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Chile style forge clone questions


MarcD

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Hello! Long time fan of this forum. This is my first post so I want to start by thanking all of the knowledgeable smiths, the admins, and everyone else who makes this community as great as it is. Thank you! 

Ok so I am trying to semi-replicate the shape and size of a Chile Cayenne (oval) 2 burner forge. I like what Mikey has to say about the benefits of running an oval forge and since everyone seems to love Chileforge so much I figure that I should try to design my forge to match instead of reinventing the wheel. I understand that I won't have the same burners but the size and shape match what I need so why not? Now I have been known to overcomplicate projects before so I would like to see what the experts think about my design, if it can be improved or if it's a foolish endeavor. I can't afford to mess this up! This will be my second propane forge build but my first is obviously made by someone who was uneducated and under-funded so let's call this my first real forge build.

Pardon the low tech sketch.  The inside forge dimensions are approximately what Chile says their Cayenne dimensions are; 4"x9"x16" which is around 576 cu. in. I will be lining the inside of the body with 2" Inswool HTZ 2600 degree 8#, 1/4-1/2" thick layer of Greenpatch 421, and Plistix 900f all applied following the instructions, tips and tricks that I found on this forum. I will paste the links of the specific threads at the bottom. Thanks to Mikey98118, Frosty, and Lou L for writing and compiling such great resources.

I plan to use  2x 3/4" atmospheric burners. It's up in the air what type of burner and if I will purchase or if make my own because I ordered some from a company called Burncraft and I was very disappointed with the design. But that's for another post if anyone wants to know more.

Here is a sketch of the cross section of the forge:

Yellow: Forge Opening

Orange: Burner position?

Red: Space inside forge

Blue: Ceramic insert

image.jpeg.fe1c30e151298b3a651dc67ce351230c.jpeg

My questions are as follows:

(I apologize in advance if some of these could be answered elsewhere or if they're redundant. I know no one likes repeating themselves but this is one big forum!)

- Is it better to undersize your forge box to the burner capacity i.e. 2x3/4" burner with a  700 cu.in. potential in a 576 cu. in. space? Does this save fuel?

-I have a little leeway in the ceiling of the forge box. I can make it flat or curved. I sketched both options in red. Makes the box a little bigger but are there any other considerations that anyone can think of? Any advantage for one over the other?

- The Chile forge burners look like they at about 70 degrees from the forge box floor and the flame is aimed about and inch off center TOWARDS the side that it points to. Mikey says that the important thing is to avoid having the flame impinging on weaker materials so I would assume that a flame pointed directly down at the bottom of the forge would be placed in the middle and one that is angled would be placed so the flame is off center AWAY from the side that it is pointed at. I sketched the approximate angle and location of the burner in orange but I left it wide because I'm quite sure the the designers of the Chileforge know more than me and I at a loss as to why they built it the way that they did. Or I'm just seeing things incorrectly... 

- Is Greenpatch 421 as resilient as Kast-O-lite 30 when it comes to have a  burner flame hit it directly or does it need to be shielded?

-There is a common size of a 16"x16"x5/8" kiln shelf. I could use the off cut from the square to form a wall on the side of the forge that the burner points to. Would this be worth the trouble? I have my ceramic marked blue in the sketch.

 

That's it for now. I'm sure that I will come up with another litany of questions before I'm done with this project.

Thanks again!

 

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I looked up Greenpatch 421 and it is listed as a mortar (patch) which is used to fix and stick bricks together. I don't know of anyone who has used it. I would stick with what has been proven to withstand the rapid heat & cool cycling of a forge like Kast-O-Lite 30. Also the smallest quantity I could find was 55 pound pails (way more than you would need).

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Hey thanks for taking the time to look it up! My interest in this particular mortar comes from reading about it on two different forge supply sources: 

https://www.irondungeonforge.com/Greenpatch-421-5-lb-container_p_16.html 

and 

http://zoellerforge.com/faq.html  If you read the last part of step 2 in this FAQ Mr. Zoeller explains why it is a good choice for forge building. 

