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Planning my 32" cast oven

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  • #61
    Originally posted by AndreasP View Post
    Wasn't able to build the form for the gallery today, but took off the front template so that I can reuse it for the front of the oven.
    I think I need:
    • For the entrance to the gallery I will reuse the same template but add to the bottom, so that it can sit in front of the firebricks
    • For the end of the gallery that abuts the oven opening, I will make a new template, 1 1/2" narrower and lower
    This gives me a 1 1/2" recess against which I can rest the door and a 1 1/2" thick gallery.
    I actually made a mistake when I first cut the template for the dome opening and made it only 1 1/2" larger than the opening itself. That's why the duct tape is there.

    I can see some voids on the face where the gallery will connect. I'm not planning on doing anything with those voids. Most of them will be covered by the gallery.
    Will be interesting to see how many voids I get on the inside when I remove the sand.

    Covered it back up with a wet linen and a plastic sheet to keep it moist.
    You won't really be able to tell until you remove the newspaper strips on the inside of the oven chamber.You need to force the mix into the voids, an old butter knife works well. The mix needs to be fairly stiff, if too wet it shrinks away. Peanut butter (smooth not crunchy) consistency is what you want. Sieving out the coarse sand is also important.(#30 way too coarse imo)
    Last edited by david s; 10-26-2021, 09:38 PM.
    Kindled with zeal and fired with passion.


    • #62
      Looking really good!
      My 70cm (28") build:


      • #63
        Thanks Kris.

        Just took out the sand and bricks. The inside looks pretty good. Just a few small voids. I attached some photos, one has a penny for comparison next to one of the larger voids.

        The major issue I had was that the form for the opening to the dome must have been to shallow. When we pressed in the Homebrew it must have slipped behind the form, so there is an extra lip.
        I took an angle grinder with a diamond disk and cut off most of it, then used a grinding disk to grind off the rest. Worked OK, but lots of dust even though the concrete was still pretty moist.
        Definitely easier to work with fresh concrete than when it's fully cured.

        Initially I wasn't going to fill the small voids, but did it anyway. Not sure if it was necessary. Once I started filling, I could just keep going. Every time I look I find more and smaller voids.
        Pressed in the mix with a flexible putty knive, then scraped it off and smoothed it over with my finger. Seemed to work pretty well.
        Covered it up again. Will try to cast the gallery tomorrow evening if I get a chance. Otherwise it will have to wait until the weekend.

        Photos attached are without any filling. After photos in the next post.
        My oven build thread


        • #64
          Here are some after photos with the lip ground off and the small voids filled.
          My oven build thread


          • #65
            That looks terrific, you've done well. I've seen plenty of commercially cast ovens with far more voids.
            Kindled with zeal and fired with passion.


            • #66
              NIce cast job.
              Google Photo Album []


              • #67
                David, Russell,

                Thanks, that make me happy it was backbreaking work especially due to the location of the oven
                It's so hard to judge when doing this for the first time, even with all the information on this forum.

                My oven build thread


                • #68
                  Was able to make the form for the entrance last night. Was trying to build it so that I can remove all of the screws from the outside once it's cast. I attached the piece for the inside of the arch to the front plate, then cut out strips with a circular saw. Hopefully that will help me in removing these pieces.

                  We will see how that goes.
                  My oven build thread


                  • #69
                    If it's any use to you, here are some pics of my cast design (but in castable refractory not home-brew). I've made it as thin and as shallow as I dared, so reducing
                    the heat sink effect.

                    The buttresses on the sides were added to later castings as the corners were a weak point. It only weighs around 9kg

                    Click image for larger version  Name:	P6160030.jpg Views:	0 Size:	177.2 KB ID:	442761 Click image for larger version  Name:	P6160027.jpg Views:	0 Size:	116.4 KB ID:	442762 Click image for larger version  Name:	P6160029.jpg Views:	0 Size:	184.0 KB ID:	442763 Click image for larger version  Name:	P6160028.jpg Views:	0 Size:	171.0 KB ID:	442764
                    Last edited by david s; 10-29-2021, 11:38 PM.
                    Kindled with zeal and fired with passion.


                    • #70
                      David, thanks for the pictures. I cast my gallery last night. I am sure it got a lot thicker than yours. I used one 5 gallon bucket of dry mix. I think that turns out to about 36kg including the water
                      just a guess based on the spreadsheet with densities.
                      the sides are 1 1/2 in thick, the top probably more like 2 in and thicker in places. It was difficult to judge the thickness since my firm wasn't the best design.

                      How big off an issue is the heat sink effect? I assume you talk about loosing heat through the gallery part when doing retained heat cooking? I have more material and could simply cast the galley again. Would that be worth it?

                      Doing it again i would also put cardboard between the gallery and the dome so that I can remove the gallery once cast and connect it back again with lean homebrew.
                      My oven build thread


                      • #71
                        Here are some photos of the gallery in front of the oven as well as once it has been cast
                        My oven build thread


                        • #72
                          No, don’t do it again, you’ve done a great job. Don’t worry about any heat sink effect. Brick builds that build their galleries will have a 4” thick gallery, probably 3x the thermal mass of yours. Just insulate it on the outside, Although casting it, then removing and replacing it may have some advantages, casting it in situ like you’ve done creates a perfect fit and is so much easier. Just cover it for a week once you’ve removed the front mould plate.
                          You’ve done extremely well for the first time. Like I said, when you build a second for a friend it will be faster easier and better. What you’ve done in a few hours work takes the brick builders months and it’s as cheap as chips.
                          Kindled with zeal and fired with passion.


                          • #73

                            Thanks! I just took the mould off. Actually looks pretty good, a bit thick at the top where it meets the chimney, but not too bad.
                            I'll have to see how much space i have for insulation. I was planning on only 2 in for the gallery. The sides are where I don't have a lot of space. I can certainly do more towards the top.

                            I'll post photos later.

                            Thanks for all the help and reassurances. This forum is great.
                            My oven build thread


                            • #74
                              The gallery does not see the kind of temperatures the dome gets, so insulation thickness can be reduced there. 2" should be plenty.
                              Kindled with zeal and fired with passion.


                              • #75
                                Here are some photos.
                                Covered it back up and will let everything cure wet for 7 days. That brings the curing of the dome to 11 days.
                                Then dry for a week in the sun and after that the 7 days of ever larger fires.

                                Need to figure out a good pizza dough recipe. The one we have used with our BBQ before is really hard to stretch.
                                My oven build thread