Turning this to a mass rocket heater

So i was given this wood stove that's homemade but made of steel. I've put rocks around it to make it work and I'm thinking about trying to make this into my mass rocket heater as the base so to say.

So will this work?

It's just a box made of steel with a door at the bottom, fore bricks lining the bottom and 3 sides near the bottom. The legs are off the ground about 12 inches or so ( I'll have to measure to be certain) and goes up to where the flue pipe connects.

My thoughts are using rock and cob around all the steel except the 2 openings. Putting cob in a flue pipe up into a half barrel (my house isn't that large) that sits on a cob and rock base on top of the stove and then the pipe runs the floor for about 8 feet total making a couch/ counter top.

Would the flue pipe be ok dropping below the stove surface or does it need to stay level? Is it going I ng to burn correctly?

If the steel box dimensions are large enough, you could probably use it as a shell to hold a J-tube core made from firebricks. Your current partial firebrick lining will need to be inspected and the walls will probably need to be replaced, based on the irregular bit visible in the photo. You would need to cut out the back of the steel top to allow the heat riser to run straight up.

What are the internal dimensions of the steel box? With that information we can advise if it is worth using this as the shell, or if it would be easier to just build a firebrick core from scratch.

30"long
14" wide
16" high
Minus the bricks inside. I'll try to include a picture it keeps not submitting on me and I've written a big woop whap 3 times for nothing.. ugh

That is a comfortable space to build a J-tube inside. You would want to use firebricks (4 1/2" x 9" x 2 1/2"). As you say your house is not big, I presume you are thinking of a 6" system. You want the core to be 6" square inside for feed, burn tunnel and riser. This would require cutting some firebricks, though you could make the sides two bricks high and add brick pieces (from the old liner material?) to the floor to bring the internal height to 6". You could run a single firebrick row down the middle of the floor and fill beside it with clay, which would fire hard soon. Filling around the brick core with cob would stabilize everything.

You could actually make just the feed tube which sees the most abrasion from brick, and form everything else from cob. As long as it doesn't get scraped vigorously, it will last a long time. Making a 6" square box from scrap wood would make it easy to get the right size and smooth surfaces for burn tunnel walls and ceiling. You can do the same for the riser as long as you reinforce the outside of it with something like chicken wire to keep cracks from opening. Here is a similar one that I built.

As I mentioned, you will need to cut a hole in the back of the steel box top to clear the heat riser. I would make it 12" x 12" to give comfortable working space. You can mount a barrel over the riser, and cob around it for mass. You do want to make something removable to inspect the top of the riser, either a barrel lid or the whole barrel.

Running the exhaust 8' along the floor may be problematic, depending on how good the natural draft of your chimney is. Does it draw any air current in when the system is stone cold? If so, you are probably good. I would suggest making this pipe 8" to reduce friction, or even better half barrels laid flat, and encased in cob.

Glenn thanks for your insightful and encouraging ideas. I recently posted a out the same kind of stove, well I should say similar. Mine is in good shape for a 50 is  year old stove but I need to increase efficiency... but was discouraged from modifications. My query now might have a new solution,  will let you know about my progress

Starting anew with a classic rmh would be suitable for another homeowner, but I like your brainstorming,  cheers

Good luck on your project, and please let us know about your progress. You can start a thread for your own stove if you like, so we can give advice specific to your case. I would make sure to keep the new modifications to the "classic" J-tube inner proportions, as any halfway measures will not be likely to work as well.

Yes indeed Glenn, will comply. We would all be poorer in craft and spirit without your expertise.  I was especially excited hen seeing the all cob rocket you built.

My wholehearted thanks,
Rico

Folks please bear with me, I  am still learning our system here at Permies
This thread would be perfect for the low tech, high efficiency guru William Bronson, I think. He has posted of efforts to create an rmh without ceramic blankets, refractory mortar and those types of materials

How could I send him a notice about Glenn's ideas contained herein?

I have added this thread to the RMH forum, so I expect he will see it before long.

https://permies.com/t/272815

Not sure if I pasted that correctly,  a bit of a Luddite and  make many mistakes
Glenn, the post from 3 weeks back had Thomas and Gerry urging me to forego improving cast iron box, to start anew. But your idea makes sense, and The South provides easy winter conditions...I could possibly rebuild in late May for next winter
Working on a sketch to illustrate what I have theorized