I have no experience with any sort of curing other than air drying so it seemed less intimidating to me. 

 

 

 

 

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Okay, let's start at the beginning, and if you're willing to invest the time, we can write back and forth throughout your whole project, and you will end up  with a forge that is well worth the time you put into it. Why would I bother going over every detail of your forge? What could possibly make it worth dozens of hours writing out instructions, and answering the same old questions again and again?

The answer is that hundreds of other builders can pour over this material, and be helped for years to come. I will assume that this is worthwhile to you as well; if not you will soon abandon the effort.

No commercial forge design is so expensive that people will end up ahead of the game, money wise, by building it instead of purchasing. Even Chilli forges don't cost that much, if you factor in sweat equity. Since there are more good commercial gas forges coming into the market every year, why build?

(1) If you build your own forge, you will learn a lot about it, which will stand your in good stead whenever you need to build a special forge for special projects. Any serious metal worker will end up wanting that ability, sooner or later.

(2) You can build special features into your forge that aren't an option in the commercial version.

(3) You can make the forge whatever size and shape you desire; a little larger, a fittle higher, wider, narrower, etc.

So, let's begin with what I like about Chili Forge, and find out if you particularly want sn oval forge like Chili.

(A) The owner consulted me when he was designing his product, and used my burner design, and he did not cheapen it; this is a very hot burner, which allows his customers to rapidly heat their projects; this is excellent for a forge owner in business. But that same burner design can be made in several sizes. Chile forge only uses 1" burners. If you don't need the speed they give, you may want to use smaller burners. It is difficult for commercial forges to allow burner size options.

(B) These  are oval forges; this was the latest shape, back when Chili Forge was was designing his product, and it is still an excellent forge shape...but it is no longer the latest design; "D" forges are. If you want a travailing forge, oval is the strongest shape, and therefore can be made lighter than any other design, except tunnel forges. But tunnel forges aren't a great shape for getting the most usable room out of the space you are paying to. If you only want a shop forge, you may want to consider a "D" shape; it is a lot less work for a great product. Oval forges also keep their exterior cooler, but if your forge has a little extra insulation in it floor, so what?

(C) You can get a very hot forge with less work, and good fuel economy with a multi-hole burner; especially in a "D" shaped forge, with the burner block aimed upward from one side of the floor. Will it get as hot as mine? No; but it will get hot enough to forge weld. What more do you actually need?

The only thing is that I don't make ribbon burners, so if you go this rout, one of the other guys will have to help you with it.

Any questions?

That is to say that I cant help you in making the burner block. The burner that feeds air and fuel gas to the block, is something that I can still walk you through. On the other hand, simple "T" burners seem to feed ribbon burner just fine and dandy.

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As to using Greenpatch, you will note that he uses Plistex 900 over it. So, that is going to help alleviate the cracking problem. Larry showed me one of his forges at the ABANA show in Kentucky (2004). I believe he had just started using Plistex. The Plistex layer looked pretty thick to me. Your mileage may vary, but why not simply use Kast-O-lite 30, and avoid the whole issue?

Next, Chili forge has a box shaped interior. Why? This is a commercial product, and one of the limits any turn-key forge faces is shipping damage. This forge uses hard ceramic board for its flame faces, to get around that problem. If you you use rigidizer in the ceramic fiber insulation to support your flame face, than you can use a highly insulating cast refractory flame face as your inner layer; this allows you to sculpt the inside of your forge for a vaulted ceiling and rounded  corners. After all, if you have rounded exterior, why settle for a box forge shape inside?

 

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2 hours ago, Mikey98118 said:

As to using Greenpatch, you will note that he uses Plistex 900 over it. So, that is going to help alleviate the cracking problem. Larry showed me one of his forges at the ABANA show in Kentucky (2004). I believe he had just started using Plistex. The Plistex layer looked pretty thick to me. Your mileage may vary, but why not simply use Kast-O-lite 30, and avoid the whole issue?

