Not much here in the way of guidance for smaller ovens (28inch internal or less)

[xizenta]

Have you factored in a clay liner for the chimney. Look at Gulf's chimney design. Are you enclosing the oven or not. If enclosing, I have seen builders placing a CMU butting up against the vent wall. If not enclosing, I have seen another brick wall butting up against the vent wall brick. If you go the second route, the second brick wall could also help support the brick chimney as well. There is a really cool brick chimney that was done recently, it is a spriral screw shape. Think it was done in the UK.

Although this comes out the top vs the front which is not the best design, you get the idea of the brick work

https://community.fornobravo.com/for...chimney-design

Very cool spiral. No I was not planning to enclose the oven. I will think about this and try to design some brick buttressing for the arch walls.

I am really confused about the clay liner you mentioned. I think I know what you are talking about. Those clay flues which are like a half cylinder shape? Would I need that? I was planning to judge have a rectangular opening inside of my brickwork.

[UtahBeehiver]

Have you factored in a clay liner for the chimney. Look at Gulf's chimney design. Are you enclosing the oven or not. If enclosing, I have seen builders placing a CMU butting up against the vent wall. If not enclosing, I have seen another brick wall butting up against the vent wall brick. If you go the second route, the second brick wall could also help support the brick chimney as well. There is a really cool brick chimney that was done recently, it is a spriral screw shape. Think it was done in the UK.

Although this comes out the top vs the front which is not the best design, you get the idea of the brick work

https://community.fornobravo.com/for...chimney-design

[xizenta]

Typically the best placement of the pivot point on the IT is at the brick floor elevation. So if you have a 33" ID oven at floor level or 16.5 " radius, then the dome will also be 16.5" from the floor level at the top of the inside of the dome. If you chose to have a different internal height at the top of the dome vs the radius at the floor level then you will either have to raise the IT or adjust the radius of the IT as you go up. You cannot have both. I am confused by what you said in you edit on using a shiner instead of a stretcher, the cad drawing indicates a full soldier. I am looking at this from a using of a IT to build your dome. As noted by DJ, I mentioned that the arch design may require buttressing depending on the type of chimney you chose. Based on a brick chimney vs a SS steel vent buttressing of the side walls of the vent area is recommended.

Thank you Utah for your reply. I see where our measures were different for the dome height. I did my calculations assuming the first course of brick would stand proud of the floor by 2.5 inches, as would be common in most domes with a header orientation for the first course, then I added some extra height based on having a soldier orientation. In other words, my dome had the IT pivoting from 2.5" below the top of the soldier course. What you are suggesting, alternatively, is placing the pivot at the floor. I can do that. I guess I would even prefer it as it would result in a lower ceiling.

Regarding my previous post about the shiner vs a stretcher orientation, I was talking about the brick chimney. My cad drawing has a stretcher orientation, which would require something like 32 full size bricks to create a 2 foot long flue. I thought it might save weight if I reoriented the bricks so the chimney walls were 2.5" instead of 4.5".

Any links to suggest the design of buttressing for the sidewalls of the arch? If I can do that well, may as well go ahead and try to do the brick chimney.

Thanks bud.

[UtahBeehiver]

Typically the best placement of the pivot point on the IT is at the brick floor elevation. So if you have a 33" ID oven at floor level or 16.5 " radius, then the dome will also be 16.5" from the floor level at the top of the inside of the dome. If you chose to have a different internal height at the top of the dome vs the radius at the floor level then you will either have to raise the IT or adjust the radius of the IT as you go up. You cannot have both. I am confused by what you said in you edit on using a shiner instead of a stretcher, the cad drawing indicates a full soldier. I am looking at this from a using of a IT to build your dome. As noted by DJ, I mentioned that the arch design may require buttressing depending on the type of chimney you chose. Based on a brick chimney vs a SS steel vent buttressing of the side walls of the vent area is recommended.

