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Post by Robert on Dec 5, 2012 17:47:03 GMT -8
Hello dear rocket ppl.
I am just starting so please kindly guide me in this one. I am building a masonry rocket stove... I got plenty of fire bricks so i decided not to use a barrel, also not to use the exit flue pipes... instead i want to make all in fire bricks... it will get damn warm... but... just a burning question i have.... i got a nice metal tube - 80mm thick, and i am placing it as a heat riser... around the tube i want to build the masonry structure (instead of a barrel), hoping that it will slowly get warmer and warmer, and once it get hot it will stay like that loong time, giving the heat to the room... from what i am thinking the best would be not to insulate the heat riser (i have a very limited space), so the structure will get much warmer...
but, it would not be a rocket if the heat riser was nor insulated, its a rule number 1... at least as i know it.... but...
i made a small model without isolation and it was working... i`ve seen people building heat risers from fire bricks surrounded by a masonry wall, also without isolation... so it is working...
what do you think about that? since best for me in this situation would be not to insulate, but also i would like to do the rocket as it should be... according to the art of making it...
what is your opinion dear rocket masters?
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Post by satamax on Dec 5, 2012 22:31:32 GMT -8
Well, metal 80mm thick? That will spall anyways. I think you'd be better using bricks in a vertical position, which depending on the model are between 50/60mm, here you've gained 3cm for insulation, then again, using a square shape for the heat riser make it smaller for the same CSA (not accounting for gas friction in the corners) So you can use insulation. Plus, you could do your outside bell with bricks on their edge, for a bit more room and faster heat transfer. Tho, a barrel is better imho. Since metal heat transfer speed is far faster than the one of brick. You could also do something like this  Courtesy of Len Ovens at permies. |
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Post by Robert on Dec 6, 2012 17:53:01 GMT -8
Well, metal 80mm thick? That will spall anyways. WHAT "SPALL" MEANS? I AM SORRY MY ENGLISH IS PREETY BASIC, SO IF YOU COULD SPEAK AS TO THE CHILD WOULD BE REALLY NICE  I think you'd be better using bricks in a vertical position... YES. MAYBE NEXT TIME - NOW I ALREADY DID WHAT I DID , which depending on the model are between 50/60mm, here you've gained 3cm for insulation, then again, using a square shape for the heat riser make it smaller for the same CSA (not accounting for gas friction in the corners) So you can use insulation. MY HEAT RISER IS A NICE TUBE... BUT REALLY VERY SMALL PLACE TO INSULATE ANYTHING, Plus, you could do your outside bell with bricks on their edge, for a bit more room and faster heat transfer. Tho, a barrel is better imho. Since metal heat transfer speed is far faster than the one of brick. IN THIS PROJECT I WANT THE FIRE BRICK. I WILL NOT AGREE THAT BARREL IS BETTER. I WANT THE EFFECT OF FIRE BRICK. IT WILL STAY WARM VERY LONG, AND IT WILL NOT GET SO HOT SO I CAN BURN MYSELF. SO THIS IS HOW IT LOOKS INSIDE: www.facebook.com/photo.php?fbid=314635888652470&set=a.314635671985825.76569.270777849704941&type=3&theaterI HAVE TRIED IT TODAY. WITH NO INSULATION. WORKS GOOD. NICE DRAFT. BRICKS GOT WORM AFTER 30 MIN OF BURNING...AH, BUT... AGAIN MY QUESTION IS... HOW IT WILL BE BEHAVING RIGHT NOW? - IS BECAUSE OF LACK OF THE INSULATION, THE BURNING WILL BE NOT AS EFFICIENT AS WITH INSULATION? - IS THIS ONLY MAKES DIFFERENCE WITH HEAT TRANSFERS? - IF THERE WILL BE SOME SMOKE IN MY FLUES? PLEASE, WHAT DO YOU THINK? sINCE I HAVE SEEN MANY MASONRY PROJECTS WITHOUT INSULATIONS AT ALL... SO HOW IT IS? |
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Post by Donkey on Dec 6, 2012 21:39:50 GMT -8
The internal burn works MUST be insulated.
