New Forge Build

[Mcholla]

So I am currently working on a new forge primarily for pattern forging and knife making.  The internal dimensions (after insulations) are 7x7x6.5 for a volume in cubic inches of 318.5.  My question is this, with the intention of consistently achieving a welding heat, would it be optimal to do a single 3/4" burner dead center, or burners (more than likely 1/2") centered over the chamber on the diagonal.

Thank you in advance,

Jeff

[Buzzkill]

I'd recommend looking into ribbon burners.  They tend to provide a more even heat in the forge, and I personally prefer that for forge welding.  With the dimensions you gave it would be fairly easy to make a ribbon burner that runs nearly the full length of your forge.  We have a rather lengthy thread on here about Naturally Aspirated Ribbon Burners, and a number of people have also posted regarding fan blown ribbon burners.

[Frosty]

That sounds like a nice sized forge, I like the proportions. Any of the 3 options should work nicely in it. I'd angle the 3/4" to produce a strong vortex to even the heat. A pair of 1/2" burners evenly spaced so they're the same distance from each other as the ends and angled to produce a strong vortex is a good option. That configuration will produce a more even heat more quickly than a singleton though a single will heat evenly given a few minutes for the temp to even out. Yes?

Single nozzle burners have the advantage of making a hot zone with cooler temps either side. One of the serious disadvantages of a gas forge is every darned thing in it gets hot and sometimes you need an isolated heat. Say you're peining a large tenon but don't want to distort the morticed element into which you put so much work drifting that beautiful bulge. Make sense?

A ribbon again mounted at an angle to produce a vortex will produce the most even heat of the three. A ribbon is the most appropriate for a vertical down orientation, It will produce a more chaotic flame pattern in the chamber with no flame shadows and they are very stable so you can throttle them way down. 

Any will work fine, all have their advantages and disadvantages.

Frosty The Lucky.

[Mcholla]

If I was going to go with a naturally aspirated ribbon burner, is Mizzou an acceptable castable for this or does one need to step up to green cast?  Currently I don't have any of either as I typically use Kast-O-Lite for my builds (but I have seen some suggest it is not preferred for ribbon burners).

And thank you to both of your for the insight, I appreciate the help.

[JHCC]

IFI member Latticino is one of our resident experts on refractory burner nozzles (he used to be a professional glassblower), and he has frequently recommended Mizzou.

A number of folks here have successfully used Kast-O-Lite 30 for ribbon burners, myself included.

[Mikey98118]

I'm one of those lovers of Kast-O-lite 30. However, I would go looking for a much smoother refractory for ribbon burners, or any other refractory flame nozzle. If we can coax Latticino to talk about Mizzou at some length, that would be valuable.

[Frosty]

I used Kastolite for my burner blocks but sifted out the more coarse aggregate and it was still work getting it to flow between the cores.  (candles)

Mine have suffered no cracking but I was really careful to cure them properly. 

Frosty The Lucky.

[Mikey98118]

Flame retention nozzles benefit from smooth surfaces. Multi-hole nozzles, such as ribbon burners have far smaller flame openings than single flame nozzles, which will only aggravate  turbulence created by irregular surfaces. So, starting out with a smoother refractory would seem like a sound starting point?

[jwmelvin]

^^^ Yes I agree. KOL has fibers in it that make it seem difficult to screen. The refractory that Wayne Coe sells does work better for ribbon-burner blocks. I’d like to understand the range of possible materials better to really get a feel for where the finished characteristics come from.