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Review/Critique of small forge design


4447

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Hello everyone, I am currently using a 2 brick forge which, while it has served me well is starting to feel cramped and is falling apart rather quickly. This has led me to design a new, larger forge, I have attached a rough schematic in a picture. The kaowool would be rigidized, and covered in satanite. I will be using a JF#1 burner off eBay.

Any tips/recommendations as to how I could lay the forge out better would be great. Though I don't have access to a welder or heavy cutting tools so I would rather construct the shell out of sheet metal and bolts rather than go with an old tank shell

IMG_20201216_105338.jpg

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Soft firebrick. I will be doing all kinds of forging. I do eventually want to get into bladesmithing but for now I've just mainly been making smithing tools. I also want to start making just generic tools/household implements

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" All kinds of forging" ---that design will not fit anchors for ocean going ships!  Since you will be forge welding in it; how many hours a day will you be welding and with what types of flux?  There is NO forge that is good for "all kinds of forging"!

Is that 2 layers of blanket; I can't read the writing clearly.  Will you be "armouring" the flame impingement area?

Have you noticed how much that looks like an old tool box?  Also look at some of the mailboxes available to get a similar shape.

How many cubic inches is that burner good for heating to working/welding temps?

Basic design looks like a propane forge, not excessively long nor large. You will be putting some sort of end covers on it right?  Even if it's just firebricks they make a difference.  (I use firebricks and I have a set of tongs just for moving them around.)

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4 minutes ago, ThomasPowers said:

" All kinds of forging" ---that design will not fit anchors for ocean going ships!  Since you will be forge welding in it; how many hours a day will you be welding and with what types of flux?  There is NO forge that is good for "all kinds of forging"!

Yeah, my bad, I will be doing mostly small stuff, knives, tools, household implements, and decorative items. I have never forge welded before (crappy 2-brick forge) so I don't really know how much/what I will be using for that

 

6 minutes ago, ThomasPowers said:

Is that 2 layers of blanket; I can't read the writing clearly.  Will you be "armouring" the flame impingement area?

That is 2 1-inch layers of blanket, except for on the bottom where there is 2.5" of firebrick and only one layer of blanket. I don't know what armouring is or how I would do it

6 minutes ago, ThomasPowers said:

How many cubic inches is that burner good for heating to working/welding temps?

The burner specs say it should produce up to 160k BTU which should mean that I'm good to above 320in^3. Current design is around 250in^3 so I should be good there.

8 minutes ago, ThomasPowers said:

Basic design looks like a propane forge, not excessively long nor large. You will be putting some sort of end covers on it right?  Even if it's just firebricks they make a difference.  (I use firebricks and I have a set of tongs just for moving them around.)

And yes, I will be using some spare firebrick to cover the ends. Probably covered with a layer of satanite

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What's the designed width of the forge opening? Based on the scale of the drawing, it looks like 7" but also based on that scale the kaowool is only 1" thick. I think there's an inconsistency in the drawing.

Do yourself a favor and use pop rivets instead of bolts, or use 2 nuts per bolt. Bolts loosen themselves when heated and cooled repeatedly (like the forge will be). The extra nut stretches the threads and locks it up. If you use pop rivets, just make sure you don't use aluminum pop rivets. 

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There are two layers of kaowool, each 1", the sheet metal is represented with a line not a section, and yes the opening is 7"

16 minutes ago, twigg said:

o yourself a favor and use pop rivets instead of bolts, or use 2 nuts per bolt. Bolts loosen themselves when heated and cooled repeatedly (like the forge will be). The extra nut stretches the threads and locks it up. If you use pop rivets, just make sure you don't use aluminum pop rivets. 

That's a good idea, though popping steel rivets sounds like a chore..., I was actually considering sheet metal screws

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I've used plenty of pop rivets, used to do a lot of sheet metal work back in high school, we always did aluminum rivets and they were a pain to do by hand without a pneumatic gun. I'd imagine that steel rivets would be harder to do 

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In this design.  rivets, screws, etc. should be irrelevant. Why? Because rigitized ceramic blanket will have no need of them. And, if he doesn't rigidize the blanket, his choice of finish coating will fall apart  super fast. In fact, without rigidizing the blanket, nothing short of a think layer of hard refractory is going to last.

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One other thing that stood out to me: the way you've angled the burner at a 45 you'll need extra satanite on the side wall opposite the burner port to protect it from the flame. Since you already included a firebrick floor in the design, I'd move the burner closer to vertical (at the expense of living with the chimney effect).

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3 hours ago, 4447 said:

I'd imagine that steel rivets would be harder to do 

That depends on your pop-rivet gun. I can use steel rivets up to 1/4 in. diameter, with the grip of one hand and I'm not as strong as I used to be. For a forge that size, I would use 3/32 or 1/8 rivets.

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Just to clarify, the only reason I recommended moving your burner to the vertical was because in your drawing you had the brick floor on the bottom. If you work up a thick layer of refractory on the side wall opposite the burner port, then horizontal is better! Just make sure the propane line is out of hip-check range! As far as how much satanite you need for the side wall, I'm going to let one of the more experienced members give you that info. I did 1/2" on my last build but I haven't really stress tested it.

It sounds like you used some real big pop rivets in high school. The 1/8" stainless pop rivets I use take 3 squeezes of my manual pop rivet gun, each squeeze about as much force as a manual stapler.

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15 hours ago, 4447 said:

Hello everyone, I am currently using a 2 brick forge which, while it has served me well is starting to feel cramped and is falling apart rather quickly.

If you don't mind going into details, others who are thinking about going the two-brick forge rout could benefit from it.

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For sure, my 2-brick forge was quite rudimentary, just some wire mesh, angle iron and all-thread holding everything together. However the bricks began to crack quite badly starting even from the first firing. The wire mesh helped hold them together but not forever. The forge also has very thin sidewalls and as such has not been particularly efficient, I generally run my small 30k burner at 20psi to get a workable forge temp, anything lower than that generally doesn't get hot enough and causes the burner to stutter. Finally the form factor of the opening is very restrictive for anything other than bladesmithing and the softness of the firebrick means that the bottom of the opening of my forge is almost completely worn through after not too much use.

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