I am approaching the point where I will be meshing the firebox (4x13 firebrick) to the clay flue (8x13). I originally pictured a firebrick wall tapered to meet the dimensions of the flue, but in looking over the build, I don't like that idea. Seems there will be an unacceptable lateral force on the firebox. So now my thought is to make a steel frame out of angle iron that will sit on top of the firebrick walls with the vertical blade on the outside of the firebrick. More angle welded on an angle upwards to a second frame that will accept the flue. Never ventured into this, so I am hoping there are some options out there.
I posted this link in your other thread, http://en.wikipedia.org/wiki/Rumford_fireplace It may be too late, but hopefully not... Here's a great PDF on some construction details on a Rumford fireplace. http://www.masonryconstruction.com/Images/Building a Rumford Fireplace_tcm68-1375163.pdf These designs burn very cleanly and throw a ton of heat out to the seating area.
