jegt
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Post by jegt on Nov 4, 2018 12:24:55 GMT -8
Hi,
I'm fairly new to rocket stoves but have been reading about them for a while and found this forum recently. I'm building a tent sauna and plan to make my own sauna stove for it. Looks to be like I could use some rocket stove design for this but I haven't been able to find many examples.
Basically what I want to do is heat up a big pile of rocks as fast as possible so I'm guessing a batch box design would work best?
I want the stove to be portable (in the back of a car). I'm thinking compact a DSR design in ceramic fibre board might work. Assuming the pile of rocks rests on top of the stove as is the conventional way, the stove needs to be as low as possible.
That leads me to the second part. How do I transfer the heat to the rocks as efficiently as possible? I need the heated air to spend as much time as possible in close proximity to the rocks.
Does anyone know of some existing designs like this that I could look at or have some ideas?
/ Jonas
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Post by rakettimuurari on Nov 10, 2018 2:16:00 GMT -8
Jonas, Sounds really ambitious, I must admit... Would u think some kind of metal frame/ stand would be necessary for supporting the rocks? Also some kind of chimney is usually quite crucial for proper rocket action; gets quite bulky for transport very soon. That said, many nordic army tents often have stoves which come with attachable chimney pipe, divided in parts of some 50cm each; u can build chimney in 20 seconds with those; they're also light weight... they should be easy to DIY too... According my tinkering with normal sauna stoves, I would say there cannot be any kind of insulation or gap (ceramic fiber board?) between the rocks and fire path (usually it is some 5mm of steel) - and I am now talking about the sauna with constant ongoing fire on it also during the sauna session ---> chimney necessary. Another option would be to lead the fire and gases directly through the rocks for a proper time in closed system, which is then finally opened for throwing the water on the rocks when they are enough heated and fire is gone. This is the way I would go. U also would like to have enough space for big enough rocks as the small ones would cool down by the first throw of water. Now tucking some largeish rocks (size of two fists at least) in to the top box of DSR would definitely have some kind of effect to "flow pattern" etc. This should be tested If u find one, I would be really interested also! Greetings from Finland, Antti
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jegt
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Post by jegt on Nov 12, 2018 23:59:19 GMT -8
Hi, Yes a chimney would definitely be neeed and the top part that supports the rocks would have to be make from steel. I imagine a bell simular to what is used in a mass heater design, with rocks on top, could work. What I have done so far is what you suggest and lead the hot air through the rocks to heat them, then put out the fire and put the tent on top. I used a barrel shaped vertical smoker for this. The first try was without any rocket stove. www.icloud.com/photos/#0X8ftziM2qB9rSUqwfzkEjeZwI lit a fire in the bottom and the smoke went through the stones (resting on a grate) and up the chimney. After two ours the termometer said 300C and I put out the fire, removed the top and put the tent on top. Worked well but I would need more stones for a longer sauna. This was with about 30-40kg stones. The second try I tried to use a j-tube rocket stove below the same setup instead of the regular fire: www.icloud.com/photos/#0JKCqR2BED_hkHxS0JIAjh6kwUnfortunately this did not work well. This was my first try at building a rocket stove and I had trouble with a large buildup of coal in the fire tub that blocked the airflow. It took several hours to get the stones to a reasonable temperature. I’m sure it would have worked better with a better rocket stove below. I used birch as firewood, I don’t know if that is a problem or if it was just something wrong with my rocket stove design. Unfortunately I only have 25 of the insulating fire bricks so I’m somewhat limited in what I can build. / Jonas
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jegt
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Post by jegt on Nov 13, 2018 0:00:50 GMT -8
I’m trying to get hold of some ceramic fibre board and if I do I will try to build a lightweight rocket stove core and then start experimenting with a sauna specific bell on top.
