Vegasheathen Posted December 3, 2024 Posted December 3, 2024 I recently acquired 2 air tanks to make forges out of my current single burner just isn't enough I have 1 tank that's 10" wide and 20" long and the other is 14" wide and 28" long the smaller of the 2 i was thinking setup as a 2 burner lined with 2" of kaowool then refractory cement and I was planning on cutting it at both ends on the weld seam and hinging both side to open or close as needed. Both ends I'll cut a 3" tall 6" wide slot to pass through anything that's longer. The bigger tank I'm not sure if I should do it as a 3 or 4 burner. But I'll line it the same way only thing I might change is in the bottom make a slot that has only 1" of kaowool and is the size of a fire brick so I have a low spot to put fire bricks in. If anyone knows of a good source for burners that would be great i was planning on ordering them from ebay or Amazon. Any input would be appreciated since this will be my first time building a forge my current one I got as a kit and just had to put rigidizer and refractory cement in. I added pics of the 2 tanks if it helps at all. Quote
Buzzkill Posted December 4, 2024 Posted December 4, 2024 What are you doing (or planning to do) that requires that much length? For me it's more important to have height and width to accommodate odd shaped pieces. Long pieces can pass through the back of the forge. I rarely need more than 6 to 10 inches of steel heated at a time, but you may be doing something entirely different than I do. As you've indicated, more length means more burners. More burners means more fuel cost - and possibly iced up propane tanks. To determine the number of burners you need to calculate what the forge chamber volume will be after adding all your insulation and refractory. You'll want one 3/4" (well built and tuned) naturally aspirated burner for every 350 cubic inches of volume you have in your forge. If you do install more than one naturally aspirated burner keep in mind that they can interfere with each other, especially if placed too close together. At the intake end they can compete for air if not oriented correctly, and on the flame end the back pressure from one can affect the performance of another. If you have some basic tools and shop skills you can build Frosty's T burners. That's probably the best bang for the buck. Of course it helps that you can discuss any problems you have with the guy who designed the burner here on this site. Here's the link to the topic that has the plans: https://www.iforgeiron.com/topic/43976-t-burner-illustrated-directions/ I don't have any experience purchasing burners off the internet, but maybe someone else here can chime in. Quote
JHCC Posted December 4, 2024 Posted December 4, 2024 To follow up on what Buzzkill says (all of which I agree with), you might consider cutting down the larger tank to make the shell of a D-tunnel forge. Cut 2-1/2" from each end (these will become the doors), and then cut an 11" length of the center (this will be the main body of the forge). Line each door with 2" of ceramic wool (two 1" layers are easier to rigidize) and 1/2" of kastolite or the equivalent. You can either cut the main body to 9-1/2" high or add a shelf on the inside to create the appropriate height, and then line the body in the same way as the doors. This will give you a semicircular tunnel that's 9" wide, 4-1/2" high, and 11" long, which is almost exactly 350 cubic inches. (Drawing not to scale. Also, ignore the letters in the lower left corner; that was from something entirely unrelated.) Quote
Latticino Posted December 4, 2024 Posted December 4, 2024 I used the same, smaller, air tank when I constructed my most recent forge. I cut enough length out of it so the internal length after insulation is on the order of 12" and wish I had removed more length. The only time I use the full length is when heating for long tapers under the power hammer or twists. More often I wish the forge was shorter so I didn't heat all the stock since I can't work effectively on more than around 6" of length at a time (and constant heating to forging temperatures can lead to decarb in the primarily blade work I do). I have a single forced air/Natural Gas burner on mine and it gets up to welding temperatures just fine. Another possibility is to orient the tank vertically and make door openings in the side. Don Fogg was a big fan of this type of forge. I've used on like this and it certainly works well since you can have the burner set in the "lower" section without direct impingement on your stock, but the drawback is that there is no real floor to set the stock down on that you can access easily. Quote
