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rocket mass heater riser - firebrick wrapped in high temp wool

 
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Mud and I are working on a book.  This is the part about firebrick+wool risers.  We strong encourage everybody to share their experiences.  We hope that this thread will grow to ten pages of information about firebrick+wool risers.


Simple and quick.  Quite good.  Probably the most common riser.

On the downside, when you start a fire, you might need to prime the riser twice - the bricks start off cold and can be a little slow to warm up.  On the upside, if you accidentally let the fire go out, the riser is still very warm for hours - so no need to prime the riser.  

Stack the firebrick to define the interior of the riser and then wrap with high temp wool (two inches thick is better than one inch thick) and then wrap that with a bit of wire.  Since the wire is entirely outside of the riser, the temps it will be exposed to is in the 400 to 700 degree range - well within the tolerances for the wire.

The stack of firebrick can be dry, but some people choose to coat each brick with a thin, clay slip as they are stacking the bricks.

Total cost is about $80 to $120.

Mud says

Cutting a notch in the end of each brick will allow them to hold each other in place without mortar or slip.





See the riser near the end of the video





This video is an excerpt from the full 4 movie set "Better Wood Heat."  But it does give you a taste of this type of riser

 
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    I recently viewed the two videos below about a 'fire proof' material and wondered if anyone at permies or anyone working with the rocket stove engineering knew about this material and whether it could be used in the rocket stove risers. It would be interesting to see if the material would hold up over time.

    The first video shows the presenter using a propane torch burning against this material he is holding in his hand. The second video shows the presenter using the material as the insulation in a small forge.

VIDEOS
History of a Lost Supermaterial & How To Make It (Starlite Part 2)

How to Make a "Cookie Dough" Forge (Starlite Part 3)


Starlite Mixture for Fire Proof Insulation Forge of 1 gal can
2 Parts, 40 grams Flour 400 g
1 Part, 20 grams Corn Starch 200 g
1 Part, 20 grams Powdered Sugar 200 g
1 Part, 20 grams Baking Soda 200 g

Forge = 1 Gallon can – using ‘soft’ torch, not pencil flame
 
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Jesse Glessner wrote:     I recently viewed the two videos below about a 'fire proof' material and wondered if anyone at permies or anyone working with the rocket stove engineering knew about this material and whether it could be used in the rocket stove risers. It would be interesting to see if the material would hold up over time.


After I saw that first video 2 or 3 years ago I tried making a small cob oven in my backyard with that material as a lining. It turned out awful! I had misunderstood--it is not insulative, but rather heat-resistant and heat-reflective. It needs to burn a bit to become a black body radiator, and it has a pungent smell when it burns, and that smell stayed in my oven. I had put it on moist, and over time it cracked and fell apart. I think you would want to make it in the right shape and dry it first, maybe do it as panels.

In short, it did not work for my application (it was a bad idea--for an oven you want a mass to heat up, not a heat reflector), but I think it possibly COULD work as a rocket riser. I may give it a try by molding it around a large PVC pipe, letting it dry, removing the pipe, burning the inside with a torch, and then using it. I think it will be brittle, and will need support, but I'm guessing it may just work.
 
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paul wheaton wrote:
Mud says

Cutting a notch in the end of each brick will allow them to hold each other in place without mortar or slip.


What kind of notch? Simple diagram?
 
Hey, I'm supposed to be the guide! Wait up! No fair! You have the tiny ad!
Rocket Mass Heater Jamboree And Updates
https://permies.com/t/170234/Rocket-Mass-Heater-Jamboree-Updates
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