prtb

10 hours ago, Mikey98118 said:

What  kind of brazing hearth ? A small square of high alumina kiln shelf with two low walls of fire bricks, making a corner to bounce heat back from

Thank you. You just designed my brazing hearth.  
My plan wasn't really thought out yet, i got distracted by burners. I was thinking  insulating fire bricks base + corner with  2 or 3 additional loose firebrick to place around  as required.

10 hours ago, Mikey98118 said:

You are correct that jet orifice diameters are tied to mixing tube inside diameters; that said, jet orifice sizes are also effected by gas/air mixture flow rates, so that a Frosty "T" burner will generally run one MIG tip size larger, than most other burner designs, including most of mine; the Vortex burner being a possible exception to the rule, as it is to everything else! Finally, the larger the burner the more that jet orifice sizes can be relaxed, but the smaller the burner the more critical they become.

You can find an early chart on page 22 of Gas Burners for Forges, Furnaces, & Kilns (available free on the web); it is eighteen years out of date, but still provides a starting point for jet sizes. In the end orifice diameters and lengths frequently boil down to personally tuning the fine points for your individual burner; not least because people decide to "just change the burner 'just a little bit" every way they feel like , and then expect it to act as advertised

That table in the book is actually  what prompted me to ask the question. You have a "2-inch (probably)"  burner in the table. So i figured  behind the "probably" bit, there was some "magic mathematical air jet induction  theory with  formula"... or something.  Sounds like  there are too many contributing design factors to give an generic answer.

Anyway, I'm satisfied. Thank you for for responding.

I did come up with the following table by digging through you various "Mikey Burner" designs ( a few assumptions here).  

There's always patterns to be found in  these things. If the patterns scale and are even useful is different matter.

Thanks,

Peter

Location updated.  I'll likely be a flash "Flash in the pan" here.

I do think you guys are doing great work here. 

I'm looking at building a brazing hearth (wanted for another project) and i was researching refractory materials. I somehow stumbled across Mikey98118 posts on potential makeup of ITC-100. I said to myself "That guy knows his stuff". So started stalking his posts, found a book and the "Mikey Burner". 

So here I am... Researching burners.. down a researching rabbit hole.

Peter.

Mikey,

 For your "Mikey Burner" Jet burner designs, can you explain how do you calculate the ideal gas jet inner diameter for a given mixing tube inner diameter?

Thought these forums, several times you quote an ideal jet orifice diameter for a particular burner diameter/design (usually the mixing tube inner diameter). 

• The 1/4" burner design has 0.370” inner diameter for mixing tube, and a recommended gas jet inner diameter  of 0.016” .
• The 3/8" burner design has 0.495” inner diameter (which happens to be closer to 1/2") for mixing tube, and a recommended gas jet inner diameter  of 0.019”.
• You have said for 1/2" burner ideal get jet  inner diameter  of 0.028” (which does not exist as a mig tip). is this 1/2" #40 pipe  book design? e.g.  nominal  #40 1/2" pipe (so google says inner diameter of 0.622"? )  
   

I'm suspecting 1:28 ideal ratio of propane:air is important in the calculation, but i can't work it out or find a reference.  I think i'm getting nominal pipe and actual ID sizes all mixed up.

Thanks,
Peter