Vortex Stove

[Vortex]

Today's run:

[AA]

Hi Trevor, first of all I want to thank all knowledge shared here. I am still wondering how to finish this piece of art in full safety. My lack on knowledge does not help me on figuring out one detail... I am willing to build this older model, with one big bell, the 2 mm gap on door, one top plate of iron 5mm (probably with some welded iron bits under the cookplate zone, for eventual use without bending... assuming it will help) and with a 2 cm insulation plate underneath for moments when less instant heat might be desired.

Now my question is;

How do you isolate this top plate, touching the bricks and concrete top condute? Is it air tight somehow? (Or is is only of importance that the firebox has no cracks and it to be airtight...) So, can air skip in or out through this top connection, specially if the plate starts bending in length due to heat? (as you mentioned some time ago while referring to a posted picture)
Somewhere also a drawing shows "fireclay" as used in between plate and bricks. But if fireclay is a hard material, wont produce any airtight seam here, so why this fireclay?

Thanks in advance for your reply!

P.S. One day I will go for this rams horns model! Amazing!!!

[AA]

Hy again,

I forgot to mention, that this concern is also because I would like to keep the top iron plate free to open for cleaning, inspection, etc.. I do not have the intention to create a second door for this like on some of your models (in front on the left) , and will have only a loose brick halfway under the fireboxfor cleaning (diagonally, trapezium cut so he cannot be fully pushed in...), behind the (almost airtight???) ashes drawer...

Thanks again!

[Dan (Upstate NY, USA)]

So what made the third graph run so much better then the other two?

Seems like the testo is teaching you how to run your stove better.

I'd love to test my plain old J-tube... to see how she runs...

[Vortex]

The problem I seem to be having is since changing to the low resistance chimney cowl and larger afterburner exit, the fire is prone to over-fueling at the startup, especially when it's windy. Today it did it again and it took me a while to get it back under control. Ill have to try making the afterburner exit smaller again. With less resistance to gas flow I can close the bypass a lot sooner, but the downside is its more prone to runaways. The second half of today's burn looks great.



Turns out my chimney thermometer gets more inaccurate the higher the temperature. I thought the testo thermo-sensor was off so I used my electric thermometer probe to do a comparison, it agrees spot on with the testo - so my my flue temps are higher than I'd thought.

[Vortex]

Nov 10, 2019 0:46:26 GMT -8 AA said:

Hi Trevor, first of all I want to thank all knowledge shared here. I am still wondering how to finish this piece of art in full safety. My lack on knowledge does not help me on figuring out one detail... I am willing to build this older model, with one big bell, the 2 mm gap on door, one top plate of iron 5mm (probably with some welded iron bits under the cookplate zone, for eventual use without bending... assuming it will help) and with a 2 cm insulation plate underneath for moments when less instant heat might be desired.

Now my question is;

How do you isolate this top plate, touching the bricks and concrete top condute? Is it air tight somehow? (Or is is only of importance that the firebox has no cracks and it to be airtight...) So, can air skip in or out through this top connection, specially if the plate starts bending in length due to heat? (as you mentioned some time ago while referring to a posted picture)
Somewhere also a drawing shows "fireclay" as used in between plate and bricks. But if fireclay is a hard material, wont produce any airtight seam here, so why this fireclay?

Thanks in advance for your reply!

P.S. One day I will go for this rams horns model! Amazing!!!

Hi AA, Thanks for your comments.

I wouldn't use the 5mm steel for the cooktop if I was building it now, it twists and bends too much. If you don't need to put as much mass as possible into a small space like I did, then I would use old ceramic cooker tops like Matt Walker did on his cookstove, with a angle steel frame to hold it in place. You can use ceramic blanket cut into strips to make seals for under the edges, it's easy to lift off for cleaning that way. If you can lift the top off, you can clean the whole thing out from above and via the lose brick behind the ashbox using a hoover.

Don't forget to show us some pics of your stove when it's done.

