Brick oven reconstructed to a steel one

[v12spirit]

Hi FB forum
I have a poorly designed brick barrel vault indoor oven that ran on gas and decided to replace it for a new rounded steel combo oven. I choose steel because I always complained about the heat up time of the bricks as steel is far faster.
I started the project today by removing the whole inside of the oven as in the pictures:



all I have now is a square inside space of 750*750 mm in which my new steel oven will be installed.
I need help for determining the dimensions of the new steel one: Dome height, hearth diameter, door opening, door height, and even steel thickness, taking into account the limit of 750 mm maximum free space that will encapsulate the furnace and its insulation.
Thanks.

[v12spirit]

Re: Brick oven reconstructed to a steel one

Hello every body
After some research I ended up with the dimensions in the photo below. They are almost proportional to the Forno Bravo CASA2G80 oven with a small compromise: The base diameter increased from 600 to 650 mm.
My plan for building the steel igloo is to wild a circular disc ((A) in the photo) -which is the base i.e. oven hearth- to the rims of the lower (big) base of a trunk of a cone (oven side walls) (the yellow area in the photo), then to weld the rims of the upper (small) base of the trunk of the cone to a flat dome (the pink area in the photo) which is available in my area with so many sizes and used for making tortilla bread. The second and third photos are for the readymade flat dome from inside and from top respectively.

The side walls are actually a circular section that can be drawn using a compass and a protractor. One only has to know the two diameters trapping the angular section from top and button (r,r+L), and the angle (g) of the angular section. I did the math and here are the relations:
L = H /cos(f) , g = (c2-c1)/L , r = (L*c1)/(c2-c1).

Where c2 and c1 are the circumference of the big base and small base of the trunk of the cone respectively.
If the circular section turns out to be too wide (as in my case), divide it into four quarters, and weld the quarters together.

[JoeyVelderrain]

Re: Brick oven reconstructed to a steel one

interesting build

[Laurentius]

Re: Brick oven reconstructed to a steel one

Hi V12,

Curious, is that oven inside the house??

[v12spirit]

Re: Brick oven reconstructed to a steel one

Hi Laurentius,
Yes it is. Every body says "curious" when she or he enters my kitchen. However, it was one of my dreams to have one in my kitchen, but it was built by an idiot so I decided to rebuild it after having been reviewing the forum for months.
The oven will be combo gas/wood fired and will mostly be run on gas for indoor convenience. But I prepared for the case when I want to run it on wood: I will provide the chimney with a turbo ventilation fan so that no smoke will leak out of the oven.
v12spirit

[david s]

Re: Brick oven reconstructed to a steel one

Be extremely careful. The combination of a gas burner and wood can be very dangerous. Eg if a live wood fire is in the oven and the gas flame fails at the burner, then your oven chamber will fill with gas and the wood fire will ignite it with explosive results. The burner must be fitted with a flame failure device and should be fitted by a licensed gas fitter who knows what he's doing.

[v12spirit]

Re: Brick oven reconstructed to a steel one

Thank you David for the caution.

[v12spirit]

Re: Brick oven reconstructed to a steel one

Hello everybody
Today I have removed the back wall and the opening of my old oven to accommodate the new steel oven. I think that I will remove the two side walls later on for aesthetic reasons; they do not go on the same line with the base. The cardboard disc represents the position where the steel oven will be installed. The card board will be cumulatively built into a cardboard replica of the steel oven so the blacksmith will just imitate it without unnecessary calculations.

[v12spirit]

Re: Brick oven reconstructed to a steel one

Hi,
I?ve been offline for a while. It became common here to have some services gone for several days? However, I was still on project all that period long. I frequently sleep while daydreaming about the pros and cons of this technique or that, this substance or that? Having the ISP back to service a couple of days ago I realized that the more threads I read and the more cool guys at the forum I ask the more I find myself WFO ignorant and that it is too soon to start buckling down.
Here is a brief ?I hope? summary of my activities.
1- Using the so called flat dome (see the pics above) in my build was entirely excluded because it is too thin and according to the cool guys in the forum it may twist or even tear in a short period of time.
2- A minimum of 4 mm up to 10 mm thick iron was my goal. But sadly, according to my dimensions using some math, my oven would weight 60?120 kg which is rather expensive (Things started to disappear from the market and their prices increased dramatically). Being short of cash to pay for this weight (iron is priced per kilo), I was definitely not going to buy it.
3- I visited my cousin and when we sat in his backyard I saw a piece of scrap iron pipe 90 mm diameter, 125 mm long, and 5 mm thick I was glad to have it (this reminded me of david s. He was the first to suggest using a pipe like this to make a barrel vault oven). However, my plan was different. I insist on a rounded oven (I?m limited with footprint). I took the pipe for free from him to the iron fabricator. I needed to cut from the pipe and weld the pieces to form the dome. The essential challenge was to imitate the flat dome that is in the pictures above using a piece cut from the pipe. Unfortunately, the only one to have the equipment to do that in my area (local fabricators call that an impulse machine) closed. My cousin?s pipe started to look useless!
Actually, an armed conflict has been running all over the country causing many good craftsmen, manufacturers, and merchants to move to the surrounding countries and resulting in dramatic increase in prices and lack of materials. That is the primary thing that is slowing me down and redirecting or even limiting my plans.
All of that was an enough feedback to tell me where I can go with steel construction (maybe no further!). I backtracked my decision tree. Why did I decide to build a steel one?
1- Because I cannot withstand 2 hours for the bricks to get to pizza temp for just a couple of pizzas while steel takes roughly less than 20 minutes to build up the heat.
2- Because I don?t use the oven frequently so I will not be making advantage of the retained heat.
3- Because mine is an indoor oven. So it is cleaner to run it on gas most the time (although it can be run on wood), and heating the bricks with a gas burner is rather expensive.
Today an odd idea came to me that may make a brick oven overcome the three above mentioned disadvantages (to me at least).
I am using the cooker every day for making coffee, tea, cooking the lunch. I use it for 1-2 hours a day. The heat exhausted out of the utensils and the cooker flame is scattered to the air. Why do not I make use of this scattered heat? What if I do all the cooking, coffee and tea making just inside the oven? This will trap the scattered heat inside the oven contributing to the cooked meals quality (They will cook evenly) and the oven temperature too. Assuming the oven is WELL insulated. One or two hours of gas flame inside the oven every day will keep it warm enough 24/7. What I mean is to provide the oven with two burners; one on the side for baking and one in the center for cooking. If I want to cook the oven would be already warm and cooks evenly with the help of the center burner, and if I want to bake it would be warm and needs just a little more heat maintenance from the side burner. The specifics and techniques of the two burners can be discussed and overcome later on but the principle sounds reasonable at least theoretically. Or does it?
Sorry for the long post I could not express it shorter.
Cheers.

