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2 Burner Or 3?

Discussion in 'Forges, Ovens, Kilns, & Salt Pots' started by Tom Stegner, Dec 6, 2019.

  1. Tom Stegner

    Tom Stegner New Member

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    I started building a new forge and would like some advice on spacing burners. I have joined 2 propane tanks together and have a 6 inch opening at each end. I have 17 inches of flat straight line to place what I was hoping to be, 3 burners. Now that I have it built, it don't look like enough room for 3 burners. The entire forge is 22 inches long from 1 opening to the other. I wanted 3 burners because I can't heat treat a long sword. The first one only one I made looks pretty but not tempered. Just an ornament. Will 2 work?
     
  2. dancom

    dancom Dust Maker Best Shop Tool

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    Not sure what burners you have, but as sort of a rule of thumb, plan for one burner per 330 cubic inches of volume inside. I have read anywhere from 320 to 350 ci. I have two fairly efficient 3/4" burners in mine, 450 cubic inches, roughly 6" x 16" cylindrical volume. Works great. Most of the time I brick off the back half and use the front burner only.

    Dan
     
  3. Tom Stegner

    Tom Stegner New Member

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    Thx Dan. 2 burners it is. I want to maintain that 6 inch opening all the way through. First layer will be fire brick, then ceramic fibre. You must have your burners fed independendly?
     
  4. dancom

    dancom Dust Maker Best Shop Tool

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    I have the two burners fed from a single line, each burner has its own valve. A 20# tank with an adjustable 20 psi regulator. The problem comes with poor evaporation rate when the ambient temperature is cooler. Propane needs sufficient whetting area and temperature to maintain a decent evapouration rate to keep the burners running strong. One solution is to have more tank surface area (can be multiple tanks) exposed to the ambient temperature, or apply heat to the tank. A 35 Watt battery warming blanket wrapped around the bottom part of the tank works good. Some guys use a water bath, but for me that can become ice at some point in the winter.

    Dan
     
  5. ToddR

    ToddR Putterer, Tinkerer, Waster of Time Staff Member

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    I did a two burner forge similar to Dan's with both sharing the same line with separate valves. I also rarely use both burners.

    I have no experience with swords but everything I've ever read about heat treating long blades seems to be all about getting the speed and rhythm down for cycling the blade through the front/back port of the forge. They say it's very doable in an "average" sized forge but it seems as though most people don't practice enough and lose patience. Sorry but that's all I got, I've never tried it myself. My problem is the opposite of yours. I built a forge WAAAYYY bigger than I actually need. I end up using my old soup can forge and a propane torch to treat most of my blades lately. I've done mostly carving knives and EDC knives this year (none for a while now) and could heat treat them with a Bic lighter I think.
     
  6. Mythtaken

    Mythtaken Staff Member CKM Staff

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    That's a awful lot of space to heat evenly, and three burners will just give you a chance to have three hotspots. And I don't even want to think about how much gas you'd burn. A much simpler way for heat-treating a long sword blade is to use the pipe method. Get a length of black pipe just big enough to fit the width of your blade, close one end and lay it in your forge. Once the pipe is up to heat, insert your blade and you'll get a nice even heat down it's length.

    Another option is to build a separate heat-treating forge from a long tube, using a ribbon burner that runs the whole length.
     
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  7. dancom

    dancom Dust Maker Best Shop Tool

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    With most things I am constantly moving them around in the forge. I put a backside opening in the forge to accommodate long objects. However, on my forge the back opening is much smaller than the front opening, so I work the steel in and out from the backside. I learned this after bashing into the back of the forge when trying to slip the object through the opening.

    Although I have never made a sword, I did heat treat a crossbow prod for a friend and that worked out fine. One of the better uses for a leaf spring.

    And yes, have a spare tank of fuel handy.
     
  8. Tom Stegner

    Tom Stegner New Member

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    Thank you for all that info. It has got me thinking in new directions. This will be my 3rd forge and I like the idea of being able to use one or 2 burners depending on the application. I have cut the ends off of 2 propane tanks and welded them together, with a 6 inch diameter opening front and back. It gives me about a 23 inch long enclosure. I just finished the first layer of fire-brick. I cut 2 inch wide strips with a 9 degree angle on each side so I have a nice tight fit all the way around. Next will be ceramic fibre. I won't bore you with the rest but...thx again.
     
  9. Tom Stegner

    Tom Stegner New Member

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    Thanks Todd, 2 is gonna be all I put in it. I came to my senses, lol.
     

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