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My Gas Forge Build

Discussion in 'Forges, Ovens, Kilns, & Salt Pots' started by Daniel P, May 18, 2019.

  1. Daniel P

    Daniel P New Member

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  2. John Noon

    John Noon Well-Known Member

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    Don't forget some high temperature clay to seal the joints, ceramic wool helps as well. A pottery supply store should have both used for kiln repair
     
  3. Daniel P

    Daniel P New Member

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    Thanks John,
    Yes I did not know about the clay
    Have a great day
    Daniel
     
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  4. John Noon

    John Noon Well-Known Member

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    The best part is to come, firing up the fire breathing monster :)
     
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  5. Daniel P

    Daniel P New Member

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    I have lots of 1” sld 40 pipe in stock
    Plus I can thread
    Will this be ok for the burners using a 1-1/2x1 reducer?
    Or should I use 3/4”
     
  6. dancom

    dancom Dust Maker Best Shop Tool

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    1-1/2" reduced to 3/4" makes a good Venturi at about 9" long with a slight flare on the flame end. This is what mine look like.
    [​IMG]
     
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  7. Mythtaken

    Mythtaken Staff Member CKM Staff

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    Question, Dan. Why did you add the flare to the burner? Does it offer some advantage?

    To me, it isn't needed, as the forge acts as a flare. I Like the simple black pipe burner (below). They work well, but I wonder now if a flare would improve it somehow.
    Burner.jpg
     
  8. dancom

    dancom Dust Maker Best Shop Tool

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    Yes the shape of the burner port inside the forge chamber can be cast in refractory as part of the forge itself. If the taper is maintained at 1:12 and the burner tube is centered in the port it can be very efficient, but likely won't work very efficiently outside the forge.

    I made my burner to work both in the forge and on its own outside the forge. I found it easier and more accurate to taper the inside of the nozzle and have it attached to the burner. Attached with set screws it can be adjusted and set to work over a wide range of pressures. As a bonus, I made it out of stainless steel which stand up better in an oxidizing environment.

    There are several ways to make the flare. One is the taper is made by removing material inside the nozzle, another is to forge/expand the nozzle to create the 1:12 taper. Michael Porter has a great book on the subject called Gas Burners for Forges, Furnaces and Kilns.

    Dan
     
  9. Daniel P

    Daniel P New Member

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    Dan what is tacked on the top?
    Onto the 1- 1/2”nipple
     
  10. Daniel P

    Daniel P New Member

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    On my way out to pick up the 1-1/2” reducers
    Hopefully I will find a 30lb regulator today
     
  11. dancom

    dancom Dust Maker Best Shop Tool

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    I made a bracket for the gas system. It's a short length of schedule 40 3/8" pipe and a piece of 1/8" steel to hold the gas jet directly in the centre of the intake. A setscrew holds the gas system in place, but lets you slide it in and out to get the best burn. The idea is that it is preferred to have the gas flowing directly into the burner vs. making a right angle turn like in the Reil design. Note that Tim's (Mythtaken's) side arm burner also sends the gas straight into the burner, but the air is coming in at the side and mixing with the gas.

    Efficiency is improved when there are smooth direct paths for the fluids to move. Rough edges, steps, blockages all reduce efficiency. I ported the inside of mine like one would port and polish the intake and exhaust ports on an engine head to improve flow. I took a die grinder and smoothed all the rough casting from the inside of the reducer and the step where the burner tube meets the reducer.
    [​IMG]

    Dan
     
  12. dancom

    dancom Dust Maker Best Shop Tool

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    Caveat. I am not an expert. Perhaps @FORGE can give us a lesson in fluid dynamics. He makes a very efficient burner. ;)
     
  13. Mythtaken

    Mythtaken Staff Member CKM Staff

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    I agree with Dan on the porting/polishing. Also not an expert, but my idiot's grasp of physics confirms that smoothing the rough surfaces inside the burner (especially in the mixing area) will reduce turbulence that can affect the efficiency.

    Also, thanks for the flare info. I can see how adding a flare that is fine-tuned for the particular burner and operating pressure would be an improvement on the natural flare provided by the burner cavity itself.
     
  14. Daniel P

    Daniel P New Member

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    I should end up with 438 cubic inches inside this forge.
    I think I have enough bits and pieces to make 3 burners.
    Each burner has its own valve
    And I plan to make a plug or a sliding door to block off half the forge to save on the gas when doing knives.
    Thanks for the tips guys
    I just need to find some time now to put this together
    Daniel
     
  15. John Noon

    John Noon Well-Known Member

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    Polishing will improve flow of liquids and gasses, correctly shaped roughness can make even greater improvements. Chances of getting polish good is high but near zero on the roughness due to small size partly and lack of million dollar research budget.
    A cousin gave me a nozzle to experiment with that may work much better for a forge and for a quenching system we thought up. just have to get off my rear and start building the assemblies
     
  16. Magnus

    Magnus New Member

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    Daniel, those fire bricks look a lot like the ones I used to buy from Canadian Tire which were only rated for about 2000ºF and definitely melt at welding temperatures.

    Magnus
     
  17. Daniel P

    Daniel P New Member

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    There about 1.25 thick
    Thanks I will look into this

    What are fire bricks made of....and where can I find good bricks that will take welding temperatures ?
     
    Last edited: May 22, 2019
  18. FORGE

    FORGE Maker of the Year Best Knife

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    Dan, at one time I would have agree with you on polishing. I now find that the rougher and bumpier the surface the better the gas and the air mix.
    In fact on my latest burners I drove a 3 inch long coil spring inside the burner tube on the flair end to mix the gases and it also keeps the flame from blowing out on the end of the burner. If you really want a venturie burner to work put a small blower on the end of it. If you know someone in the plumbing business that scrapes high efficiency water heaters those blowers are perfect for a forge.
     
  19. dancom

    dancom Dust Maker Best Shop Tool

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    I agree on the turbulent flow for mixing post fuel injection. My thoughts are that on the intake side we want laminar flow to get plenty of air in. A similar smoothed trumpet shape is seen on velocity stacks that are used on the intakes of some performance engines. The smoother the funnel walls the better the laminar flow, the larger the air volume for the given pressure differential. Venturi burners are essentially Teclu burners by design, only we want larger volumes of fuel/air than these laboratory cousins.
     
  20. Magnus

    Magnus New Member

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    The good ones are made of metallic oxides (alumina, silica), I'm not sure what the ones I melted were made of. Pottery supply stores should carry K26 insulating firebrick (I've found the K23 ones to be a bit weak for a forge). Pottery Supply House is based out of Oakville (is that close to you?) and also does internet sales.

    Magnus
     

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