measurement questions and big idea

[apricotslice]

Hello people,



My name is Phil, I live in the north of Scotland and I am a virgin rocket builder. I am rather nervous because I'm not sure what to do and am a little afraid of being laughed at if I do it wrong.



As you might expect, I got some big ideas that are probably destined to fail.



So I'm going to build a small shed. About 13ft square with an upstairs. Made with 4 inch blocks and have full fill cavity insulation. I want it to hold the heat.



Being quite small, I need the heater to be as compact as reasonably possible without resorting to expensive materials.



So here comes the first 'big idea'. After realizing that assembling the usual types of brick, there is a limitation to what can be done without excessive cutting or ending up with an overly large pile to achieve the desired internals. So I had this idea of making the entire combustion chamber out of the same perlite and clay mix as the heat riser.

I am a bit worried it could fail. I don't think I've seen anyone else do it so my guess is no one does it for a reason.

Any thoughts on that would be appreciated. (I'll try and put a pic in if it will let me)



Also, I'm a bit confused about pipe size when it comes to the round and the square. Some people say, for example, when using a 6 inch square feed tube and burn chamber make the circular heat riser be 6 inch in diameter.

Others say to make sure to keep the cross sectional area the same. I would extrapolate that if the square burn chamber and feed tube is 6 inch, then the diameter of a circular riser pipe should be 6 5/8 inch.

Keeping the area the same seems right to me. What's the consensus?



And there is the basic 1,2,4 ratio which seems well agreed upon. But there is a difference of opinion as to where to measure from exactly.

Where should I be measuring from?



Oh my goodness. I have so many more questions but I will leave it there for now.

[martyn]

Hi, I assume you want to build a J tube rocket mass heater?
There are other styles of mass heater that don't need to be fed so regularly.
Most household, mass heaters, now use a brick bell to store the heat combined with a batch style heater.
Having a good chimney is a key factor too.
Things like perlite risers are still being used but honestly, are really dated nowadays!
If you use fire brick backed with insulation you can expect decades of use, there are other alternatives depending on your budget ….

[apricotslice]

Thank you Martyn,

Yes, I was looking at the J type of heater.

Hadn't really thought about the other styles. I think I got caught up trying to design something and didn't explore what are probably more sensible options.

I have designed and made a lot of things but have found a stove to be surprisingly challenging. I think its the variety of different sized 'off the shelf' components that gets me in a tangle.

Would you regular fire bricks throughout the internals?

[martyn]

First of all you need to decide what sort of design you want, look at batchbox rocket stoves and other styles on this forum.
Once you have made a decision we can guid you through the build.
Most if not all of the stoves can be made smaller or bigger to suit your needs.
There is nothing wrong with a J tube design, in fact they are easy to build and use but, you have to re fuel every 20-40 minutes where as the stoves with larger fire boxes and doors can last up to two hours on one load.