Derek H Posted December 4, 2012 Share Posted December 4, 2012 Hello everyone, I am new on here but have been visiting the sight for several week researching gas forges. I have finally decided to dive in and build my own. The forge I plane to build is going to 8” inner diameter and about 16” long. It is going to be made from an old air compressor tank with 2 or 3 inches of durablanket and sealed with a cast able refractory. I am planning to heat the forge with a single 1” “t-rex” style burner that I am currently in the middle of building. My question is, will a single one inch burner be enough to get the forge to welding heat or would two ¾” burners be a better option. I will post pictures as the build progresses, but it will most likely be after Christmas. In order to get my wife to agree to let me buy the refractory I told her it was my Christmas present and she is refusing to let me have it until then. Lol. We have only been married 6 months and life is good!!! PS: I found my 2,300 degree 1" thick durablanket for $1 per squar foot from Porter-Warner Industries. They also have 3,000 degree castable for $23 for a 55 pound bag. Quote Link to comment Share on other sites More sharing options...
jcornell Posted December 5, 2012 Share Posted December 5, 2012 Assuming that 8" is the inner diameter _after_ you install the insulation, you're looking at 804 cubic inches. The rule of thumb for the 3/4" Reil style burners (which aren't quite as efficient as the T-Rex) is one burner for every 350 cubic inches of volume. My not-so-humble opinion is that if you're just starting out, this forge is too big, and it's certainly too big for two 3/4' inch Reil style burners. I don't have any personal experience with the T-Rex burners, although they're supposed to be a bit more robust. The company says that one 3/4" T-rex can replace two 3/4" Reil style burners, but I have no way of confirming that. There are all sorts of ways of making the space adjustable (make it shorter, make it longer) but I think you might want to build a smaller forge first to get the experience and then build a second (third, fourth) forge when you have projects that really need it. Quote Link to comment Share on other sites More sharing options...
Derek H Posted December 5, 2012 Author Share Posted December 5, 2012 Thanks for the input. I was looking at it again last night and I think that I can cut the size by as much as half and it still be big enough to do almost everything that i would ever want to do. Especially if I add a small door to the back, as has been suggested on other threads, to pass longer pieces through. Quote Link to comment Share on other sites More sharing options...
C.D. Mitchell Posted December 5, 2012 Share Posted December 5, 2012 I would cut it down to 12 inches in length. Not only will that make your chamber smaller, but it also allows the most efficient use of your insulating blanket. That stuff typically comes in a 24 inch wide roll, so having a 12 inch long forge body allows you to simply cut the roll in half which leaves no material to waste. Then you can add doors or bricks to cover the openings and you're set. If your body is 8 inches I.D. without the blanket in it, that will leave you with a 4 inch I.D. forge chamber once the blanket is in. A 3/4 inch burner would definitely heat up a 4x12 round chamber, and a 1 inch would make it searingly hot...not a bad thing. Just remember that a 1 inch burner will use about twice the amount of fuel as a 3/4 inch, so if you can adequately heat your forge with a 3/4 inch it will save you fuel in the long run. Keep asking questions if you have them. I've built two forges, a large square one and a small round one, and I'd be happy to offer an advice/lessons that I've learned in the process of building them. And congratulations on being newly married! My wife and I just celebrated our 4 month wedding anniversary yesterday. Life together is definitely better than life alone. Just make sure that your new hobby doesn't take priority over your wife...giving our wives the attention, love, and care they deserve usually results in a much happier life for everyone. Quote Link to comment Share on other sites More sharing options...
Derek H Posted December 5, 2012 Author Share Posted December 5, 2012 Thank Wolverine, and congradulations to you too. I will deffinatly take fuel consumption into account. I think I am going to go ahead and finish the 1" burner since a already have the parts and build a 3/4" burner as well. That way i can change them out if I ever need the forge hotter or cooler. After all they only cost about $20 and a little time to build. Quote Link to comment Share on other sites More sharing options...