If you do not insulate, the negatives will begin to stack up.
Rocket stoves are NOT like standard masonry stoves. The basic design is entirely different.
Insulate your burn works..
Period.
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Post by satamax on Dec 6, 2012 23:02:33 GMT -8
First of all, don't write all in capitals, please.
Then, spalling is when metal heats, and delaminate in chips. Metal for the heat riser, if it's not stainless; is no good. If you can find a stainless tube, you could make a rocket with metal. And instead of a barrel, you could use 35kg gas bottle for the radiator. And you need insulation. Your bricks getting warmer after 30 minutes means that there is something wrong. If it's rocketing well, i think they should be getting hot faster.
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Post by Robert on Dec 7, 2012 4:11:59 GMT -8
Thanx for reply... I am feeling that i do not exactly know why should i insulate... Of course i know all of the design of rocket, and i understand quite a bit but just wanted to confirmed with you. Someone wrote:
"The internal burn works MUST be insulated.
If you do not insulate, the negatives will begin to stack up."
So why does it have to MUST be insulated? If the answer is that the negatives will begin to stack up? Does it mean that the ashes will start collecting around the heat riser? If it is the only problem i can take that risk...
And then someone replies:
"Rocket stoves are NOT like standard masonry stoves. The basic design is entirely different. Insulate your burn works"
Yes, i know the basic design of a rocket... I made 8 of them allready... 7 insulated, and one as a model without (working good). So then you write : "Insulate your burn works"!!! - Yes i know that i should, i read the book and few others research...Just want to know what happens if in my case i will NOT INSULATE... Right now i have a one answer for that question:
1. Negatives will start to stack up.
If thats the case i would make a decision of no insulating...
But maybe another idea? And please don`t repeat you must, you must... Explain WHY, and what happens if NOT.
Thank you very much.
With signs of rocket respect.
robert
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Post by satamax on Dec 7, 2012 5:33:20 GMT -8
Dobra robert.
Well, the rocket is based on a thermal differential, and if you don't insulate, the thermal pump generated by the thermal differential will slow down, giving an extremely sooty burn. Which could be dangerous when lighting up the next time for example. It can also revert with the wind, and smoke your house in, or even kill you. First of all, i'm not too keen on replacing the barrel with massonry, tho, that can be done. Because it doesn't cool the gasses as well as the metalic barrel, impeding the "siphon" effect, but if on top of this you don't insulate, that's not a rocket anymore.
Other things, spalling will happen, and destroy your heat riser in a few burns, usualy between 15 and 30. Heat riser, have you thought about the word? Rising the heat, as in temperature, not elevating the gasses in it, tho, it also does that. If you want to make it that way, no prob, we're not willing to stop you. But the burn will be of poor quality, the heat exctraction will in turn be poor too. Then the wood consumption will raise, up to the point of having a rocket doesn't mean anything anymore.
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Post by Robert on Dec 7, 2012 6:14:51 GMT -8
No Dobra Satamax This is the answer i been waitin for... this completely convinces me and confirms, that heat riser MUST be insulated... and thanx for nice explanation WHY... So i will wrap the heat riser with metal sheet and fill it with ash... that will leave me with one wall of a mosonry "barrel" open - thats the best what i can do right now... HMM. but that slows down a little bit my enthusiasm about masonry rockets... Next one i want to make quite big, with the place for baking bread, and now i will have to reconsider the heart of the Rocket in it... Now i reUNDERSTOOD that the barrel "needs" to be cooled quickly and give the heat away to perform much better, actually just to perform according to the art of rocket... ah and then again making a fans that cools the barrel quicker is also a good idea... being a perfect place to put the TEG module as well... But then what about masonry stoves... Any idea on how to make the really good working Masonry ROCKET? Maybe an idea would be to make a bench and accumulation out of bricks... Ah is there anyone on a forum that specialazies with MASONRY rockets? Thank you so much for help... I will keep you updated... And well - seems that this one will not be a full "rocket"... Anyway much much better than the regular stove they had in here... yours Robert |
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Post by Donkey on Dec 7, 2012 9:08:22 GMT -8
