savage_sultin

11 minutes ago, Buzzkill said:

I can't speak for others, but on my NARB the final 3/8" or so exposed to the forge chamber stays hot enough to glow the same color as the rest of the forge interior when in use.  The plenum gets warm enough that it's uncomfortable to leave my bare hand on it for long.  I do not know if this is because of heat creeping back from the burner head or if it is due to the heat that eventually makes it through insulation and outer forge shell. 

It's a bit of a balancing act I think.  The more air/gas you push through the burner the more it can cool things off, but you're also generating more heat inside the forge at the same time.  My NARB will definitely backfire at a higher pressure (still less than 3 psi) after running full out for a while than it does when I first get going, so there does appear to be an impact on the ignition point due to the temperature at the outlet nozzlettes.  I suspect that the metering tubes you showed in the illustration are deep enough in the refractory so that the difference in thermal expansion between the 2 materials is insignificant.  My guess is if you run the tubes all the way to the ends and then reach incandescent temperatures the difference in thermal expansion will create some issues in fairly short order.

Ok thanks. I wasn't sure if the cooler air would keep it  cool. I think ill keep them short

this is the concept but I would bring the metal straw closer to the end maybe all the way to the edge. I was wondering about pre-ignition as well, but with cool air blowing over it constantly I thought it might not get that hot.

thanks, regarding the "3a. Pro tip #1: When doing your research, don't bother with the Search box up at the top of the page; it's pretty worthless. Go to google and include "site:iforgeiron.com" as one of your search terms." thats pretty much what I used but checking out google now. thank you im navigating through the site now, ive been forging for a while but just switching from Venturi to a ribbon burner

Hey folks, im new and this might be discussed before but when I searched I didnt see my question. im making a ribbon burner and for the holes im going to use stainless steel straws cast into the cement. would you think they would be fine? I dont see them being an issue, seen the pine ridge burner and they use a steel metering tubes