[Vortex]

Last night I reduced the size of the afterburner exit back down to what it was before, but with the gap between the shelf top and the bottom of the hotplate above - not between the end of the shelf and the glass as it was previously. The idea being to create the same level of restriction as before but without forcing the heat against the glass as that causes etching.

It was blowing a gale outside when I lit the stove this morning so wasn't surprised it still tried to over-fuel a bit but it was much less than before. Calmed down into quite a good burn after the initial CO spike.

[cork]

Hi Trev,
Have you got a handle yet on what the CO levels are when your afterburner glass starts blackening?

[Vortex]

Hi James, The carbon black levels don't seem to have much bearing on the CO levels. I've watched the stove black the glass while the CO was very low. Lighting from on top produces less CO at startup, and any fire that is burning fast when the afterburner isn't fully hot seems to produce high CO.

Last night I reduced the afterburner exit again, this time down to 90% CSA. It was a bit slower to get going but didn't produce the huge CO spike. Afterburner made a low roaring sounds between 20:35 and 20:55.

[Vortex]

Loaded horizontally and lit from above again this morning. Large split of oak and ash on the bottom then some small rounds of hazel and holly, pine split kindling on top. Very gusty wind. Long 2 hour burn. Thought I'd avoided the CO spike but it turned up just a little later.

A couple of things I've noticed using the testo; if the flames stay in the afterburner the CO stays low, if they start streaming out around the shelf up under the cooktop then it spikes up. During the coaling phase when I have the air open up through the ash-trap, the CO stays low so long as the ash-trap hole is covered with embers, as soon as a hole burns open the CO starts rising. A steep V shaped grate would probably deal with that, mine is quite shallow.

[Vortex]

Two more runs done, both laid horizontal and lit from on top. I'd noticed in the graphs that a CO spike always seem to come straight after I close the bypass, so last night I tried a half load starting with the bypass closed. No big CO spike at the start but CO was a bit higher overall.



This morning I tried a full load started with the bypass open, then closed the bypass as soon as the kindling was properly alight. CO spike came straight after but not as big as when it's been closed later. The high excess O2 in the middle confused me as I presumed it meant it wanted less air - but it wanted more - seem it can be caused by too much or not enough.

[Vortex]

The stove doesn't seem to need the bypass damper now it's running with the new chimney cowl, starts fine without it and eliminates the CO spike that always seemed to follow after it was closed.

This morning I tried a half load, quite tightly packed in at 45 degrees in the back of the firebox. Ash, Holly and Hazel, with some Pine kindling in the middle. Lit from the front bottom behind the primary air. It burned beautifully, the CO was low right through but the O2 would not come down. I thought there must be a leak somewhere as half the burn it was above 20%, I had to make the graph go up to 22% just to get it on. (The efficiency (% n) is calculated from the O2.)



This evening I tried exactly the same configuration of wood but a three quarters load. O2 was a bit high again but not as bad as the morning. CO nice and low again. I think maybe the 45 degree surface of the timber behind the primary air hole, might be directing it straight up and out through the port.

[Vortex]

I think the oddly high O2 readings I've been getting have been caused by a dirty filter in the testo. I've been waiting for a delivery of new ones. Tried a quick test at the end of this mornings burn - switched to an old but cleaner looking one and the O2 went straight back into normal range.

EDIT: Filter was very wet. They need drying out between tests.

[Vortex]

First run with a new clean dry filter in the testo. Half A load; 2 splits of Ash with smaller rounds of Holly and Willow and pine kindling on top. Laid horizontal and lit from above with the bypass closed. A little too much kindling led to an initial peak of CO, but otherwise very pleased with it.

[Vortex]

Another test run. Half load, laid horizontal and lit from above, with the bypass closed. Ash, Holly and Willow with 3 pieces of Pine kindling and a handful of wood shavings on top. No wind at all today so the curves are quite smooth compared to the last one.