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Steel Dome Oven

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  • Wiley
    replied
    Re: Steel Dome Oven

    G'Morning berryst, Yes, I purchased the 1/4 minus crushed basalt at Shine Quarry. Nice people to work with.

    At present I am putting down my first layer of splits (1 1/4" thinckness firebricks). This is the surface that the dome itself will set upon. This is because I am concerned the expansion and contraction of the steel dome would other wise wear into the vermicrete over time. That would cause a separation between the steel dome and the basalt/fondu concrete and make for heating problems.

    Upon the splits and only inside the dome itself will be a layer of full size (2 1/2") firebricks. This will make for a thicker bottom layer than is called for in the Pompeii Plans. That will increase the time needed to reach pizza temps, but on the plus side it should also increase the holding capacity once at temp.

    Today is the Fourth and while my wife gets to go to Seattle and watch the fireworks at Gasworks Park with the kids and grandkids I get to stay home and watch the dogs and work on the WFO... Lucky Me :-)

    Wiley

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  • berryst
    replied
    Re: Steel Dome Oven

    did you get your crushed basalt at shine quary? Is it working yet? .....the basalt that is.

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  • berryst
    replied
    Re: Steel Dome Oven

    AAAAHHHH!!! End of propane tank....read the first post again!

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  • berryst
    replied
    Re: Steel Dome Oven

    I'm doing things a little different too. I'm using perlite. It does not absorb water at all as far as I can tell. I poured a 4" perlcrete insulation layer last night and today played with the first fire bricks . Yes, I did go to work a little bit late.

    I'm sort of doing a cross between an igloo and a barrel. The operative word for me is barrel with tapered ends.

    With the amount of steel you have it seems like you could just insulate the dome and skip the brick...just a thought Where did you get the dome?
    berryst.

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  • Wiley
    replied
    Re: Steel Dome Oven

    SpringJim,
    I tried soaking the vermicrete once the problem became obvious, and instantly realized the mistake in that as the vermicrete was a unit/mass only when dry and the cement holding it together was too new to actually hold anything together when wet again. When pouring the vermicrete a thin layer of cement rich water rises to the surface, as it dries/cures this thin layer of cement holds the surface together; sprinkling with water simply disolved that layer and made the vermicrete a loose mass of wet vermculite again. :-(

    The whole problem would have been avoided by pouring all the concrete first and then the vermicrete.

    As for plastic I would be wary of placing plastic anywhere that couldn't be removed. It may take a while for heat to get down to where it is in the structure and the fear of some point in the future having a pizza party and the oven ripping hot and all of a sudden the crinkled noses and the question, "What's that smell?" I've smelled plastic bags that have been blown under cars and caught by the catalytic coverter. Not a very nice smell and I would not be willing to take the chance in my WFO.

    Wiley

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  • SpringJim
    replied
    Re: Steel Dome Oven

    soaking that vermic layer or using a layer of plastic could help too!

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  • Wiley
    replied
    Re: Steel Dome Oven

    Thanks Berryst for the kind words.

    Note to self in next life (and anyone else who might be interested): When making a form for pouring concrete that is a double form (pour one; inset 2nd form and pour it) pour all the concrete parts first. Pouring the slab and then pouring the vermicrete worked fine ...fine that is until I went to later pour the concrete surround. Oh, I did all the obvious things: stub rebar so the slabs would mechanically join and rough texture for same reason, but I didn't allow for the sponge characteristics of the vermicrete. When I went to pour the surround the vermicrete wanted to soak all the water out of the fresh concrete. Made it a pain to work and finish. Would have been alot easier to pour what would end up being a basin and then later pour the vermicrete into that.

    Live and learn and forget by the time the lesson is needed again :-)
    Wiley

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  • berryst
    replied
    Re: Steel Dome Oven

    That thing is awsome. Should work very well.

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  • Frances
    replied
    Re: Steel Dome Oven

    ...so far it looks just like everybody else's build......

    Well, except my framing never looked that neat. Nice double form you've built there!

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  • Wiley
    replied
    Re: Steel Dome Oven

    Continuing Update: I tied the rebar and made the form for the hearth pour today. My plan is to pour concrete to the level of the inside line and then lay in my internal form for the vermicrete. Then pour the internal form full with vermicrete.

