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I Forge Iron

Planning a Ribbon Burner Forge


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I am rapidly outgrowing my first KAO Wool lined pipe forge. I have been playing with building some bookshelf brackets and a couple other ideas that my current forge is just too small to handle. On the other hand I don't want to heat a huge area when I am doing smaller things. So I have been thinking about a design for a Ribbon burner powered forge. As you guys are experts on this stuff, I though I would pick your brains on this if I may.

The body will be constructed of 2x2x 1/8" wall angle for the corners on the outside and 2x2x1/8" flat stock for non corners or hot corners (where insulation meets on doors and so on. The left side door will fold down and the back and front doors will swing to the side. The floor will be insulating fire brick topped by hard fire brick. I wanted the stacked brick floor because it allows me to increase the size of the forge if needed and also when borax eats the floor, I can just toss the bricks and replace them. The walls will and ceiling be 2" thick KAO Wool type insulation with a 1/8" to 1/4" later of 3200 degree refractory mortar on top and finally a light layer of ITC 100. The ribbon burner will be the size of a fire brick and centered over the fire bricks. The hinges are designed to prevent any doors locking on another while providing maximum protection to the right side. I had thought about mounting a bracket for the blower directly to the right side of the forge but haven't come to a conclusion there. The whole structure will sit on top of a layer of insulating fire brick on my improvised forge table.

Question 1: One thing I had been wondering is that i planned to use 2" of KAO Wool with the refractory mortar on top but could I compress the KAO Wool or would I reduce its heat insulation capability? I would like to keep the wall to 2" thick and if I could I would press it after applying the mortar so it cures smoothly and 2" total.

Question 2: Do you think I have enough insulation on walls and sides to carry this off even at welding temps?

Question 3: With the Refractory mortar on top and ITC-100 protecting the KAO Wool, do you think I would have a problem with 2370 degree rated KAO Wool at welding heat? It stands to reason the mortar and ITC would mean the KAO Wool would take less direct heat but I am not sure.

Question 4: Are there any tips or bonding agents you could suggest for holding the KAO Wool to the wall and ceiling? I had planned to use a rigidizer but I don't want it separating from the metal shell.

Question 5: WIth the insulation I have do you think I would be ok Mounting the blower to a bracket on the right side or would I be better off putting more distance between them?

Please see renderings from my CAD program below.


post-15449-035624700 1288501206_thumb.jp

post-15449-063988500 1288501213_thumb.jp

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One can do large work with a small forge. The work does not have to fit into the forge. If you make a porch at the mouth of the forge and set up a soft firebrick wall to reflect back the heat, you can certainly bend and get stuff to yellow. I've even done welds like that. But I get the impression that you are all fired up (har har har) about your forge design so it's moot. It looks like an interesting design.

If you haven't done so already, you should check out Frosty's design for a variable forge. It appears similar to yours, essentialy a roof and a floor while the walls are fire brick stacked to the required height. MonsterMetal also, has just built a ribbon burner forge with what appears to me to be a variable chamber. If it were me, I would proceed incrementally. Construct the roof with the burner, set it up with stacked soft firebrick walls and see how it goes. After using it that way for a while, I would then design the side modules.

AFAIK there really is no way to get kaowool or fire brick, or refractory to span a horizontal gap when laid straight across without support. The brick will sag when it gets hot and then crack when it cools. Kaowool can be glued onto metal but you will only bond the top layer and the rest will just sag and cause the protective coat to flake off. The solutions that I know of are:

1. Insboard or equivalent.

2. Kaowool tethered to the roof with nichrome wire and refractory buttons.

3. An arch structure made of wool or refractory or carved fire brick.

4. A block of pleated kaowool. Grant Sarver (NakedAnvil) discusses this and has a picture posted in one thread.

Ribbon burners don't turn down very well. They depend on a minimum flow of air/gas mixture to cool themselves. If you turn them down too low, they are prone to ignite the mixture in the plenum at the back. This means that when you want to operate in small volume mode, you may have way too much burner. The Pine Ridge 4x4 burner is matched to a 1 cu ft volume.

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