6" rocket stove in straw bale building

I just watched your video, I dont like the look of that wood you are burning, it looks like bark covered twigs!  
Try using some nice dry logs or buy some kiln dried logs to get you going.
I would chop up some really dry logs into 25-50mm diameter sticks and try that.

How is it working now?

we've been having amazing weather over Christmas (22C / 72F), so no real need to burn much. But 2 days ago it was colder and i had 2 burns and we could barely sleep because of the heat radiating from the bell It reaches 60 degrees C (140 F) after an hour or so. I am surprised that it keeps warm until the morning

We don't have the issues anymore with smoke coming from the walls, so I guess everything has settled and dried properly. We hoped the bench would perform a bit better, it doesn't radiate much heat...

On the first moments of the burn, it does still smoke a bit from the door, but that stops quickly when the draft kicks in.

So generally we're happy with the stove! Usually February is coldest here, so we will see how we can manage keeping it nice and cosy in the house.

We've been firing up the stove almost daily lately. We are now using some older/ drier wood, but we still have lots of smoke inside. We have to keep the windows open for at least 30 min from the time we start the fire. Even though there is enough draft (when there is wind), we still get the CO alarm beeping. There is no visible smoke coming through the walls anymore on windy days.

The black smoke comes back through the door of the stove and thus we need to open the window. When it runs good, we can close the door of the stove and it will then run until it burns out. But when we close the windows, it still trips the CO alarm...

On days when there's no wind, we might still get some smoke puffs from the clean-out port...

What can we do about this? Any ideas what could be wrong?

As you know the batch box is very well tried and tested so there will be a reason,
Perhaps you could post another video?

Erik Slagter wrote:We've been firing up the stove almost daily lately. We are now using some older/ drier wood, but we still have lots of smoke inside. We have to keep the windows open for at least 30 min from the time we start the fire. Even though there is enough draft (when there is wind), we still get the CO alarm beeping. There is no visible smoke coming through the walls anymore on windy days.

The black smoke comes back through the door of the stove and thus we need to open the window. When it runs good, we can close the door of the stove and it will then run until it burns out. But when we close the windows, it still trips the CO alarm...

On days when there's no wind, we might still get some smoke puffs from the clean-out port...

What can we do about this? Any ideas what could be wrong?

So your heater is giving you a hard time when there's no wind. That's not a good sign, either the chimney isn't up to scratch or there's a restriction somewhere. You might get away with lighting a very small fire right in front of the port (not inside the port!) and build the fire up while it's going. When the masonry is already very dry and it's still smoking there's definitely something wrong.

Sorry to say, this is what you could get while trying to build the thing as small as possible. The whole batchrocket concept is very picky about friction in the smoke path, too spacey is much better than too cramped. Can't make it sound better, sorry.

It is so difficult to get a true perspective from so far away but there must be a way to get your stove running properly.
The pictures you show of the actual stove looks like it is well made and if the internal dimensions of the fire box are correct it should work unless there is an issue further  down the line.
I am sure a walk around video showing you lighting the stove would help work out the issues.

I have not been able to make a video yet, but first starting the fire in the back of the burn chamber reduces the initial smoke a whole bunch. It starts quick and then I burns hotter than before. I think I will make a video tomorrow afternoon to show you the whole thing

Video 1 https://youtube.com/shorts/9nYqIYqEGmc
Video 2 https://youtube.com/shorts/VaRJzRdPXZE

It's very windy (gusts up to 80km/h) lately and with a full batch it is working pretty well. Now we don't need to ventilate and the CO alarm is not going off. It also runs nicely with the stove door fully closed.

The question is: is it because of the lack of draft that it kept smoking before?

So it is running better now, that is good, there have been a lot of bricks to dry out  and that is often an issue for the first few weeks.
Your chimney has a elbow that can be seen in the picture, are there any more along the route?
Can you tell us more about the chimney.
It almost looks like condensation on the glass ? That could be from high moisture  in the wood.

the stove has 2 45deg bends and goes out 1,5m above the roof. It's 125mm pipe.
The window has some crusty carbon deposit on it, I hope that will burn off now it runs better.

On in the inside, it looks like this now, the pipe is spaced 10-15cm above the bottom (i believe 10cm, but could be a bit more )

I cant remember if you built your stove to 5” or 6”  specifications?
Those two 45% elbows will not help the flow, to what extent do not know and I dont think the 125mm dropping straight down like that will help the performance either.
Hopefully @Peter will chime in with his thoughts ……

we built it based on 5" spec. The bends were a necessity because of our roof.

The core is slightly scaled down to 5" as I understand it, which is very close to  the 125 mm dia of the chimney. It might be that the initial difficulties were just teething problems, such as a wet heater. Give it time, within 4 to 6 weeks of running on a daily basis the thing should be dried out completely.

Having two 45 degree bends in succession shouldn't make a huge difference, if at all.

Today there was not much wind, we burned for less than an hour and it did smoke back when we opened the door. We could not run it without the window open and even with a small window open the CO meter showed ~50ppm

I think I might have to revise the door, because it doesn't have a seal around the other ring of the door...  I think that might be an issue

It's really nice that we only have to burn once and then have the house nice and toasty until the night. But temperatures are dropping the coming weeks so we will have to burn another time in the evening to be warmer in the night.

First burn in winter 2023! I still have to get a hang on getting the temperature right It is nice and toasty in the house after 2 burns. It keeps warm all night, with 17 degrees in the morning.



The first burn she was a bit smokey, but now she's a bit warmer, everything is going great!