krisfaeth Posted February 21, 2009 Share Posted February 21, 2009 hi I'm building a propane forge And have a few questions. I want 2 use a piece of 12'' pipe 16'' long. I plan on lining it 2'' thick with ep kaolin & silica sand 50/50 (I have them on hand). I am going to use a 3/4'' oliver upwind burner. what I want to know is will this be to thick for the clay to set? Is this going to be too much volume ( 8'' by 12'' after making end caps)for just one burner? Quote Link to comment Share on other sites More sharing options...
Frosty Posted February 22, 2009 Share Posted February 22, 2009 (edited) I recommend you do some reading about building gas forges before you put in a lot of work for a not so good result. Off the top you're choice of kaolin and sand isn't going to make a very good refractory, especially 2" thick. It will shrink check to destruction unless you mix it very dry and hammer it in place. It will provide almost no insulation and will be a huge heat sink. This will mean your burner won't stand a chance of getting to forging heat even if it was of a volume a 3/4" ejector type burner would normally heat. An "Oliver upwind burner" is okay but a lot of work compared to other ejector types like the "Sidearm" or the "T" I build. Search IFI and you'll find pics and descriptions of both. I'm not saying an Oliver is a poor burner, there are just easier ones to build. What will work well is lining your pipe with 2" of 1" 8oz. Kaowool or Insulwool (2 layers is better than one layer of 2" ceramic blanket) and mixing your kaolin into a medium thin slip and painting the ceramic blanket to stabilize and ridigize it. Leave out enough of the inside layer of kaowool at the bottom to accept 3,000f spilt fire brick(s) for the floor. This will leave you with your 8" ID, a flad durable, easily replaced floor and you can adjust the length with a movable back wall of stabilized Kaowool. For a 8"ID x 12" chamber you will need two, 3/4" ejector type burners. Being well insulated this will provide enough overkill the forge will reach welding, heck melting temp without trouble. You can always turn it down if it's too hot but you can never get it hotter than it can go. If you can afford it painting a coat of ITC-100 on the inside will improve efficiency quite a bit. Last time I bought it it was more than $30/pint + shipping but it will pay for itself in saved fuel in a short time. Then again, if you can lay your hands on some zirconia flour say between 80 and 100 mesh, mix it with your kaolin slip and you'll have the same thing. Place your burners about 4" apart and 4" from the front for a reasonably even heat. You can shift them closer to the main opening and tilt the front burner towards the back a few degrees too. If you go ahead and add a third burner you can open the back and use all 18". Put a 1/4 turn ball valve on each burner so you can use only as many as you need. Often you'll only need one burner in the front, sometimes you'll need it 12" long and occasionally 18" will be handy. It's nice to be able to tune the volume to what you need and what is most economical. Whether you mount them tangentially or perpendicular to the floor is a matter of some debate and not terribly significant for general smithing. I've tried both and have decided it doesn't make much difference regardless of what you're doing. Frosty Edited February 22, 2009 by Frosty Quote Link to comment Share on other sites More sharing options...
howardrw Posted February 22, 2009 Share Posted February 22, 2009 Frosty, since my first forge, which is a bought one is falling apart and I am considering building one very much like the one you are discussing, your info was very informative. My question is how do you keep the kaowool in place in the pipe? I have tried replacing it in the door of my present forge, which is rectangular, and treating it with stiffener and it seems to keep breaking up in small pieces and falling apart. any info is appreciated. Thanks, Bob Quote Link to comment Share on other sites More sharing options...
Frosty Posted February 23, 2009 Share Posted February 23, 2009 You roll the blanket and it will hold itself in place. Keep the seams at the bottom. Keeping it on a large flat surface is harder. One trick is to run sheet metal screws in from the outside. Another is to lace it on a couple few rods that are held in place by holes in the door frame. The rod is sharpened on one end so you can push it through the blanket edgewise. To keep in in a lid you can cut it in strips, fold it in half lengthwise and skewer it with sharpened rods so the fold faces down. It's work in walls too I suppose. The screws, rods, wires, etc. need to be SS or another high temp alloy. Frosty Quote Link to comment Share on other sites More sharing options...
saintjohnbarleycorn Posted February 23, 2009 Share Posted February 23, 2009 thanks frosty, I am also building one for 2 3/4" burners, is twelve inches length the better length? I was also thinking of three layers of 1" wool, so I could start with 13" or 14" diameter to start with. kevin Quote Link to comment Share on other sites More sharing options...
