OPTION B: Small Propane Furnace prototype with aircrete (rev 2)

Overview
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This maybe easier to build providing one can make aircrete. I have made a test block.

When finished this furnace will be similar to OPTION A but with aircete where there was perlite. For the first furnace I am going to try about a 1" refractory shell with 4" of aircrete cast around it..

"The insulating R-Value of Air Crete blocks that are 8” thick is 18."

No idea what the R value of the refractory is.    I only want to melt copper based metals.  When I go to cast iron I may use more.


Build Sequence
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• Cast the aircrete sub base
• Cast a refractory base for under the cylinder
• Cast the refractory cylinder 
• Cast an aircrete cylinder around the refractory cylinder
• Cast a refractory layer to cover the aircrete cylinder
• Cast the lid maybe a layer of refractory over an aircrete base

The options for the refractory core are the same as in the OPTION A furnace. A removeable outer form will have to be made for the refractory.

The refractory shell will be the core for the aircrete insulation layer.   The furnace outer skin will serve as the outer form but it will need to be supported.

Forms Required

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Sub base, A circle shaped depression with a Styrofoam drain hole plug.

Refractory base. Same as above but smaller.

Refractory cylinder.  The core is the same as furnace OPTION A.   The outer from will be sheet metal supported by wood rings.  This will be removed.

Aircrete cylinder.  Only need the sheet metal outer skin but it will require wood support rings.

Failure Mode

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I am counting on the sheet metal shell to hold the furnace together should it fail.  The lid is something I need to think about.  Maybe a angle iron frame.  Rebar inside aircrete is not such a good idea.