[GianniFocaccia]

Re: Brick oven reconstructed to a steel one

If you want quick, clean gas-driven heat, why not just install a conventional, thermostat-controlled oven?

If you want the romance and performance of a true wood-fired oven, build it 50-60mm thick. You can build a flatter dome, but the oven will require buttressing, which should be easy with your existing enclosure. The dome will heat to pizza temp in a hour (give or take) and the residual heat will last a day or so if properly contained. Just make sure you insulate thoroughly, especially under the floor.

You are already aware of the consequences of a gas explosion. If you are lacking of a qualified gas-fitter (or funds for proper shut-off device) go with wood. It appears the original oven's flue exited directly above the dome itself. Without a proper vent, attempting to heat your oven with gas (or wood) will be useless.

[wotavidone]

Re: Brick oven reconstructed to a steel one

If ever a situation called for a cast oven, it'd be yours, I reckon.
If you can get some castable refractory, make a mould to your preferred shape and cast yourself a dome maybe 50mm or so thick.

In your situation (building it into your kitchen inside your home) I reckon you should err on the side of caution and use a commercial formulation rather than a homebrew.

Put it in and fill as much space with insulation as you can.


I've seen some incredibly disturbing photos of the Syrian crisis.
There must be a way the Arab world could step in and stop it.
I hope all goes well for you.

BTW, where do you get firewood? I'm suppose it is just a perception thing, but there never seems to be many trees in the previously mentioned photos.

[v12spirit]

Re: Brick oven reconstructed to a steel one

Hi wotavidone
Thanks for your kind wishes. You are right. This has to be stopped, but easier said than done.
I don't know much about the castable refractory. Is it like a mix that you can just add water to it and shape it in molds? Can it be homemade if I fail to find it?
I live in a small town and we have a garden and farmlands. This is not an apartment. I can get wood easily. I just want my indoor oven to be efficient, clean and CLASSIC. I'm planning to build another cheap one in the garden that is wood fired.
Cheers.

[wotavidone]

Re: Brick oven reconstructed to a steel one

Commercial castables are generally bagged products that you mix with water.
I doubt it would be a good idea to try and cast the oven in place over a sand dome. The mess might make you a touch unpopular with your wife.
So you'd need to be making a mould to something approaching the dimensions you drew.

For castable, you have perhaps three choices.

Some people have used the 3 sand, 1 cement, 1 lime, 1 fireclay homebrew to make domes, most notably michelevit's "Brickless oven on a shoestring"
Homebrew isn't really a refractory, but his oven seems to be lasting well, and dozens of builders have used it to hold their brick ovens together.
Mine (brick with homebrew mortar) hasn't fallen down yet, but I reckon that, since it is inside and therefore oven failure is more than just an inconvenience, you should consider a more "conventional" mix.

For example, Abulsamman in Jordan, to name but one builder, has made an oven from calcium aluminate cement (ciment fondue) and aggregates.

https://www.fornobravo.com/forum/f43...ild-17455.html
Calcium aluminate is much more heat resistant than Portland cement.

If you can get a commercial castable, that is probably the best. But be sure your supplier knows it is for a "low" temperature application. No point getting one that needs to be fired to over 1000C. You may never cure it. As with cement fondue, it would be very important to follow the instructions, especially with regard to the amount of water, or the result won't be very good.

[v12spirit]

Re: Brick oven reconstructed to a steel one

Thank you wotavidone for the clarifications. I have been hearing about homebrew and thinking that it is the same mix you pointed to (portland cement, lime, fireclay, sand), but I can understand from you that it is not? What is homebrew then? and what is the minimum thickness I can have for my cast oven?
Cheers.

[v12spirit]

Re: Brick oven reconstructed to a steel one

Hi,

This is my oven removed entirely waiting to be reconstructed. The opening of the oven exhaust is right behind the oven (see the yellow arrow in the picture). Any suggestions regarding the chimney so a proper air draw can be achieved without the help of a ventilating fan, and of course without making the oven ugly ?