Vortex Stove

[Vortex]

Sorry DC, I still haven't got around to measuring those temperatures, I must get one of those magnetic thermometers as I'd be interested to see what it is. There's a 1 meter length of single skin stainless steel pipe coming out the top of the stove before it goes into insulated pipe, I can touch it without burning myself even at the hottest part of the burn cycle.
An average burn takes about an hour to get down to the glowing red coals stage. The thermal battery holds a surprising amount of heat, it is still hot to the touch (like a household radiator) after 12 hours, warm to the touch after 14 hours and usually takes about 18 hours to get back down to room temperature and even then there are a few warm areas around the firebox. I like watching the baffled visitors trying to work out where all the heat is coming from

[DCish]

Radiator-hot after 12 hrs sounds pretty positive. The really neat thing to me about your stove (in addition to the cook top) is how compact it is. This seems to be facilitated by your use of more or less flue-sized "micro-bells" facilitating high mass and ISA on a small footprint without resorting to draggy contraflow channels.

[Vortex]

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.

[DCish]

I'm wondering also how you find the balance between instant heat from the cook top vs stored heat -to. Does there seem to be a good balance for the size of space you are heating? (How big a space are you heating, incidentally?) Also, whatstarter sort of firingthe pattern do youyou find effectivethe on colderthe days (is one charge sufficient to achieve a full charge, or do you do multiple batches at a time, or morning /exploring night firings?) Given the talk of horizontile burn chambers on the other thread, I'm contemplating perhaps a refractory cap atop the firebox to keep the flame area insulated for more complete combustion, but effectively cutting the cook top in half. Maybe even trying to work in a peterberg-style burn chamber sans tall riser somehow.

[Vortex]

I find the balance between instant and stored heat perfect, I wouldn't want to change it at all. I'm heating a 70 sq/m cabin with the stove in the centre. On cold days I do two firings, one morning and one evening. One charge is always sufficient for everything except the most extreme cold weather. The stove needs no priming, with the bypass flap open it draws better than any wood burner I've ever owned, a couple of minutes after lighting the flap can be closed with only a slight slowdown noticeable. I use newspaper and kindling in the bottom left of the firebox, and then load the firewood with the largest piece at the bottom right, this seems to work best.

Remember that the farther your cooktop is from the firebox the less heat will reach it. The cooktop is effectively a horizontal heat riser, it has firebrick on 3 sides and steel on the 4th. You can cover the top with an insulating cover when not in use for cooking or more stored heat is wanted, like the hinged fold down ones on Arga range stovetops. The one thing I want to add to this stove is a chimney damper that can be closed after the firing is completely finished, so as to slow down the heat loss through the chimney, that would be very really useful on windy days.

[DCish]

How cold does it get where you are? I have a 110 sq meter house (well insulated, heated with a box stove on the lower level at the moment), but here in the DC area it only gets moderately cold, so I might be able to get away without scaling it up.

[Vortex]

I'm live right on the coast so the temperature doesn't go so low here but we get a lot of wind chill. Average winter the lowest temp would be about -5 *C / 23 *F, worst we've had here in 11 years was -10 *C / 14 *F. My cabin only has 2 inches of insulation in the walls and 1" in the roof. Temp in the cabin is usually around 21-24C / 70-75F, by the morning after the stove has been out for about 14 hours its usually between 16-19C / 61-66F.

[DCish]

Very cool, looks actually quite comparable as we have similar lows but much lower wind effect in a hilly, moderately wooded area and with pretty good insulation. I think I'm to the point of drawing up a variant of your stove and starting up a thread for it to get some feedback. Thanks again, the detail is quite helpful!

[Vortex]

No problem, I look forward to seeing how it turns out.

[Cramer]

That is not a stove my friend, it is a piece of art. I thought it quite nice even before it was skinned! What a fine job! Kudos Vortex!

[DCish]

Hey Vortex, the thread "secondary air modifications on batch rocket" by Pioniers has got me thinking... do you have any secondary air delivery at the point where your smoke exits the firebox over the lip of the shelf? Ever thought of such a thing? Do you suppose it would add efficiency to your system at all? I really like how Peter has fine tuned primary and secondary air to maximize efficiency and want to include that in my build.

[600monkeys]

Great design, I am not able to see how or where the flap is controlled. Could you please send pictures or note how this works and discuss why you made the change?

