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JohnK

Neat little oil forge blower

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OK so I've been experimenting with quite a few different oil forge design's and I believe I've found about the best so far. First what I notice on many sites and YouTube <_< videos is generally the same sketchy thing over and over, none are shown actually powering a forge. From experience I can say most won't work in a forge, mainly due to back pressure. Secondly most are quite large and have multiple flame holders. That's a hazard all in itself. So I thought why not give it that much needed flame holder but put it to work instead! Also see just how small I can make this thing. Presently I'm using a small propane bottle 3"x10". This was another test to see if the design would work. Indeed it does! :D however if anyone intends to build it I'd strongly recommend a thicker steel tube (say 1/4"+) and around 3"-4" in diameter. And possibly thick threaded collars welded to the burn chamber for intake and 2 exhaust tubes as they will eventually degrade and need replacing. If there's any questions or suggestions I'll happily answer. Currently I'm testing efficiency. And while I'm not sure if it'll weld I know it easily maintains forging temps. I probably need a better air supply. 

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32oz lasted for 40 minutes. That equates to a gallon running for 2.6 hours at forging temperature. Fuel mix: 2parts waste engine oil, 1part diesel, 1part gasoline. 

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Do you get any carbon build up from the flame? 

We used to have a waste oil heater in one workshop I worked in we had to de coke it at least once a week! 

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Indeed it does(well provide carbon) @Martin Tiney. Luckily no carbon buildup. Generally a little soot layer when running a caburizing flame. It can run neutral or reducing but I always let it run a little over so I don't get carbon loss. The tank and exhaust runs to hot to allow buildup and the interior of the forge has nowhere for it to cling(it's clay). The only downside I've seen is that the oil does need mixing with gas because of the small size and how thin the metal is. A thicker chamber should omit the need once hot.

Edited by JohnK

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Refractory mix: a guesstimate. 10 parts drywall compound. 2 parts white latex paint. 5 parts plain sandless clay.??. I'm not sure just a guess. Seems to work well and I only used it as a sealant for my forge. But it seems to hold quite well. I used what I had. I'll keep updating as I improve. 

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Turns out nearly anything roughly that size will do. However this being quite thin the efficiency has been reduced. 

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Update. Seems 3x10 is good. Thicker metal is still advised. Brings steel to bright yellow. Chamber itself remains dull red to black. 

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Blower design.png

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Have you fitted a restriction to atomise the fuel going through, or is the only form of regulation the tap on the fuel supply? 

 I do like the simplicity of this build and I shall give it a try as I have an almost endless supply of waste oil and waste fuel from my place of work.

   

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It's a plain ole drip feed with the fuel outlet near the end of the intake tube/tank joint. It doesn't atomize the fuel but it does turbulate? It. Is very simple and reliable method. Intended to be simple so anyone can build it. I'll try to make a better schematic later. The fuel in is about an inch from the tank end of the air intake tube. I doubt it's important. Keep in mind the chamber must be hot before the addition of just oil. I use gasoline but propane should work just fine. 

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Thanks, I look forward to seeing the schematics 

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I may have missed something. I apologize about spelling.

Blower design detailed.png

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Addendum. If 6"ID or greater chamber is used id suggest shorter length, say 8" or less(6"x6" is great). this of course may not work as a double burner design but will make an excellent single burner for a smelter or small knife/general use forge though a 1/2" pipe as a flame holder, opposite of exhaust, is needed. Also the fuel flow should be finely controlled. 1/20th of a turn on mine is the difference between oxidizing, neutral, and carborizing atmospheres and im using the valves from an oxy/acet torch head. Inline fuel filters a must. I dont care how much you "think" youve filtered it.

Edited by JohnK

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2 1/2" chamber with 1 1/4" intake/exhaust. Turns out just about any size will work. The smaller chamber is much more aggressive with flare up but generates the same heat and is a little more fuel efficient. 

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Test design. Ease of ignition and will not extinguish itself. Very fuel efficient. Heat lacking. 

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Posted (edited)

Discovered an interesting clay mix for forge body by half accident today. Seems adding around 1% powered softwood charcoal gives it an interesting insulation boost. Quite high might i add. Ive had it running for approximately 3 hours now and the outside is still wet and lukewarm at best. The inside is yellow. Im taking a shot in the dark and assume the charcoal burned out leaving a porous clay shell. Originally added charcoal powder as a way to assist in drying without cracking when fireing instead of waiting days for the clay to do so on its own. Overall thickness is 3 1/2in all the way around 

 

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Edited by JohnK
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That is very interesting.  I'm wondering if this could be adapted into alternative fuel forges.  I'd assume so.  How does waste oil rank on cleanliness?  I refer to forge welding.  One of these days when I have land I'll build a proper forge but for now my little propane rig will work while I'm in a single car garage.

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My oil forge will actually burn any fuel once up to heat. vegetable oil, waste engine oil. probably gear oil if thinned. easily anything else. i start mine on gasoline or kerosene depending on my mood and switch to waste engine veg oil once hot. cleanliness is a bit of a personal matter. it seems to always want to burn neutral or slightly decarb with no smoke or smell. however i recommend a small amount of black smoke, very small, to provide a safe forging atmosphere. overall im happy with it and its fairly easy to deal with.

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tomorrow ill post pictures of the dimensions of everything and a clearer view of the atmosphere inside the forge.

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