Casting Question I want to expand a kit oven

[pzachef]

Someone please help me out here. I am new and have not built yet. I can't wait to get started. I was going to build with fire brick but someone selling an unbuilt kit, practically gave it to me. Its precast 4 dome sections and 2 floor sections. It has a 33.46 inch Diameter cooking surface and the dome walls would sit on the 39 inch diameter floor. I got a bag of refractory mortar, the chimney, cap, and door.
I really wanted something bigger so I was wondering can I move the dome walls outside the floor and fill in the gaps with refractory casting and needles if needed? I realize the diameter differences between the 2 but I would add brick adjacent to the floor to provided extra floor surface for the dome to sit on.
The gaps would be about the widt of a brick.

Thanks, Bob

[dmun]

I'm not sure this is going to work. If you want a bigger oven it may pay to sell this one on ebay, and buy the materials to build what you want.

[pzachef]

Thank you,
I appreciate the response. Why do you think it would not hold? Does Cast Grade Refractory Mortar crumble? Would expansion and contraction be an issue?

[dmun]

First of all, I have to say i'm a little out of my element here. I don't much much about castable refractories, except how expensive they are. I do suspect that the castable and the firebrick material of the dome might have different expansion rates: you could find that out by studying the material data sheets.
I do know something about domes, and I think i think stretching it in four directions will effect the stability of the structure. Interestingly, in the past week, someone has started a rounded square oven, which i argued against on the same grounds:
http://www.fornobravo.com/forum/f6/u...ress-6797.html (UK 34" rounded square Oven Progress.)
Before you try to stretch and flatten your dome, read this page about arches, and study the illustrations:
Auroville Earth Institute is a research, design and developing agency for vaulted structures, construction of various Vaults, Arches, Domes (VAD).

[david s]

Other issues to consider are
1. You will probably be changing the oven door height to internal oven height ratio
2. A small increase in diameter means a large increase in oven volume. Your modifications could well leave you with an oven that has an inadequate flue diameter.

[pzachef]

Thanks, I was going to brick arch the difference in the opening where needed and maybe use brick for the expansion. My casting question is really because it would be easier.
The bottom line here under all this is do I live with a 33.46 inch cooking surface or do I want a bigger oven???

[david s]

It depends on how many people you want to feed. My oven is only 22" diam and occasionally I wish it were bigger, but more often I rejoice at its suitable size for a small family.and its economical use of fuel. You certainly use a smaller oven more often. I have had a couple of parties where I've done pizzas forover40 people. It's all about the management of the fire and the cooking.

[David Reekie]

I don't know which way the dome is split, or the floor is split - but if you look at all the Forno Bravo ovens, one of them is a round oven with an extra 'tunnel' section added in the middle to turn it into an oval (rounded ends, straight sides). You can buy it as a round oven too, without the middle floor and 'tunnel' roof sections. Have a look at that - maybe you could do something similar?

That's not to say your idea won't work, but this might be an easier option than having to move all the dome pieces outwards and deal with different radiuses between the floor and bottom of the dome etc etc.

[David Reekie]

p.s. It's the casa 160: Casa160 Pizza Oven specifications | Pizza Oven Design, Installation and Construction

[pzachef]

Thanks Dave,

Looking at it from the front opening, the floor is split in the middle of the oven, left to right. I'm thinking I could use Mizzou or something similar to cast the gaps and carefully cure it. I never mentioned, the joints have a 1/2 inch step in them making a nice fit. The fact is I only paid $300 US, no kidding for all of it. I could probably sell it and build or buy something bigger.
Mizzou is 140lb per cubic foot, I calculated I'd need about 2 bags to cast the gaps. If I can find it locally I may do it.
I'm probably thinking about it too much but many people on this site prefer 36 inch and above, so I want to make the right choice. A couple inches may not seem like much but???