Mikey98118 Posted December 4, 2024 Posted December 4, 2024 I agree with what all three have said. The only advice I would change is about "D" versus "tunnel" forges. While air tanks usually provide a natural choice as shells (bodies) for tunnel forges, and while all of us have been inclined to slice off the bottom of an air tank, or propane cylinder, when making a "D" forge, it is time that we all to stop, and ask ourselves why? It is easier to add a little more insulation in the bottom of a tube shape, raising up the resulting "floor," than to go through all the trouble to change the shape of the shell. Since this extra insulation can be thought of as tertiary, something cheap, such as Perlite can be used for it, with better insulation on top of this bottom layer There are only two sources for acceptable commercial burners, at present. The expensive source is Chile Forge, and they only sell 1" burners. The only cheap source for acceptable burners is Larry Zoeller Forge. You would like his "Z" burners. As to all the "also ran" junk burners for sale online, none of them has a designer behind them; they are all a collection of stolen ideas slapped together by fast buck artists; the problem with them, is that some of those ideas, were just plain wrong to begine with, while others don't work together; you know; kind of like mismatched socks In fact, you could buy a Diamondback forge, just to steal its burners, and be way ahead of the deal, as compared to buying an eBay burner. Finally, it seems odd to me that so many guys shy away from building sure and simple Frosty "T" burners, while planning on building a gas forge, which is quite a bit more work and expense. Quote
JHCC Posted December 4, 2024 Posted December 4, 2024 1 hour ago, Mikey98118 said: slice off the bottom of an air tank, or propane cylinder, [...] It is easier to add a little more insulation in the bottom of a tube shape, raising up the resulting "floor," Hence the suggestion of adding an interior shelf, although perlite fill would work just fine. Quote
Irondragon Forge ClayWorks Posted December 5, 2024 Posted December 5, 2024 That is what we did with our propane tank forge. We made it into a D interior by adding more refractory and bubble alumina. We also used a kiln burner Gaco 750 and it works just fine in our forge after drilling the orifice. If you want to look at that burner you will have to google it as we are not allowed to put in live links to commercial sites. I can't control the wind, all I can do is adjust my sail’s.~ Semper Paratus Quote
Vegasheathen Posted December 7, 2024 Author Posted December 7, 2024 I make knives and do basic blacksmithing most of the steel i use for knives is scrap steel almost always coil or leef springs. I do like the idea of cutting the larger one into a D that's kinda why id had the idea of putting fire bricks in the bottom that and there cheap and easy to replace. The place i was looking at for burners and other forge building supplies on ebay and i think Amazon there's a shop called Simond store that I've been looking at for stuff I honestly have no idea if the burners they have are any good, they do have kaowool and there refractory cement and rigidizer does seem to be quality. Wich I should definitely look into the frosty t burners the 2 people I know who have made burners 1 is dead and the other might as well be. I'd helped make burners for a large BBQ when I worked at a sheet metal shop but that was nothing like this. I do like the idea of on the front side using fire bricks on a track to close off the opening. Quote
Mikey98118 Posted December 8, 2024 Posted December 8, 2024 I think the stuff from the Simond store on Amazon.com is consistently overpriced. However, to each his own. Quote
Frosty Posted December 19, 2024 Posted December 19, 2024 Why do you want such huge forges? Heating more than about 6" which is about all a person can work by hand in one heat damages the stock that isn't worked. The hammer refines the crystal structure (grain) of the steel it otherwise causes enlarged crystals and the boundaries between crystals are inherent failure points. Unless you're twisting or bending long lengths heating more than 6" is not a good thing. Heat treating long sections or twisting can be done easily and more precisely by passing the stock or blade back and forth through the fire. If you're using old spring stock to make blades you're already increasing the probability of failing either in the heat treat or in use. A catastrophic blade failure in use can cause SERIOUS injury and the maker could be on the hook. Don't put firebricks in your forge, hard fire brick tends to dissolve when molten forge welding flux lands on it and things like hot scale, bits of glass, etc. stick pretty much permanently. There are much better ways to "line" a forge floor with easily changeable sacrificial materials. Refractory "Cement" is for sticking masonry together in fire places, and is NOT intended or formulated to survive direct propane flame contact. My advice in general is to hit a propane dealer and pick up an old 20lb. propane tank then follow the directions you can find in the "Propane forge" section of Iforgeiron. Same for the burners I posted the plans for a T burner in the propane burner sub section years ago. There have been some minor changes I haven't updated but they're just build changes rather than changes to the burner itself. Frosty The Lucky. Quote
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