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Post by mintcake on Mar 19, 2014 10:16:18 GMT -8
I was reading up on all the different types and traditions of masonry heaters from around the world for about 5 years while playing with designs in my head and on paper before I settled on this, I wanted something compact but with really good heat storage but also able to supply instant heating, a cooking surface, and the ability to use it as an open fire if I wanted. The 'high mass micro-bells with minimum drag' was what I was aiming at, I dont know if they work better than one big L shaped bell or not, I plan on doing that in the next one to see. Hi, Our house (rural Romania) came with something very like the one on the left here:  It's just been rebuilt; inside we found up/down channels in a very similar pattern to Vortex's stove, roughly speaking, the channels matched the system size. Much like a batchbox + bell, it's designed for one/two firings per day, but if you like you can put several loads in for more heat (but less efficiency). However... because it has a non-insulating firebrick firebox, no insulated heatriser, etc. etc, the smoke that comes from the chimney, even with a only , is pretty much black. Also, while the "micro bells" give a lot of ISA, because there's no way for incoming air to get to the chimney without passing all that ISA it is 100% dependant on stopping the airflow if you want to store heat for a long time, as vortex found with his leaky door being helped by the damper. The point of the bell is that cold air be pulled in and get to the chimney while heat stays in the stove, and these channels just don't do that, sorry. They'll extract heat, but you do need to have some way of stopping the airflow, once the fire's out. Once or twice I've made the mistake of leaving the door open for half an hour past the end of the burn; the stove got no more than warm to the touch rather than radiator-hot. :-( |
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Post by Daryl on Mar 19, 2014 10:45:42 GMT -8
That is priceless first hand information about the tile masonry stoves. Thanks for sharing.
BTW, your stove rocks, Vortex.
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Post by DCish on Mar 19, 2014 13:00:24 GMT -8
@mint: to make sure I've got this right... So like the Vortex, it doesn't have a single continuous channel, eh? And the idea is that the turbulence of the flow of cold air below the "micro bells" creates mixing that exhausts the heat?
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Post by Vortex on Mar 19, 2014 15:35:24 GMT -8
Blakeloverain- I've lived in trailers and other small spaces with woodstoves and little insulation, a small space like that doesn't take much to heat it but once the stove is out they go cold very quick, so I'd say smaller firebox with a similar amount of mass would probably be the way to go. The main problem i see is the vibration in a moving vehicle, it would shake my stove it bits in no time. If you built something with just castings held together by a metal frame that could work. The middle is definitely the place to put it, my cabin temp only varies a couple of degrees from end to end.
Standing in front of it when it's in the middle of a firing is not advisable, once the burn is over the temp evens out over the stove quite quickly and it's ok to stand in front of then.
The stove weighs somewhere around 500 to 600KG. The only place you could really put a white oven is where the micro-bells are - it would really look like a large cookstove then - I use the firebox after the burn is over I rake the hot coals to the back and put in a rack to stand what I'm baking on and it works great. We dont measure wood in cords here, my wood pile for a whole year is 8 or 9 cubic meters. Google says 3.6 cords to the cubic meter, so that's about 2 and a half cords.
Good luck with your plans.
Mintcake- In a larger stove I have no doubt a single or double bell would work better but I dont know if that's true of a small stove like mine, there's a trade off with the amount of mass to store heat and the ISA to soak it up. Also I think a damper will increase the length of time any mass stove will store heat, a bell stratifies the heat but it's still losing heat out the chimney just at a slower rate.
My stove never has black smoke, there's white smoke for the first few minutes after lighting then it's clear.
