I’m going to post about this project as it assembles itself, to remember what I did, and/or what I was thinking at the time. So, it’s going to be kind of self-referential and possibly contain bad sketches.

Feel free to chime in with suggestions. If you want to suggest, I hate to say this but: suggest in advance of where I am, because if I am posting what I am doing, that generally will mean I’ve already done it or sourced the materials. Sorry about that, it’s just how things work out in project land. On the other hand, this may not be the last forge I ever build, so any and all hints are good. As I said above, I may turn this into a build plan or video, and if there’s a point where I can say “do as I suggest, not as I did” that’s fine.

This is what I currently have:

It’s based on an idea I saw someone do on youtube, [essential]. The idea was pretty much what it looks like: can you build a cheap and easy forge where the forge’s refractory and frame are all there is, plus some burners? It’s the exact opposite of my gigantic overkill forge, with all its overkill thermal mass. This one is built of what blacksmiths sometimes call “soft brick” – foamy lightweight refractory – as opposed to “hard brick” which is what covers the table-top it is standing on. In fact, that hard brick is going to make up the frame of the next forge, because I’ve learned a bunch of stuff from the current forge. There are places where I invested effort that was wasted, and a few where I did not. But it has been a great hard-worker for me, and comes up to welding temperature in about 10 minutes, which is spectacular.

As you can see it’s built from 4 pieces of L-bracket (I have a lot of L-bracket in my steel scrap pile) and some 1/2″ID square steel tube and some allthread and washers and wingnuts. There is a steel plate along the bottom, which is pinched between the square tubes and the L-bracket, and is the size reference for the entire thing. That is it!

From the other side:

I made a big heat deflector/hand protector on the burner side, because I thought that might be Smart(tm). It turned out to be unnecessary, entirely. The soft brick is so insulating that you can put your bare hand, with some trepidation, on it while the forge is at welding temperature. I mean “put your bare hand on it, and pull it off again, undamaged.” Gaps eventually form between the bricks from oxidation, but in this build they are not too bad of a problem unless you’re putting your bare hand on the forge and put it over one of the gaps. The deflector is mounted on 4 pieces of the square tubing, with bolts coming through from the back, supported by the burner mount, which you cannot see. The burner mount is just a piece of 2″ steel 1/8″ bar that is screwed into the square tube uprights, has holes in it, and serves to support the burners. As you can see, the other thing supporting the burners is the heat deflector, and the burners are wired in place with steel wire. I have seen what happens when a burner shakes loose and decides to go walk-about. Make sure your burners are really solidly attached to something.

We’ll look at gas distribution systems in a couple episodes but spoilers: the red thing is the regulator. On the other side of the regulator is a ball valve (spray painted red), a quick release propane coupler, and the hose that runs to the propane tank. There is another ball valve and quick release on the wall, and a cutoff valve outside on the tank. If I need to, I can disconnect the hose, run it outside, and connect it to the quick release connector on my smelter or anything else that wants to run propane.

If you look carefully at the pictures of the forge you can see that eventually thermal cycling got the better of the soft brick. The hard brick is fine, but I assembled the soft bricks into a sort of air-tight mass by sawing and lapping them, to get the exact interior size I wanted. … All of which brings me to a point: the current forge is too short, and to big for what I mostly do. Sure, it is great to have lots of space but mostly I am working on things that are 3″x3″x6″ to 12″ long. [By the way, Trump says that when he is inaugurated, we are going to put a tariff on any country that does not use “freedom units” which are based on the foot size of the very English monarchs we went to so much trouble to get rid of.] Lately I have broken my treaty with myself, to mostly make cooking implements and useful things, and have been making the most evil flesh-rending pieces of cruelty that I can. For that the existing forge is too short and could easily be half the interior dimension.

New design strategy point: I am going to use hard brick plus ceramic felt cloth, and will not be cutting or adjusting brick sizes because it is painful and breathing dust from refractory is bad. The old one’s interior was parged with satanite and infrared reflector, and I will repeat that in this design as well.

New design strategy point: Instead of the small 1/2″ID square tube I am going to use 1″ square tube. There’s a reason for that, which is that I can also drill crosswise through the tube and have enough room to put 1/4″ allthread or bolts through it. When I mounted the burner bracket, I had some fiddling to do to get the screws in without hitting the vertical allthread. So I will use something a bit bigger, which will also be more sturdy since it’ll have a larger cross-section at the top and bottom.

New design strategy point: The old forge has a “roof” made by spanning the top with bricks. To do that I had to table-saw soft brick and make the sides come in enough to support it. The old roof is crumbling. The new roof will either be: a) just 2 layers of ceramic felt and some wool on top b) a frame made of L-bracket with 2 layers of ceramic felt stretched across the gap, poured on top with cast-o-lite or mizzou c) a frame made of L-bracket that holds a number of hard bricks sitting on a layer of ceramic felt. The objective of this is to make it very easy to remove the roof, so I can clean inside and/or move a movable baffle that allows me to shorten the inner space if I am not making something long. (see next point)

New design strategy point: The old forge has 2 burners and the back is closed with a pair of hard bricks that sit on an L-bracket that holds them at the right height. That worked remarkably well since I can open or close one of them. But, if I have the forge open at both ends, it loses heat. I really only need length in the final stages of making a katana blade, so I am going to make the new forge a 3-burner forge, where one burner is generally shut down, and there is an interior baffle that shortens the length by moving back and forth inside. Just lift the lid a bit, move the baffle, turn on the 3rd burner, and it’s ready for full length swords. Best wait ’till its below welding temperature before you try to move the interior baffle. I’ll need to put a few thoughts into the overall length I will be working with in a given session.

