Vortex Stove

[Vortex]

6"/150mm Vortex Stove core Sketchup file









Summer 2020 I built a 4" / 100mm scaled version: donkey32.proboards.com/post/34699/thread
Scale Drawing: vftshop.com/images/others/Stove/aryancore4.jpg




OVERVIEW

3 Chambers: Fire Box, Afterburner & Top Chamber.

3 Apertures: (Firebox) Port, (Afterburner) Stumbler / Port & (Top Chamber) Exit Port.

Dimensions below are for a 6 inch / 150mm system. (To get the dimensions for a 5" / 125mm system multiply by 0.833, 4-3/4" / 120mm system by 0.800, and for a 4" / 100mm system multiply by 0.666)

Firebox: 305mm High, 305mm Wide, 420mm Deep (not inc the door frame).

Firebox Port: 50mm Wide X 175mm Long. (approx 50% CSA)

Afterburner: 114mm High, 230mm Wide, 420mm Deep.

Afterburner should be low mass and well insulated. I do not recommend using ceramic fiber products in any stove if you can avoid it, but if you have to, then enclose them so they are not releasing fibers into the gas stream. Insulating firebricks I believe are ok as they do not contain fibers.

Afterburner Shelf (roof of the Afterburner / floor of the Top Chamber). I originally made this adjustable (forwards / backwards) because at the time the gap between the front edge of the shelf and the inside of the glass was functioning as the Exit Port. That had the downside of the glass getting 'etched' from the intense heat against it. So I moved the shelf back a bit and put the Exit Port / Stumbler up on top of the shelf. I found the increase in size of the afterburner was also an improvement. A gap of 110mm between shelf front and glass seems to be good, as it is large enough to avoid damage to the surface of the glass, but close enough that if the stove overfuels and smoke deposit is left on the inside of the afterburner glass it burns of clean again quickly.

The roof of the afterburner should be made of an insulating or low mass material. Ideally I think a material that will glow as quickly as possible would be the best. A kiln shelf or ceramic glass may be ok, but I haven't tried them yet. I'm presently experimenting with a Vermiculite board shelf.

(Afterburner) Stumbler / Port: 230mm Wide X 40mm High (52% CSA).
located on top of the shelf about 80mm back from the front edge of the shelf.

Top Chamber: 75mm High, 280mm Wide, 460mm Deep.
The roof of the Top Chamber in a cookstove may be a hotplate (ceramic glass or steel/cast iron plate) or the base of an oven.
Top Chamber Exit Port: 117mm Wide X 118mm High (78% CSA).
The top chamber exit Port can be at the rear middle, left or right hand side.

CSA = Cross Sectional Area. Example: On a 150mm system: (the radius) 75mm x 75mm x Pi (π 3.142) = 17673mm²

Air Supply: Primary Air: adjustable upto 20% CSA, low at the front of the firebox door. Secondary Air: adjustable upto 10% CSA, in from the sides and top behind the door (this can be done with a steel box section behind the door frame or simply a 2 position door catch to leave a 2mm gap open). They can be combined into a 30% CSA primary but this has not been analysed with a testo.

The three apertures; Firebox Port (0.50 CSA), Afterburner Stumbler / Port (0.52 CSA), Top Chamber Exit Port (0.78 CSA).

It looks like there is some degree of flexibility with regard to some of the dimensions and materials eg. Firebox, but that the dimensions and configuration of other parts (apertures) seem critical to achieving the clean, highly efficient burn.

_________________________________________________________

UPDATE: This thread is now nearly 8 years old, the original stove has been dismantled and a new one built.

Discussion of the new stove starts around page 15: donkey32.proboards.com/thread/703/vortex-stove?page=15
Building of the new stove starts on page 20: donkey32.proboards.com/post/23834/thread

2018 I started experimenting with a new Vortex style afterburner on the stove, discussion of that starts on page 28: donkey32.proboards.com/post/30273/thread

START OF ORIGINAL THREAD:

I recently stumbled across your great little forum and thought I'd share my stoves with you. The design is not classic rocket stove but includes elements of it. It's a horizontal front load, batch fed, mass stove with cook top. Now on it's 5th winter and going strong. ;D







With bypass flap open it can even be used as a classic open fire



The initial construction: I changed the top after the first trial - rising it another 3 inches and moved the bypass flap to the right hand side.



Two years ago I built another one for a friend who is a carpenter, and in return he made me a set of reusable wooden moulds to cast the refractory core in pieces that slot together. It was going to be tiled but hasn't happened so far. The door and ashbox (bottom right hand side end) has yet to be made - for a door he's still using the metal plate held up by a brick that I used for the first few years.



Top View (without metal top on): Firebox throat / riser on right, bypass flap opening to chimney in centre (flap not installed), contraflow down channel on left drops down below firebox level and travels around anti-clockwise under four bell chambers before exiting up the chimney (centre).











Some Videos Here

Vortex Stove Plans PDF
All Scans in Zip file

[cab]

Nice! What are the dimensions outside and of the firebox?

[matthewwalker]

Yeah, so cool! Thanks so much for posting.

[mechartnik]

nice work, thanks for sharing it

[grizbach]

Yes, very cool!
How hot does the flue get?

[pinhead]

Very interesting, indeed.

[Vortex]

Thanks, that's a nice change from the usual blank expressions I get from most visitors when I try to explain how it works

The dimensions are:
Outside size inc metal: Length 40-1/2" X Width 22-1/2" Height 33-1/2"
Firebox: Width 12" X Height 12" X Depth 15-1/2"

I dont have a flue thermometer so I'm not sure of the flue temps, though I can touch it for about a second without burning my hand even at the hottest part of the burn cycle, and it's single skin stainless pipe. The purple tempering colours you can see on it are from when the bypass flap is open for lighting and the flames sometimes go up it.

