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rasorface 08-03-2010 05:18 AM

Mobile Hand-Formed Dome Oven Build
4 Attachment(s)
I'm building a hand-formed dome oven on a 5x8 utility trailer. I purchased a trailer rated at holding over 2 tons and with brakes.

I've studied a lot of people's trailers and decided to use some of the advice of Dan Wing in his Technical Notes on building trailers for mobile masonry ovens. For the folks who don't know who Dan Wing is, he is the co-auther of the book The Bread Builders: Hearth Loaves and Masonry Ovens.

In any case, I'm using his advice regarding building a metal pan to hold the oven floor. In his notes, he states: "Form a 14 or 16 gauge sheet metal pan (4-5 inches deep) that will serve as the trailer “bed.” It will also serve as the form for a) a thin insulating vermiculite/concrete or pumice/concrete layer and b) a thin, reinforced full strength slab that serves as your hearth base." My oven bed won't do double duty as the trailer bed. See the attached pictures.

I believe he means to pour a reinforced base slab first. Then, an insulating slab atop the base. Then firebrick atop the insulating slab. Does anyone read that differently?

I made my pan about 6" deep. The standard firebrick I will be using is 9" x 4-1/2" x 2-1/2". I will be laying it on the larger face, for a height of 2-1/2". That leaves about 3-1/2" for the base and insulating slabs.

I have several questions that I would love to get feedback on:

Do I worry about building a base slab at all since my metal pan has a sheet metal bottom that will hold whatever I put in it?

Do I use the entire ~3-1/2" for an insulating slab?

Should I use less insulation and add a little bit of mass beneath the firebrick?

The way I designed the pan, I could get away with adding more base/insulation. The firebrick would show a little more side than I had planned, is all.

Anyhow, I'd love to hear some thoughts. I've been lurking long enough. I'll post pics as I progress.

david s 08-04-2010 04:23 AM

Re: Mobile Hand-Formed Dome Oven Build
I broke most of the rules from your oven trailer advice by Dan Wing, mostly because my oven is small and light enough to fit on an existing trailer.On the subject of the supporting slab, I used reinforced aerated concrete, 75mm thick which provides both strength and insulation, although it has cracked either because it's not strong enough or maybe because I went over a speed bump too fast having forgotten I was hauling an oven. It still holds together because the supporting base sits in a steel cradle.

rasorface 08-05-2010 06:07 AM

Re: Mobile Hand-Formed Dome Oven Build
Your advice and reading a little more of the FB Pompeii docs leads me to pouring a reinforced insulation base upon which I'll set the firebricks. This will be mainly for baking pizzas. I don't need the deep, long heat for things like bread.

david s 08-06-2010 12:08 AM

Re: Mobile Hand-Formed Dome Oven Build
The dilemma is to make a supporting slab that is strong (heavy aggregate) but not a good insulator, or use a lightweight aggregate like vermiculite or perlite and end up with a slab that is a good insulator but not particularly strong. Or go somewhere in between. Alternatively, a sandwich that has a strong base and an insulating top layer. Just go with your gut feeling and hope for the best.

david s 08-06-2010 12:13 AM

Re: Mobile Hand-Formed Dome Oven Build
Sorry, sting should read strong.When I'm stung I think I'm strong, but probably actually weaker.( Stung is Australian vernacular for inebriation.)

rasorface 02-13-2011 05:39 AM

Re: Mobile Hand-Formed Dome Oven Build
1 Attachment(s)
Back from hiatus. Decided to use 2" FB Board for insulation. Pouring a thin slab in the bottom of the frame to bring the hearth floor to the proper height. Did some dry fitting and constructed a dome base template and door form.

Tscarborough 02-13-2011 08:59 AM

Re: Mobile Hand-Formed Dome Oven Build
Won't you be fighting the wheel? Why not orient the entry to the rear of the trailer?

david s 02-13-2011 12:38 PM

Re: Mobile Hand-Formed Dome Oven Build
Did you give that concrete slab plenty of time to dry? Because it is in a steel pan, if you build straight over it you are trapping moisture which will be very difficult (and slow) to remove later.

rasorface 02-14-2011 03:57 AM

Re: Mobile Hand-Formed Dome Oven Build
Tscarborough: I oriented the opening to the side since the rear of the trailer will be used as the prep area.

david s: I haven't poured the slab yet. Thanks for the heads up. I will give it plenty of time to dry. Your suggestion gives me an idea: perhaps I'll drill some holes in the pan bottom for air. I'll think about it.

Thanks for the input, guys. I do appreciate it.

david s 02-14-2011 04:27 AM

Re: Mobile Hand-Formed Dome Oven Build
As your trailer only has two wheels and the centre of gravity will be well above the axle you must be careful to guard against the drawbar going skyward and the oven wanting to fall out the back. Maybe some smaller retractable wheels at the rear.

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