Fox James

Hi Mark, searching forums via google is normally much more successful than using the  forum search engine.
In any case this is one of the most popular threads ever posted on this forum and I think it may interest you…..
https://permies.com/t/122458/Advice-RMH-build-Hokkaido-Japan

I built this one a few years ago ….

Very simple construction and very hot.

I would suggest you find out if vermiculite board is available where you live, if so you can build a super efficient rocket hot plate stove in a few hours and it will fit inside an barrel if you want.
If you build a 4” J tube to my design, it will be easy to move around or store inside.
I have plenty of build videos on my YouTube channel.

Have you done any revision about the internal temperatures inside your bell?
Apart from the very top 8-12”  you might not need to worry about  expansion or high temperature cement.
In any case you can use the standard pizza oven cement mix called ‘home brew’
3 Parts Silica Sand
1 Part Portland Cement
1 Part Fire Clay (powdered)
1 Part Hydrated Lime
This is cheap, very easy to use and good for 4-500c

Hi Mark, what a great project and it sounds like you are having fun already?

I just read your opening post and wonder about your logic regarding your one year old verses a J tube!
Firstly I will just say that I really like J tube’s designs, they make a lot of sense for many applications, relatively simple to build and very easy to use.
However the open top fire box will be an irresistible draw any child of any age and a perfect hight too!
Something like shorty batch box design can be set quite high off the ground and also have a door.
Secondly I would advise reading up on the use of any high temperature matting or wool, its use is very popular on this forum but as an example, if you use it inside your bell and you get a down draft of wind (very common with open top J tubes) you could be allowing your room to be contaminated with potentially toxic dust.
Of course that is totally up to your discretion as the product  is very effective but does come with some risk!
Your ideas about building an internal brick chimney is unusual but sound….. and should be very long lasting, the down sides might be the work and cost involved or maybe the fact that you just can’t check to see if it has cracks or leaks but that would also apply to  any internal chimney. Something like a cast iron pipe or stainless steel pipe might be an option.
You may want to look at cement board and find out what is available near to you. I often use high temp cement board for chimney construction. That would be long lasting and simple to use.
Vermiculite board would kill two birds with one stone as it is very insulating and also very easy to work with.
Good luck in any case……

I have this short video showing a slightly different lay out, it looks awesome but is a a bit sensitive.

Hi and welcome to the forum.
There is a good reason why you are finding it difficult to find info on such an endeavor!
 There are a few issues to overcome and very few people actually succeed to successfully reach this goal.
To start with the very nature and design of a rocket stove is to burn hot and fast for short amounts of time in order to store gentle heat is a dense mass.
Where as most cooking situations require a consistent but adjustable heat source, and that is not easy to achieve with a rocket stove.
This sort of project will be quite a big undertaking and very unlikely to be cheap!
At the very best you will end up with a compromising oven, certainly compared to a clean easy to use, fully temperature adjustable, gas or electric over anyway.
However when there is a will there is a way……
Incorporating a hot plate is probably the easy way, you can quite easily and for a reasonable cost, build a dedicated 6” J tube rocket stove with a large hot plate.
You have to be a bit more careful  not to loose to much heat through the hot plate if you want to further heat a mass and heating a half decent oven with a door is going to be a challenge.
I guess the next step is for you to tell us more about what you would like and expect. The area you want to heat and the actual space you have?

Yes 500 + at peak burns depending on what you are burning and how diligent you are at feeding the fire.
Every stove will perform slightly differently (some times very differently) it is a compromise of how much wood you cram in and how much air is being pulled through the system.
No doubt you will soon discover what is best for your particular circumstances..

Hi Mark, If I recall rightly you are thinking about building a 6” J tube?
If so then you may possibly see 500c exiting the top of the riser but a more average temperature would 300-375c.
Given perfect conditions, a well insulated straight up and tall chimney, 1” square lengths of softwood in the fire box with no ash build up, then maybe 500c for a short time.
A 6” batch box is more likely to offer 900c at peak burn.
There is a good reason for the big temperature difference, a J tube burns the tips of the fuel in a six inch square box, a batch box burns a whole load (batch) of wood right down the whole length in a much bigger box!