Help with burner design

Discussion in 'Burners and their construction' started by Azzmodeus, Nov 26, 2020.

  1. Azzmodeus

    Azzmodeus Lead

    Happy gobble day y'all.. I need help with my burner design. My first try. What looks right and what I gotta scrap or change. I'm building a crucible forge/smelter with ceramic firebricks and a sheet steel box to protect it. The inside will be 9" on all sides/top to bottom, and the outside is a 12" cube.1-1/2" thick bricks with reflective coating inside. I will carve small ditches to a center hole in the floor incase a crucible breaks to drain metal into sand and cover hole with a firebrick.
    I'm using my grill propane tank for now to try it out. I ordered all the parts for the forced air burner. Just need the black steel piping to match, and a ball valve for blower control. The blower has a 2" output at 70 cfm, and the gas gauge goes up to 10psi. Pipe diameter: 1" or 1-1/2"?
    I was going to keep the end of the pipe without a flange feeding into the smelter. I read the smelter acts as a "flange" to drop the pressure and give a proper burn in the box, and a flange on the pipe is unnecessary. Is this true?
    I'm looking to melt copper to make bronze.
    I want to make it as efficient as I can to use less fuel and balance airflow to get as hot as I can.
    Does anyone have a thermocouple setup to monitor temperatures? Can you explain how to do this?
    Oh and I read that a flashback arrestor is not needed as propane can't combust with no O2 and is unable to run back to the tank. Is that true? I'd rather not blow myself up..
    I'm hoping some experienced, knowledgeable peoples can give me some guidance, critical feedback, and possibly a little clap on the back if it looks like I have a clue what I'm doing. Thanks!
    Dave

    Oh yeah I got the idea from Paul Pinto here. He set it up for a forge and it's working off 1.5 to 2 psi I believe. It looks good. I just have no idea how much it takes to reach melt temps.

    This thermocouple looks ok? Digital reads up to 2372°

    https://www.ebay.com/itm/Digital-Py...761334&hash=item1a3aa264ff:g:yRYAAOSwMNxXWT1f

    Also I see talk about doing things to better mix the air and gas before burning. Has anyone thought of using scotch brite stainless steel scouring pads? Pull em apart and lightly fill part of the tube? Maybe it would help?? And they should last I think

     

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    Last edited: Nov 26, 2020
  2. Tobho Mott

    Tobho Mott Gold Banner Member

    I use a 0-10psi regulator with a hair dryer for a blower and a piece of 1" black pipe as the burner tube. The hair dryer is set on "cool" and controlled by a dimmer switch. On full blast it likes the regulator about halfway open, give or take. Melting aluminum, bronze, and copper is no problem.

    You should not need a flare on the end of your burner to get it to run inside a furnace, but usually the furnace would be round, with the burner aimed to swirl around the crucible in a circle.

    Jeff
     
  3. I agree flashback is not a problem. The flame front will soon run out of oxygen.

    Admit your propane ten diameters or more from the end of the burner and you will get adequate mixing of fuel and air. My burner usually burns in the furnace anyway.

    A forge you can weld with is much hotter than you need to melt copper. However I think everyone will agree, go ahead and build your burner and start running it. That's how you learn. There are also lots of nice burners described on this site. They all boil down to one thing, air and propane blown into a furnace will burn. You just have to be able to control the air flow and the propane flow.

    Your square furnace will work, but you may want to cut some brick on a 45 to fill in the corners a bit and at least make it eight sided.
     
  4. Azzmodeus

    Azzmodeus Lead

    Yeah Jeff that sounds easy! Hope my girlfriend doesn't miss her hair drier! Any idea how long it takes you to get to melt temp for copper?
    I'm thinking of an octagon shape inside so it should whip around. My nephew got me looking into it. I've been welding and machining awhile and always wanted to try casting. He got the idea from minecraft so I want to make it a cube shape and paint something from the game on it.. maybe the TNT block
    I only bought the blower cause I didn't know if hair driers, leaf blowers or shop vacs would hold up with repeated long running times?
    Thanks for the help
     
  5. Azzmodeus

    Azzmodeus Lead

    Wow thanks for the help! Yeah I'm doing the angled pieces in the corners. The sides will be almost the same length. So you're saying with a 1" pipe the propane inlet is at least 10" back? Do I need the elbows or will a straight pipe be good enough? Thank you
     
  6. Tobho Mott

    Tobho Mott Gold Banner Member

    Buy her a new one before you take the old one, trust me. To be honest I only melted copper once, and didn't time it. And now that I think about it I also had the diesel drip and shop vac blower going that time... But I have no doubt I could do it with just propane and the hair dryer. For bronze I usually get a #6 crucible up to pouring temperature in a little over 20 minutes. Melt times will partly depend on how well insulated your furnace is and how much mass it has in it to heat up. You can also accidentally slow it down a lot by not getting the air/fuel mixture right.

    Jeff
     
  7. I've been using a cheapy leaf blower for a couple hundred hours of run time now. Still runs like a new one.

    It takes me about 35 minutes to melt an A6 of brass.

    You might want to learn to cast aluminum first, then move on to brass, then copper. The tin to make bronze is a little expensive. Scrap brass is readily available. You can make a lot of cool stuff with aluminum. Just use kerosene for cutting fluid when you machine it.

    An elbow doesn't hurt but straight pipe works well. Just an opening into the side of the pipe for propane, nothing fancy. You'll want a needle valve in the propane line to adjust the flow, then a ball valve to shut off flow without affecting your adjustment.
     
  8. This one time we'd like you to be honest, Jeff.
     
  9. Azzmodeus

    Azzmodeus Lead

    Yeah that's good using a ball valve to keep gas pressure the same. I want to start with aluminum like you say. Its cheaper to screw up. This dayton blower says 45 cfm at .5 in sp. Theres cheaper ones with less cfm. Do you think they're worth the money? I have an electric leaf blower I got for free 10 years ago. I dont mind using that. You guys are cool really helping me a lot
     
  10. Tobho Mott

    Tobho Mott Gold Banner Member

    :oops: That copper melt was the only time I ever bothered setting up the oil drip line to run the little Red Dwarf furnace in oil burner mode.

    If you are going to use the leaf blower you might as well build an oil drip tube into your forced air propane burner to run waste oil or diesel, you'll have plenty of air for that. Search the forum for posts mentioning moya burners or hot shot burners or brute burners to get an idea how they work. They are designed to only use propane to preheat the furnace for burning oil, but a couple of us here just use them as propane burners at least some of the time.

    Jeff
     
  11. I think a free leaf blower is worth the money. They're a little loud.

    I meant a needle valve to control propane then a ball valve for propane shutoff. It's nice to leave the needle valve alone when you get it set to where it's all running nicely.

    You can just block the suction to the leaf blower with cardboard or something, or make a simple knife gate to control it. A ball valve works too but it's a lot more money. some people use a dump valve on the side of a tee to expel excess air but that keeps the leaf blower working at full capacity. It all works.
     
  12. Tobho Mott

    Tobho Mott Gold Banner Member

    If you prefer, a router speed controller works on my leaf blower. Unlike a dimmer switch I tried (which does work to control my 5 gallon bucket sized shop vac). I haven't run the leaf blower that way for longer than just to test these electronic control options, but FWIW the same dimmer switch controlled hair dryer (charcoal, propane) and shop vac (oil/diesel) have been running all my furnaces for the past 7 years.

    Jeff
     

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