supraboy82 Posted May 28, 2023 Share Posted May 28, 2023 I have got a 12” piece of carbon steel pipe that’s about 3 foot long I also have an entire roll full box of 2” insuwool they were both free from work I am wanting to build a 2 burner forge is the pipe going to be too big to use am I going to waste a lot of propane. I realize I will have to shorten the pipe which I am prepared to do. I just need to know how long of a piece I should cut off it Quote Link to comment Share on other sites More sharing options...
Frosty Posted May 28, 2023 Share Posted May 28, 2023 Welcome aboard supraboy, glad to have you. 12" ID pipe is a good size, 2" of insulwool and maybe 3/8" hard castable refractory and a kiln wash gives you a forge a bit over 7" ID. two well tuned 3/4" naturally aspirated burners will reliably bring 600-700 cu/in to welding temperature. That adds up to a nice size forge. Frosty The Lucky. Quote Link to comment Share on other sites More sharing options...
supraboy82 Posted May 28, 2023 Author Share Posted May 28, 2023 How long should I make it frosty and thank you for the welcome Quote Link to comment Share on other sites More sharing options...
Frosty Posted May 28, 2023 Share Posted May 28, 2023 Sorry, I don't do basic arithmetic for people anymore. Calculate the area of the as lined ID (Inside Diameter) in inches and divide by the target volume you like. Take a look at Mikey's thermal baffles for efficient and effective doorway closures. Frosty The Lucky. Quote Link to comment Share on other sites More sharing options...
supraboy82 Posted May 28, 2023 Author Share Posted May 28, 2023 Problem is I have no preference I was merely looking for suggestions. As I am brand new to this Quote Link to comment Share on other sites More sharing options...
Frosty Posted May 28, 2023 Share Posted May 28, 2023 Either volume is well within the 2 burner range and at that ID workable lengths. Pick one, flip a coin even, the length isn't a big deal. Either will be longer than necessary. Frosty The Lucky. Quote Link to comment Share on other sites More sharing options...
supraboy82 Posted May 28, 2023 Author Share Posted May 28, 2023 So I figured 15 inches long which makes it 735 cubic inches if I did that right Quote Link to comment Share on other sites More sharing options...
Frosty Posted May 28, 2023 Share Posted May 28, 2023 You might squeeze enough energy from two burners to drive 735 cu/in but it's a bit over the high end. A common beginner mistake is building too large a forge, most of us who've been doing this a while have oversized forges collecting dust somewhere. Heck, my current shop forge is crazy too large and it was purpose built to be what it is. I've only used more than 25% capacity when there were several guys in the shop at once. Something to know about steel is it doesn't like spending much time at high temperature without being worked. In our case forged. At high temps the steel begins to form crystals commonly called grain because it looks like grains of sugar. Crystal boundaries are the problem, every connection is a weak point and the larger the crystal boundaries the larger and more numerous the weak spots. What's that have to do with forge size? Well, you can only realistically hand work between 4-6" of stock at a time so heating more causes grain growth and the other factor of high temp steel, decarb. Meaning the carbon in the steel burns on contact with oxygen at high temperature. Decarb is one cause of the patterns in pattern welded steel. Lastly there is scale loss. The hotter the steel the faster it oxidizes (rusts) which forms black scale which falls off reducing your work every time you remove it from the fire. After all that the short story is make it smaller, I'd aim for the 600 cu/in length. It will still heat too much length except for special occasions and it will be a HOTTER forge so you won't need to burn as much propane. Frosty The Lucky. Quote Link to comment Share on other sites More sharing options...
Mikey98118 Posted May 28, 2023 Share Posted May 28, 2023 Very well put, Frosty. How many do think will listen and learn, the easy way? Quote Link to comment Share on other sites More sharing options...
Irondragon Forge ClayWorks Posted May 28, 2023 Share Posted May 28, 2023 I did when we built our forge with y'all s help. It is still running just fine and the interior is 430 Cubic inches. If anyone is interested in our build here is a link to it. Some of the pictures were lost when Photo-bucket/ Tiny Pic decided to kill the picture hosting site. 20 pound propane tank forge in progress - Gas Forges - I Forge Iron Quote Link to comment Share on other sites More sharing options...
Frosty Posted May 29, 2023 Share Posted May 29, 2023 Thanks Mike I have lots of experience talking about forge size and practicality. It's getting hard not to be short when new folk ask me to do the basic arithmetic for them but I have to remind myself what modern education is like. It's not their fault when they graduate high school and can't figure out how much carpet to buy, let alone how large an exhaust fan to put in the kitchen. Anyway, for every person who listens and learns, it's another person who can and will help others. Hopefully what we pass along will spread exponentially and some day we can just kick back and watch the action. It's getting that way with burners, I spend more time reading and absorbing than writing. I just hope I haven't scared supraboy off. Frosty The Lucky. Quote Link to comment Share on other sites More sharing options...
supraboy82 Posted May 29, 2023 Author Share Posted May 29, 2023 No not at all frosty I just was over thinking it as I do with everything. By my calculations if I major it 12” long I will have 588 cubic inches which should be plenty. And I appreciate the help and input. Quote Link to comment Share on other sites More sharing options...
Frosty Posted May 29, 2023 Share Posted May 29, 2023 Everybody overthinks a new craft, especially the tools and equipment. One of my base philosophies is, "It's better to have it and not need it than need it and not have it." I have yet to build a forge that wasn't larger than necessary. 588 cu/in and 12" is a a good size, you can always turn the burners down. Even make a baffle wall to close off the back half and run one burner. You're always welcome, it's my pleasure. Frosty The Lucky. Quote Link to comment Share on other sites More sharing options...
supraboy82 Posted May 29, 2023 Author Share Posted May 29, 2023 Should I run the burners in the 12 o’clock position or run them I. The 9 or 10 o clock position? Quote Link to comment Share on other sites More sharing options...
Irondragon Forge ClayWorks Posted May 29, 2023 Share Posted May 29, 2023 We ran ours at the 10 o'clock position, worked well with our Gaco-750 single burner. 12 o'clock will contribute to the heat running back up the burner port with the "chimney effect". In this picture the body of the forge is rotated clockwise a little making it look more like 11 o'clock. Quote Link to comment Share on other sites More sharing options...
Mikey98118 Posted May 30, 2023 Share Posted May 30, 2023 There is no such thing as perfect burner positioning. Really awful burner positioning is a different matter. All you really need to aim for (yuk, yuk) is to point your flame so that it creates swirl. Everything else is personal preference. Some of us (guilty as charged)want every teeny weensy advantage, and spend years majoring in the minors. Others just want to avoid major pitfalls and get on with hammering metal (sigh). You're all so practical... Quote Link to comment Share on other sites More sharing options...
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