pftaylor, great thread and great project! I am in the same boat, researching the best oven I can get for our kitchen remodel. In the process, I have learned a few things which you seem to be incorporating in your design. Was curious whether they were intentional or not
1. You are putting the floor inside of the dome. I assume this lets it maintain its heat better as opposed to having the dome sit on it.
2. You are using wedges instead of larger casting. I assume you are doing so to avoid cracks from expansion of much larger castings.
3. You have a low dome as to get more heat to the top of the pizza and also to reflect more of it to warm the floor.
4. You are using ceramic blankets which achieve better insulation factor as opposed to insulating refractory material. You get to have more insulation for less space. I assume commercial companies don’t like to go this route due to higher cost. For me though, given the indoor situation, lower weight is important.
Now the part that I don’t quite understand is the poured refractory for the center piece. Other designs have that be a separate casting. By pouring it, aren’t mechanically bonding the pieces together and hence, increase the chance that there will be cracks? I assume this is helpful in one dimension as it reduces the thermal impedance of the pieces due to lack of seams there, where most of the heat is concentrated. But still, if you have a crack in the dome in the center, that would be an awfully bad place to have it I would imagine!
Did you make the above decision because it would have been too expensive to make the cast for the top piece separate from the others?
One other point Marco has made which kind of made sense to me was to curve the flu as to hug the dome. This is said to warm it faster and/or to higher temp, aiding in combustion of the wood. I notice that a number of Italian designs use metal flu formed this way. Of course, others argue that a cast flu section has more thermal mass but I have seen no explanation as to why I would need to have thermal mass in the flu compartment.