Thanks
-jim-

[Vortex]

Jim, If you look at the top left of this picture you can see 2 rectangular holes, the 2nd in from the left with the raised sides is the chimney exit, on the left side of the hole is the metal bypass flap, it is connected to an L shaped lever on the outside rear of the stove via a small hole through the firebrick, the flap rotates down 90* to the left to create an opening into the chimney. I moved it to the righthand side because it gave better draw when using the stove as an open fire which I did quite a lot in the evenings when I first built it. (The L shaped handle has to be made at a 45* to the flap, this is so it is weighted correctly to stay in the open or closed position, otherwise it will tend to open or close on its own when there is a gust of wind).

Dec 28, 2013 20:49:31 GMT -8 DCish said:

Hey Vortex, the thread "secondary air modifications on batch rocket" by Pioniers has got me thinking... do you have any secondary air delivery at the point where your smoke exits the firebox over the lip of the shelf? Ever thought of such a thing? Do you suppose it would add efficiency to your system at all? I really like how Peter has fine tuned primary and secondary air to maximize efficiency and want to include that in my build.

DCish, Good question. I have been thinking of adding one via a tube with holes in along the edge of the throat, (coming in through the side of the stove) up till now I've just relied on the fact my door has no seal and quite a lot of air gets in around the top - if I lie on the floor infront of the stove and look up I can see the jets of flame there where it's flowing in.

[Vortex]

I took some temperature readings with my new infrared thermometer this morning, it was just an average burn, I wasn't trying to break any records or anything. The hottest reading on the cooktop was 431*C / 808*F, at the same time the temperature of the thin single-skin stainless stove pipe half a meter above the stove was 78*C / 172*F I tried to get a reading in the firebox but it was above the maximum range of the meter.

Also added a stove damper into the chimney about a meter above the stove, shutting it after the fire is completely burned out really helps slow down the heat loss through the flue, there's a noticeable difference in the mornings, especially in windy weather.

[blakeloverain]

Vortex,

I want to thank you for sharing your project. It's quite inspiring. I've spent several days trying to understand masonry heaters and most of them are extremely tall, which are great for a 2000sf house but not my situation. I am intending on building a "tiny home" on wheels (wood-framed trailer home, basically), something I can tow with my pickup truck as a 5th wheel. Weight for me is obviously an issue, but your design seems quite compact versus traditional masonry heaters OR rocket mass heaters. My space is only 8'x30', so it's only 1/3rd the size. My walls will be R-19 (6" thick fiberglass), and the ceiling insulation will be higher (8-10" thick). Your situation addresses many of the concerns I've had - compact design, lasting warmth (even 12 hours would impress me), insulation worries, etc.

Do you think with my 1/3rd space, it'll get too hot surrounding the stove that it will be unbearable? How hot is it when simply standing in front of the cooktop? Is it comfortable or more like a blast of hot air? Do you think I need to scale anything down? Perhaps simplify the exhaust and add a horizontal bench that can even the heat out more across a larger area? Or merely scaling down the cooktop, perhaps adding some modular firebrick slabs to cover when not in use, etc? Maybe adding a 2 inch layer of firebrick above the riser instead of the steel? I definitely don't need 800 deg F at any point in time!

Where I might be this winter may be colder (10 deg F average low), so maybe it evens out.

How comfortable is your cabin at the extremes? I would place a heater like this in the middle with about 15 feet in either direction to the extremes. Depthwise, it's really only about 8 feet. Do you think it would be wise to consider a narrower and longer design than yours (ie instead of the width being half the depth, the width be four times the depth)? Also maybe because this is all on a trailer. The flooring is steel framed, but the load would be spread wider. Any idea how much your stove might weigh?

My own other modifications would be to include an oven. Maybe you would have a recommendation as to placement and exhaust routing. Somewhere in the middle of the 'vortex'? Or before, ie in between the riser and the vortex? I guess I'd want some sort of damper/adjuster to reroute the gases so I can tweak temperatures, at least somewhat. I'd also have hot water available, likely copper coils wrapped around the riser.

One final thing I would love to know, is how many cords of wood do you consume in a year? Besides even heating, I'm aiming to have less work finding/managing the firewood.

Either way I love the design, it's extremely elegant AND practical. The tutorial is extremely helpful, with the pictures, the progression, facts and figures. Some other project threads here are hard to follow.

Thanks,
Tomas