Mikey98118

Forges 101

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22 hours ago, AngryDaddyBird said:

I wonder how hot it it outside the shell?

I would imagine no more than any 2" ceramic fiber shell.  It's basically the same as any ceramic fiber forge, just doesn't have a layer of sheet metal around it.

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I normally recommend a steel shell for tunnel, oval, and "D" forges as a practical method of constructing a forge; they are a simple handy way to hold somewhat delicate refractory materials like ceramic fiber blanket together in a rigid frame, and hold exterior items like doors, burner portal tubes, and legs in place :)

I never recommend sheet metal shells for box forges, which are usually made of bricks and other rigid stacked materials, which need nothing more than a little angle to keep their refractory materials in place and to hang items like doors, burner portal tubes,  and legs on.

Both paths are all about practicality.

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Aiming burner ports properly in a tunnel forge

Aiming burners at 45 degrees is the second most common mistake; right after wanting an oversize forge. It takes very little flame angle to promote swirl in a tunnel forge.. All that we accomplish with such a great angle is to have the burner's flame impinge on wall area, instead of on the floor. Whatever we use for a hot-face on the forge floor is going to be much tougher than what will be employed on the wall.

If you position your burner to target the near side of the floor area, its flame will still swirl around a tunnel forge just fine, but it won't be overheating the wall, or  your work, which would also be bad, because of scale buildup and carbon loss in the steel. So you'll want to mount the burner after you place your floor, but before you rigidize and seal ceramic fiber insulation.

Consider mounting your burner port centered at 2"  away from top dead center on a forge from a five gallon paint can or propane cylinder. Cut out a hole a little under the outside diameter of the pipe, and then  power sand it into an oval shape with a cheap rotary tool (you can pick them up used from eBay for twenty bucks). Rotary tool accessories are dirt cheap too. It takes very little elongation of the hole to permit the burner port, and thus the burner it holds to be aimed perfectly at the near side of the forge floor; comfortably away from your work pieces.

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Engineering by the sales department?

The more that forge design is strictly driven by necessity the better the forge is going to be. If you think that is too obvious for words, spend some time looking closely at commercial forges, which unfortunately are mostly driven by marketing. Tunnel forge shape is driven by the desire to cause exhaust gasses to swirl, greatly lengthening their path toward the  exhaust exit; thus increasing hang time. Meanwhile shop air circulates well around  their curved shells, doing a good job of cooling the forge exterior; thus allowing it to sit safely within inches of its stand or table. Oval forges give up a percentage of those advantages in order to increase stock area within the forge.; "D" shaped forges give up an even greater percentage in return for even greater space. The point of box forges, originally, was to conform conveniently with flat rigid materials; in return for which it gave up all the aforementioned advantages.

So what are we to think when we see a box forge that is insulated with ceramic blanket; no rigid board or brick in site? Where is the advantage? And what are we to think when it costs more than an oval forge, with the same burner setup, from the same manufacturer, and for more money? It's all about marketing; not engineering.

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1 hour ago, Mikey98118 said:

So what are we to think when we see a box forge that is insulated with ceramic blanket; no rigid board or brick in site? Where is the advantage? And what are we to think when it costs more than an oval forge, with the same burner setup, from the same manufacturer, and for more money? It's all about marketing; not engineering.

It costs more to manufacture a steel box than roll a cylinder or oval. They have to charge more to make their margin. $

Frosty The Lucky.

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Half cake pan, half helium tank. 

Pan will be filled to 1/2"  to the top of the ports with perlite. Then a 1/2" of blanket rigidized and coated with Kasto. This is a bottom burner mounted forge powered by three 3/8" burners. 

Overkill? I think maybe! But it will be hot overkill.

I am wondering about rigidizing the perlite? If it can be rigidized. Or glued together with silica.

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Perlite has been quite successfully rigidized with sodium silicate (water glass) by hot glass artists for decades. You can find small bottles of it on the Net.

If the burners are NA single flame, then they can be turned down enough to do fine. Ribbon burners all need a minimum amount of cold gas/aor mixture flowing through them to keep from overheating and back firing; three ribbon burners would probably be too many.

