Tom Pennington Posted July 16, 2019 Share Posted July 16, 2019 Hello everyone! I'm a high schooler and a beginner to blacksmithing. I'm making my own forge this summer, and would really appreciate any advice or suggestions about my forge design before I commit. I'm thinking about making a 24" long forge, with a forging volume of 1,370 cubic inches. The opening is an 8 x 4 rectangle with a half-circle on top of it (radius of 4). There are 4 inches of insulation around the chamber (2" of Superwool, with 2" of castable refractory on top of it). The floor bed is 4" of castable refractory, on top of 2" of Superwool. All the metal is 1/8" steel sheet. I am planning on using three 3/4" or 1" burners (maybe T-Rex burners, or I'll make my own standard Venturi burners). Is this too few to reach welding temps, or does the overkill insulation make up for it? I know this forge is huge, but I'd like to be able to grow into the forge, instead of making new designs as I progress as a blacksmith. I'm planning on using it to make mostly knives/swords, but also custom parts and some art pieces (hence the large size). As another reason for the size, I would also like to be able to potentially have multiple people using it at once. However, most of the time, I'm planning on only using 1-2 burners, and using fire bricks and placing a castable refractory slab on the floor to decrease the volume. Lastly, would it be possible to use it as a foundry, for melting aluminum and/or copper? I've attached some CAD renderings I made, as well as the blueprint of the design to make it easier to visualize. Thanks in advance for any help and advice. Quote Link to comment Share on other sites More sharing options...
Steve Sells Posted July 16, 2019 Share Posted July 16, 2019 Why try to reinvent the wheel? Quote Link to comment Share on other sites More sharing options...
Irondragon Forge ClayWorks Posted July 16, 2019 Share Posted July 16, 2019 Welcome to IFI. Have you read this yet? READ THIS FIRST I hope you have deep pockets to feed a beast like that. Or do you live where propane is free? My best advice is for you to read through Forges 101. BTW... you may want to edit the post to reduce the sizes of your CAD drawings. Huge pictures take up too much bandwidth\data, this is spelled out in the read this first thread. Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted July 16, 2019 Share Posted July 16, 2019 You do realize that when forging a sword you ONLY want to heat what you can forge before it gets outside of the forging temp range. So Vikings forged swords in forges with a 6 to 8 inch hot spot. Heating longer than you can work degrades the steel, (decarburization, grain growth, scale losses). When you need a long heat is heat treatment and that occurs rarely in swordmaking! I've been forging for 38 years now; spent a year working full time under a professional swordmaker when I was younger, and my most commonly used forge's shell is 14" long and 9" diameter. I teach up to 6 people at a time with it too. I think Steve's point is that you don't know enough to design a good forge and so should go with one of the well documented designs. You want your forge to be suited for what you will be doing the most of NOW. Forges are cheap to build and expensive to run if you have excess internal space. Expect to build others as you need them to suit those needs. You wouldn't buy a dump truck as your daily commuter car just because you expect to need to get a couple loads of gravel in a couple of years. Quote Link to comment Share on other sites More sharing options...
Tom Pennington Posted July 16, 2019 Author Share Posted July 16, 2019 Steve, I wanted to try and modify some other designs I've seen so they'd fit my needs better, and I also wanted the construction/design project to be a challenge so I can learn some skills and improve (cutting, welding, working with refractory, etc.). Irondragon Forge, thank you for directing me to that post, and I'll make sure to follow the suggestions. I'll also try to fix the drawings right away. Also, I'm in NJ, and barbeque bottles cost about 12 dollars here, so I think running the forge with all three burners at 10 psi would cost about 4-5 dollars an hour (I hope to only use 1 or 2 burners, and run at lower pressures)? Is that above normal propane costs? Quote Link to comment Share on other sites More sharing options...
Steve Sells Posted July 16, 2019 Share Posted July 16, 2019 so a day forging will cost you $30 or more that is $1k a month and its not a good idea to try to run a 3 burner off a home BBQ tank either Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted July 16, 2019 Share Posted July 16, 2019 How will you learn if you don't know enough to judge what is good and what isn't? The skills mentioned you would still practice building a known good design. I strongly suggest you build your first forge to a known good design and learn what works and what doesn't and then plan your next forge to fit your needs; which will change over time. One of my solid fuel forges is getting ready for it's 5th rebuild to make it easier to transport as I am getting older. BTW welcome; I graduated from Holmdel High School, Holmdel NJ back in the 1970's. (exits 114 & 117 on the GSP) Finally *everybody* wants to build a huge inefficient forge when they start out before they learn what they actually need. Remember Hollywood, video games and fantasy books are a BAD source of info---as ias a LOT of youtube videos Quote Link to comment Share on other sites More sharing options...
Tom Pennington Posted July 16, 2019 Author Share Posted July 16, 2019 Thanks for your advice Thomas, that makes a lot of sense. I think I need to head back to the drawing board and find a more conventional design. Do you have any suggestions? Steve, sorry for the confusion, I was just using that because I know the price for the barbeque tank. I would've actually used a much larger tank, but I don't know the pricing for that yet. I think I need to choose a different design anyway (probably without 3 burners). Also, when you put it like that it sounds crazy expensive. Thanks for pointing that out. Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted July 16, 2019 Share Posted July 16, 2019 Have you read the gas forge 101 thread on this site in it's entirety yet? (When you do you might keep count of how many new folks want to build a huge forge and post about it there...) There is also a Gas Burners 101 thread to go with it. When I started using propane, I attended two propane forge building workshops put on by a local ABANA affiliate. Each one lasted one Saturday and everyone attending walked out with a working forge. (Two; as one was for a blown forge and the other was for a naturally aspirated forge). If your local affiliate isn't having such workshops you can also attend meetings and see what others local to you are using and base a design on what works well for what you need. Also; Wayne Coe, a member here, sells forge building supplies and has a design for a gas forge on his website. Quote Link to comment Share on other sites More sharing options...