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Post by rakettimuurari on Nov 13, 2018 1:12:25 GMT -8
Nice idea with J-tube... got me thinking some possibilities. Yes; first it should be definitely made sure that J- tube is working properly by itself. For my J- tube the type (or even quality) of the wood has never been an issue - it eats everything when warmed up. Only the amount of fly ash is larger with birch and with spruce too. It is 6" system and I usually clean out the fly ash on every third burn or so... much of the ash is probably flying through the riser and ending in to the bottom of the barrel bell. However my cooking plate on top has an uneven bottom and i suspect it makes some of the ash fall back in to the riser. It should be made sure that the rocks wont choke the system CSA on top of the riser as this will probably directly impede the rocket operation. Maybe a certain kind of flow divider guiding the gas stream evenly to many directions through the rocks? I would make the total CSA of the divider bit larger than the system CSA to accommodate the drag... Myself I would go with DSR2 kind of setup to experiment... DSR2 -thread
-Antti-
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Post by rakettimuurari on Nov 13, 2018 1:38:06 GMT -8
Just some more stuff... You are right about the amount of stones sadly. Traditional "smoke sauna" around here has no chimney, has some hundreds of kilos of rocks and is heated for hours (from 3h to even 10h as far as I have seen) and the gasses go through the rocks). On the other hand it provides heat on some occasions for two days even. The minus aspect is that it most definitely wont burn clean - ever, and it will take tons of wood. Anyway a sauna stove with not-constantly-heated-rocks will need the considerable mass in it - there is no escape; that's why I was talking about large rocks earlier.... So with small amount of rocks it is probably good thing to consider the option with constant fire in it too. Forgot to mention the modular sauna-stove -idea, a kind of which I implemented in my normal sauna (thread: " ancient aryan sauna stove"). I got smokeless burn simply by combining two burn chambers with certain kind of primary and secondary air configuration... I was wondering if any kind of light weight option of that could be possible...
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jegt
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Post by jegt on Nov 13, 2018 4:26:00 GMT -8
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serg247
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The mountain can not be conquered, it can allow it to ascend...
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Post by serg247 on Nov 13, 2018 5:52:20 GMT -8
In the expanses of Russia and Ukraine, bath stoves with continuous steam generation are now popular. And although I am not a supporter of metal stoves in the bath, I have developed several concepts of rocket bath stoves on this principle. Among them is easy for the tent. As shown by the practice of mobile baths in a tent to heat the steam faster than in other ways. I can share ideas if there is interest.
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Post by rakettimuurari on Nov 13, 2018 6:26:33 GMT -8
That thing Sir, looks solid One modification coming to a mind at first (when it finally proofs that its not enough just like that) could be to modify the lowest part of the chimney piping going horizontally and looping inside the rocks on top of stove roof and then back again inside the rocks before shooting up as a chimney. In that way u could utilize both - primary and secondary burn to heat the rocks. As you probably know, these kind of tent stoves as well as many regular sauna stoves are prone to have secondary burn inside the chimney pipe... When I was in military we often had the flame tip visible on top of the chimney. Same was with my Estonian sauna stove before the modifications I made. So looping and adding horizontal length would tame it a bit and get the secondary burn in to use. Other possibility to transfer secondary burn below the rocks would be the secondary burn chamber as discussed before... but that would end up being more complicated. Chimney modification illustrated reminder for myself: After you copy the public Dropbox link to your clipboard, just change ?dl=0 to ?raw=1 at the end of the URL.
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jegt
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Post by jegt on Nov 13, 2018 8:37:15 GMT -8
In the expanses of Russia and Ukraine, bath stoves with continuous steam generation are now popular. And although I am not a supporter of metal stoves in the bath, I have developed several concepts of rocket bath stoves on this principle. Among them is easy for the tent. As shown by the practice of mobile baths in a tent to heat the steam faster than in other ways. I can share ideas if there is interest. That sounds interesting. Please tell us more.
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jegt
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Post by jegt on Nov 13, 2018 8:46:07 GMT -8
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serg247
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The mountain can not be conquered, it can allow it to ascend...
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Post by serg247 on Nov 13, 2018 9:12:29 GMT -8
The design is a double-walled cylinder half filled with water with a device for maintaining the water level. In the cylinder is the riser. Above the riser in the hottest place stones. The resulting steam goes into the tent or can be fed to the superheater.
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Post by rakettimuurari on Nov 19, 2018 0:03:42 GMT -8
That might last, as at least some time. Should be careful with rocks though; well I don't really know how soft that pipe would be but the rocks would help it to shed extra heat away from it at least.
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