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

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

    Can anyone link me to other projects around this size or smaller? I have a 47 by 47" concrete block stand already built. I can possibly build the hearth to extend over the edge of the blocks by 2 inches on each side.

    We are doing a corner installation and I am having a lot of trouble figuring out how to design the Arch / entry and chimney with bricks without taking too much real estate away from my dome. In general the size of the firebricks makes it very difficult to create an arch and opening. I would like to leave at least 28 inches of internal space for the oven, so that means I have about 8 or 9 inches on a corner installation for an entry and chimney.

    Anyone with samples to other builds on 47 by 47 concrete block stands would be very appreciated.

  • #2
    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.
    Russell
    Google Photo Album [https://photos.google.com/share/AF1Q...JneXVXc3hVNHd3/]

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    • #3
      Xizenta,

      I take it that you haven't poured the concrete hearth on top of the stand. If not, you may be able to gain a lot more real estate than you may realize by cantilevering the hearth slab. As Russell said, David S. is definately the go to guy for an oven that size in cast. However, you may need a little more real estate to work with (at least for the entry) since you are planning to go with brick. Also, some pics of what you have to work with would help.
      Joe Watson, "A year from now, you will have wished that you had started today"
      My Build
      My Web Album

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      • #4
        Welcome to the forum! I was typing up a response that was essentially what Joe posted above but he beat me to it
        Several builders have either poured or added a protrusion to their hearth to accommodate the vent landing. Let us see what you are working with in terms of surrounding structure and what you have built so far and we might be able to provide some ideas.
        My build thread
        http://www.fornobravo.com/community/...h-corner-build

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        • #5
          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.

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          • #6
            Originally posted by UtahBeehiver View Post
            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.
            Last edited by SableSprings; 11-22-2016, 08:27 PM.
            Mike Stansbury - The Traveling Loafer
            Roseburg, Oregon

            FB Forum: The Dragonfly Den build thread
            Available only if you're logged in = FB Photo Albums-Select media tab on profile
            Blog: http://thetravelingloafer.blogspot.com/

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            • #7
              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?
              Attached Files

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              • #8
                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.

                Russell
                Google Photo Album [https://photos.google.com/share/AF1Q...JneXVXc3hVNHd3/]

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                • #9
                  Originally posted by UtahBeehiver View Post
                  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.

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                  • #10
                    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.
                    My build thread
                    http://www.fornobravo.com/community/...h-corner-build

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                    • #11
                      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.
                      Last edited by xizenta; 11-23-2016, 10:11 AM.

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                      • #12
                        Originally posted by JRPizza View Post
                        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...

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                        • #13
                          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.
                          My build thread
                          http://www.fornobravo.com/community/...h-corner-build

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                          • #14
                            Originally posted by xizenta View Post
                            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.
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                            • #15
                              Originally posted by deejayoh View Post

                              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.

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