Frosty Posted February 23, 2009 Share Posted February 23, 2009 The rule of thumb is 1 ea. 3/4" burner for every 300-350 cu/in volume. To bring 350 cu/in to welding heat you'll need to build the burner precisely and have it tuned just right. Many guys who need to be able to rely on consistent good welds, mostly blade smiths figure for less volume per burner in the 250-300 cu/in range. I don't know where the point of diminishing returns is where insulation is concerned. I know 2" works well, especially with a coat of ITC-100 and I also know there are guys who have 3". I just don't know if 3" is that much better than 2". 2" is quite a bit better than 1" coated with ITC-100 or not though. So, I wouldn't say 3" is too much but can't say it's a significant improvement over 2". How wide and long you make your forge is a matter of personal preference and even most bladesmiths don't seem to use all 12" or 18" or in a number of cases 24"+ of their big forges. However, if you build your forge with burners you can light independently and have a movable rear wall ala Ron Reil's forge you can adjust it's size to your current needs. Not having to have several forges taking up space is why I built my Variable Volume forge. The lid lifts and lowers on the scissor jack and I can reconfigure the volume and shape of the forge chamber by moving the sidewall bricks, and use between 1 - 4 burners depending on volume and shape. Frosty Quote Link to comment Share on other sites More sharing options...
saintjohnbarleycorn Posted February 23, 2009 Share Posted February 23, 2009 thanks for the info, I have been thinking about it for a while now and have seen a lot of different ideas and was getting confused. You like to think that there is a right way and a less right way, but in this case it looks like a lot of different ways. I am not really a knife maker so I guess following a knife makers gasser wouldn''t work out that well. thanks again. kevin Quote Link to comment Share on other sites More sharing options...
Frosty Posted February 24, 2009 Share Posted February 24, 2009 Right and wrong is pretty subjective where most of this stuff is concerned and gas forge making is near the top of the list. I'd say the only really must do items have to do with safety. It's important to minimize the chance propane can pool from a leak and blow you into the next page, or generate enough CO to send you and anyone else around on to the next (whatever) or just burn you out. After you're sure you aren't going to kill yourself and or others thinking about efficiency for what you want to do is important. A farrier's forge is pretty good for general smithing, especially with a couple pass throughs. A simple box forge is pretty easy to make from virtually any steel box. I like a .50cal ammo can myself but I've seen a nice one built from an old steel tool box. The shell doesn't need to be very heavy, especially if you're using a ceramic blanket refractory. I usually recommend SS stove pipe for those wanting to build a pipe forge. For myself however I've had enough of pipe forges and will stick to box forges from now on. Frosty Quote Link to comment Share on other sites More sharing options...
Dodge Posted February 24, 2009 Share Posted February 24, 2009 I don't know where the point of diminishing returns is where insulation is concerned. I know 2" works well, especially with a coat of ITC-100 and I also know there are guys who have 3". I just don't know if 3" is that much better than 2". 2" is quite a bit better than 1" coated with ITC-100 or not though. So, I wouldn't say 3" is too much but can't say it's a significant improvement over 2". Not having to have several forges taking up space is why I built my Variable Volume forge. The lid lifts and lowers on the scissor jack and I can reconfigure the volume and shape of the forge chamber by moving the sidewall bricks, and use between 1 - 4 burners depending on volume and shape. Frosty Speaking from experience and specifically in terms of thickness, I found, more is NOT necessarily better!! My forge has a castable shell with two Reil type burners in a chamber about 357 cubic inches. The math says there should be plenty of heat and while I can weld, it takes a significant quantity of fuel to do so. The only factors I can account for this is the shell walls are 3" thick and no ITC or similar coating. Could the coating make that much difference?? I know of others using similar materials but thinner walls welding at much less fuel consumption. My theory is that my 3" thick walls are acting like a heat sink. I blanketed the outside of the shell with a 2" thick blanket of inswool and I don't know what it does to the equation because now the walls are 5" thick but it now welds with less gas consumption. Go figure. ;) Quote Link to comment Share on other sites More sharing options...