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Post by mintcake on Mar 20, 2014 9:27:26 GMT -8
@mint: to make sure I've got this right... So like the Vortex, it doesn't have a single continuous channel, eh? And the idea is that the turbulence of the flow of cold air below the "micro bells" creates mixing that exhausts the heat? Sorry, I mis-interpreted Vortex's airflow path.  Our stove has a continuous channel with up and down loops. Vortex's stove is much better in that respect. Well done Vortex! By the way, these tiled stoves are not at all easy to put together. The rebuild took an expert and his assistant 2 full days. Since the joining edge is so thin, with no mortar, each glazed section is clipped to all its neighbours. Tightness of joint is ensured by abrading down the matching edges (they used a firebrick). Then joint area and the section is filled with sand/clay mixture along with bits of pre-fired clay e.g. rooftile or red brick, all carefully made to fit, and then the inner pathway is shaped from firebricks. In the rebuild he added more mass by lining the whole thing with firebrick, and the path had to change quite a bit. I'm not sure which is better.. we'll see. David |
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jrl
Junior Member
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Post by jrl on Jul 3, 2014 5:55:22 GMT -8
Blakeloverain- I've lived in trailers and other small spaces with woodstoves and little insulation, a small space like that doesn't take much to heat it but once the stove is out they go cold very quick, so I'd say smaller firebox with a similar amount of mass would probably be the way to go. The main problem i see is the vibration in a moving vehicle, it would shake my stove it bits in no time. If you built something with just castings held together by a metal frame that could work. The middle is definitely the place to put it, my cabin temp only varies a couple of degrees from end to end. Standing in front of it when it's in the middle of a firing is not advisable, once the burn is over the temp evens out over the stove quite quickly and it's ok to stand in front of then. The stove weighs somewhere around 500 to 600KG. The only place you could really put a white oven is where the micro-bells are - it would really look like a large cookstove then - I use the firebox after the burn is over I rake the hot coals to the back and put in a rack to stand what I'm baking on and it works great. We dont measure wood in cords here, my wood pile for a whole year is 8 or 9 cubic meters. Google says 3.6 cords to the cubic meter, so that's about 2 and a half cords. Good luck with your plans. Mintcake- In a larger stove I have no doubt a single or double bell would work better but I dont know if that's true of a small stove like mine, there's a trade off with the amount of mass to store heat and the ISA to soak it up. Also I think a damper will increase the length of time any mass stove will store heat, a bell stratifies the heat but it's still losing heat out the chimney just at a slower rate. My stove never has black smoke, there's white smoke for the first few minutes after lighting then it's clear. , I'd very much like to see a youtube video of your stove in operation. Is there one? |
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Post by Vortex on Jul 3, 2014 8:55:17 GMT -8
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Post by patamos on Jan 31, 2015 21:36:00 GMT -8
Hi Vortex,
I am preparing to build a heater for a similar sized dwelling, and am giving thought to your design.
Early in this thread you mention shortening the depth of your firebox. Can you say why? The people for whom i am building are hoping for a baking chamber of 12"x12"x18"… so i wonder how the extra 3" depth would affect performance…
Alternately, you have mentioned ( i think?) the prospect of adding an oven over top of the fire box. So i am wondering if that ever came about, and if so, how things went...
Also, do you think this heater would work with a 6" flue?
many thanks for sharing all that you have
pat
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Post by Vortex on Feb 1, 2015 3:42:39 GMT -8
Hi Pat,
My cabin is only 42 meters square, plus 2 small bedrooms in the roof space - it was too hot. The firebox didn't need to be so big, and a small fire in a big firebox doesn't work so well, so I made it smaller.
I have a 6" flue, 12 foot high, top two thirds is insulated. Works perfectly.
I never got around to making a white oven in it. I think putting one above the fire would be too hot, maybe to the left side would be best, but you'd loose most of the micro bells. Until recently I used the firebox as a black oven, but since I've been experimenting with wood gasification I haven't been able to as it makes the fire last for ages. I'll post more on this soon.
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Post by patamos on Feb 1, 2015 11:21:44 GMT -8
Hi Vortex, Thanks for your responses  Well, by all that you are saying, i am increasingly convinced that this design is the way to go. If i can deepen the firebox to 18+" this will meet the needs for a black oven large enough to hold my friends big roasting pan. Do you have a sense of how well the baking chamber holds heat over 3 or 4 hours? The heater will replace a metal box stove in the basement of a 40 year old, 2400sq.ft. house, so the extra heat will not be a concern. The difference is we will be encouraging heat to travel primarily in one direction, so i will widen the footprint to 5' with an hollow bell bench and possibly a shallow vertical tower above the firebox. Maybe they will want a small griddle just above the throat instead. We are also considering a small second bell on the upper floor where the flue travels through an otherwise wasted space chimney chase. With all the inevitably wet soft-wood we burn around here … creosote in the flue is a real issue - particularly with a bypass start up. So having those resin-rich gasses cool and condense in an easily cleanable upper bell can be good safety feature. I'll be writing more about this in another thread soon. I am very interested in your application of Matt's secondary air port. I had thought you would place a small adjustable port near the top of your door (where the leaks are happening anyway), but sounds like you have come up with something different. I'd love to see pictures. Would you change anything in the firebox design to better optimize the inclusion of the Walker port? well being pat |
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Post by Vortex on Feb 2, 2015 9:20:23 GMT -8
Hi Pat, The Depth of my firebox (without the 2.5" cast slab that I originally put in the back to shorten it) is 18" exactly to the inside of the door. I dont have any figures at the moment for how long the baking chamber holds the heat but I'll get a new battery for my IR thermometer tomorrow and take some measurements for you. I just baked a Quiche in it 4 hours after lighting, so should be fine A while back I was experimenting with Walker Ports in my stove. Eventually I realized what was going on there is that it's turning the stove into a wood gasifier. The important thing is to get the whole firebox upto maximum heat before closing the air almost right down, that way you create a super hot box full of dry wood, which in the low oxygen environment gasifies, and the heated air coming in through the Walker port mixes with the gases and allows them to burn. This extends the combustion by 3 or 4 times, without any noticeable loss of a clean burn and with an apparent increase in efficiency. After a lot of thought I realized that my stove with it's deep dead-end firebox, (with both the air inlet and exhaust at the front,) is perfectly suited to wood gasifing and so shouldn't actually need the Walker port. (The PB Batchbox rocket has the primary air inlet at the front and exhaust port at the back, which creates a cross flow that isn't ideally suited to gasifying. By filling the primary air port with the metal tube of the Walker port, it's creating that super hot dead-end, heating the air in the tube and feeding it into the fire at the right spot to mix with the wood gasses and burn them.) So I thought if I stacked the wood tightly together right at the back of my firebox, with the kindling and small pieces at the front, I should get the same effect without the Walker port, (as the air leaking in around the hot metal door frame on my stove is doing the same job). The result was amazing, the stove burned for 5 hours with a beautiful golden glow and slowly licking flames above and in front the wood, the house got so hot I had to open the door for most of the evening. I think some kind of heated air inlet holes across the top of the stove throat might be suited to this kind of burn, I'll have to see what I can rig up to try it out. At the moment I'm experimenting with varying the depth of the firebox to see what difference that has on it. I'll keep you posted.  |
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Post by Daryl on Feb 2, 2015 9:27:05 GMT -8
Wicked beautiful photo.