So here's the thing, I already purchased Greenpatch and Plistix 900F based on what I read from zoellerforge. I came here to ask questions after the fact. Kinda kicking myself now! I'm not opposed to buying some Kast-O-lite 30 and using my Greenpatch in a different project or as an experiment. 

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The Plistex 900 is still a fine idea as a finish coat over whatever you decide to use for your castable refractory layer. But the Kast-O-lite 30 is the refractory of thoice around here for a lot of reasons; it is insulating, strong, not inclined to crack. Best of all; it is way lighter than any other castable refractory. Wieght is important with wider forges (oval or "D", rather than tunnel shapes).

 

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1 hour ago, Mikey98118 said:

Okay, let's start at the beginning, and if you're willing to invest the time, we can write back and forth throughout your whole project, and you will end up  with a forge that is well worth the time you put into it. Why would I bother going over every detail of your forge? What could possibly make it worth dozens of hours writing out instructions, and answering the same old questions again and again? 

The answer is that hundreds of other builders can pour over this material, and be helped for years to come. I will assume that this is worthwhile to you as well; if not you will soon abandon the effort.

Well I've been messing around with blacksmithing on solid fuel forges for around 17 years when I had space available to me... I don't think that I will soon abandon my hobby! Just taking the leap into gas forges is all. I am most definitely here to learn and if you're willing to message back and forth about my forge project I will gratefully accept all of the help that I can get. 

I see where you're going with your comments about the Chile forge being more difficult to build and a forge built with mass production in mind. I like the idea of being able to form the walls and ceiling with more curves and less seams instead of a block construction as well. 

So you're saying that the best balance between value, ease of assembly and performance is a D shaped forge with a side blast ribbon burner?  Also the ribbon burner is a cast block of some sort that I would be making? 

 

Edited by Mod30
Trim excessive quote.
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17 hours ago, MarcD said:

So you're saying that the best balance between value, ease of assembly and performance is a D shaped forge with a side blast ribbon burner?  Also the ribbon burner is a cast block of some sort that I would be making? 

Keeping in mind that I still think oval forges are the cat's meow...nevertheless, Yes; that is exactly what I am saying.

    I have designed and still design brand new versions of very hot single flame  burners, which are as far from ribbon burners as you can get. Nevertheless, I see ribbon burners as a totally better deal for most blacksmiths. This is because I started out doing ornamental iron for a living for my first 16 years of steel work. And ended up working in shipyards and on on vessels at ancor for the fishing fleet. What I prefer in equipment design will always be slanted by personal job experience.

    What I suggest for normal sane people are what I think will be best suited for their working experience; not as a "blast from my own past." Despite my personal druthers, ribbon burners give more bang for the buck to the average blacksmith. What kind of burners will be best suited for jewelers, etc. is just irrelevant.

    The ribbon burner position I recommend is bottom mounted up facing, and at one side of the floor. Once again, You could easily decide to mount it somewhere else; most people do. Mounted high up on a side wall would work about as well. I have seen loads of ribbon burners mounted in what I considered poor positions, which where still working brilliantly.

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So, what is the easiest method of building a "D" pr oval shaped forge can be similar, or quite different, depending on your tools and preferences. Either forge can be made from an old (or new) ptopsn cylinder, used drum, etc. They idea is to mix and match existing forms with sheet metal to get the most work done for you, before you starts cutting and/or bending steel. What will prove least expensive depends on what tools you have on hand.

Are you equipped to weld or torch braze parts together, or will you screw (or pop rivet) them in place? Do you have a source for sheet metal at reasonable prices, or do you need to avoid using it? Understand that these factors don't limit your ability; they just dictate what construction choices are ,most practical.

