Horizontal rocket powered insulated Lorena style cookstove

[tallgrass]

After seeing Donkey's double dragon rocket cookstove last Fall, I asked a lot of questions and got curious to try my hand in a similar style stove for the interior of the strawbale and cob cottage I've been working on for the last 2 years.  Upon returning from the MHA meeting this Spring, I started designing this cookstove in my head.  I am still figuring out the design and this is very much a proto-type for myself to expand upon.  I thought I would share my process here in case anyone else was interested.

 
laying the first courses of brick and infill


Installing the ash clean-out, and insulating around the base and sides of the burn chamber with perlite/clay mix. For some reason when theorizing the thing I didn't think about placing the clean out access directly below the firebox, and for some reason built my firebox into the side of my unit which would cause me some challenges later in the build.  I think the idea was to keep the fire as far as I could to the right so that I had room to direct it under my cooking elements to the left. 


Birds eye of the base of my firebox.  I cut firebrick splits to span as my grate.  Below the grate one course is the ash pit.  Dimensions for the air inlet are aprox. 20% of CSA for my 6" system


I snapped a chalk line across my bricks to help make sure I had my spacing proper.  I elevated fire brick splits with shims loosely set on my perlite/clay insulation and tamped it gently with a mallet to bring the base to level.  


Top of the firebox.


Exit ports before capstone.  Bypass to run to a tea kettle at the top and cooking range elements to the left port.


Here is the bypass damper, built to swing pivot.  Building refractory with a mix of kaolin, perlite and wood ash from white oak.


Capstone put in place with bypass plate installed.


Cooking Element Port



Tea kettle and bypass port.


Installing ducting, cutting opening to conform to CSA of 28 sq. in, covering ducting with refractory mix of local clay soil, perlite and wood ash from white oak.


Mocking up cooking elements and tea kettle.


Laying perlite clay underneath passage ways and on interior brick facing to keep heat transferring to the food and away from the stove body.  Using the same refractory mix as in the last step to trowel up tight around the dutch oven and skillet.  I placed sticks underneath the pot and pan in a square, and tamped each one down from up above, gently mallet-ing each cooking element to level to make sure oil or water doesn't pool to one side of the pan.


View.  You can see the charred pieces of wood remaining which allowed me to adjust my elements to level and use as support for initial firing and drying of the mix which should be sufficient in its own rite for holding up the pot and pan.  My plan is to soon replace the wood with fire brick cuttings.


Building the stall for the intersection of the bypass and the cook top exhaust.  This stall will also serve as a base for the cast iron tea kettle.


Back to kaolin, perlite and woodash mix.  Firebrick cut to act as stand for tea kettle.  


Testing the cooker.  Even with the mix fresh and wet applied around the tea kettle, you can see the burn is complete combustion.  There was smoke for only about 25 seconds upon first lighting the fire, then the draw became smooth and the smoke disappeared.  Here I am venting the exhaust gasses straight into the room, and the exhaust port is clean and clear.  


Resealing around the dutch oven and the skillet after initial drying and expansion/contraction space left between edges of the pot, leading to heat and gas escaping the system.  Here you can see the 3 elements in place.  Lots of burnishing around the edges of the pot and pan to keep cracking and contraction to a minimum.


Starting to play around with earth plasters and mosaic-ing with scrap tile from a previous project and quartzite at the base.  Not sold on this aesthetic yet.  

I will check back in soon and let you know how its cooking.  During the 3 test fires I've lit so far, the burn is very clean and very hot.  I will update with stats about burn time for a liter of water to boil in the kettle and the dutch oven.  I got the ratios for the 20% csa for the air intake from the Aprovecho website and ebooks on stove design.  Cheers!

[manuel]

I'm not able to see the images. Maybe some problem with my Firefox browser?

[patamos]

same issue. can't see pics

sounds interesting

[tallgrass]

just tried to upload photos to a different website for my url links. Not sure if there is some privacy setting I was missing to share from google-docs. These are hosted on photobucket now... can they be seen? Any suggestions for an upload website?

[Vortex]

I couldn't see them earlier but I can now.

[patamos]

Ya, i can see them now too.

A thought regarding L-feeds. What with Matt's recent discoveries with bottom air feed batch boxes… I have started playing with reducing the overall air intake on previously built L-feeds (with doors) by drilling holes near the bottom of the doors to give 10% CSA. Keeping the door slightly ajar while the fire is building up heat, then closing it once going strong.
It slows the burn for sure, and likely enhances overall efficiency by reducing excess 02.  But it can be a bit fiddly to keep the burn from crashing. The doors are not tightly sealed so it is hard to say what the actual numbers are.

