, and so they have changed very gradually. It took a long time for die grinders for 1/4” mandrels to change from pneumatic weaklings, to high torque electrics, and then from extended neck to compact designs; but they’re here. Unlike their underpowered predecessors, these tools are inherently dangerous. High-speed plus high-power equal’s high hazard!!!

    You’re unlikely to end up with a serious injury from a rotary tool. If you follow safety advice, the odds drop very close to zero. Medium and high power grinders—of any type—are a different matter. When running grind stones, wheels, or sanding pads, your most likely injury is a strained wrist, or bruised and bleeding fingers. But cutoff, grinding, and wire wheels are all high risk in an electric die grinder; added to this are compact designs, which invite single-hand use (never try that with any medium or high-power tool). If you goof off with an electric die grinder, you’re going to end up thinking you just slapped the junkyard dog.

    Yet the power available in compact electric die grinders is nearly irresistible. If you can control your urges, todays die grinders are utterly superior tools; especially for sanding and grinding operations. Grinding wheels in die grinders can flatten internal weld beads, in seconds. Flap wheels also perform perfectly in die grinders. While pressing against the work surface is counterproductive with rotary tools, that isn’t true with die grinders, during sanding and grinding operations—not during surface cutting, or when drilling. Getting back to that junkyard dog, you must know when to keep it leashed, and never turn your back on it!

[Mikey98118]

 

Compact electric die grinders, and cutoff tools:

Power tools evolve in response to market forces, and so they have changed very gradually. It took a long time for die grinders for 1/4” mandrels to change from pneumatic weaklings, to high torque electrics, and then from extended neck to compact designs; but they’re here. Unlike their under-powered predecessors, these tools are inherently dangerous. High-speed plus high-power equal’s high hazard!!!

    You’re unlikely to end up with a serious injury from a rotary tool. If you follow safety advice, the odds drop very close to zero. Medium and high-power grinders—of any type—are a different matter. When running grind stones, wheels, or sanding pads, your most likely injury is a strained wrist, or bruised and bleeding fingers. But cutoff, grinding, and wire wheels are all high risk in an electric die grinder; added to this are compact designs, which invite single-hand use (never try that with any medium or high-power tool). If you goof off with an electric die grinder, you’re going to end up thinking you just slapped the junkyard dog.

    Yet the power available in compact electric die grinders is nearly irresistible. If you can control your urges, todays die grinders are utterly superior tools; especially for sanding and grinding operations. Grinding wheels in die grinders can flatten internal weld beads, in seconds. Flap wheels also perform perfectly in die grinders. While pressing against the work surface is counterproductive with rotary tools, that isn’t true with die grinders, during sanding and grinding operations—not during surface cutting, or when drilling. Getting back to that junkyard dog, you must know when to keep it leashed, and never turn your back on it!

[Espen E]

Hi,

I have been reading and tried to get some pointers on how to build a propane tank gas forge and have now made a concept drawing. I would really appreciate some feedback on my idea before I start building it. 

Some background: I have been forging for some years and already have a smaller two burner gas forge but I´m now planning to get into the larger production of pattern welded knives. I like to make large billets so I can get 2-4 knives out of it, hence I want a larger forge to speed up the process. I´m in possession of a 50# machine hammer so I can move a decent amount of steel and want the whole billet warmed up to welding temperature throughout the whole process.

I have a larger propane tank that I will retire and use for this project and the dimensions are on the drawings.

Living in Norway it is hard to get all the stuff mentioned on this forum, but I have ordered insulation wool, Kaowool Rigidizer and ITC 100 HT from Canada.

I have found one manufacturer of castable refractory here in Norway Rated for 2730 Fahrenheit / 1500 centigrade with the following composition:

Borgcrete 50:

AI2O3: 50%

SiO2: 38%

CaO: 7%

Fe2O3: 1,3%

I told the manufacturer what I intended to make, and he claimed that he would not be worried to use it as a liner and for the ribbon burner.

I plan to make a FARB as instructed on Wayne´s site. I can only get 80x80 mm ( 3.15x3.15”) square tubes and plan to make it 12” long. Will that be enough on the size of forge I have planed?

Any feedback would be greatly appreciated!

 

[Mikey98118]

2730 Fahrenheit rated refractory could be a touch low, for a forge being used commercially. You will want to keep it down to yellow-white heat. Two different guys on this group measured this temperature in their forges. 3000 F refractory would make a better match in a commercial forge, but so long as you keep an eye out for that, you should be okay.

You seem to be drawing two different forge shapes; a tunnel forge, and an oval forge. Oval forges have been around for about twenty years that I know of. Probably the best known oval commercial forges are made by Chili Forge; if you look at the forges on their website, you may decide to modify the shape of yours.

Also, you may want to look at "D" shaped forges, before going any further with your plans; they are easier to construct, and some of them accommodate multi-flame burners better than any other shape. The only advantage an oval forge has over a "D" shaped forge, is rigidity in a traveling forge. For a shop forge, I haven't seen a better design than the "D".

The oldest examples of "D" forge seem to have been constructed from mailboxes, but they have come a long way since then.

Good Luck

[Espen E]

Hi Mike,

 

Thanks for the reply! 

The drawings are made of the same forge. the first picture is a cross cut of the propane tank.. the other drawing is the front and back of the same forge.

 

I will do a search for a better alternative on the refractory. What about the exhaust outlets?