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If sheet metal can't be obtined from a scrapyard it is likely to be shockingly expensive for most people. In that case, $70 or even $100 to buy a ten gallon brand new propane cylinder may be your best choice, when building an oval forge. You simply have to cut three or four inches out of its middle, and suddenly a cylinder becomes an oval shape, with  ends to match. Starting from a drum is far less expensive, but leaves you needing to build and install two end pieces.

if cheap sheet metal is available to you, both oval and "D" shaped forges can be made by bending the sheet over your own propane cylinder.

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When hand bending sheet metal, thickness becomes critical. I would suggest keeping the sheet about 0.035"; this will seem flimsy will it is being worked, but rigidizing the insulating blanket, can be mixed with ceramic board, and a 1/2" to 3/4" refractory layer on the forge ends, and finally a 1/2" flame face to stiffen the shell up. If that looks expensive, take a second look at propane cylinders for the forge shell.

 

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I intend to make the shell out of steel 55 gallon drum material. I have the tools and expertise to do it well enough. I also have various pieces of angle and plate steel to brace or reinforce where needed. I have plenty of wool, rigidizer, and plistix. I don't have any bricks worth mentioning or Kast-o-Lite yet. 

I'm going to repeat this back to you in my own words for confirmation (instead of a picture of my terrible sketch) You recommend that the ribbon burner be installed facing up lengthwise down one side of the forge so that the flame brushes the length of the wall following the arch up and over to the other side be it a D or Oval shaped forge. If that's where I mount it I would have to plan extra width into the forge to avoid having a piece obstruct the burner. Would there be a risk of flux or other debris getting into the nozzlettes? 

I read Frosty's post about his NARB experiment. That seems like a doable project for me but I just don't know enough about ribbon burners to understand what is better for my application a NARB or something with an electric blower. I did try to track down the plans to the Wayne Coe burners but the plans are no longer on his website. 

Now I will probably make a D forge but this is by no means proof that I am normal, or sane. Also I have the oval forge itch now. Maybe I'll make a mini oval sometime down the road for traveling purposes.

 

 

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This is from HWI, Harbison Walker International" the manufacturer.

GREENPATCH-421

A 53% alumina, wet, air setting thick patching mortar

It's a 3,200f MORTAR, it's for cementing things like bricks together and patching. Nowhere does the maker of the product say it's suitable for a flame contact refractory. 

If you decide to use it anyway, it comes as a paste in the can so you're paying shipping the water in it. 

Frosty The Lucky.

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46 minutes ago, MarcD said:

You recommend that the ribbon burner be installed facing up lengthwise down one side of the forge so that the flame brushes the length of the wall following the arch up and over to the other side be it a D or Oval shaped forge. If that's where I mount it I would have to plan extra width into the forge to avoid having a piece obstruct the burner. Would there be a risk of flux or other debris getting into the nozzlettes? 

    Not brushing the side wall, but near it. Remember that ribbon burners have many small flames; they can be quite near a wall without touching it.

    Not for the entire length of the forge. You want to stop the flame holes about four inches short of the inside of the forge's front and back walls.

    Yes, stuff can fall into the flame holes. If plan to do much forge welding, than place the burner block up high on a side wall; with the top how of hole about 2" below the ceiling in an oval forge, or high enough into the ciing curve is a "D" forge for the flame to be shutting across from one side wall at the oposite wall, but plenty high enough to encouarage atmospheric swirl in the forge gases.

1 hour ago, MarcD said:

I just don't know enough about ribbon burners to understand what is better for my application a NARB or something with an electric blower

    Most gas are quite happy with a NARB. I would be inclined to use a variable speed fan, but this is only becuase I am a perfectionist. That is to say I wouldn't be satisfied with  very good flames, if I could tweak them into perfect flames. Be practical and leave perfection to the perfectionists. In other words, avoid my bad habits :P

 

1 hour ago, MarcD said:

Maybe I'll make a mini oval sometime down the road for traveling purposes.

A wise choice.

