Rocket Mass Heater, Part 3

THIS IS AN OLD POST. WE MOVED THE UNIT TO A DIFFERENT INTERIOR WALL SO THAT WE COULD ACCESS THE EXISTING BRICK CHIMNEY. STILL USING THE SAME BRICKS BUT NO FOAM BOARD UNDER OR AROUND THE UNIT.

Got our bricks.

Thank you to Shawn and Amanda for taking a drive to Eugene to pick these up

These are not the dense heavy firebricks that I was expecting, but the lighter insulating firebrick.  These are supposed to be easy to cut with chisel or hacksaw.  I am going to need to do a little research and make sure the characteristics of these bricks are suitable for the rocket stove.  It seems like they should work, they will allow the heat to build inside the chamber and they should not absorb much of that heat.  I think that works because I want the heat to travel through the j-tube, build to high temperature in the riser/barrel and then I want the heat to transfer to the thermal mass before the exhaust exits the building.

I started laying out the bricks and thinking about brick count, how to construct the J tube, the heat riser, the support for the barrel and the ash cleanout.  Here are some pictures:

bricks1
The bricks here are set on top of the poly iso foam board.

I don’t think that’s going to work.  The weight is going to deform the foam board. All of the foam board ideas are gone.

I was mainly just laying out the burn chambers and stacking brick to see how the rocket stove will fit in the space.  I really wanted to light up some paper and see if the rocket stove would draw as it is set up here, but I resisted the impulse.  I don’t think we are ready for that step yet.

bricks2

The picture above shows the heat riser extended up a bit so that the top of the heat riser would be about 2 inches below the top of the barrel. I also played around a bit creating an ash cleanout pit.  That is the the rectangular space in the foreground of the picture above.  The ducting would then come out of the ash cleanout cavity,  run forward toward the position of the photographer in this picture (thanks for camera work, Marylea) then it will turn 180, run back and end in a stack that will rise and go out the “window” space just above the rocket stove.  I am going with the stack up and out of the mass heater in close proximity to the heat riser as Ernie and Erica have suggested.

bricks barrel

Here is a picture of the rocket stove with the barrel lifted and in place over the heat riser.  (pretty barrel, right?  need to spray that down with some bbq high temperature paint)

I think I will have to bring the whole rocket stove forward at least a foot so that I can get 2 feet of clearance between the barrel (that is going to get very hot) and the frame wall behind the stove and the ceiling above the barrel.

I think I will end up with a fireproof material on the walls near the barrel and on the ceiling above the barrel.  I am thinking about durock board, then maybe I end up with tile on wall behind or maybe just a cob type plaster.

Question for today:

  • Am I going to need to “glue” the bricks together with a firebrick mortar or cement or will I be able to mix a cement/cob material with vermiculite and seal the burn chamber, the j tube, the heat riser and the ash cleanout?

Going slow.  Having fun laying out this project.  We have been thinking about this for a long time.

It will be a few days before I can get back to this project.  I get my first day of jury duty tomorrow and also need to get back to the office grind for a reasonable number of hours.  Words need processing, phones need answering.