Monday, November 19, 2018

Apocalypse Builds: Concrete Block Stove

Last week I reviewed a rocket stove and gave it a less than stellar review. This week I decided to look into other options, either commercial or home made.

Since I have a bunch of stuff sitting around, much of which I would like to dispose of, I decided to look into concrete block rocket stoves. The siren call of bacon and eggs after the fall of civilization appeals to me; marauding bands of Mad Max style raiders can have fun, but I want my breakfast!

The idea behind concrete block rocket stoves is that you have five hollow concrete (or “cinder”) blocks, called breeze blocks in some places. Four of them will be standard rectangular blocks, with the last one a square block with what looks like serifs on it -- kind of like an “H” with an extra center bar between the two long ones.

If you want to use a frying pan (I recommend cast iron for this), you'll also need some sort of pot standoff. I use a couple of rocks on top of the rocket stove, but most people use something nicer like a gas cooktop pot standoff.

1 & 2) Foundation
Lay two concrete blocks so that they form a long thin bar, with a continuous top and the holes on the sides. This forms the foundation.

It's technically possible to do this without the foundation, but after experimenting, it seems to make a large enough difference to make it worth it.
3) Begin Combustion Chamber
The third block is the differently shaped one. Lay it so that it is dead center on top of the two foundation blocks and aligned with them. The hole in it needs to be aligned so that you can see the seam of the two lower blocks in it. 

This forms a sort of pyramid with the blocks, and creates the back of the combustion chamber.

4) Complete Combustion Chamber
Lay the fourth block on its end, perpendicular to the foundation. The bottom hole of this block will align with the gap in the nonstandard block. 

This completes the combustion chamber, and allows you to feed fuel into it in a protected area. This also allows you to place kindling and small amounts of fuel in the top part of that block, giving you a partially covered area if you have to dry out fuel.

Be aware that the back of the combustion chamber has a small divot that will fill up with ash as you use it, so you'll need to clean that out between uses.

5) Chimney
Lay the fifth and final block so that it's directly on top of the third block, holes aligned to form a chimney. The combustion chamber back will be only partially underneath the hole in the block, but don’t worry, it's supposed to look like that.
    Place kindling in the combustion chamber, roughly half way in. Light it, and place small pieces of wood or other fuel in it. Slowly push the fuel into the back of the combustion chamber as it burns.

    Grab your kettle, put it on there, and make yourself some hot chocolate. Congratulations! You have a rocket stove. It takes me less than five minutes to heat up a ten inch cast iron frying pan in order to fry eggs.

    They aren't terribly portable and aren't the best possible design, but they are a fairly nice option for those of us who expect to bug in and don’t want a larger permanent structure.

    My Rating
    • 4/5 as long as you are bugging in, or have the materials handy at your bug out site.
    • 1/5 if you are bugging out.
    Good luck, and don’t forget to practice.

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