One of the things that is easy as pie to do with a "D" forge, is to extend the amount of insulation in its bottom, by giving an extra couple of inches below the space planed for your floor. You add very little expense by filling that space up with packed Perlite from the garden department of a bix box store, and than placing two inches of rigidized ceramic blanket between it and the Kast-O-lite refractory floor. It isn't something for nothing, but is is a lot for a little :)

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If you're a reasonably skilled metal worker a D or oval forge shell is pretty easy to form up, even without much for tooling. All a shell has to do is hold thee liner the weight of your work and fire. Stove pipe is IIRC 20ga and having helped make a number of cylindrical forges from them can say from personal experience it's plenty strong. 

However, a reciprocating saw some wire and a nail allows you to cut plywood at virtually any radius you want. Play with some construction paper and cardboard to determine what space and shape suits you. (For now that is ;) it'll change later.) Remember to make your CONSTRUCTION mock up at least 5" wider and taller to allow for the liner, 2" of ceramic blanket and 1/2" total hard refractory and kiln wash. Yes?

Before you take the Construction (C) mockup apart to use as the template for marking the sheet steel to cut for the shell, stand it on end to mark the plywood to cut for the bending dies. Use a piece of chalk or pencil to test the wire COMPASS length matching it to the C mockup you haven't taken apart yet. Yes?

When you cut the arch do so 1 1/2" - 2" from the base of the arch to allow for the joint between arch and floor. The shell floor piece will have 2" or so extra width for the joint too. The toughest part of making the shell is bending the sides of the floor piece at 90* angles to screw or rivet to the arch but a shop expedient brake is pretty easy OR you can GENTLY cold forge it. By GENTLY I mean wooden mallet over the edge of a wooden bench top, GENTLE. 

Cut and bend the floor first and when you have the arch bent, drill and rivet / screw the floor to it in the jig. The "hem" sticking down below the bottom of the forge shell makes a nice stand off to prevent the forge from overheating whatever you put it on. Hmmm?

Smooth linoleum flooring or counter top makes a good form material for Kastolite, a good layer of wax or stiff grease will prevent the Kastolite from bonding from it. Once you've mixed a batch of Kastolite you'll know at a GUT level just how sticky the stuff is, if you don't get it washed off before it begins to set it's good luck getting it off with les than a grinder. The stuff bonds nicely to milk jug plastic, my recommended mixing container.

You can make an internal form from linoleum and ram the Kastolite in place after the Kaowool has been installed, rigidized and cured. Roll the linoleum and tape it together so you can peal the tape and remove it after the Kastolite has set. After it has cured you can just burn the grease and wax off OUTSIDE, it won't hurt anything. Remember Kastolite or ANY water setting refractory needs to cure in a 100% humidity environment so the binder can absorb enough water to come to full strength. Water setting binders absorb water on a molecular level, they DO NOT DRY! Drying is a B A D N E S S thing!

The above is probably the best and easiest method. However the first time I made a double liner forge I made the hard refractory flame face first, then wrapped it in Kaowool and compressed it with newspaper "like a ring compressor" enough to slip into the forge shell twisted it around until the the mark on the paper lined up with the burner port and burned the paper off allowing the Kaowool to spring out and hold it all in place. After that I cast the ends to keep everything solidly in place. Yeah, it's complicated and took a few days but it worked, that forge is still available if I ever need the beast. NO, I don't recommend it, it was a PITA but if it's the only way that'll work, there it is. Lots of wood stoves are relined in a similar manner. 

Kastolite being a water setting material does NOT shrink as it sets and cures so you can make your forge whatever shape you like, D, oval, starfish:rolleyes:, whatever and it'll keep it's shape once it's set. An oval will have you cutting ovals for the bending jig and coming up with lets. You'll need a bending jig for the linoleum too but what the hey, it's an oval forge. 

Frosty The Lucky.

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"...2" of ceramic blanket and 1/2" total hard refractory and kiln wash. Yes?" Yes.

"...plywood to cut for the bending dies." Funny, that's how I was making my chile style forge before I came here and learned about D forges!