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Post by matthewwalker on Feb 2, 2015 11:07:47 GMT -8
Awesome write up and findings! Good stuff Vortex. You can do kind of a classic secondary air set up with yours. I believe a lot of masonry heaters use air in the throat designs. The RMH batch is a bit different for sure. The cross flow does make the fuel/air management a challenge, and you can't stop it, or slow it down too much, or the thing crashes. I was relying on a leaky door for air as well, but since I made a new one that seals well, I've realized I need to keep a decent amount of primary flowing through the box. I think you could do some neat configurations with yours, maybe a tube across the window with holes in the top, so you could see the secondaries right against the glass. I have a bit of that going on and it's spectacular, but you could do it very well with your set up. Thanks for the update!
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Post by patamos on Feb 2, 2015 22:19:38 GMT -8
A highly efficient 5 hour burn?! This is very enlivening news! I feel downright grateful to be hanging with y'all and swirling around in the midst of all this unfolding... Ya, door vents. Some of the masonry heater doors have slider vents across the top and bottom edge faces of the door. Right across the width of the opening. SOmething like that across the top could work nicely with the shape of the throat. Although it would make sense to experiment with the leak/port in the door seal til the ideal dimensions arise. So interesting... I've not taken a super close look at the drawings and the height at the back of your throat, but am guessing it to be around 8" tall? If an 18" roasting pan with lid is one of the desired criteria i had best nut that out and look at potential adjustments of pan or of firebox design. Maybe a few careful whacks of the pan's lid will do the trick. Quiche 4 hours after the fact sounds promising... One of the two builds i am preparing for will have insulation around the right side and back, so that is bound to boost thermal storage. Rather than a full cook top, i am picturing a cast iron griddle above the throat. The deck will go back about 8" and transition into thicker ceramic warming deck. The idea of the griddle is to offer up both a very hot plate for smudging and cooking (maybe with removable pot decks) and a way to amplify the secondary burn coming around the corner. Thus I am wondering what pattern of ribs and fins along the bottom of the griddle will most enhance the full combustion process? For the thermal battery the contraflow flue run will be replaced by a lower bench bell. One of the issues i am presented with is how to send most of the heat forward into the room. To this end i am experimenting with common hi heat red cay bricks with the three holes in the centre. I'm filling these holed only slightly with a thin plug of cob at one end... and then facing the plug outwards… with a cob skin over top the surface, and finish plaster - maybe with fiberglass in higher heat cycling areas. This will hopefully speed thermal release time and possibly enhance ISA in the bell. The first test of this idea will be in a little heater in my workshop with a low longish bench bell. My guess is that that it ought to work, but new ideas can make for all kinds of surprises  The other build i am preparing for will likely involve a vented water tank on top with hydronics and adjustible insulation. Might still be worth have some such griddle atop the throat there too. Vortex, thanks so much for all the energy you have been and keep putting into this design and application. While i am at it (and next going to bed) i send out a huge thank you to Joris for sending me very clear information on the most evolved of his design. And to Robert for weaving the threads… well being pat |
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Post by patamos on Feb 3, 2015 3:06:52 GMT -8
Early am
full moon
mind alight with ideas
how about a series of 4 or 5 trip wires set into the throat just before it rounds the bend?
Or maybe they are on the inside face of the front lintel brick above the door...
staggered in location to account for faster flow down the middle…
Or parallel but staggered in size to achieve the uniform hole one finds in moving water over a uniform wier
? ?
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