[xizenta]

I would worry more about the arch than the slab. A segmented arch like the one you have in your design is not designed to carry a lot of weight. There will be tremendous pressure on the side walls and you would need extensive buttressing.

edit: or what JR said above . Didn't see that.

Good point. I see what you are saying. The walls will pop outward.

[deejayoh]

I'm also thinking about possibly doing a brick chimney, if my hearth can support the weight. My father-in-law who I am building the oven for really insists he wants it, rather than a stainless steel vent. At about 30 bricks for the addition, it would add considerable weight to the arch area to get to about a 2 foot height from the flue opening at the top of the archway. (I calculated something like 240 pounds).

Should I try to do this? I can try to use a ton of steel reinforcement under that part of the slab.

*edit* Maybe if I do a "Shiner" installation instead of a "Stretcher", I can build 2 feet of height with less weight and fewer bricks.

I would worry more about the arch than the slab. A segmented arch like the one you have in your design is not designed to carry a lot of weight. There will be tremendous pressure on the side walls and you would need extensive buttressing.

edit: or what JR said above . Didn't see that.

[JRPizza]

Not sure about the aerodynamics, but if you are going to put a ton of weight on the arch you might want to consider a hemispherical design to reduce the thrust loads on the side of the arch and have some protrusion of the inner arch at the top to give some additional support for the weight.

[xizenta]

I see you are using a cad program - this can help you with where to place the inner arch. Build a simple side view with the dome bricks at whatever oven size you are considering. Place a brick with the bottom at the height of your oven opening, which will represent the top dead center brick of your arch. Move the brick into and out of the oven keeping it intersecting the dome - as long as it intersects the dome will be round and the arch will mate up properly. You can move the brick all the way in to minimize landing length, but it takes a little away from the cooking area and does not give a ledge to help support the chimney. Once you get a dimension that looks good you can go back to your top view and see how the arch intersects the base of the dome.
I did quite a bit of mocking up using Freecad - you might be able to get some ideas if you look at my thread.

Thanks! This is basically exactly what I did w/ respect to the top brick. I just wasn't sure if there were any rules about how much intersection should be allowed into the dome. At some point it has to mess with the convection properties or whatever...

[xizenta]

I'm also thinking about possibly doing a brick chimney, if my hearth can support the weight. My father-in-law who I am building the oven for really insists he wants it, rather than a stainless steel vent. At about 30 bricks for the addition, it would add considerable weight to the arch area to get to about a 2 foot height from the flue opening at the top of the archway. (I calculated something like 240 pounds).

Should I try to do this? I can try to use a ton of steel reinforcement under that part of the slab.

*edit* Maybe if I do a "Shiner" installation instead of a "Stretcher", I can build 2 feet of height with less weight and fewer bricks.

[JRPizza]

I see you are using a cad program - this can help you with where to place the inner arch. Build a simple side view with the dome bricks at whatever oven size you are considering. Place a brick with the bottom at the height of your oven opening, which will represent the top dead center brick of your arch. Move the brick into and out of the oven keeping it intersecting the dome - as long as it intersects the dome will be round and the arch will mate up properly. You can move the brick all the way in to minimize landing length, but it takes a little away from the cooking area and does not give a ledge to help support the chimney. Once you get a dimension that looks good you can go back to your top view and see how the arch intersects the base of the dome.
I did quite a bit of mocking up using Freecad - you might be able to get some ideas if you look at my thread.

[xizenta]

Couple issues and questions:

Is there a particular reason for using soldiers on the first course, ie builder's choice, looks, ?? I know the old pompelli plans show this but there are other and possibly better design options. A half header may be better than full soldiers, even half soldiers would be better than full soldiers due to outward pressure domes place on vertical components. See attached brick pic

The dome height is reflective of a 36" diameter (assume, 2.5" floor thickness - 20.5" height -2.5" oven floor time 2) a 33" oven should have a dome height of 16.5" . It will be harder to use an Indespensible tool (IT) with the dome height not being 1/2 the diameter of the floor diameter.

door height should be 63-65% of dome height or abt 10.75" for a 33" oven based on a 16.5" dome height.