I love the design; it seems you will be getting the best from a "D" forge this way.

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10 hours ago, Mikey98118 said:

three ribbon burners would probably be too many.

I love the design; it seems you will be getting the best from a "D" forge this way.

Thank you Mike.

This was originally designed for a single 1/2" ribbon but the ease of construction of the 3/8" has changed my mind...for now.

 

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Shells casted and curing. I am wondering about the joining of the two. Thinking of strapping them together then patching the seams with Kasto. Any thoughts?

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Judy wet the surfaces you want to join first, and everthing should work out okay.

Judy??? I meant to write "just."

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Judy,

Another option: Just cut a 1" or so wide piece of ceramic fiber and just put it between the two pieces like a gasket.  Rigidize it, and then if you want to change the top for a different shape you can!  That is the beauty of this type of forge.  OK...not Judy, just had too....

Dan

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Yeas, and there is ceramic fiber rope too. But what about airborn dust from them?

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Just rigidize and put satanite on the outside edges.  You can put a piece of paper or masking tape on the forge bottom and edge of the top shell so it doesn't stick. The paper/tape will just burn away leaving a perfect seal (way better then the doors on my forge).

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11 hours ago, D.Rotblatt said:

if you want to change the top for a different shape you can!  That is the beauty of this type of forge.

Oh boy, now I'm thinking of putting individual valves on all three burners to utilize as many as I need. Makers mind.

 

13 hours ago, Mikey98118 said:

Judy wet the surfaces you want to join first, and everthing should work out okay.

That is what I was thinking, since buttering things up is in these days. I like D Rotblatts suggestion of changing the shell.

Judy

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28 minutes ago, Another FrankenBurner said:

talk of baking cake in the 3d printed burner thread.

We made a pound cake the other night, went to work and there was pound cake there too.

 

4 hours ago, John in Oly, WA said:

But can you bake a cake in it?

Been taking challenges lately. I'll have to get the timing right, I am at elevation.

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Recipe...let's see, set the "oven" at 2100F, put the cake pan in, set the timer for, oh, say 3 seconds...Ding, it's done! Oh dang it, I used an aluminum pan. Now I have aluminum swirl cake.

Back to forging - I like the flexibility in the design of your forge. If you're doing something large, you can raise the top "clam shell" with firebricks to get larger interior space.

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Definitely put a ball valve on each burner.

How about sanding the refractory  smooth on the floor and lid and just put them them together?  I've had many brick pile forges and just stacked the bricks without trying to seal them and no major flame leaks. 

Hmmmm?

Frosty The Lucky.

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It takes a very straight joint not to leak flame, without help some some kind of working gasket. Flame in that area would overheat the pan's lip.

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22 minutes ago, Mikey98118 said:

It takes a very straight joint not to leak flame, without help some some kind of working gasket. Flame in that area would overheat the pan's lip.

For me, stacked or overlapped, bricks only leak at corners or ends after they warm up and shift and I usually stand them on edge rather than flat in a brick pile forge. That's minimal if any leakage through 2.5" thick joints.

It'd be hard to smooth the floor and dome as it sits now. However if a person were to sift the aggregate out of the refractory, apply say 1/4" or so layer and lay it joint surfaces down on a piece of formica it'll be smooth as glass. Plus the bottom pan's lip will be below the refractory out of the flame if it did leak.

Making another version would be easier to make the joint surfaces glossy smooth. 

Thinking about what makes my brick piles leak the most has me considering the effect on something the shape of the dome being discussed. My brick piles rarely leak until they begin expanding with heat. So that's a hmmmmm.

Frosty The Lucky.

 

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51 minutes ago, Frosty said:

Plus the bottom pan's lip will be below the refractory out of the flame if it did leak.

That would be the factor I would lean on :)

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1 minute ago, Mikey98118 said:

That would be the factor I would lean on :)

NO DON'T you'll get burned! :o That factor gets HOT even if it doesn't leak.

Frosty The Lucky.

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