hans138 Posted December 19, 2011 Share Posted December 19, 2011 HI guys Im new hear and was hoping some of you wise individuals could shine some light on a subject for me. i just bought a johnson ng heat treating forge {model # 120 }. its also good for small forging. now i would like to know if any body here has any expiriance with one. if so please enlighten me. i wanted something bigger but i looked it up at the johnson web site and its 6000$ new!!!! i paid 250 so i had to have it. can i forge weld with it, any other info i can get. like maybe converting it to lp? here is a pic its the one on the right, and it doesnt have the box thing on the right of it. what is that btw? also it puts out 90kbtu/hour and gets to 2300degrees Quote Link to comment Share on other sites More sharing options...
Rich Hale Posted December 19, 2011 Share Posted December 19, 2011 2300 degrees will forge weld. Whether you can do it right off is up to you. Kind of kidding as I couild not forge weld until I learned and then It was odd wondering how it took so long to learn when it seems so easy now. You need to get in a group and get some help learning. It is really tough to read how and then be able to do it. Groups or individual instruction shorten the learning curve. Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted December 19, 2011 Share Posted December 19, 2011 The "box thing" is the "engine" of this forge. It contains the mixer and blower for the gas/air and would be where you change the orifice to convert it from NG to LP. I used to have two for mine but traded the extra off several years ago; sorry. Quote Link to comment Share on other sites More sharing options...
hans138 Posted December 19, 2011 Author Share Posted December 19, 2011 cool thanks guys, well thats probably why i got it for 250 huh? well it has a valve where the gas comes in and a variable speed fan, and its all connected together rather competently (at least as far as i can tell) , but where in this type of set up where do you guys think i would find this gas orifice, i was under the impression that a forced air didnt really have a burner like on a venturi style. but instead the gas and air would mix in the intake line and and cause hot stuff to come out in the forge! im pretty new here as you can tell so let me know how right or wrong i am thanks Hans Quote Link to comment Share on other sites More sharing options...
Nakedanvil - Grant Sarver Posted December 19, 2011 Share Posted December 19, 2011 I believe that what you need with the newer model is a low pressure regulator. They used to just use a simple orifice just to limit the amount of gas you can let in. I've had the old ones hooked up to high pressure gas and could send flames 20 feet high! Check with Johnson, they'll be happy to help you. Quote Link to comment Share on other sites More sharing options...
hans138 Posted December 20, 2011 Author Share Posted December 20, 2011 well ill be sure check check very DEEEEEP into it, im talking Marianas trench deep. i definally feel confident that the guy i got it from was really using it 2 months prior to my purchase but ca you ever really trust a stranger trying to sell you something??? on craigslist to boot? it has a 1/30hp continuous cycle blower on it, witch im used to coal forges so that sees waaay underpowerd comparatively. even compared to the gas forge i had access to at the school where i took a semester of smithing classes. would you guys have a moment to look a some detailed pic i put up tomorrow of the whole rig.?? im in no hurry to blow my self up so take any time you need grant, and any other who have a few cents to add. Thanks Hans Quote Link to comment Share on other sites More sharing options...
Nakedanvil - Grant Sarver Posted December 20, 2011 Share Posted December 20, 2011 Their blowers are perfect for their forges. I used one on a small home-built too, they put out a lot of air. Quote Link to comment Share on other sites More sharing options...
hans138 Posted December 20, 2011 Author Share Posted December 20, 2011 would you know any thing about sng, aka lng. its a synthetic liquid natural gas that can b put in propane style tanks. would that be a good option so i dont have to mess with converting to propane? p.s. grant you have been a really good help. this is my first day on here and i feel like im getting somewhere Quote Link to comment Share on other sites More sharing options...
s meyer Posted December 20, 2011 Share Posted December 20, 2011 Hi I have a 121 witch I beleve is the same forge. Mine hase a low presure ( 1.5 lb ) lp regulator. Mine was set up for natral gas when I got it and I orderd the lp orface frum johnson.The orfice should be in line after the fan. The fan is plenty big. I almost always run mine with the fan half choked or less You can forge weld no problem in them but the flux will eat up your linning. and the fire brick linning isn't as easy to change as other forges. They are pritt good forges exept limitted in that you can't put things all the way through. They also are cinda gas hogs but are veary controlable. I use mine for heat treating for this reason. Steve Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted December 20, 2011 Share Posted December 20, 2011 OK so it sounds like yours has been retrofitted to work without the box. Good. It still has an orifice where the gas is introduced to the air stream and currently that is the wrong size for the gas you want to use. LP uses a *smaller* orifice than NG as it's a "denser" fuel and so you need less of it per unit of air to get the proper mix. Last time I converted a system from NG to LP I just took the orifice to the local Gas place and they silver soldered the old orifice closed and re-drilled the proper size for the new. If you can source an orifice the proper size for not too much money it might be nice to have *both* sizes to hand in case you move or sell the forge. It is interesting to note that Johnson's are quite expensive new and much cheaper on the used market. I picked up mine quite cheaply at a school shop auction, ($40; but next time the dealers were buying them at $100) I think they cater to the PO market and places where liability is of great concern. Your price is not a bad one for a unit in good working order these days. They do have a reputation for being a gas hog though. You will probably need to learn to "tune it" Generally I adjust the gas air mixture till I get the noisiest burn and then tweak it for my intended use. (For heat treating I often go a bit reducing) Quote Link to comment Share on other sites More sharing options...
hans138 Posted December 20, 2011 Author Share Posted December 20, 2011 thanks you guys have been a big help! Quote Link to comment Share on other sites More sharing options...
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