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Post by ridleycove on Mar 8, 2020 5:21:54 GMT -8
First and foremost, thank you to all those folks that have taken time to share their knowledge - and to those who keep us all in line!
I am trying to gather the RMH design data from the many different threads and sites and I have found an item (I believe from Peter van den Berg) that says the 6" heater can only handle 6kg of wood at a time, with a burn time of an hour or so. But given the formulas, I get the "base" as 4.34, the firebox dimensions (W, H, D) of 8.68 x 13.02 x 19.5 inches, and a volume of 1.3 cubic feet. Converted, that's 0.037 m3. What I can't discern is how you get from that volume to 6kg of fuel. Any observations?
Thanks
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Post by peterberg on Mar 8, 2020 6:25:14 GMT -8
Hi Ridleycove, welcome to the boards. The answer to your question is simple: empirically. Another way to calculate the maximum weight of fuel the firebox can hold is the following. See as the volume of the firebox filled with water, this has a known weight. Most fuel species' weight is half of that or a bit more, for the sake of simplicity say it's half. In the metric world, one kubic decimeter or liter (dm³ or l) of water weights one kilogram (kg). Firebox volume of a 1.5 dm system is about 28 dm³ so in theory it could hold 14 kg. But... there need to be some space between fuel and ceiling as well as between fuel and air inlet. And because of the non-uniform nature of firewood there are lots of air openings. Depite the fact that the fuel can be loaded front-to-rear without criss-crossing or log cabin style. In practise it turns out that less than half of the theoretical weight can be crammed in, as a rule of thumb.
And before you say my numbers aren't the same as yours, that's right. One-and-a-half dm is close to but not quite the same as 6" and volume will also be less because of the 45º sloped sides of the firebox.
In short, take the volume of the firebox in water and what that would weight. Divide it by four and there's the figure what it approximately could hold.
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Post by ridleycove on Mar 8, 2020 14:44:17 GMT -8
Thank you! I knew there would be the empirical answer, but my techie brain wanted some science - or at least a logical calculation - behind it. And you provided it. Much appreciated.
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Post by ridleycove on Mar 14, 2020 7:26:55 GMT -8
With all new understanding comes new questions! Based on BTU requirements for the camp, I think I have my dimensions pretty close - a 9" RMH for an old structurebwith single pane windows and planning two firings a day when it is chilly (no winter occupancy). But I want a white oven in the bell. Has anyone taken a defunct electric oven and slid it in to a bell heater? If it can handle 1000 degrees F for self cleaning, might it work in the output of the riser?
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