Thank you for the bottom hem idea. What a simple solution. I dig it.

"Water setting binders absorb water on a molecular level, they DO NOT DRY!" I wish someone had told me this in high school. 

Kast-o-Lite is pretty cool stuff considering that it can bond to something like HDPE. I'm having trouble wrapping my mind around that one! 

I think remember reading somewhere that you can cover bricks with a kiln wash (re-emissive?) but I can't find it again. Is it as simple as putting a coat of Plistix on a k26 brick? I'm hoping to use something like this for my doors. 

Is a high alumina ceramic shelf the only option for a replaceable forge floor?

 

I think that I will go with a ribbon burner that has a fan. I like the idea of having an easy way to adjust the flame. 

 

 

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There are Air Setting refractories, my first forge used one but it's no longer available but there are high end air set flame face appropriate products out there. Just keep a watch for "Mortar or Cement" in the product description. 

There's a big difference between "Bonding" and sticking to. Kastolite is sticky like the dickens, it's formulated for extreme sticky so it doesn't have to bond to stay in place when patching furnace liners that are still at red heat. There are other Kastolite products but 30-li suits our purposes so well we don't need to play with the high priced spreads. :) 

My l pleasure, take a look at the shell on the Mr Volcano forge for a good example of the shell joint = forge legs / stand.

Sure you can "wash" bricks or virtually anything that's going to be exposed to high temp flame. Before I started making NARB burners I dipped my thread protector nozzles in Kiln wash to protect them from the flame. It won't keep them from melting if you overheat them like Pigsticker discovered recently but it does help protect them from "burning" out. 

Any time metal is brought to high heat oxidization,  "burning" is accelerated so a coating of a kiln wash is a prophylactic. It can't prevent some oxygen contact, especially on the outside but it really lowers how much can make contact. Call it prolonging the sacrifice.

What makes a good kiln wash a "re-emissive" layer is what makes it good armor, it is a POOR thermal conductor so it's there in flame contact absorbing energy cut can't conduct it to the next layer effectively so it just keeps getting HOTTER and radiates back to the interior as IR radiation. It's trying to shed energy in all directions but can't sideways into itself because there is zero differential and the Kastolite is an even poorer conductor AND it an insulator making it even worse. The energy has only ONE direction it can go "easily", back into the forge. Energy ALWAYS TRYS to take the easiest path. We make that path to where we wish. B)

No, lots of guys use a stainless steel pan to catch flux when they weld, you only need it in the forge when welding but it won't last long regardless. It's still the only practical way I know of to keep thee forge floor from accumulating really sticky icky molten flux residue.

What do you mean by "adjust" the flame? If you mean hotter colder then Naturally Aspirated (NA) is WAY easier, just turn the psi up or down at the regulator.  If on the other hand you mean change the Air fuel ratio you need to make an NA burner with an undersized propane jet and mount a choke. An undersized jet naturally draws more combustion air than ideal so you MUST limit it to make a neutral flame, hence a choke. Pretty easy. Mike uses a sleeve choke on his burners and the position of the openings also controls how well the air and propane mix. It one of the things that make his burners one of the best on the market. It's actually easier to adjust one of his burners than a bun (blown)  burner.

When using a gun burner you don't have to worry as much about back pressure because the blower can overcome more and you can close it off more. However to turn it up or down you have to adjust the psi and THEN adjust the blower to match the change. It isn't terribly difficult and before long you'll become expert in tuning the burner for flame quality. 

Before you decide on using a GUN ribbon burner take a look at some videos and still pics. Almost all of them show dragon's breath, flame blowing out of the forge openings, sometimes 2'-3'! That is fuel burning outside the forge in YOUR breathable air, heating the room NOT your project! The plans available online have a serious flaw that has been passed down for I don't know how many years.