Wood ash as insulation works quite well for the short term, though it will compact over time, and eventually stop working as insulation. Mixing your wood ash with just enough clay slip to keep it in place should solve for this. The wood ash/clay solution will be less insulative than the wood ash alone, but it won't compact and it will retain it's qualities over time. As to insulation ITSELF, I suppose my answer was rather terse and information poor.. It seems to me that the question has been answered quite effectively in the book itself (though it's been so long since I've read the thing that I don't remember it), it's been answered here on the boards ad-nauseum. It's a settled question. Insulate?? YES! It's a MAJOR reason why rocket stoves work so well and without it, well... Just do it. If you want more info on this, use the search function here on the boards. I personally like the masonry barrel idea. Yes, it will take heat away slower than a standard metal barrel and likely as not the system will equalize faster than the metal barrel, making it slow and maybe even back burn quicker than a metal barrel will.. It seems to me though, that as long as you get the timing of the burn right, none of this should matter. It depends on how much heat is needed, or rather how much fire. If the needs are below the equalization threshold, then there's no problem and the extra thermal mass can be a helper. Just understand that if the system is over-fired, is will stop working properly, burn back, blow smoke into the house and exhibit various other obnoxious tenancies. A way to solve for this is to make your bench run (or any other heat path solution) very short so that there is ample heat left over to run a standard chimney. The chimney itself will overpower the stoves tendency to back-burn as long as it's good and hot. 'Course, this is a less than ideal solution, it misses one of the big points of rocket stovery which is to keep the lions share of the heat inside the house where you can use it. Throwing away a lot of heat to make up for poor design makes no sense whatsoever. Another factor to consider, the metal barrel provides instant heat to your living space, which can make a big difference to comfort. I have no barrel on my stove here at home, it's MUCH like what permacultura has in mind (though it's REALLY well insulated). Very little heat is transferred to the space at first. It takes an hour or two to take the edge off of the house, so I've really got to plan ahead for my heating needs. If I come home to a cold house, I've gotta just suffer through it while waiting for heat to work it's way through the thermal mass. Metal barrels (or other metal radiating surface(s)) don't suffer this problem, you can also just keep stuffing wood in the things for as long as you like, the likelihood of a metal barrel equalizing with heat riser temps (as long as the heat riser is WELL insulated) is low to none. Permacultura, if you want to make an ALL masonry stove, check out what peterberg has been up to between his rocket bell-stove and horizontal feed experiments. |
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Post by permamax on Dec 14, 2012 13:53:57 GMT -8
Hiya, I'm glad I introduced Robert to this board; seems he got the answer he sought for. I received an answer a week ago, much like what Donkey writes above "Insulate?? YES!" To my little defence I'd like to point out that the book actually only talks about the feed tube and the heat riser needing insulation: Not about the burn tunnel! ...But I've corrected it now...! Anyhow, not to capture the thread, but to shed further light on the tube issue: I utilized round chimney cores for the heat riser in the RMH heater I recently built. 2 dimensions with perlite in between. Anything wrong with that? picasaweb.google.com/lh/photo/mvvNmavqJSYHyImERyj3ZNMTjNZETYmyPJy0liipFm0?feat=directlinkCheers, Max |
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Post by pinhead on Dec 14, 2012 14:18:47 GMT -8
Permamax, that's how I built mine at first. Worked really well until the inside core burned out and spilled the insulation all over the place.
I replaced the insulation (vermiculite in my case) with a mixture of furnace cement and vermiculite and re-cast the same configuration (6" chimney T inside an 8" chimney T). This didn't insulate quite as well by itself but makes the core extremely robust. I then insulated around that core. This gives the best of both worlds: Extremely good insulation and an extremely strong core. The 6" T has burned out but the furnace cement is still there, holding it's shape. I suspect the 8" T will probably last as long as the furnace cement (which, after 3 years of use is showing NO signs of degradation - no cracks, no missing chunks, etc.
[EDIT]: SORRY!!! I was confused!
The "cores" I am referring to were metal cores such as would be used for the chimney on a propane heating appliance - propane stove or water heater. NOT the clay cores you're using! [/EDIT]
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