Frosty Posted February 25, 2009 Share Posted February 25, 2009 You have two obstacles to getting it to welding heat. #1 is too small a chamber for the number of burners. Properly tuned one of Ron's EZ burners will reach welding heat in that sized chamber especially if it's insulated. It's right at the reasonable limit but they'll do it. #2 is too much thermal mass in the refractory. 3" of hard refractory is way more than you need, it's sucking the heat right out of your chamber. It'd get hotter if there were only 1" and the outside of the shell glowed red with waste heat. I'm a fan and advocate of double lined forges. Ram up or cast a hard inner liner of good quality tough, high temp, preferably high phosphate or phosphate bonded refractory an inch or less thick. Then surround it with 2" of Kaowool or Insulwool and put it all in a thin sheet metal shell. Phosphate bonded or high phosphate refractories will laugh at molten borax or any other flux I've heard of being used in a forge. Frosty Quote Link to comment Share on other sites More sharing options...
Dodge Posted February 25, 2009 Share Posted February 25, 2009 This will leave you with your 8" ID, a flad durable, easily replaced floor and you can adjust the length with a movable back wall of stabilized Kaowool. For a 8"ID x 12" chamber you will need two, 3/4" ejector type burners. Being well insulated this will provide enough overkill the forge will reach welding, heck melting temp without trouble. You can always turn it down if it's too hot but you can never get it hotter than it can go. Frosty Forgive me for perhaps stealing this thread, but I'm sure that the original poster can benefit from my questions as well. Frosty, I'm a little confused by your comments to my post. #2 confirms my suspicion as I theorized in my earlier post, that my refractory is too thick, but my confusion is this: "You have [two] obstacles to getting it to welding heat. #1 is too small a chamber for the number of burners. Properly tuned one of Ron's EZ burners will reach welding heat in that sized chamber especially if it's insulated. It's right at the reasonable limit but they'll do it." Above (in bold) you suggest overkill can simply be overcome by turning it down if its too hot. That was what I was thinking when I chose to use two burners. But why would two burners prevent me from achieving weld heat if they are too hot? Thanks in advance to any insight, Scott :) Quote Link to comment Share on other sites More sharing options...
Frosty Posted February 25, 2009 Share Posted February 25, 2009 Sorry, I'm starting to run several forge and burner threads together in my head and I didn't elaborate where I needed to. The problem with too much burner is back pressure. The EZ or any of Ron's burners is they are linear induction devices with a factory made max induction ratio of around 19:1. A neutral Air Propane ratio is 17.5:1 so when you build a linear yourself it's really difficult to get it to a neutral mix. There are tricks you don't see but they're there. The tricks don't make a lot of difference, they'll you get sufficient heat but they have some consequences. One of the consequences is sensitivity to back pressure or stray breezes over the intake. They can be tuned to give a neutral burn into excessive back pressure but they won't develop the potential heat they should. Just too much resistance to get enough fuel and air into the chamber. I hope that's a little more clear. Frosty Quote Link to comment Share on other sites More sharing options...
Dodge Posted February 25, 2009 Share Posted February 25, 2009 so too many burners or too small a chamber = too much back pressure? Could you not turn off one burner or run both at a lower rate to overcome this? Reason I ask is I plan on also making a new forge, correcting my heat sink problem but maintaining about the same sized chamber, pehaps a little bigger, but I don't want to make the same mistake again. I have considered other burner types such as the Larry Zoeller side arm(?) but these seemed to work so well off the bench, I wanted to reuse. Thanks again for your input, and my apologies for taking over the thread, Krisfaeth. I assume you will benefit from the dialog if your still following ;) Quote Link to comment Share on other sites More sharing options...