New design strategy point: I have made a few postings in blacksmith forums about this, and have generally been ignored, which (as I am sure you can guess) annoys the living shit out of me. I called the Chili Forge people and Coal Iron people and talked to their engineers about this and … nothing. OK: flux (borax) if you use it, glassifies quickly and forms an oxygen barrier. But, when it cools it contracts a lot, which is a problem because it has soaked into your bricks. One or two sessions with flux, and your bricks begin to crumble into powder. I was watching one of Everyday Astronaut’s Elon Musk SpaceX worship sessions and got to thinking about exactly what the fuck the afterburner nozzles on an SR-71 are made of. Afterburner nozzles have to handle heat (and lots of it) as well as oxidation (lots and lots) so they have to be made of some crazy stuff. Turns out they’re made of the same stuff as the rocket bell on an X-15. It’s a material called Inconel which is a sort of nickel-chrome-steel alloy that has a melting temperature up in the mid 3000Fs, and oxidizes like stainless steel – some but not very fast. So I made a flux tray out of 16-ga Inconel, thinking it would not be much thermal mass and much to my surprise, it took dozens and dozens of sessions with flux and all that hot gas, before the Inconel started to decay. Since I am making the new forge very well insulated, I don’t think that the additional thermal mass of having a couple pieces of Inconel inside will make much difference. I am going to see if I can put half-height sides in, and a long tray in the bottom, then smaller disposable trays for work. I will polish the inner surfaces of the sides to mirror shine to reflect heat. Who knows? This is experimental and if it doesn’t work, I can go back to hard brick or just cast the bottom full of mizzou.

New design strategy point: There is no “lintel” on the top of the frame, so the whole frame is held square by the square bottoms of the tubes. In retrospect, I could have invested the extra 25″ or whatever of L-bracket. I have lots. The new one will have front and rear lintels and possibly the front lintel will support a sliding door.

One of the great things about the allthread/wingnut/tube steel assembly is that you can assemble the unit loosely, make everything fit, then snug it down. My plans for the sides, for example, involve wrapping ceramic felt around the inside of the vertical hard bricks then letting the L-brackets just hold it in place. No gluing no sewing no lapping or layering.

This is the current state of affairs:

In my supply piles I have washers, wingnuts, allthread, L-bracket, etc. “not shown” here. The bricks represent the total dimensions: 6 vertical hard bricks long and one horizontal hard brick wide. The interior should be roomy but not big enough to turn a cadillac around in. I have overlap so if I want to make the roof loose, I can just drape a piece of ceramic felt over it and hold it down with hard bricks. The bottom will not be as shown – that is just to get the dimensions. The bottom will be a metal plate in place between the bottom L-brackets with some ceramic felt on top of it and then the Inconel tray.

The vertical brick partway down represents the movable interior baffle, which may require cut to fit but ought to be more or less the right size. The burners will go with 2 in the front area and another behind where the interior baffle currently is. If I want to work on something long, the interior baffle can come out or be moved all the way to the end of the tunnel.

Not shown here is a “porch” like I have on the current forge. Wow are those useful! All I did with the old one was extend the bottom L-brackets and put some hard bricks in to get the right height. I will probably extend the L-brackets on the bottom so they are long enough to hold 2 width-wise hard bricks and I’ll trim them if I have to. Or I’ll use an angle grinder to cut away the top of the ‘L’ in the L-bracket so that the hard bricks can just sit right there. The porch is crucial, since it’s where you put things down to change your grip on them, etc.

Another topic I have not touched on is the question of a front door. Having a front door makes a huge difference in heat-up time. I was thinking I could put an L-bracket across the top as a ‘lintel’ of sorts with the ‘L’ edge up and facing out, then make a frame with some pulley wheels that could be casted full of mizzou or cast-o-lite. [Remember: I have a metal lathe] it’d be fun to cast some kind of logo through the door, like some hands doing “goatse” or something but as you can tell I don’t have any good ideas about that yet. Last year I did some experiments with a frame that I put ceramic felt across and cast refractory into, and it works great. You wind up with an insulated refractory that is strengthened by the fibers in the ceramic. It is a great technique and I think making a door would showcase it.

I apologize for dropping postings here, and not interacting with you all as much as I used to. I have become a much slower writer, which makes it hard for me to sit down and hammer out responses to comments in a half hour or so, it becomes a 2 hour project which then means I need a nap. I do not know if this is a normal age thing or a brain injury thing but I have noticed that if I remain still (as in: sitting behind my desk) my eyes drift closed and then I have ruined my chances of sleeping that night.

It has occurred to me that I could easily enough build a ribbon burner. That is well within my capabilities but I am not sure if I actually want to go that route because then I need a pressurized air system and yadda dadda dadda etc. Venturi burners are plenty hot enough and once the fire chamber is up to temperature, everything heats evenly. I guess I am saying I could do it but I might be just showing off. I know you all know I am immune to that particular weakness.