Oystein Tandberg

thomas rubino wrote:
Riser height should not be more than 48"(122cm)...

I took some pictures for illustration, the heat riser is too tall and the burn tunnel too long in this picture..

I have some questions. Since I'm casting the core, it will be quite easy to create a passageway for air to be feed into the system along the length of the burn tunnel. I would make them "bottle neck style", and maybe two is enough, one on each side. I would make it in a way that I can cover them easily, and I'm planning to do the same with the feed tube, so I can strangle the fire easily If there should be a blow-back, and for other reasons as well. Any thoughts on this?  

I don't know if the pictures become more clear by me explaining them at this point, but its one showing the front, and one showing whats to the right of the fireplace. I've wanted to create an oven under the core, but I doubt it will get very hot, maybe to dry something... I've left a big opening to be able to remove ashes.

Then to the question - is it better to have the feed tuber slightly tilted, will it effect draft?

thomas rubino wrote:The effect of a larger distance from the riser to the barrel top will be, lower radiant heat released from the barrel and more heat passed into the mass.
Riser height should not be more than 48"(122cm) but not less than 36" ( 91.4cm) measured from the floor of the core.

Thank you, really appreciate it. That solved many issues. So I will make it 120 - and the burn tunnel will be 60 cm, and the feeder 30cm. And I will aim for a 20 cm distance, as its very beneficial to heat the bench and not the air.

thomas rubino wrote:Hi Oystein;
5 cm (1.9")  is much too small
10cm (3.9") will work well.
20 cm (7.8") will also work.

Thank you! And, what would be the effects of a bigger distance?

And - should I make the heat riser twice as tall as the burn tunnel? And what would the combined effect be - bearing in mind that pars of the system will be built in, leaving less barrel surface to be exposed.  

From my reasoning, it would be good to have a longer heat riser, as the gap between the riser and barrel increases. I reason this because I remember having read that a small gap makes for an added bottle neck effect. Now that I am making a very good chimney to go on the outside of the house, I will have a good draft at the exit of the system, and that will take some of the stress off the heat riser, as it will have a good pull from the external chimney. And that is another reason I go through the stress of making a fire place at the bottom of the external chimney, because I want to reduce the time I have to burn at a low temperature, and get the fire going on the inside. I'd rather freeze a moment or two making a strong fire at the base of the external chimney to get things moving right from the start. And then under normal circumstances, that wont be necessary as the temperature in the house normally, hopefully, would be much higher than the outside temperature, and draft is no problem - windy as it usually is as well..

It's a J-tube. I've used the mix in another mass heater and it works. In that build I used the standard dimensions, but since the barrel will be partly covered by rocks this time, I expect it will change things - and I'm trying to figure out how. And how to use it to my advantage. (the second fire has other functions as well, to produce woodchar, to have a fire place outside, in case of inspections, and more)

So what I want to know is if I should extend the distance from the top of the heat riser from the barrel, make it 10 cm -or do the opposite, make it 5 cm.

I'm heating a small place, I don't need the oven to be as big as possible.

Greetings RMH community!

After more than 12 years of reading, planning and preparing the groundwork, I am getting ready to move into the construction of what I think of as the heart of the house.

There are some final considerations I need to make.

First, I needed to dig out the space for the construction. I made the bench in natural stones. And, I made a stone wall where the core will be built. So it will be partly built into a structure of stones. Within that space, I can fit a burn tunnel of one meter. That will leave enough space to insulate the walls, so that the heat will not damage the cement, and tumble the walls.

I will cast the core. I will make a mix of puffed silica (bought in bags, used here on the sidewalks in winter, to prevent people from falling on the ice). I will use water glass as the binder, and I will mix a small amount of refractory cement (resisting 1000  Celsius) into the mix. And some sand.

The considerations I need to make now is what dimensions to choose. I find it easier to navigate when I understand the principals - for example, the distance between the top of the heat riser and the barrel, how would that be affected by the two different dimensions - or rather, how can I calculate the length based on how I expect the build to function? Should I for example make a shorter and smaller core, to leave even more space to separate it from the stone walls? I will also use leca (puffed clay) to protect the stone walls, and glass.

I will make a chimney on the outside to ensure a good draft. And I will include in this chimney a place to make a small fire, to be able to heat it before I start a fire on the inside.

Best regards

To all the people looking for community, remember that what you are living in this moment is the fruits of the society you live in. Use the possibility to change in yourself what you judge in others.

Luxor was built on the ground. There was a special preparation of the ground first.

I really appreciate any comments that help me improve mye stove.  

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You know you are a permie when the birds and the animals in the garden communicate with you, and you understand them.

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