My opinion is that you have constructed a huge forge which will have serious trouble getting up to forge welding temperature with the insulation style and relatively small ribbon burner included (though a forced air ribbon burner will be much better than one or two 3/4" naturally aspirated burners). The Mizzou lined walls will be extremely scuff resistant, fairly flux resistant, but poor insulators and significant thermal bridges. If you didn't rigidize the underlying refractory blanket before casting the Mizzou, you may also have compromised the blanket's insulating value. Even if it gets up to temperature it may end up being rather inefficient. Check the forge skin temperature during operation to be sure. You may also have a problem with the Mizzou cracking due to thermal cycling given the configuration of the arch. In addition to being a thermal bridge the Mizzou is a significant thermal mass and will take some time to get up to temperature. I certainly could see this as an industrial grade forge that runs 24/7, but find it hard to picture being practical for a bladesmith.

Was your smaller forge constructed using similar techniques?

You may drastically improve operation with well designed door systems for both the front and back. This could help a lot with the radiant and conductive losses. I'm having trouble understanding why you need such a large forge. Are you planning on doing architectural smithing as well as axes and pattern welding? I don't think even Albert Paley's gas forge was that large.

I don't think that additional refractory will help (unless you mean refractory insulation, which would mean relining the entire forge). If you put in more Mizzou you are just adding thermal mass. It does have some limited insulating value, but nothing like castable refractory insulation (like Kastolite 30 or similar). Mizzou is more like hard firebrick. Interior volume isn't your enemy in this case, it is losses due to radiation, convection, and conduction. Volume is directly related to exterior forge surface area, which is where a lot of the rules of thumb for forge design come from, but that is presupposing that you use walls with the same insulating values as the rule of thumb writers (not to mention the radiant losses, which are also significant and have a lot to do with door configuration).

Of course I'd love to be proved wrong. Please keep posting regarding your progress with this one.

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My opinion is that you have constructed a huge forge which will have serious trouble getting up to forge welding temperature with the insulation style and relatively small ribbon burner included (though a forced air ribbon burner will be much better than one or two 3/4" naturally aspirated burners). The Mizzou lined walls will be extremely scuff resistant, fairly flux resistant, but poor insulators and significant thermal bridges. If you didn't rigidize the underlying refractory blanket before casting the Mizzou, you may also have compromised the blanket's insulating value. Even if it gets up to temperature it may end up being rather inefficient. Check the forge skin temperature during operation to be sure. You may also have a problem with the Mizzou cracking due to thermal cycling given the configuration of the arch. In addition to being a thermal bridge the Mizzou is a significant thermal mass and will take some time to get up to temperature. I certainly could see this as an industrial grade forge that runs 24/7, but find it hard to picture being practical for a bladesmith.

Was your smaller forge constructed using similar techniques?

You may drastically improve operation with well designed door systems for both the front and back. This could help a lot with the radiant and conductive losses. I'm having trouble understanding why you need such a large forge. Are you planning on doing architectural smithing as well as axes and pattern welding? I don't think even Albert Paley's gas forge was that large.

I don't think that additional refractory will help (unless you mean refractory insulation, which would mean relining the entire forge). If you put in more Mizzou you are just adding thermal mass. It does have some limited insulating value, but nothing like castable refractory insulation (like Kastolite 30 or similar). Mizzou is more like hard firebrick. Interior volume isn't your enemy in this case, it is losses due to radiation, convection, and conduction. Volume is directly related to exterior forge surface area, which is where a lot of the rules of thumb for forge design come from, but that is presupposing that you use walls with the same insulating values as the rule of thumb writers (not to mention the radiant losses, which are also significant and have a lot to do with door configuration).

Of course I'd love to be proved wrong. Please keep posting regarding your progress with this one.

Thanks Dan. I want this one to hold heat. This one is going to be used for damascus and axes.It will take longer to heat than my other ribbon burners. I did rigidize the floor. But not the top. I ran out of rigidizer. I cut 3.5 " off the bottom. I'm no expert but I have a smaller ribbon burner Ive been using for several years with no problems. This smaller forge will reach welding temps in 10 min. Ive got to still do the doors. By cutting 3.5 inches off the bottom. I will not have to make the floor taller. I have about 1bl of gas running to it with the air barley turned on. I am curing out the Mizzou. I done some measurements. It comes out to .80 cf of internal forge space.

Im working on designing doors. The front door will have a 6.5"x5" opening. The back door wont. Im gonna use linear actuator to push the door up from the bottom. I was going to make them remote controlled. But I think I will just use a rocker switch on the front and back. I dont have the linear actuators yet but I can get them for 42$ apiece. And 2 switches for 15$ apiece. I have the transformer to step it down from 120v to 12v.

Forge looks much more proportional with the 3.5" removed from the height. Hope it will work for you once you get the doors finished. Make sure you keep the aluminum actuators far away from the doors. You may want to consider a cable and pulley system as well as some kind of loose track to move the doors. I've also been very pleased with a floor switch to activate similar doors. Nice when you have your hands full...