C.D. Mitchell Posted December 6, 2012 Share Posted December 6, 2012 That's exactly what I did. If I really want to torch something I'll break out the one inch, but for normal use I just use a 3/4. I can get over 12 hours of forge time out of a 20lb propane tank with a 3/4 inch burner. Have you looked into the Mongo style burners that Rupert Wennig designed? The first burner I built was a Ron Reil EZ burner, but since finding the mongo burner design I've started using those. They're easier and cheaper to make, more adjustable, and more effiecient. I've built both 1" and 3/4" versions and they both work great. Here's a link to the design: http://ronreil.abana.org/Minimongo.jpg These plans are for a 1" burner, but as long as you adjust your measurements and sizes proportionally you can build any size burner with this design. Keep up the good work on the forge! I've found that taking the extra time to do things right is usually worth it...but it's hard not to rush when you want to get to pounding steel! Quote Link to comment Share on other sites More sharing options...
Derek H Posted December 6, 2012 Author Share Posted December 6, 2012 I am building a slightly modified version of the mongo burner. I am adding a sliding collar to adjust the airflow. I am also using slots instead of simple holes and adding a cone to help hold the flame. I know that if you make a burner to short it will not function properly. But is their a limit on how long it can be or is it better to make a longer tube to give the gas more time to mix? Im sure this has probably been discussed somewhere else on here but I cannot find it. Quote Link to comment Share on other sites More sharing options...
Derek H Posted December 6, 2012 Author Share Posted December 6, 2012 Also take a look at the idea i posted on the ""venturi" burners". One of the guys suggested some burner experiments and I was wondering if it would helpful to / appreciated by the other people on here? Quote Link to comment Share on other sites More sharing options...
Frosty Posted December 7, 2012 Share Posted December 7, 2012 Welcome aboard Derek, glad to have you. A single 1" burner in a 8" dia. x 16" forge chamber will make for uneven heat. also, 800cu/in is a bit more than a single 1" burner is really good for. Sure it'll get to welding heat under the burner but the rest of the chamber is going to be doing well to get to high orange. Burner output in direct relation to the cross sectional area of the burner tube, so yes two 3/4" burners have the same output as one 1" burner of the same type. Rex Price builds ejector type inducer burners while a Reil is a linear inducer. Ejectors are for some reason I don't understand about 25-30% more efficient though that doesn't quite equate to 25-30% more heat. Inducer efficiency is in several categories, mostly in ow powerfully they induce. "Induce" for an induction device means to draw in for a burner that's the combustion air it's drawing in. The more robust the induction the less likely stray breezes or back pressure are to disrupt the flame. The difference in efficiency makes a 3/4" linear burner like Ron's good for about 300 cu/in to welding heat where an ejector burner like a "Sidearm," a "Porter" (about the same thing as a Rex) or the "T" burners I make are generally good for 350cu/in. My recommendation for you goal as stated so far I suggest shortening the chamber about 3" and using two 3/4" ejector Rex burners aligned to produce a vortex and aimed slightly towards the center of the chamber. Oh yeah, fuel consumption is a factor of BTU output and has no relation to what kind of burner you use, be it a linear, an ejector or gun. (blown) Burner efficiency does have effect on how fast it heats, how stable the fire is, loudness and such. Using 2" of insulation and a hard refractory for your liner will have more effect on fuel consumption and speed than many other factors. I generally advise folk to buy a phosphate bonded or high phosphate hard refractory for flux resistance though a hearty coating of ITC-100 really helps. A high silica refractory is very caustic susceptible and borax at 2,000f+ is REALLY caustic, it'll etch glass. Don't try etching glass with vaporized borax though glass doesn't like being that hot. Frosty The Lucky. Quote Link to comment Share on other sites More sharing options...
Derek H Posted January 6, 2013 Author Share Posted January 6, 2013 Well I finally got my forge finished after Christmas. Here are some pictures of the finished product. I am very happy with its performance right out of the box. Let me know what you think. Quote Link to comment Share on other sites More sharing options...
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