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Post by nonius on Aug 30, 2012 2:31:54 GMT -8
Hi
Just registered with the forum to ask this question. I must say there is a wealth of data here, but I still do not find answers on internet about output.
I want to use the stove outdoors for cooking ~20 L (about 5 gallons?) in less then 30 minutes. This can be done with 100bar propane burner of 50K + BTU/h, but I have no idea if it can be done using a rocket wood stove. All info is about cooking 1 L in 5 minutes, which seems to little power :-)
Anybody can give proven dimensions for feed, burntunnel and heat riser to get this output?
tnx
Nonius
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Post by satamax on Aug 30, 2012 2:48:52 GMT -8
Well, why don't you build yourself a temporary one, to check out if it's possible? Do an eight incher. Well insulated. High'ish heat riser. And see! IIRC, someone said a 6 incher was outputing the equivalent of 2KW.
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Post by nonius on Aug 30, 2012 3:14:51 GMT -8
Satamax, I already made myself a very small one (4x4 cm) from some tiles lying around, and later in cement-brick leaving an opening of 8x8 cm. In both cases 1L of water would take more than 10 minutes to cook. Earlier this week I built a metal 'pipe' L rocket out of tin cans (diam 9 cm) embedded in small lava stones I had lying around. But the fire died every 5 minutes, so I need to tune it a little... :-( In any case did not feel hotter then previous attempts. For 6" (15 cm correct?) system, I need to find the right scrap to start experimenting. I was wondering if anybody has hands on experience so I can skip these experiments  BTW: 50K BTU/h is ~ 15 kW/h... I think that needs a stove consuming 3Kg wood per hour. |
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Post by satamax on Aug 30, 2012 5:40:07 GMT -8
3kg of wood per hour, no problem. Where are you located?
So, imho J tube lends itself better to boiling, since you want max heat all the time. Your atempts were all too small imho. Lava stones werent the best insulator neither.
You can't get your hands on a few refractory bricks? Or even normal ones, if it's for testing purposes and they are surounded by insulation, you could get by. And a metal tube. 6 inch 15cm yep. Has a cross sectional surface of 176cm² 8 or 20cm has 314cm of surface. With bricks it's easy to do 11x16cm, 11x10cm rectangles. 11x22cm too. For testing purposes, you can try with big tin cans, you can find theses at the school restaurants, restaurants, and à few other places.
Best of luck with the testing.
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Post by peterberg on Aug 30, 2012 11:01:49 GMT -8
nonius, Maybe you'd need a slightly different concept. This is called "institutional rocket stove", developed by Aprovecho Research Centre. It's a stove around a dedicated pot of 60 liter, too large for your wishes, I am aware of that. I've built two smaller versions around a 10 liter pot, and they work fabulous. Aprovecho claims their larger version could get 60 liters of water to a boil in 30 minutes or something around that figure. All what you need is a building plan which is to be found on the internet. Or in any case, that's how I've done it. The build has been described in 8 videos, the first one is here. www.youtube.com/watch?v=VdhLWMW7IXA&feature=channel&list=ULThe 7 others are not hard to find when you've got the first one. Moreover, at picasaweb.google.com/109613689566640406616/LeidseStoof you'll find my own extensive photo report of the build. A year ago I've started a thread about this same stove at this forum, title "Mini barrel stove".
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Post by nonius on Aug 30, 2012 21:45:06 GMT -8
Thanks Peter for replying. I saw your Leidsche Stoof on the Dutch forum, and the Aprovecho design when starting my research.
I do not have an easy source for tins and barrels, and do not like to work with metal. I want to build it permanently in the garden, next to the brick grill/bbq.
I understand a skirt will raise the efficiency.
My experiments till date do not have any skirt, as I try to compare with a regular gas burner. The institutional rocket stove has not only a skirt, but a complex one at that: I try to keep it simple.
Are you suggesting without a skirt it can not work in any case?
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Post by peterberg on Aug 31, 2012 0:11:46 GMT -8
I do not have an easy source for tins and barrels, and do not like to work with metal. That's not very handy, because the stove should have as little mass as possible. So thin sheet metal is your best option together with reasonable quantities of insulation material. I understand a skirt will raise the efficiency. My experiments till date do not have any skirt, as I try to compare with a regular gas burner. The institutional rocket stove has not only a skirt, but a complex one at that: I try to keep it simple. Are you suggesting without a skirt it can not work in any case? A skirt definitely will raise the efficiency. When you are as far as producing a metal rocket stove with skirt, the institutional stove is just one step further as far as complexity goes. By the way, are you living in the Netherlands? |
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Post by nonius on Aug 31, 2012 1:16:36 GMT -8
Thanks again Peter for your advice, So even for an fixed outdoor setup, you would advise metal innards? So why many of the RMH's have a brick J? It seems I miss the essential difference between heater and stove in this area  Ben inderdaad Nederlands, maar ondertussen al 15 jaar in Israel. Groetjes Nonius |
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Post by peterberg on Aug 31, 2012 9:32:07 GMT -8
So even for an fixed outdoor setup, you would advise metal innards? That's only because of the low mass possibilities. Low mass, more of the heat into the pot. So why many of the RMH's have a brick J? It seems I miss the essential difference between heater and stove in this area The mass heater's purpose is to warm the house, the stove is a cooking device. That last one isn't supposed to warm anything else but what's in the pot. Mind you, an optimized cooking stove can be very efficient. On the other hand, a good mass heater can boil a kettle of water for tea, but that's only a sidestep. Both devices can't perform both tasks equally well. The price of specialization. |
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Post by earthshakerecho on Jan 9, 2013 2:14:38 GMT -8
I would like to ask if what is the best insulator to use in my rocket stove oven? Ash? thank u |
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Post by earthshakerecho on Jan 9, 2013 2:30:32 GMT -8
And another. I have made a rocket-stove oven with the dimension of the body of 1inch by 1inch.
What would be its major problem(such as: The time needed to cook foods) compare to the conventional oven? Thank you very much.
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Post by peterberg on Jan 9, 2013 2:53:44 GMT -8
I would like to ask if what is the best insulator to use in my rocket stove oven? Ash? Best high temp insulator is perlite, in my opinion. Vermiculite will absorb a huge amount of water which isn't easy to get rid off inside an insulation canister. Wood ash can be used but this will compact over time so you have to mix it with clay slip to stabilize. Superwool can also be used, high temp rockwool as last resort around fire brick riser etc.. |
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Post by johnmaster on Jan 16, 2013 5:55:44 GMT -8
Why is rockwool a last resort? I am making an rmh and using clay slip perlite, to insulate a stainless riser. It is a pain to make the slip and mix the perlite, was thinking the rockwool would be way easier the next time. Downsides to rockwool?
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Post by peterberg on Jan 16, 2013 6:24:37 GMT -8
Why is rockwool a last resort? I am making an rmh and using clay slip perlite, to insulate a stainless riser. It is a pain to make the slip and mix the perlite, was thinking the rockwool would be way easier the next time. Downsides to rockwool? The riser will get too hot for the binder of the rockwool. Besides that, the surface of the wool will crumble, looks like it has been melting. Same effect with glasswool, this is even worse. In one application, I've used braided glass tape, this lost its flexibility and got hard and brittle. The metal riser will get red hot, rockwool isn't heat resistant enough. |
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Post by pasto76 on Jan 17, 2013 8:15:59 GMT -8
ive crushed lava rock (scoria) to pebble size and smaller and have used that as insulation. It works pretty well. if thats what you have. Without a mill or mechanical crusher...it took a long time to crush it all with a 4 pound hammer
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