Vortex Stove

[Dan (Upstate NY, USA)]

Nice

[Vortex]

Thanks Guys.

When the new stove is finished, the old one will be dismantled and the new one will be moved into it's place. The new stove can be taken to pieces moved and rebuilt in a couple of hours.

The original stove was a prototype, only built with the intention of it lasting one winter, and it's on it's 10th. I've learned what I wanted from it and now that's all gone into designing this one. Also I've made the new stove so it can be easily adapted for improvements or experimentation.

Yesterday I got the cooktop subframe pieces cut and in place. They're made of 75mm X 10mm flat bar and will be welded together. Then 10mm thick plates cut to fit in the 2 holes, which will then have larger 5mm plate welded on top, (to come up to the inside edges of the angle steel top frame). These will form the cooktop expansion plates.

[drooster]

Vortex for this build with the willow-holes in the slabs did you change your casting mix or is it the same as for the previous 9-year-old stove?

[Vortex]

I was originally planning to use my own mix for the firebox parts of this new stove - I even made some test pieces that have been in the back of the old stove for the last year - but I got a few leftover bags of castable as part payment for a job I did this summer, so I ended up using them instead. It's the same brand as I used on the old stove.

The test pieces are still both going strong. The mix I used had a lot of clay in it, and after vibrating it all the gritty bits had consolidated at the bottom and mostly clay at the top, so when I put them in the firebox I put one each way around to see which preformed best. The Clay-side-out one has spalled very slightly from the surface, the gritty-side-out one it exactly as it was when it went in.

Why do you ask, are you planning to try your own castable mix?

[drooster]

Indeed, I'd like to try a clay-perlite-castable mix in my own design,
but being very stingey I want to keep the castable refractory part to the minimum and wondered if your mixes had developed.
My design will be similar to the principle to yours : a hot secondary burn area with low velocity flow.

[Vortex]

The best insulating mix I've made was 4 parts Perlite, 1 part furnace cement and 1 part Calcium Aluminate cement. It wouldn't take much abrasion but then what IFB does.

The mix I used for the test pieces (in the back of my firebox) was just the local clay/sand/grit deposit, sieved through a 3mm screen and mixed 4:1 with calcium aluminate (fondue) cement.
I noticed when reading up about the local geology that the rocks and clay were almost the same constituents and ratios as the dense fire bricks I was buying, so I thought I'd test it out.

You can make your own castable mix by creating a grog of any waste ceramics that have been fired to a high temperature. Crush it up into a grit and put it through a 3mm screen. Mix that 4:1 with calcium aluminate (fondue) cement, and a bit of clay if you want.
I helped a friend make a load of large slabs like that, using crushed old glazed fired clay roof tiles and some broken red clay bricks and fire bricks. I still have a 1 ton bag of it left

[Chad]

Vortex

I was looking at your design and am contemplating a smaller design. If I scale down to a 4 inch flue will I have issues. Also I will have to vent through 26 ft of in-insulated flue through my existing chimney, will this cause me any issues?

Thanks
Chad

[Vortex]

Hi Chad,

You can't use a 4" flue on a 6" system, you would have to scale the whole stove down. Also I wouldn't recommend going down as far as a 4" system, 5" would be the minimum.

Why do you want to use a 4" flue? What diameter is your 26' flue, and what kind of insulated flue is it? Is the flue smooth skinned or wrinkly on the inside?

Here's the scaling figures for different size fireboxes:

5" gives a scale factor of 0.83 so the firebox comes out at 10.6" High by 10.2" wide by 12.9" deep
7" gives a scale factor of 1.16 so the firebox comes out at 14.8" High by 14.2" wide by 18.0" deep
8" gives a scale factor of 1.33 so the firebox comes out at 17.0" High by 16.3" wide by 20.7" deep

[Chad]

Vortex

The 26 ft flu is a older non-lined chimney running through the center of my home, with a 6 inch shift in the attic.

My current furnace also runs through a 6 inch flu through the same chimney.

Does the flu have to be insulated?

I will have to climb on the roof take the cap off and see what I can manage to fit in the chimney.

I really appreciate your work on the vortex stove, I plan on building one before next winter.

Thanks

Chad

[Vortex]

Chad, All the ones I've built have been on insulated flues, but IIRC Patamos in Canada has built them on uninsulated chimneys. I think the only problem one was on a chimney lined with stainless flexi-pipe. Maybe Pat will chime in here.

[Deleted]

Hi Vortex,

Thanks for all the information you're sharing here, it's very interesting and inspiring ! Great welding skills also !

I've been doing some calculations on your core and since the volume of the firebox is approx. 40L it would be classified (in France) as a 2500W heater considering two fires a day.

Do you know the approximate weight of your heater ? I've made a rough estimation and it should be around 600-700 kg. Is that right ?

If both calculations are correct, your heater as a ratio brick weight vs. power output of approx. 300 kg/kW which is very very good ! With bell systems I have trouble to go that low so i'm very interested ! I think it may be your heat extracting system that is more efficient than bells.

For example, in my last cookstove I'm around 600 kg/kW and Peter with his red bell is around 1100 kg/kW. Common contraflow heaters that I've built are between 300-500 kg/kW. For the french climate with daily temperature variations and old, uninsulated buildings it's very nice to have heaters of moderate weight with a surface temperature that is quite high.

If your heat extracting system is as efficient as it seems it would just be a perfect addition to a batch core !

Could you try to measure the temperature inside your exit flue, approximately 1 m above the plancha exit ? If I may push a little bit further, could you do that measurement by doing only one full firing and by taking the temperature every 10 minutes from the beginning of the firing ?

A simple way is to use those BBQ thermometers : www.amazon.fr/gp/product/B00L314SOY/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1

I know you've already done temperature measurements, but it seemed to me that you were measuring the outside temperature of the exit flue so it's different.

Regards,

[Vortex]

Hi yasintoda,

Yes, I measured the temperature on the outside of the stove pipe using an infra-red thermometer. It may have been effected by the emissivity of the stainless steel. I have a BBQ thermometer like the one you linked to, the range is 0-120*C. I bought it to use on the stove pipe but have never got around to installing it. The single skin stove pipe changes to double skinned insulated pipe at 850mm high above the stove top, I could install it there if that's OK, as the insulated is too think for the thermometer to go through?

I think your estimate of 600-700KG is about right for my original stove. I'm aiming for 1 Ton with the new one. When I move it into position I'll weigh the parts and add it up.

[Deleted]

Hi Vortex,

Thanks ! 850 mm is perfect. It's very nice that you can make those measurements.

Regards,

[Vortex]

Hotplates are finally finished. I didn't fancy cutting the 10mm plate myself so I spent half a day driving to the nearest engineers shop and got them cut, only to get home and discover they were both 10mm out of square... So ended up having to cut them myself anyway.



Lift out grate. (it's 5mm smaller than the hole so it doesn't expand and break the cast).



Copper sheet in place and firebox door frame pieces sat in position awaiting welding.



Next I will make a hearth shelf from the same 50mm angle steel as the rest of the frame, and bolt it to the front just below the door frame level with the bottom of the copper.

[drooster]

So pretty Vortex, great job!

Will it be possible to run both at the same time?