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Is my forge design good?


Jaewon

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Hello, I am new to this stuff and I am trying to build forge because I could not get finished forge. So, I designed with fusion 360 but I'm not sure my design will work or perform well. I'm planning to use T burner by Frosty with 3/4 pipe and I measured volume to be ~320 in^3. My major concern is placement of burner. It seems too off from floor of forge. Thank you for reading!

hexforge 1.png

hexforge 2.png

hexforge 3.png

hexforge 4.png

hexforge 5.png

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Welcome aboard Jaewon, glad to have you. If you'll put your general location in the header you'll have a better chance of hooking up with members living within visiting distance. Also, lots of answers are pretty location specific.

Without knowing more about the specifics of your forge it's hard to evaluate it. The basic design is sound and should work well. Factors that will effect it's effectiveness are what you line it with, it's thickness, order of layers, etc. We can talk about that later you have a specific question.

The last pic tells the story nicely. Your burner is aimed directly at the far wall. If measuring the burner tube is scale and the chamber is actually 9" across the burner is okay where it is. A forge 9" across doesn't match up with 320 cu/in though so I have to assume it's not that large. 

As drawn the flame will impact the far wall and turn into a turbulent boil. It's not ideal but it'll work okay. A swirl that flows in one direction keeps the flame in the forge longer allowing for more complete combustion. The hang time also allows the flame to transfer more energy to the forge liner so the IR radiation can re-radiate and heat your work. That's kind of hard to do with a Hex shaped forge, if you angle the burner so the flame impinges a far wall at an angle so it flows one direction (more or less) the burner ends up at quite an angle. The problem is NOT aiming it into the angle of two far surfaces, the pocket will cause more back pressure for the same turbulent boil of flame. 

As much as hexagons are my favorite structural shape I've given up on them as an adequate forge shape, I just can not come up with a burner alignment I like. 

A Hex top on a flat floor might work nicely but it's so much easier to form a curved top.

Nice renderings by the way.

Frosty The Lucky.

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I would definitely defer to Frosty’s knowledge here on forge design/performance, but I’d be concerned over the hinge setup in general use. If you have to open the front door for large forgings, I’m pretty sure you’ll end up fumbling around fighting to keep the door open while your pulling you piece in and out. I’d change it to a double hinge on a vertical axis or let it open down rather than open up.

Keep it fun,

David

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Looks way more complex than needed to get started.  I built my first one at an ABANA affiliate forge building workshop out of a 10" dia grain auger tube.  The kaowool lining just slid in with the arch holding it up. Cover with refractory, same thing.  Burner hit the wall at an angle to swirl and I used that for years.

As your uses may change over time I would not recommend doing a fancy build till you know what YOU need/like from experience.

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You're right about how the doors are hinged David. While self closing doors might be a good thing, you shouldn't have to fight them to keep them open. I don't like the fronts that open upwards on box forges and I've used those. Even though they stay up when opened all the way, that big flat face of HOT refractory is aimed straight at you. 

It improves swirl Mike but it's still impinging perpendicularly and so tries to spread in 360*. the angle it's next to helps it swirl but not as much as you might think. The flame impinging a flat face at any angle is deflected more strongly. 

I have thought about orienting the burner so the flame is parallel with one face and impinges on the next angled face at the intersection. This makes about as good a swirl as you'll get in a hex and might be a winner.

If you cut two faces off so it's house shaped and replace the missing V with a flat floor, aligning the burner and manipulating the swirl is much easier.

All the above is said nicely be Thomas, this plan is WAY more complex than necessary. A simple cylindrical forge with a flat floor is easier to make and has been proven effective for the last century. Modern insulating refractories like Kaowool has turned them into power house forges.

Jaewon: We aren't picking your plans apart because we can. You asked and we're being honest about some inherent problems with a hex shaped forge. So you WAY over designed it, that just makes you part of the club. Almost everybody here really overdesigned every darned thing we built when breaking into the craft. You get high KUDOS for making it a reasonable size. I STILL make the things too large, I don't think I've ever made one too small.

You're off to a great start, we'll be honored to help you build a good, effective propane forge.

Frosty The Lucky.

 

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Welcoime aboard from 7500' in SE Wyoming.  Glad to have you.

I agree with Frosty.  IMO a better design would have the doors pivoting up  in the same plane as when they are closed.  That is how my modified Sandia gasser works and it has never been a problem.  Also, you don't have to open the door all the way every time you put something in or take something out.  If you are heating. say, 1/2" stock you only have to open the door about 3/4".

Also, some sort of ounterweight on the door will balance it and make opening and closing easier.

You might think seriously about some sort of chimney or exhaust on the side opposite the burner to cut down on dragon's breath when you open the door and to allow a way out for exhaust gases. 

If you search for "sandia forge I Forge Iron" you will see some pictures of a couple of versions including mine.  This will give you some better ideas of what I am talking about.

Two doors are a really good idea.

"By hammer and hand all arts do stand." 

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Posted (edited)

Thank you for the sincere answers! 

I am residing in Busan, Republic of Korea. So I have some trouble with acquiring materials that are common in the USA. 

I asked about insulation to insulation material company and they told me to use combination of fire bricks and silica board. 

Goods, I will try to change or think better method to open the door. 

Frosty, I fixed my design and I've attached pdf file of my plan. Did I solved major issue?

Thomas Powers, I designed my forge to be portable since I can't stay in my current workshop too much. If I can found cylinder that is equivalent to 10" auger tube maybe I'll make simple forge first. 

