Vortex Stove

[fruitbat]

martyn great work- thanks also due to you for recording your experiments, which I've been keeping an eye on. Inspired by your work I'm planning to try a small-as-practical Shorty core (3.5"?) in vermiculite board, inside a small steel bell lined with sorage heater bricks.

It will be a subject for a new thread, I'm in a tiny caravan while rennovating an old timber frame house I've saved from being demolished and replaced. I need something tiny but heavy (will be supported directly underneath!) until I can get a proper mass heater built in the house and through UK building regs....

[martyn]

Vermiculite will be perfect for a short term use, really easy to work with, safe too!
You could just build a basic core and line the outside with bricks, you can use a dap of silicone on each brick to hold them together.

[martyn]

[martyn]

I lit the stove this morning, conditions are not good at the moment with 18c and no wind but it still fired up easy enough,
Every time I tried to put the door in place it smoked up but it did work fine without the door!
So the secondary air works very visibly with the door in place as there is obviously restricted air (until I sort that out) the jets of ignited air can be seen very clearly!
However I can see that the holes are probably not placed in the best position but to be fair I need to tinker a lot more as this was a first run……
Also as I expected the supposedly 1000c rated cement board has cracked, the cracks have appeared on the sides in the top box but they are hairline and not an issue so far.

[martyn]

So I made some changes, I think for the better but, of course one good run is not a conclusive result. We will continue tomorrow with some other ideas. Hopefully I will be able to build a more permanent stove with fresh glass and vermiculite but for the time being, we will struggle on with the bits and pieces I have to hand.

[Vortex]

Great work martyn. I think it's even better that it works so well without a door, and I love the see-thru top shelf, I'd imagine the underside will get pitted quite quickly though and a layer of fine ash collect on top obscuring the view, but hopefully I'm wrong as I'd definitely copy that.

These are the areas I found it would draw in secondary air to the afterburner:




Trev

[martyn]

There just seems so many possibilities, it all becomes a bit daunting as there is no way I can test every one!

If I could only find a glue that will stick the glass pieces together that would open up a lot more doors. I have tried quite a few possibilities with no luck so far!

I dont have a shortage of small pieces of glass as I can get all the off cuts I want for free.
The local stove store sell 300 x 300mm sheets of 2 or 4mm thick ceramic glass for around £50 - £70 a sheet but … they just dump the off cuts!
So I just go along to the store and help myself from the off cut bin, most pieces are 300 long by 50-100 wide but the old glass that is being replaced is also dumped so I can often find cracked, used pieces, 200 x 250mm or such like.
It is amazing how a relatively small population of 70k people can require so many stove glass replacements but, the guys tell me they go through 400 sheets a year and over 200 sheets of vermiculite too.
One of the draw backs of the modern wood burning stoves is that the higher temps inside the box due the vermiculite linings, cause in turn, to shorten the life of the glass.
Many of the new designs box stoves have very specific air wash designs to cool the viewing windows and keep them smoke free.
I have already tried making an air wash for the top glass on the vortex stove but I am going to give this more thought……

I could do with lots more vermiculite as although it can last ok, is does not like being recut and re used once fired so my experiment are becoming quite expensive, that is one reason to experiment more with the ceramic glass and see where I cam make use of it.

I have been sort of forced into early retirement due to health issues, that gives me more time but less money to play with.

I would like to try and move the secondary air to the back so it enters dead center of the vortex through a single 20mm hole each side……

[fruitbat]

Really interesting how stable it seems to be running without a door- have youtried adding fuel part way through a burn?

I just wanted to make a point about something you mentioned in one of your older vids regards secondary air- I can't find the specific video now- but you mentioned about getting blue flames. This was a setup with copper pipes to feed secondary air- blue/green flames are caused by he copper oxides burning off, sadly not due to perfect combustion being achieved... although I'm sure you've probably sussed that out for now.

I can sympathise with material costs as I'm on a budget too, as mentioned I'm planning to push the boundaries with a 3" or 3.5" shorty in a tiny mass heater (all as low friction as possible) for a caravan.... but watching your videos make me want to try a tiny Vortex! I imagine it would be even more friction sensitive than a shorty core, so could be an expensive failure given the extra glass required.

[Vortex]

Jun 13, 2024 23:43:17 GMT -8 martyn said:

I could do with lots more vermiculite as although it can last ok, is does not like being recut and re used once fired so my experiment are becoming quite expensive, that is one reason to experiment more with the ceramic glass and see where I cam make use of it.

