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Mobile oven design Buoy...HELP - Forno Bravo Forum: The Wood-Fired Oven Community

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  • #16
    Re: Mobile oven design Buoy...HELP

    I guess I assumed the foil was a temporary barrier anyway, to keep the thermal layer from bonding with the steel dome. What are the negative effects of losing the foil after the cement layer has cured?

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    • #17
      Re: Mobile oven design Buoy...HELP

      "I guess I assumed the foil was a temporary barrier anyway, to keep the thermal layer from bonding with the steel dome. What are the negative effects of losing the foil after the cement layer has cured?
      Yesterday 10:41 PM"

      Correct, the foil is simply acting as a "parting film". That it is corroded away is no problem as it is quite thin and so doesn't pose problems with expansion as it corrodes. I never made a case for any thermal increase nor for reduced cracking (I included it between the polygonal sections of refractory so that it would crack where I desired rather than randomly) . I included it in my build primarily to keep the calcium aluminate concrete from sticking to the steel dome during the construction and first firings. It was placed so that the two (refractory and steel dome) are in intimate contact yet not bonded. The intimate contact allows for rapid and efficient heat transfer from the steel dome to the refractory. The "not bonded" is so that stresses due to differences in expansion between the two materials can be accommodated.

      Whether this same action is desirable in the construction of a more traditional brick domed WFO is for each to decide for themselves. Each builds their own WFO. When one diverges from the tried and true path (Forno Bravo Pompeii plans) one suffers or gains from their decisions.

      Hope this helps,
      Wiley

      I disagree, friends are not over-rated. Sorry if your WFO has cost you a friendship, WFOs usually bring friends together.

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      • #18
        Re: Mobile oven design Buoy...HELP

        Guys, my apologies if I insinuated you didn't have a clue what you were doing with the foil.
        Foil seems to raise its ugly head every few months, its roots going back a long time with old school builders. From what I have read, their intention was a slip plane that would allow the layers to move independently, thus reducing movement of outer layers and reducing cracks. Problem is, even if the foil does not corrode, the slip plane would only work in one direction (like rubbing your palms together) and would do nothing for outward expansion.
        In your application, stopping adhesion of the layers, I see no reason not to use it...foil is cheap.

        RT

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        • #19
          Re: Mobile oven design Buoy...HELP

          Back to the main issue. For the life of me I can't see how you haven't painted yourself into a corner. Are you still planning to use the steel dome as your interior oven surface? Without any thermal mass? Sitting on what?

          Your firebrick floor still touches the metal trailer housing? I work with metal a lot, and believe me, that stuff conducts heat.

          I think you need to do some serious thinking at this point. If it were me, I'd be thinking in the direction of using your steel sphere as a waterproof covering to a real oven, with proper insulation all around. That sphere is immense by brick oven standards. You really don't need anything like that much interior cooking space for a portable pizza oven.
          My geodesic oven project: part 1, part 2

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          • #20
            Re: Mobile oven design Buoy...HELP

            Originally posted by dmun View Post
            Back to the main issue. For the life of me I can't see how you haven't painted yourself into a corner. Are you still planning to use the steel dome as your interior oven surface? Without any thermal mass? Sitting on what?

            Your firebrick floor still touches the metal trailer housing? I work with metal a lot, and believe me, that stuff conducts heat.

            I think you need to do some serious thinking at this point. If it were me, I'd be thinking in the direction of using your steel sphere as a waterproof covering to a real oven, with proper insulation all around. That sphere is immense by brick oven standards. You really don't need anything like that much interior cooking space for a portable pizza oven.
            I concur,
            Wiley

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            • #21
              Re: Mobile oven design Buoy...HELP

              Thanks guys for the comments, it helps keep me thinking about new ways to make this work.

              My initial plan was to lay down the FB insulation board between the fire brick and the steel deck. The insulation board MSDS states that it will reduce 800F to 170F. If this is not the case I assume I'll have a serious problem.

              As far as the dome is concerned, I thought seriously about a traditional brick dome for a long time but everyone I asked in the Alan Scott camp advised that mobile and brick domes do not get along. The bouncing and bumps of the trailer end up causing serious damage the the dome. I do not want to deal with this. We will be using this oven as a tool for a professional catering company. So my plan is to finish the deck. Tack weld the dome back into place at a few joints so as to keep it in place but also reduce its ability to transfer excess heat into the trailer directly through the steel parts. THEN...

              foil the dome (to create a slip layer) and add 2-3 inches of refractory heat for thermal layer. I understand the steel dome itself will not cook great pizza. Then basically follow Wiley's steps with insulation blanket, rebar, chicken wire, finish with stucco.

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              • #22
                Re: Mobile oven design Buoy...HELP

                mobile and brick domes do not get along
                This is correct. Most successful mobile ovens for catering use modular ovens: fewer pieces means fewer problems.
                FB insulation board between the fire brick and the steel deck. The insulation board MSDS states that it will reduce 800F to 170F
                This too is correct. My concern is that your brick floor is butting up against the steel ring without any insulation between the two. Heat travels sideways, not just up and down.
                Tack weld the dome back into place at a few joints so as to keep it in place but also reduce its ability to transfer excess heat into the trailer directly through the steel parts.
                I think any metal to metal contact is going to kill you as far as heat transfer.

                Your oven, no matter what it's made from needs to completely isolated from your metal support structure. Think about your oven enveloped in insulation, with no direct contact. safety issues aside, you're going to have to haul a second trailer for firewood.
                My geodesic oven project: part 1, part 2

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