Frosty Posted February 26, 2009 Share Posted February 26, 2009 First off we're talking about burners and forges so you aren't taking anything over by asking good questions. These will just be questions others won't have to ask. Yes, too many burners in too small a volume = detrimental back pressure. Typically turning the psi down means weaker induction so NO, that isn't likely to work. LIKELY being the operative word your forge may be close enough to range that it will work, so give it a shot, can't hurt to try. Running a single burner might do the trick though. If the chamber is too large for a single burner you can reduce volume by taking up space with a couple fire bricks or a piece of kiln shelf across the bottom. The problem with this working however is the heat sink of all that hard refractory liner so I doubt it'll do the trick. Again, it can't hurt to try. If you take 1" off the ID of the liner you'll probably be right on the money volume wise and the problem will solve itself. I always recommend an ejector (Sidearm, Porter, Rex, my "T", etc.) type burner over a linear. A factory made ejector has an induction ratio of around 29:1 so there is a LOT of leeway to get a home made burner to operate in the 17.5:1 neutral burn range of air : propane. This means a Sidearm, Porter, Rex, etc. are all running at about 60% efficiency, it makes them very easy to tune. Another benefit of the ejector type is they are much more robust inducers and are much less susceptible to back pressure, stray breezes, etc. You might get away with just turning an ejector type down but my gut says if it wouldn't overcome the back pressure at throttle turning it down probably won't do it either. So, in short. Match the number and or size of your burners to the volume and shape of your forge. This is as easy as a little math and maybe a sketch or two. This will pay off big time, as it stands you like the size of your forge but it doesn't get hot enough but making it a little bigger will let the burners breath and it'll ROCK. Sometimes bigger IS better. If you make your forge the same dia, make it longer to meet the Burner : Volume ratio and space your burners to heat it evenly. Insulate it. Use Sidearms, Porters, Rex's, etc. if you have or want to build them, they're just more efficient and less sensitive to outside influences. That should do it for you. Frosty Quote Link to comment Share on other sites More sharing options...
viktorkrupp Posted February 26, 2009 Share Posted February 26, 2009 (edited) Hi Guys been lurking for a while reading all the info I can get my hands on, as not to ask too dumb a question. I started out making a few knives, now I spend about all my free time building tools to build other stuff. I'm sure you can relate. Onto the ? I built a forge it is square 13"w x12d x9 h (ill attach a pic when I find my camera cord). I started out lining it with firebrick (soft) and with a hard firebrick floor. The burners come straight down. I was modeling it off of the diamondback ironworks forge. The dimensions were off slightly because I can't weld very well (1st welding project) and I didn't take the overlap of the metal into account when building the forge. Also I was having issues with my burners because I couldn't find the right pipe fittings for my sidearm burner (and didn't want to wait for an online order). I decided to cast the flares out of refractory cement, and as luck would have it, I talked the guy at the supplier out of a free bag of Harbison Walker castable refractory (and some refractory boards that look like wooly Styrofoam) and went apes**t lining the forge with it. I left the interior volume shaped lie a side view of a football. I used the whole bag! My burners are humming along now that I got all the right parts, but welding heat is hit or miss so I have TOO much refractory in the forge? Could I chip away some of the castable or use the board to make it more efficient? All in all I learned that it's best not to reinvent the wheel, but it was 140 bucks for a box of koawool and I got all this for free! Fosty, I read about your T burners and haven’t been able to find a drawing on the site I’d love to see how you build them! Sorry for the long post, but I’ve been building it up for a while! Vik Edited February 26, 2009 by viktorkrupp Quote Link to comment Share on other sites More sharing options...