Tom Pennington Posted July 16, 2019 Author Share Posted July 16, 2019 I read a bunch of it and noticed that. That's why I put those justifications for the size. I'm going to go back and read the rest of it though. Also, I'll definitely look into ABANA, as it sounds like a great learning experience. Quote Link to comment Share on other sites More sharing options...
Mikey98118 Posted July 17, 2019 Share Posted July 17, 2019 On 7/16/2019 at 7:13 PM, ThomasPowers said: Forges are cheap to build and expensive to run if you have excess internal space. What they all wrote is right on the money. Furthermore, no matter how large a forge you may use occasionally a few years from now, you will still go on using the smallest forges you can for each job, because fuel will only get more expensive as time passes. Quote Link to comment Share on other sites More sharing options...
Frosty Posted July 17, 2019 Share Posted July 17, 2019 Welcome aboard Tom, glad to have you. We're not dissing you when we tell you you don't know enough to know a good design from a disaster, same for the justifications you mention in your last post. It's like me justifying my design for a space suit. But to address some of the aspects of the . . . forge idea you posted: No, 3" of refractory wool will NEVER make up for such a crazy oversized forge's fuel hoggishness. About your burner placement, this is a glaring example of not having a clue about how a furnace of any kind works. Of the 3 burners all are aimed at each other, not straight down the tube but close enough to really screw up induction due to severe back pressure. 1,300 cu/in. would require a minimum of 4 ea. WELL TUNED 3/4" jet ejector type burners. You've drawn linear type so expect at least 5 well tuned burners to reach welding temp. Just out of curiosity how would you weld something 24" long? Perhaps you have a roll press fast enough to set a weld before most cools too much? The points Thomas made about just how destructive heating steel above critical temperature without working it are exactly right. I believe everybody here who built a propane forge without following a proven plan has made silly stupid too large a forge, I've made dozens and my most recent is too large, about 1/3 the size of your proposal but still way too large. Forget making a gas forge that'll last long enough for you to grow into. First perfection is an illusion, ain't no such thing. If you build one half that size you'll grow OUT of it maybe before the liner is shot. Second forges wear out liners must be replaced now and then depending on how much you use it. Before I built NARB I could get about 5 hrs out of a 5 gl. propane bottle running 2ea. 3/4" Ts. IF I kept the bottles in a tub of water to keep them from freezing up. I'm thinking I'd have to float the bottle in boiling water and even then get maybe 1.5 hrs from a 5 gl. bottle. Not counting the propane I'd need to burn to keep the water in the tub hot enough to keep the propane from freezing. Two 3/4" Ts will put a skim of ice on my 100lb. 20 gl. tank in about 4 hrs. I understand what you're looking to do, most of us have done it one way or another. We design the IDEAL device, tool, machine, whatever before we know how to do the job, use the tool, etc. It's normal human thinking and part of the learning curve. We're just offering you the benefits of our mistakes and hoping you'll learn from them so you can maybe make new mistakes we can learn from. Hmmm? Frosty The Lucky. Quote Link to comment Share on other sites More sharing options...
Irondragon Forge ClayWorks Posted July 17, 2019 Share Posted July 17, 2019 3 hours ago, Tom Pennington said: would it be possible to use it as a foundry, In my opinion no. Read up on foundry's in this section. https://www.iforgeiron.com/forum/91-smelting-melting-foundry-and-casting/ Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted July 17, 2019 Share Posted July 17, 2019 Tom has impressed me with how well he has been taking our suggestions so far without getting, shall we say "petulant", like some folks who have washed ashore here. I expect to hear great things from his attempts in the future! Quote Link to comment Share on other sites More sharing options...
Irondragon Forge ClayWorks Posted July 17, 2019 Share Posted July 17, 2019 I agree Thomas, I have a lot of respect for someone who asks for advise and actually heeds it (even if I'm stubborn and don't according to my wife). Quote Link to comment Share on other sites More sharing options...
Latticino Posted July 18, 2019 Share Posted July 18, 2019 One thing that no-one has addressed is the huge amount of thermal mass the OP design has. While 4" thickness of castable refractory for the floor and 2" for the walls will make the forge pretty bulletproof, it will also make it very slow to heat up. There are also many different flavors of castable refractory, and depending on whether you chose a light weight, insulating material (Kastolite 30, for example), or a heavy weight material (Mizzou, Greencast 97...) you can be making a heat sink that will take an unusually long time to get up to temperature. I used wall thickness of Greencast 97 on that order for the inner walls of my glass furnace, but that was heated up over a period of several days each time it got turned down (typically ran 24/7). Even Kastolite in those dimensions will take quite a while. 1" of Kastolite backed with superwool should be more than sufficient. You also don't want your steel panel from the entrances to project inside the forge at all. For what it is worth, we have a 3 burner tunnel forge around that length in the group shop/school I sometimes work out of. It rarely gets used, is prone to hot spots, has trouble achieving welding temperatures, and is piped up to (2) 100# propane tanks. Doesn't have any real doors though and only is insulated with 2" of castable insulation (I didn't design it), so your design may heat better. Nice 3-D modeling though. Quote Link to comment Share on other sites More sharing options...
Mikey98118 Posted July 25, 2019 Share Posted July 25, 2019 Thank you for bringing this up. I felt to discouraged to deal with it. We all cope however we can. Quote Link to comment Share on other sites More sharing options...
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