    Once the vermicrete is poured, the idea is to add an additional 1" strip of wood all around the top edge of that form and set in the piece of high tech insulating board. This I got as a gift and it is unfortunately not quite big enough to fill the 51 inch by 51 inch area of the vermicrete. The areas not filled by the insulating board will be filled with more vermicrete. I'm using the board because it came at the right price (free), is most likely a better insulator than the vermicrete, and will create a flat surface upon which to more easily lay my firebricks. The final thickness will be 4 1/2 inches of insulation.

    Once the main hearth and vermicrete have had a day or so to set up, the internal form will be removed and an additional 1 inch strip will be added around the top of the outside form. Then concrete will be poured in the remaining space.

    With any luck I should be enjoying homemade WFO pizza by the middle of July! With final completion by ????

    Wiley

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  • Wiley
    replied
    Re: Steel Dome Oven

    Just as a followup on Dick's idea on using Hardibacker in place of the plywood for supporting the hearth during the pouring of the concrete. Today I cut two sheets of Hardibacker to be 3/4 inch larger all around than the two openings I have. My openings measure 2 ft by 4 ft... 8 square ft.

    I then make a simple stiff leg consisting of a 30 inch piece of 2x6 across the top and a cut to length piece of 3 x 4 dunnage supporting that and resting upon a short piece of 2 x 12. This was to support the center of the 2 x 4 sheet see photo if that's unclear.

    I then wanted to get some idea of what sort of weight it could support. So I started stacking 8 x 8 x 16 concrete blocks on the top. I stopped at seventeen blocks. Not because it was indicating problems, I think I could have placed many more, but because my calculations for weight of the poured slab (area supported by the Hardibacker) indicate it should weigh about 400lbs and I had 510 lbs on it in this test. I calculated the weight of the slab from the data on the bags. They said that it took 5 bags to pour 9 square ft at 4" thickness. That's bigger than the 8 square ft but gives a saftey margin to account for water weight. 5 bags at 80 pounds equals 400 lbs.


    I then unstacked and glued the Hardibacker down to the top of the block walls and stacked until the glue cures. Tomorrow is a day off and Thursday it should be tight and I can proceed with framing for the slab pour :-)

    This is certainly easier than cutting going the plywood route and for anyone thinking of a "H" shaped stand this might be something they might consider. Hardibacker is not that much more expensive than a sheet of 3/4 plywood and one does not need the extra support nor go thru the hassle of removal. When all is done I will simply reach in with my chainsaw. One cut and the support will be removed in a moment.

    Wiley

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  • thebadger
    replied
    Re: Steel Dome Oven

    Wiley,

    I think you can cut it to fit or to overlap... I cut mine to fit and all seems well.

    I was paranoid about a "blow out" so I did use a lot of extra support. I wasn't sure of the strength diff between plywood/backer so I wanted to be safe than sorry. I think I used about 18 bags of 80 lb. quikcrete. I figure I can burn any of the 2x4 I have leftover.

    Dick

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  • Wiley
    replied
    Re: Steel Dome Oven

    Dick,
    I'm assuming you cut the concrete board slightly larger than the hole and laid it on top and supported the piece until the concrete sets. I like your idea alot and by luck have a couple of 3x5 ft sheets of hardibacker left from another job. The hardibacker I have is 1/2 inch thick and it probably wouldn't need that much more support and since my space is divided into two, it wouldn't be bridging more than 24 inches in the short span.

    Thanks alot for the tip, you just saved me a bunch of time :-)

    Wiley

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  • thebadger
    replied
    Re: Steel Dome Oven

    Wiley,

    Looking good. One thing I did was to use concrete board in place of wood when pouring the hearth. I just left the concrete board in place. Has a nice clean look to it as well.

    Can't wait to see your "metal" oven up and running.

    Thanks
    Dick

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  • Wiley
    replied
    Re: Steel Dome Oven

    Update for those following my progress. Yesterday I unstacked and restacked the base gluing the cement blocks together and to the base as I went. Today I bent the rebar for block cells and for the supported slab (hearth slab) and poured the infill. I guess I'll have to wait a few days before I can start framing up for the support slab.

    Although I'm one tired puppy, it's the having to wait for the concrete to cure that's a real drag.

    Wiley

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