That's odd, I've not had that experience with it, I have boxes of varying sized pieces used and recut many times over, maybe it's different brands? I have mostly used the 20mm thick, smooth one side wrinkly the other from dineensales.com/vemiculite-board/ Though I use it mostly in the afterburner, pieces used inside the firebox do degrade a lot faster for some reason, which I presume is due to contact with the caustic ashes.

I would like to try and move the secondary air to the back so it enters dead center of the vortex through a single 20mm hole each side……

When I was doing my second lot of experiments with secondary air into the afterburner I tried the 2 holes in the centers of the rear wall. I found all the rear wall inputs disturbed the vortex and/or pushed it forward in some way. Best of them was the throat sides. Overall I never found secondary air in the afterburner to be beneficial - as when you have a door and primary air control any air introduced into the afterburner reduces the air drawn into the firebox causing a gradual increase in the air needed in the afterburner - but your application is very different to mine, so it may well be different for you. I hope you have fun experimenting, I certainly did

P.s. If anyone wants to read them they start on page 67. This thread really needs an index...

[martyn]

I quite agree that the stove can work fine or even better without additional secondary air, in fact I would say every attempt I have tried (and that is a lot) has actually cooled the afterburner!
The hottest version I have built was running at 750 on the afterburner walls, yesterdays version was seeing only 600 in the afterburner and the fire box was 650c.
But the secondary air really helps with loading extra wood and in my case cooling the top plate is beneficial!
However we will continue testing to see what happens …..
If i run the stove without a door the afterbrner runs cooler still
I am trying a different format today, I will take a bit of video later.
Fruit bat I have seen blue flames a few times inside my vortex J tube, I think you need very hot secondary air and quite a big feed tube.
The little 4” vortex stove might not get hot enough to supply the heat required but I would dearly love to see it working just for the fun of it.
Perhaps if I had a long enough s/s feed tube actually inside the fire box I could get the air hot enough?

[martyn]

Todays offering…..

[fruitbat]

Great being able to view the Vortex in 3D, and interesting you're reloading and experiencing a bit of runaway but still no smoke. Looks like it's going to be flexible enough for your use!

Fascinated you've achieved blue flame in the Vortex J tube, shows it can be done... keep experimenting!

[martyn]

Today I made a few adjustments like making sure there were not air leaks, cleaning all the glass, made a door with hinges and a few other little bits.
So I decided to make a better video, borrowed the misses iPhone, set up a tripod and microphone and loaded the fire box with a full load.
Same conditions as yesterday, same wood just double the amount….. = total nightmare!
Within two minutes the top glass had smoked up, two more minutes there was smoke pouring out the chimney, thick grey smoke bellowing out, totally black top glass and then smoke started coming out the open door. I closed the door and stood back to watch more and more smoke!
I just walked away feeling very disappointed, made a cup of tea and watched the smoke from the kitchen window, it took about 15 minutes before it stopped bellowing but basically it never really ran clean and after one hours I just had a huge pile of smoldering coals!
The only difference wax a full load in the fire box?
I guess I will have to try a half load tomorrow and see what happens…

[fruitbat]

Eagerly awaiting the results of the next trial run... Could the large volume top chamber be the culprit do you think?

[martyn]

Yes almost certainly in the same way as adding wood onto burning coals, it cause far too much wood gas that cant be burnt off due to the restricted space and lack of very hot air.
The unburnt gas is drawn rapidly through the system causing ugly smoke out of the chimney.

Trev has found a perfect balance that works but I have been struggling to find that balance.

I am unsure what to try next, I can think of complicated methods that might be able to adjust the vortex slot opening and add super heated air at the same time.
Perhaps just removing the down flow or adding a bypass (not easy in this set up) …. I might give it a few days thought….

As we all know, when the stove is on song it works beautifully and I have always though it was worth pursuing the concept to make an easy to operate, amazing to look at patio heated come hot plate.

The amount of heat that is generated and pushed out the viewing glass and top plate is crazy!
However for my own use, I need to be able to re load when the vortex dies, the only way I have found how to do this so far, is by removing all the coals and re staking fresh wood.
I think this issue applies to all the riser-less cores and even batch box designs, it is just more obvious with the vortex stove because you have a viewing window.

One of my close mates has a six inch batch box and it also pours out smoke if you reload on hot coals!

The only stove that seems to work with reloading is a J tube but of cause it does not look as good as a vortex stove.

Also I have discovered how the stove behaves very differently in the summer or the winter, it could be that in the colder months I would not be suffering the same issues but I want to use my stove more in the summer.
I am not feeling too good today but hopefully be back on it soon….