nizhoni1 Hatfield

just giving information not bragging
sorry you took it that way

about 30 feet

My stove is 8 inch with 3 turns.No problems.

I defer to those with more experience to discuss how to make a more compact version of a rocket stove. retrofitting and not going up in flames sounds like a challenge to me.

I used concrete rubble around the flue of my rocket stove. I don't even want to think about how much it weighs. probably more than two tons but I built a bench along two sides of my house.

The crossectional area means the area if the pipe (pi.radius)squared as well as the dimensions of the fire box. If you cut through each section with a knife the area if each section must be equal.That way the force of the gasses/pressure is the same and they leave the exit instead of the entrance.

I used huge pipe because I didnt want to think about obstruction in the flue once all that mass surrounds it.You could probably carefully build a tunnel with cob around chicken wire but I would worry about constrictions from the weight of the mud in the building process.I would also wonder if any gasses could seep out through the breathable cob.

They weren't very clear about why the 4 inch flue was too small.There has to be a system mismatch since there are smaller "pocket rocket" stoves but maybe the difference lies in that they are used for cooking and we are talking mass heaters here.
the exhaust pipe at the exit is just warm after almost 40 feet of travel. I have a cleanout marked by a rock 10 feet from the firebox and it gets too hot to touch.


The

I moved into my little cob hut halloween night.It is only 12x12 by maybe 16 feet high.
It was freezing as I put the finish layers over the final structure and water was dripping from the interior windows as the cob sweated as I laid it on,

There have been several nights recently that were 14 degrees.I was sleeping with the window open and just cooked a meal on the top today. It is taller than the original and I have compensated by being able to step up on the bench to stand next to it. The the rocks in the floor surrounding are all toasty warm.

What a arelief.

I posted pics somewhere else and they said they were HUGE. What are the recommended limits for size here?

I went on and tore out the heat riser today. after reviewing  I decided the 16.5 inch water heater core and 6 inch diameter heat riser did not match the needs of the 8 inch duct. In the process I  found some clay obstruction at J which was probably too tight anyway.I also think there was some settling and the size of G was 2 inches or maybe less

I think I will be able to retrofit a regular steel drum in the space and will have the room to make a brick riser in the barrel Have to double check to see if that would need to be insulated or the brick is adequate alone.

I will take some pictures of the process.

Its a learning process. building the stove and posting the pictures

paul wheaton wrote:
Pics would be excellent!

If you don't get your info in a day or two, speak up and I'll check with erica.

Ok I built the stove and the thermal battery. Before i put all the mud and mass in the thing drew. I am working alone and I am afraid I misset the container on the heat riser. The thing worked for about a month in the summer then started to backdraft after I assume it completely dried.

I will type some dimensions here to see if anyone sees an obvious problem. I think I am going to have to rebuild.

Using the key letters from the Bible Rocket Mass heater book by Ianto

A=5X8 I loosley tried to shorten that and found no change in draft
B is 12 inches  when I was shaping the cob around the combustion unit I added 6 inches to the height of that.Today I chopped out the front of that when I was trying to tighten A and held a lit match in the mouth of the burn tube and the flame stood straight up
C=5x7
D might be 10 inches but I have to check the photos of my layout
d is 16 inches
F is 6 inch stove pipe inside an 8inch pipe  now I am wondering about this
E is 41 inches but at this point it includes G which I set at 1.5 inches
    i put the core of the hot water heater eccentrically over the heat riser it is domed so I wonder if  the slope has caused a constriction at that point
J is a crescent about 10 inches long with a maximum gap of 3 inches at the peak

K is 8 inch stovepipe. The total length is about 37 feet with 4 right angles. it does not lay flat but rather slopes up 4-6 inches from the beginning to the end

I will send another mail and attach some photos

I am in the slo mo process of doing that. Will upload pics as I do it/am done.Digging out the irrigation ditch (half mile) shearing 17 alpacas and their daily care and waiting for babies have taken priority. Plus I am dead set on finding my book !!!

I am building in a real tiny space so am still fumbling to search for something smaller than a 50 gallon drum for the heat riser

thanks for the linnk Paul. I have the book and read it a few times. It is just in a box somewhere right now.