Changed Design for Burner/Blower and Propane Fueled Casting Furnace

I am wondering about my choice of projects. This furnace project is producing math equations that I haven't had to work, in.....ever. I never took calc. (thank goodness). I am not a huge math fan. A very odd sort of fellow told me that math is the highest art form. hmmm.

Anyway, I had to have instruction on how to formulate the square inch volume of the furnace, and divide this by 1728 to get the cubit foot volume and then subtract the overall size minus the interior volume and multiply this by the weight of the castible refractory (140lbs), and then repeat for the lid! Add the two together and then go buy that amount of refractory, plus a little more in case my math was off. WHEW! I haven't even gone into figuring out the details on the blower/burner, or the pyrometer/thermocouple that I am building. I like welding better. Below are my concept sketches.