You may need to buttress the vent chamber depending on the type of chimney material you select.

Might have done my math wrong for dome height calculation but I essentially made the assumption that a "half header" installation with 0 floor height would have a dome height which is exactly half the diameter of the interior. (33" * .5 = 16.5). Then what I did was take out 2.5 inches from the floor due to installation of a firebrick herringbone hearth in the internal oven space. (16.5 - 2.5 = 14). Then I added some height because my soldier installation will elevate the dome as compared to a half header installation by 6.5". (14 + 6.5" = 20.5"). I got to 20.5 this way. I'm not sure what different assumption you made or if I made a mistake somewhere.

I chose soldiers because I had seen several other domes built that way and it would allow faster elevation building on the dome as well as less cutting of bricks. I don't have a tile saw so I'm doing all the cuts with an angle grinder.

let me know please if the above calculations are correct. Also I am most concerned about the arch design as there was little guidance provided in the pompeii book about it.

[UtahBeehiver]

Couple issues and questions:

Is there a particular reason for using soldiers on the first course, ie builder's choice, looks, ?? I know the old pompelli plans show this but there are other and possibly better design options. A half header may be better than full soldiers, even half soldiers would be better than full soldiers due to outward pressure domes place on vertical components. See attached brick pic

The dome height is reflective of a 36" diameter (assume, 2.5" floor thickness - 20.5" height -2.5" oven floor time 2) a 33" oven should have a dome height of 16.5" . It will be harder to use an Indespensible tool (IT) with the dome height not being 1/2 the diameter of the floor diameter.

door height should be 63-65% of dome height or abt 10.75" for a 33" oven based on a 16.5" dome height.

You may need to buttress the vent chamber depending on the type of chimney material you select.

[xizenta]

Guys, I realized that the vent landing can be more deeply intersecting the dome than I previously thought, which allows for a bit of a larger oven. I'm unclear as to how much the entry and flue landing area should intersect the dome. I've mocked up a 3d model which is to scale. It's missing mortar, but the size of the pad and size of bricks are accurate. This would allow a rectangular flue about 36 square inches. It seems possible for me to fit about a 33 inch internal diameter on a 53 inch square hearth like this. My insulation will be 2 inches of fiber blanket and an inch of vermicrete.

Am I missing anything?

[SableSprings]

David S is the forum's small oven king, I believe his oven is abt 26" but cast. I suggest you private message him about specifics. He has a lot of post on the forum so get hold of him.

Actually David S has a 21" (internal) mobile pizza oven that he's used to feed something like 80 people one night. As Russell (UtahBeehiver) noted, do a private message to him. His external oven size (including insulation/enclosure) is 910x910 mm ...something close to a yard across. Your space is plenty adequate to build a very functional oven and looking at the builds on the forum should help with the "landing jitters". His cast "inverted funnel" venting chambers look very efficient and takes very little space compared to the stacked brick versions. I put his link below for your convenience

https://community.fornobravo.com/for...becomes-a-kiln

Good luck and as you've seen there are lots of experienced folks here that can answer questions on lots of build types.

[xizenta]

Gentlemen,

I am already planning to cantilever a few inches around the concrete blocks. I will end up with around 52" by 52". I really hesitate to go further than that because it will shrink a hallway adjacent to my project. no I have not yet poured the hearth.

I will post pictures when I can.

Even with the 52" square though, I am having trouble seeing how I will fit much bigger than a 28" oven. The biggest problem is the vent landing. I can't find a single resource as to how to design one in a space efficient way. As a matter of fact, having read the 67 page FB Pompeii guide a few times, the construction of the vent landing area, how to adjoin it to the dome, and how to affix a chimney/vent thereto is probably the most lacking portion of the guide, in general. As some members have noted, using bricks rather than casting the oven unfortunately takes some extra space away from the interior diameter of the dome and similarly, from the space available for a vent landing.