With the supply pipe entering the plenum in alignment with the nozzles it produces a very uneven flame pattern, the nozzles directly in front of the supply pipe are often too long, getting over pressured and blown out while the ones around it are smaller. The first NARB I built had the supply in this alignment and I messed with it a LOT and the only even okay results required a diffuser plate. Unfortunately the diffuser plate in the gun burner plans is almost blocking the supply pipe making the design REQUIRE a high static pressure to FORCE enough air/fuel mix past to support a flame. In the process it is moving so fast it just blows through the forge into the room where it finishes burning. 

The solution I came up with was to move the supply pipe 90* to the side of the plenum where the flow impacted the wall of the plenum and was distributed relatively evenly to all the nozzles. It is NOT perfect the center flame on both NARBs are longer in the center and both ends but are close enough to make no significan't difference in the forge. Better still the NARB forge while being experimental only shows a couple INCHES of dragon's breath so it's burning much less fuel outside the forge. 

Hopefully that isn't more confusion than helpful

Frosty The Lucky.

 

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I find it quite helpful. What would happen if you extended the supply pipe inside the plenum chamber, and cut away its back facing half, so that the gas/air mixture bounced more evenly off the plenum chamber's rear face? I can think of other tweaks, such as cutting away the back face of the pipe in a wedge shape; then there are drilled holes in increasing diameters; this would create all kinds of eddy currents, which might help the back bounce to more evenly distribute the flammable mixture.

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3 hours ago, Frosty said:

The stuff bonds nicely to milk jug plastic, my recommended mixing container.

Did you mean "sticky" here Frosty? I'm still not sure that I follow!

16 hours ago, Mikey98118 said:

Yes, stuff can fall into the flame holes. If plan to do much forge welding, than place the burner block up high on a side wall; with the top how of hole about 2" below the ceiling in an oval forge, or high enough into the ciing curve is a "D" forge for the flame to be shutting across from one side wall at the oposite wall, but plenty high enough to encouarage atmospheric swirl in the forge gases.

 I have an idea to compromise between having the burner facing up along one side and having to move it up and mounting it to the curve  What if I mount it facing up from the bottom but at a... ooooh say 65-70 degree angle, or maybe even more drastic. This would still put it in a very good position to encourage atmospheric swirl but mitigate some of the damage and blockage that could occur. It also has the added bonus of reducing the burner's footprint on the working surface of the forge.

My forge shape is beginning to form in my mind. The chamber would be something like a half cylinder with a radius of 4". Make it 14" long. With a 3 by 19 hole, 6" hole to hole distance burner like Frosty's NARB leaves about 4 inches on each end. The volume is close to 352 cu. in.  The burner is mounted on the bottom edge pointing up at the arch at a slight angle.

 

 

 

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Everything is a trade-off in forge design, and making change within the forge, or on its shell afterward makes a very poor trade-of effort versus advantage. Every part that can be added onto the your forge, instead of built into it, is superior to one that is builtin. Thus forge doors, with changeable kiln shelve baffles, beat trying to decide about what is the best size and shape for an exhuast opening all hollow, and so do bicks used as changeable exterior balle walls.

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I do have two questions about the NA multi-port ribbon burner that you built Frosty.

1) Do you think that I need to add Zircopax to the Kastolite? I looked up what Zircopax is. I see that it has a very high resistance to heat and chemical corrosion from alkaline. But what exactly does it do for/with the Kastolite? Do you use it elsewhere in your forge construction?

2) In your original NARB post you have some good measurements to start from and the pictures do show a lot but there is one detail that I just can't suss out: How deep did the plenum go into the mold? Or another way of asking would be: How high on the plenum tube ends did you weld the temporary angle steel to hold the plenum in the mold at depth?  I'm 10 pages into the 42 page conversation but have not found an answer. I saw someone guess at 1/2" but I don't like guessing when I don't have to. Better to stick with what works like you guys say :D I would love to read the other 32 pages and I may at some point but... there's no guarantee that the answer will present itself and I need to go to bed today at some point ;) And my wife wants dinner.

 

 

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