Frosty

Naturally Aspirated Ribbon Burner. Photo heavy.

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Just a couple of questions on performance - How are people finding the performance of their NARBs compares to a regular T burner? I ask as I'm looking at building a forge that will be approx 7" x 18" cylindrical after the insulation and refractory, giving it a volume pushing 700 cubic inches (it's long I know, and I may cut is down a few inches, I've just been doing long twists lately in a little beginner forge and it's been a long and inefficient experience. I also have long-term pretensions towards blade making).  From what I have read I'd need two 3/4" T burners, but is a NARB efficient enough to enable me to cut it down to just one burner for this sort of volume? I think I read somewhere else that Frosty reckoned a well-tuned 3/4 fed NARB could just about manage it but I'm looking for further opinions/confirmation of this as it sounds like it would be a bit of a stretch and I may be better off with two NARBs. I was wondering if the NARB could be scaled up to use a 1" T burner and drive a larger outlet, but I'm guessing that without a blower this would run into problems with a lack of pressure that I'm not clever enough to work out the maths for or fully understand.

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It depends on what you mean by performance. If stability is your measure they're many times as good. That's just an example. I believe they hold pretty close to the basic rule of thumb  ratio for furnace volume to tube diameter. one each, well tuned, 3/4" NA, jet ejector type burner should bring 300 - 350 cu/in to welding temperature.  By that rule of thumb you'll need 2 of them.

However if you don't need welding heat you could probably get away with a longer furnace chamber say for heat treating. Twisting wants near welding heat though, I think you need two of them. 

The diameter of the tube means a lot, output is directly related to the area of the tube cross section.  1" is 2 x the area and output of a 3/4" burner. The numbers say you should be able to pull it off with a single 1" T driven NARB. Just off the top of my head that'd be around 40 crayon dia. outlets from a long plenum.

I'd make the plenum from larger tubing. The 3/4" T driven NARB worked well with 2" sq. tubing but spread out that far a larger volume to length might be necessary. I'm just speculating though, I haven't tried going larger. I'm set up to make 3/4" Ts so its easier to just make two NARBs. That's my set up though, if I were starting out I might tinker a different size to perform for me.

Please keep us in the loop if you give it a try.

Frosty The Lucky.

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Thanks for the info Frosty, I feel a bit of experimenting is on the cards. I assume a slightly larger MIG tip would be necessary in a 1" tube? I'll order up some different sized parts so I can see what works. The tank I intend using is currently full of propane so i should really hook it up and actually hit some hot metal instead of reading this forum. I'll let you know how it goes when I get round to building the forge.

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I ran a 0.045 mig tip in the 1" T I built early on. It was the first successful one I made and looks a lot different. The T was a 1" T so the intake ports weren't larger like the 3/4" x 1" that works so well on the 3/4" burner or the 1/2" x 3/4" on the 1/2" burners. I didn't need nearly that much burner in the forges I was using so I never tinkered with 1" burners again. I'd assume it would work well with larger intake ports. 

The gross changes in these things seem to follow a pretty direct ratio. Make the mixing tube DIA. 50% larger, doubles the output the optimum jet Dia.  (for how I build burners that is) is also 50% larger.

Were I messing with 1" T burners again I think I'd compare 1" x 1.25" and 1" x 1.5" Ts as departure points for developing my version of optimum performance. What works best could be different, maybe at that size the intake ports don't need to be larger. I don't know I haven't played with the things.

Frosty The Lucky.

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