George N.M.,  Thank you for your suggestion. I'll research about it.

About the over design I chose hexagon to have stable brick placement and strength. Also, as mentioned in reply I have to make my forge to be portable and easy to store. 

Lastly, this is definitely overdesigned but I wanted to make modular forge. If this is terrible idea I'll just stick with single forge design. 

Again thank you for your comments!

hexforge 6.png

hexforge long.png

HEXForge drawing.pdf

Edited by Mod30
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20 hours ago, Frosty said:

It improves swirl Mike but it's still impinging perpendicularly and so tries to spread in 360*. the angle it's next to helps it swirl but not as much as you might think. The flame impinging a flat face at any angle is deflected more strongly. 

I didn't agree with your assessment, and wondered about why the different viewpoints. Then, I remembered that your burners put out softer flames than mine. I have stumbled  over the difference before. It took  at long time to realize that pointing a burner across the floor toward its for edge was better, than slightly angled down toward the near edge, because I was in love with how well that worked with a very hard flame. But what works best is what is best; not our druthers.

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The burner position is much improved. The door will be fine if you simply move the hinge to a hex point at one side or the other. A hex is not as good as a cylinder for swirl, but so what? The shape is good enough; and good enough is good enough. Somthing your design still lacks are legs, to keep the forge body up above whatever surface it rests on; that is important for air circulation to cool the outer surface, and to keep whatever the forge rests on from over heating. Also, you can angle the legs outward to make the forge more stable; that will be important, because there are going to be fuel hoses attached to those three burners.

By the way, you would do better with two burners instead of three. Otherwise your burners better be 1/2" size; not 3/4" size.

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That's better Jaewon, you could aim the burner to flow down the far wall and it might be better but that would make putting handles on the sections more difficult and when you shut the forge off heat would rise through the burners like smoke up a chimney. If there's rubber hose connected directly to the burners the heat can damage them. 

Making modules if or when you need a larger forge is a workable idea, especially if you don't have room to have a modest one and a large one, I'm spoiled I have lots of room in my shop. Even if I have to do serious cleaning to be able to use most of it. 

Ditto making legs or placing the forge on something to provide air space under it is beneficial on a couple counts. It will protect the table, stand, whatever you place it on and heat will be lost more slowly through convection and radiation than through conduction to a solid surface. 

Ditto placing the hinges on a corner so the door swings horizontally. I forgot to say that earlier I think. 

You'll want to pull your burner as far out of the forge liner as possible. The liner is able to survive a LOT hotter environment than the burner nozzle. You'll need to put a flame face layer of hard refractory where the burner port is but you can form it into a widening taper and improve burner performance. 

On a last note, Please do NOT tag names with the @ symbol the operating software Iforgeiron uses does not recognize it and in fact it causes problems. Don't worry, you aren't in any trouble, it happens to lots of folks learning to use Iforgeiron but you do NOT want to irritate the moderators, they do lots of work keeping the forum running smoothly. Every little bit helps. ;)

Frosty The Lucky.

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ThomasPowers: Yes I will be using insulative fire bricks! 

Mikey98118: I think I can change burners easily with this design and yes I'll add legs in my design. 

Frosty: If I didn't misunderstood I have to place burner further in the forge right? Also I'll make change with legs and doors. 

 

Thank you for your answers!

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On 7/4/2022 at 2:18 AM, Jaewon said:

asked about insulation to insulation material company and they told me to use combination of fire bricks and silica board. 

What you do with silica board depends on the quality of that board; there are several kinds; some good and some not. Instead of brick, which will probably be the old insulating brick that is only 'good' to 2300 F, or hard brick, which barely insulates at all, I would advise Morgan K26 brick, with a hard castable refractory flame face over it. If you can't get that particular brick, I would advise you to forget brick altogether, and substitute castable refractory for it. Look around in garden supply sources for Perlite, which you can  mix into castable refractory to create a durable insulating refractory. Lots of home casting enthusiasts used this to line their casting furnaces, before we discovered Kast-O-lte 30. The old home-made formula worked quite well. If you can't find the better products, it is better to fall back on proven techniques than to put up with third-rate substitutes.

Perlite to refractory ratio is one-third Perlite to two-thirds refractory.

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22 hours ago, Jaewon said:

place burner further in the forge right?

NO. mount the burners farther OUT. It will let your burners last longer before they burn up. 

Morgan Thermal Ceramics has a location in Daegu a bit north of 451. I'll PM the particulars to you as it's not allowed on the public forum. You should be able to buy everything you need and not have to use half way materials and measures. 

Frosty The Lucky.

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You're welcome. Finding things on Morgan's web site can be a challenge but I have the important parts bookmarked so a quick search if they have a dealer somewhere is just a couple clicks for me. 

It's sort of like asking my Grandmother for a pie recipe, she didn't have to hunt long if she didn't know one from memory.

Frosty The Lucky.

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The only time Mother and Mom, my Grandmother measured was when baking cakes. Everything else was big hand full, hand full, little handful, dollop, dab, dash, pinch (large, small) sprinkle, etc. etc. B'guess and B'gosh, master chefs.

Mo kept recipes in a card index. She knew how to make it all but sometimes needed a reminder so the cards had a few notes or ingredients. I'd like to see someone outside of us three try to follow one of them. 

Since the TBI changed my sense of taste I've had to start measuring some things. <sigh>

Frosty The Lucky.

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