I played with various designs on paper over several years before I settled on this. I wanted something efficient, that I could cook on, use as an open fire if I wanted, build in my cabin without major under floor work and not look out of place.

The metal acts as its second skin, allowing it to expand and contract while helping hold it all together. I initially wanted to use copper sheet on the sides and back but couldn't afford it at the time - shame, as I still think polished copper would really look great on it.

The materials list I kept when I built it came out as:

***************************************************
101 Standard Firebricks
35 Old Red Bricks
1 Sack Castable Refractory Cement
3 Sacks Fireclay
Steel: Plate steel: for top 1015mm x 545mm (5mm)
for sides 2 @ 21 1/4" x 33" (3mm)
for back 39 1/2" x 33" (3mm)
Angle iron (40mm x 5mm): for top 2 @ 40 1/2" & 2 @ 22"
for vertical sides 4 @ 32"
Plus Door, Ash pan, damper flap etc.
*****************************************************

The door glass is an 8" Pyrex oven casserole dish lid.

Here's a couple of better daylight pics from today.

[matthewwalker]

Right on Vortex! So, if I may ask, does that materials list indicate you used a blend of castable refractory and fireclay for your casting? Would you mind sharing your mix recipe for the cast core? How has it been holding up?

[Vortex]

Hi Matthew, In my stove I used one sack of Castable refractory cement to make the grate, throat and lintel, all the rest of my firebox is made of standard firebricks. I only used the fireclay for the mortar. In 5 years I've replaced 2 firebricks, all the cast parts are as good as new. I did make a 2" thick piece a few years ago to put in the back of my firebox to shorten it a bit, which I made by pounding up all the offcuts into grit, and mixed with firecaly and portland cement, that is still going strong.
In the one I built for my friend we cast the whole firebox and it took 6 25KG sacks of castable, which was expensive, it's done 2 winters now without any cracking or spalling.

I looked into making my own refractory mix but decided I didn't want to risk it, while researching it I found this recipe but I haven't tried it:
www.traditionaloven.com/tutorials/concrete.html

[morticcio]

Great job! Similar to the cabin stove at Aprovecho Research Center, but yours is more ergonomic - the Aprovecho one has the flue at the front to the right of the hot plate so it kind of gets in the way.

Far better at the back like yours - leaves a clean working area.

My daughter disagrees with me on this as she is left-handed :-)

Plans for the cabin stove are here www.firespeaking.com/wp-content/uploads/2011/09/Cabin-Stove-Construction-Drawings.pdf

[Vortex]

Thanks Mort, I agree, I think mine has a better use of the inside space as well. I wonder if the anvil on top is an essential part? :-) The cooktop on mine is made of 5mm steel, and it bows up quite dramatically during the hottest part of the burn cycle but other than 'saucepans at a slight angle' it's never been a problem. On my friends I suggested an 8mm top, as I'd heard that was the best thickness but he insisted on 10mm, for the first 6 months it worked perfect - no bowing at all - then suddenly the front right hand corner jumped up 2 inches and could not be persuaded to go back down. I ended up having to cut out a big square above the firebox and weld a slightly larger piece of 5mm over the top to create the kind of removable cooktop you get on most ranges, which I now see are obviously there to allow for the expansion and contraction.

[morticcio]

Feb 2, 2013 3:34:54 GMT -8 Vortex said:

The cooktop on mine is made of 5mm steel, and it bows up quite dramatically during the hottest part of the burn cycle

Some of the cast iron hot plates have ribs in underside of the casting. Not sure if these are for heat transfer or strengthening purposes. www.pyromasse.ca/articles/bellcks_e.html - see photo of second from bottom on this page.

I wonder if welding some lengths of right angle bar along the direction of flow would help stop the warping?

[Vortex]

Great article, I always wondered what the layout was inside those cookstoves, looks like my design wasn't far off.
I saw a broken range hotplate in a bin at the recycling centre a few months ago, it had fins about 3 inches long on the bottom and I wondered if they were there to conduct heat or to resist warping or both. We considered welding some large pieces of angle iron on the bottom of the hotplate to strengthen it but so far it's stayed straight since I cut the square out so we've let it be, but I'll definitely do it on the next one I build.

[stovol]

Great stuff vortex, what brand and specification of refractory did you use. I use a lot of satanite, sairset, and Icf from anh, or harbison walker as I have a warehouse within 60 miles of me. Thinking of using the dense coated with colloidal silica, minusil, and silicon carbide.

[Vortex]

Hi Stovol, I'm not in the U.S. so I'm unfamiliar with the products you mentioned. I used this:
www.dineensales.com/ShowIndustrialProduct.aspx?ProductID=22

Which the information says :

Description: Castable supplied in 25kg bags

Maximum Service Temperature: 1600°C

Maximum Grain Size: 3mm

Chemical Analysis:
AI2O3 - 59.8%
Si02 -35.8%
Fe2O3 - 1.1%
CaO - 2.7%

Physical Properties:
Dry Bulk Density (kg/M³) - 2230
Cold Crushing Strength (MN/M²) - 59

FIRED TO 160O°C:
Dry Bulk Density (kg/m³) - 2200
Cold Crushing Strength (MN/M²) - 52
Permanent Linear Change (%) - 0.8
Quantity Required to Install (Tonnes/M³) - 2.23
Mixing Water - 3.5-5 litres per 25 kg bag

Type And Application:
High temperature castable using Secar for use up to 1600°C. A low iron content castable with good slag and thermal shock resistance.
Typical applications: Reheat furnace walls and roofs, burner blocks, furnace doors, kiln car tops and general maintenance use.

It's done 5 years in my stove without a single crack so I'm well pleased with it's performance, just wish it wasn't so dam expensive!