I would also consider having the front door close further (unless I'm not understanding the opening size you listed). With a forced air burner you don't need the same large exhaust opening that you do for a naturally aspirated one. A smaller front opening will certainly be reflected in a hotter forge interior for the same burner input. On mine I close the door almost all the way and just use the 1/2" gap around it to relieve the combustion byproducts.

Good luck, I look forward to seeing your first forged billet.

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Forge looks much more proportional with the 3.5" removed from the height. Hope it will work for you once you get the doors finished. Make sure you keep the aluminum actuators far away from the doors. You may want to consider a cable and pulley system as well as some kind of loose track to move the doors. I've also been very pleased with a floor switch to activate similar doors. Nice when you have your hands full...

I would also consider having the front door close further (unless I'm not understanding the opening size you listed). With a forced air burner you don't need the same large exhaust opening that you do for a naturally aspirated one. A smaller front opening will certainly be reflected in a hotter forge interior for the same burner input. On mine I close the door almost all the way and just use the 1/2" gap around it to relieve the combustion byproducts.

Good luck, I look forward to seeing your first forged billet.

How big of an opening would you suggest? I would like to see the material being heated and what it looks like. Here is a rough sketch of the way the actuator will work. It will be mounted underneath the table the forge sits on. There wont be any heat near it. Im not going to cast refractory in the doors. Im just going to line the with kawool., rigidize and coat with matrikote 90. Im goona make some diy linear bearings rails for my tubing to travel in. Im gonna use skateboard bearings. Thanks for the advice.

I'm still not getting how you keep the body of the actuator away from the heat while trying to open the door fully. In your sketch the "legs" and supporting beam will certainly be exposed to the forge heat as the door rises up. I guess it is all about how big a door opening you want for working your typical stock. I find it confusing because the forge interior is so large, so I expect you at some point will want to open the door fully. Perhaps you plan on making the supporting "legs" the full height of the forge opening, plus a couple of inches to keep the beam below the opening. Just keep an eye on heat transfer, because that aluminum actuator will easily melt from transferred heat if you are not careful.

I don't typically like to look into the forge a lot to monitor stock inside when I'm going for welding, or close to welding heats. A quick peak is usually enough, and often I just go for heats based on elapsed time back in the forge rather than closely monitoring. That is why I close mine down as far as possible. You have to make your door opening to suit your process and burner design. If it were me I'd have a solid door front and rear, standing off about 1/4" or so (adjustable) from the face of the forge. If you need a slot opening to accommodate your stock, you can just leave it open a little at the bottom. That is just me though. If I had an opening like you envision I'd probably make it no more than my typical pattern welded billet size + 1/2" for clearance and size a plug for same out of refractory insulation so I could close it up during initial heating to bring that time down. I have to be more conservative with my forge as I run residential pressure natural gas, and every BTU needs to go to heating the interior.

How large are the billets you plan on making and do you have a press, power hammer, or rolling mill to help you forge?

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I'm still not getting how you keep the body of the actuator away from the heat while trying to open the door fully. In your sketch the "legs" and supporting beam will certainly be exposed to the forge heat as the door rises up. I guess it is all about how big a door opening you want for working your typical stock. I find it confusing because the forge interior is so large, so I expect you at some point will want to open the door fully. Perhaps you plan on making the supporting "legs" the full height of the forge opening, plus a couple of inches to keep the beam below the opening. Just keep an eye on heat transfer, because that aluminum actuator will easily melt from transferred heat if you are not careful.

I don't typically like to look into the forge a lot to monitor stock inside when I'm going for welding, or close to welding heats. A quick peak is usually enough, and often I just go for heats based on elapsed time back in the forge rather than closely monitoring. That is why I close mine down as far as possible. You have to make your door opening to suit your process and burner design. If it were me I'd have a solid door front and rear, standing off about 1/4" or so (adjustable) from the face of the forge. If you need a slot opening to accommodate your stock, you can just leave it open a little at the bottom. That is just me though. If I had an opening like you envision I'd probably make it no more than my typical pattern welded billet size + 1/2" for clearance and size a plug for same out of refractory insulation so I could close it up during initial heating to bring that time down. I have to be more conservative with my forge as I run residential pressure natural gas, and every BTU needs to go to heating the interior.

How large are the billets you plan on making and do you have a press, power hammer, or rolling mill to help you forge?

The linear actuator is underneath the table. Completely away from the forge. It will just push the door up and down. I have an Anyang 88 and a 25 ton press.

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The linear actuator is underneath the table. Completely away from the forge. It will just push the door up and down. I have an Anyang 88 and a 25 ton press.

Don't feel that you need to quote my whole comment if you are posting right after me. I think folks can figure it out.

To understand what I mean regarding the actuator and forge heat you may want to sketch where your forge opening is in your previous drawing as well as where the various components of the door assembly are. If you keep all aluminum away from the heat you are fine. Your build so far seems to be sturdy and well executed, so I expect you will be able to figure out a good door system. Just trying to help head off some potential issues.

Sounds good. I appreciate the feedback. I like the interaction. There for a while I didnt think anyone was interested. Thank you sir.

Heres some more progress.