#21  
Old 06-15-2008, 02:42 AM
david s's Avatar
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Default Re: Portable Oven Designs

For my mobile oven I cast the dome in one piece which eliminates brick joints and weakness where cracking is likely to occur. I was trying to keep the weight down and made the outershell ferrocement shell 10mm thick. If you want ferrocement stronger you use more mesh rather than more cement. I've also been experimenting with fibre and would chuck some of that in too if I were doing it again. I think the big problem with a mobile oven is the transportation. Road corrugations and speed bumps are not kind to dense,dry brittle material. Oven holding up ok so far.I kept the weight of mine down to 160 Kgs.
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  #22  
Old 06-15-2008, 02:56 AM
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Default Re: Portable Oven Designs

Wiley,
The fibre to use for reinforcing is fibreglass, but it has to be AR (alkaline resistant) type. The other fibre you refer to is probably the polypropolene fibre, which is quite short and fine and does not provide a lot of strength. It was originally used to fireproof concrete. When the temp hits 165 C the stuff melts and leaves tiny holes that steam pressure can escape through, leaving a fire damaged concrete wall or floor intact. Castable refractories use it in their products for the same purpose. I think we can all benefit from using it too to help when curing our ovens although the outer shell is unlikely to get that hot. Better to use it in the oven walls and the AR fibre in the outer shell. I believe this to be a vital improvement utilizing modern materials.
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  #23  
Old 06-15-2008, 07:07 AM
Peasant
 
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Default Re: Portable Oven Designs

Wow, how did you keep it to 160kg?
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  #24  
Old 06-15-2008, 02:44 PM
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Default Re: Portable Oven Designs

The oven interior is 540mm diam and I made the inner dome thinner (50 mm) but compensated by increasing insulation. Also made the outer shell as thin as possible (10mm) and the supporting slab used Hebel (airated reinforced concrete). The flue is a sliding fit, into an outer s. steel sleeve, for transportation.
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  #25  
Old 03-11-2009, 08:06 PM
Serf
 
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Location: Selmer,Tennessee
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Default Re: Portable Oven Designs

Ive started buildilg out a duel axel trailer to put a brick oven on. i have built the steal frame out of 1/4 inch angle. like the one pictured in this web site. I was going pore my
5' x6' X2and a half inchslab and set my refractory bricks in the cement.then build up the oven with brick just like in the FB plans. then Wrap the dome in ceramic blancket and coverit with chucken wire then tucco, See or experanced any problems with this?
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  #26  
Old 03-18-2009, 09:14 PM
Serf
 
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Location: Tennessee, US
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Default Lighter weight cooking floor

Can anyone suggest a lighter weight cooking surface than 8lb bricks? Ferrocement is probably not foodsafe right?
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  #27  
Old 04-05-2009, 01:55 PM
Serf
 
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Location: Selmer,Tennessee
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Default Re: Portable Oven Designs

O k. I've built my double axel trailer out now im going to pour my 4 inch structural slab that is 50"x60". and I think Ive decided on refractory cement renforced with fiberglass and some rebar. and while it is still wet set my fire brick into the slab 1/4 th inch.Ive also concidered cutting 1/4th inch groves into the bottom of the brick for more adhearance. any thoughts?
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  #28  
Old 04-05-2009, 03:29 PM
Master Builder
 
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Location: Washington State USA
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Default Re: Portable Oven Designs

Robert,
I like the idea of making a physical join between the bricks and the support by means of the saw cuts. The only downside I can see is replacing a brick might prove problematic should that need arise.

When you say refractory cement are you referring to a heat sink type material (calcium aluminate based) or some sort of castable insulating material? If the former, then what is your plan for insulating beneath the firebricks and slab?

Bests,
Wiley
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  #29  
Old 04-05-2009, 05:12 PM
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Default Re: Portable Oven Designs

Yeah, don't forget insulation, it's not possible to retrofit your under-floor-insulation after the dome is built.
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  #30  
Old 04-06-2009, 12:35 AM
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Default Re: Portable Oven Designs

A castable refractory is not as strong as normal concrete. You should make your structural slab from regular reinforced concrete, then on top of that the insulation layer, then the firebrick floor.If the structural slab is separated in this way it will not be affected by any excessive heat so it doesn't need to be refractory. To save weight you might consider using Hebel slabs (aerated concrete) which will act as both structural and an insulator. It can be purchased with steel reinforcing already cast into it, but you will still need a steel frame with bracing underneath.
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