Mobile Forno Finally started!!

[Xabia Jim]

Originally Posted by aferaci

I'm not sure if I'm going to use the end with the hole yet !!!

Are you going to use these for your hearth? How will the thermal mass be?

... why not cut through the hole and use 1/2 blocks with the cutside/hole down? That would leave you with the original surface up from the... 8x6x24?. It sounds light enough, would the 6" hearth be overkill?

Jim

keep us posted on this project, thanks

[fortran]

Someone had asked about fiber reinforcement of concrete. There are 2 classes of fiber reinforcement: polymer fibers and steel fibers. Polymers are significantly less dense than the concrete, and steel is significantly more dense. Both can suffer from segregation. I think concrete gets more complicated, in that you need viscosity control and wetting agents to try and manage the segregation. Vibration after pouring also needs to be controlled. Polymer fibers are likely to get into a melting/burning situation close to the hearth floor.

If you want to surface bond the concrete blocks for the stand, it looks like +/- 45 degree cloth embedded in epoxy is what to do for maximum shear strength. Some people (civil engineers re-inforcing bridges) are using glass, some are using carbon fiber. Glass is probably okay for mobile wood ovens.

In terms of heat transfer (insulation), I wonder how a stack of thin sheets would do? If a person had access to cheap aluminum foil, a stack of aluminum foil that was 4 inches thick (compressed) would have a lot of layers to it, and heat would not transfer across the layers very easily. Heat would equalize within the layers very easily, and 900 F isn't too hot for aluminum. Being metal, it wouldn't break very easily. I haven't tracked down any experiments in this regard, just "idle thinking" at this point. To build an oven doing this, and find it wasn't good enough would be annoying.

If you want a practical example of the stack of aluminum sheets, you can make up a bunch of aluminum sheets as a heat shield for soldering of plumbing. Quite often a layer or two melts, as the flame is too hot for aluminum, but it doesn't take many sheets to keep from scorching wood or paper (drywall facing) on the cold side.

[fortran]

I finally tracked down how to find information this insulation idea. Call it multilayer insulation. Anyway, a paper from NASA in 2001 had some data. They are insulating a space that is 3 inches deep, so similar thickness to under the oven. They ended up using 16 foils (reflective layers) in the stack. It is possible to have too many foils, but worse to have too few. NASA was using an alumina based wool between foils, I seen a different report using glass fabric between foils. Probably anything works. You want the foils shiny. Since the oven weighs quite a bit, you might want to use spacers of some kind to support weight. They will thermally bridge, so you want to stagger them as much as possible. Stainless steel might be one idea for a spacer material, but anything mechanically competent should work. I would think something like mutton bars in a window in terms of putting them between foils. The foils don't have to be as thin as household aluminum foil.

[bdasko]

Hey any updates on this project?

[aferaci]

I've finally got an axle for the trailer and I have a buddy that's going to go over my welds one more time.....I want to be sure it's strong enough after i put all this work into it....So I should have some more progress reports with photos in the next 2 weeks or so.

[ikhan42]

Originally Posted by aferaci

I've finally got an axle for the trailer and I have a buddy that's going to go over my welds one more time.....I want to be sure it's strong enough after i put all this work into it....So I should have some more progress reports with photos in the next 2 weeks or so.

Is there no way that you can rig a dual axle on the trailer may be a smoother ride and a safer ride.

Imran