Grant Posted February 26, 2009 Share Posted February 26, 2009 (edited) Fosty, I read about your T burners and haven’t been able to find a drawing on the site I’d love to see how you build them! Victor, I will but in here. This thread is the most comprehensive about Frosty's "T" jet burner. http://www.iforgeiron.com/forum/f7/small-gas-forges-1945/ With a final piece in http://www.iforgeiron.com/forum/f7/gas-forge-9680/ post #5 grant Edited February 26, 2009 by Grant Quote Link to comment Share on other sites More sharing options...
Frosty Posted February 26, 2009 Share Posted February 26, 2009 First of all, Welcome to the bunch Viktor, glad to have you. If you'll click "User CP" at the top of the page and edit your profile to show your location you'll discover the guys living close enough to lend a hand directly, tip you to tool deals, invite you to get togethers, etc. Without know what the inside volume of your forge is it's hard to say if you have enough burner. Building it with a football shaped interior makes it even harder though I suppose you could fill it with styrofoam peanuts or something similar and then measure the volume in a box or bucket or some such. I hope I don't have to say do this when the forge is cold? However, from your description I'd say too much refractory is making an overwhelming heat sink. At this point you might be further ahead building another one rather than trying to chisel enough refractory out of this one to correct it. ESPECIALLY if outside the castable refractory there is a layer of firebrick, even soft brick. On the other hand if you have or can borrow a hammer drill it will really speed the process up. Be careful though refractory often does not react kindly to mistreatment like drilling, chiseling, hammering and such, there's a chance of it breaking up. I know how it is to get a freebie, my refractory supplier is the same way. I always end up with extras when I buy, rems of Kaowool from their fab operation, chipped and broken fire brick, broken bags of refractory, etc. On top of that I've NEVER paid retail. It gets even better, they're into fire and I mean IN TO FIRE, the hotter the better. We've sat and shot the breeze about forges, burners, various refractories, coatings, etc. etc. Great bunch of guys. The real trick though is remembering that just because it was free I do NOT have to use it all right now. One bag of castable is typically more than enough to line several forges. Old style un-insulated pipe forges with a hard refractory liner like Missou (an excellent refractory by the way) typically have 3/4 - 1" liners. It's enough to protect the pipe from the fire and "insulates" well enough to get to welding heat with enough burner driving it. I've attached a concept drawing of the "T" burner. There are no dimensions on it but I've listed the ratios it's designed around in a post yesterday. Making these will take some improvisation on your part, in fitting the mig tip jet. When I built the last batch I found some brass fittings that made it a lot easier. Some 1/2" MPT - 1/4" flare fittings have through holes just right or small enough to chase and tap 1/4"-28 for a mig tip. You need to take the drill bit necessary for the tap with you to the plumbing shop and go through the bin to find fittings with small enough through holes. It is WORTH the effort though. Oh yeah, no such thing as a dumb question. . . Well, unless you're TRYING to be a smart@$$ of course. Frosty Quote Link to comment Share on other sites More sharing options...
viktorkrupp Posted February 26, 2009 Share Posted February 26, 2009 Thanks for the replies. Found the camera cable, here is the inside of the forge i built using the castable refractory. Also attached is a picture of the ceiling of the forge. The last picture is from the back side of the forge. Not sure what the board IS since i got it free, but I'm thinking I might remove the castable at least from the floor and walls and reline using the board, then soft firebrick inside that. I like the square shape because i can make the chamber a variety of sizes. Quote Link to comment Share on other sites More sharing options...
Frosty Posted February 26, 2009 Share Posted February 26, 2009 I can't tell from looking what the board is, the stuff comes in a wide range of temp ratings. You'll need to test a piece. What I'd do is get rid of the castable refractory completely and just move the sidewalls in to make the chamber smaller. That would make yours similar to my main forge in the ability to change it's volume. Frosty Quote Link to comment Share on other sites More sharing options...
Dodge Posted February 26, 2009 Share Posted February 26, 2009 One more note about what I'm using. I said Reil "type" but they actually have an injector modification. As the drawing shows, this design was by a man named Jack Davis from Oregon I believe) in '01. 'A Shout out to Jack, where ever you are ' Haven't heard (from him since shortly after he gave me the drawing ... Anyway, I put the chokes on mine but have never seemed to need them. They seem to run the best wide open but choked a bit (carburized?) may reduce scale a little. Dunno, I never tested the theory. I tend not to mess with success. LOL I built them and aside from changing to a smaller jet, they worked right off the bench. I just need to adjust my chamber size it seems:) Quote Link to comment Share on other sites More sharing options...
viktorkrupp Posted February 27, 2009 Share Posted February 27, 2009 That's quite the burner Dodge, good thing I didn't see that before I built mine or I'd have something else to troubleshoot! I have several burners in various stages of experimentation. Sometimes making your tools is half the fun. That's why I like smithing not gardening! I guess most of us were the kids who took apart their toys! Frosty, how would you test the board? Just try to heat it until it dissolves? I think I'm going to bite the bullet and buy some wool and a ceramic floorboard. Hate to waste all that castable. I might "repurpose" that forge into a heat treating furnace for knives and build another one. VK Quote Link to comment Share on other sites More sharing options...
Frosty Posted February 27, 2009 Share Posted February 27, 2009 (edited) Dodge: There are two types of inducer suitable for adapting to a propane burner. The linear inducer and the ejector inducer. Ron Reil likes linear inducers so when you refer to a Reil type burner you are talking about a linear. What Mike Porter, Rex, Sidearm and I have are ejector type inducers. To tell the difference just look straight up the bore, if you're looking out the end or at a choke plate it's a "linear", meaning the air (or induced media) intake is in line with the jet and burner tube. An ejector's air (or whatever) intake(s) are at 90* to the jet and tube. Yours is an ejector type burner. (not Injector) You can probably increase air induction by bringing your mig tip back about 1/2" out of the throat. As drawn it's actually inside the throat. Viktor: I'd test the board by putting a small piece in my forge and see what happens. If I can take it to incandescent yellow without it showing signs of melting then it's probably okay for a forge. Frosty Edited February 27, 2009 by Frosty Quote Link to comment Share on other sites More sharing options...
Dodge Posted February 27, 2009 Share Posted February 27, 2009 Thanks again Frosty. Admittedly, I never have tried adjusting tube placement. They worked good and messing with the airflow via the choke seemed futile so I just ran them. Might have to re-visit the R&D phase when I build the new shell :D Quote Link to comment Share on other sites More sharing options...
viktorkrupp Posted February 28, 2009 Share Posted February 28, 2009 Following Frosty's advice I removed the THICK layer of castable refractory, although I kept the refractory ceiling, since my burner flares are cast into it. It is also relatively thin at @1.5" going to about 2" at the front and back. I called my supplier and verified that the material I have is 2600HA Insboard. I cut the board to fit in the sides and floor of the forge, then placed soft firebrick over that. I will replace the floor with either hard brick or ceramic refractory when I decide to weld. It is really easy to reconfigure the interior. I also closed off the back of the forge with a removable piece of the Insboard, with small venting openings at the bottom to allow ventilation. I can close it completely if I want. The front of the forge has sufficient opening though, and I like to have a hotter zone in the back of the forge. I am wondering if I can coat the Insboard with a coating such as ITC of FiberFrax to improve the efficiency further? Now my forge gets hot MUCH faster, and reaches higher heat. I reached a bright glowing yellow. Looking into the forge, I cannot differentiate any of the lines between the bricks it is blinding! I checked the temps, and at 5psi I was at 2100 F and at 9psi I was at @2500 although I cannot be sure of the actual temp because my thermocouple only goes to 2500F. 2000F was about the high temp with the thick castable floor. Here are some pics of the new config. Quote Link to comment Share on other sites More sharing options...
Frosty Posted February 28, 2009 Share Posted February 28, 2009 Sounds like you got it working right, 2,500 is more than enough to weld. Congratulations. Frosty Quote Link to comment Share on other sites More sharing options...
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