Might be of interest

[satamax]

If i may say, i would have capped the heat riser with a cast iron piece

[tallgrass]

Definitely open for critiques and improvements.  I suppose use necessitates design.  I wanted something where the temperature was easily modified by the user.  For this, the L tube seemed the way, simply by backing wood out or pushing it in I can intensify the burn from a simmer to a scorch.  This was the advantage over the J-tube or a batch box that once loaded would produce consistent heat, but one unable to be easily modified after fueled.  While playing around with the initial firing of this stove, I found when I blocked the main burn chamber during a burn, and only left the bottom air feed open, the heat would intensify further back in the feed and light the fuel along its length, and not just the tip where the burn had previously been concentrated without blocking the main feed.  To me, it looks like adding a door would make it hard to adjust the temperature.  I am constantly adjusting the size of my flame of a gas stove or the range temperature of my electric stove when cooking... you know, caramelize the onion on high heat then reduce to add other vegetables.  I would be happy to add a door if to decrease draft and increase efficiency, but I would still want some way to adjust the temperature.  As for placing a cooking element directly over the riser, it was tempting.  I suppose I chose to forgo it based on trying to utilize this system as solely a cooking appliance.  It is already breaking 110 degrees f here in Southern Oregon and its not even July yet.  The strawbale cottage is small, and has good mass to buffer dramatic temperature swings, but when coming in from the heat of the day to cook dinner, the last thing I want to stand over is a radiating hotplate, even though it would be sweet for stir-frys.  The other advantage leaving out the cast iron above the heat riser was to allow for the majority of the heat to be directed straight to a kettle for quicker water boiling, or directed to the cooking elements depending on what was desired.  I liked that this design gave me some control of where the btu-s are being initially directed.  I have an 8" j tube mass heater you can see in the corner of some of the photos and its more than ample for heating a 200 sq. ft. bale cottage, I was aiming for just a cookstove with no added heat element.  A question- when I was rehydrating some of my woodash/perlite/clay mixture to add more, I noticed an overwhelming stench of Ammonia.  I've dabbled a bit on the geopolymer thread but a lot of the chemistry goes over my head.  Just curious if anyone knows what chemical reaction was taking place after curing and hydrating with h20.  Right now, my concern is how to finish venting the thing for summer use.  Wild Fire danger is high here and I've insulated my stove so well that there is still a good amount of heat escaping the system.  I thought about running the flue through a mass on the exterior of my building to absorb the heat and release the end exhaust at a lower temp.  I figure if I'm under 400 degrees f upon exiting the chimney, there is no danger of pyrolizing say a dry leaf that landed on my chimney cap, is this true?  Is there a good way to rob a lot of heat quickly from the exterior chimney while still leaving it to function well as a chimney?  Am I being overly prudent about fire danger?  Thanks for the input so far.

[patamos]

Sounds like you have given things thorough consideration.

Ya, i hear you about temp control with the L-feed. Closing the door and bringing air down to 10-15% or so can slow the burn but does not allow you to modulate the BTUs. I guess that is more suited to the larger griddle deck that is hotter in some spots than others, and cooking temps are adjusted by moving pots around.

My first thought on how to capture left over heat is a vented water tank. Ala Donkey's experiments last summer.

We are roasting up here in Cowichan as well.
Winter snow/rainfall was only 15% of average.
Rivers water levels are 2 months ahead of usual 
In danger of losing our salmon runs

[pyroman]

Jun 27, 2015 19:28:06 GMT -8 tallgrass said:

Hi tallgrass, I'm impressed by the simplicity and the, hopefully, functionality of your project.

I'm looking for an all in one solution - heat, cooking, compactness, little fire wood, clean burn, and the fact that building materials that are not available on-site will have to be carried by foot a long way. I have plenty of rocks though and that I see potential for to be used with your design.

A bit early to start asking questions maybe but I do wonder if a stove like yours could be suitable for heating up a small, well insulated dwelling of approx 20-25 sq.ft.
The dwelling would need to be heated during 3 rather cold winter month's + a good chunk of the rather chilly rest of the year. But moderately heated because of the heat contained by the insulation (Hobbit style dwelling sort of).

Well just saying hi for now. Will be following your project with great interest.

[pyroman]

Tallgrass, regarding the fire danger you mentioned.

I'm in a cold climate and this may not fit your needs but...

While I'm looking for possibilities to implement a similar solution as yours in my plans, I came to think of connecting an additional cooking unit and that extends outdoors. For example in the direction of your current chimney out the wall.

I'm playing with the idea of being able to close off an indoor unit and instead direct the heat to the outdoor unit. I imagine that could be of use summertime, and even wintertime if it would be warm enough inside.

Such a unit could be constructed to extract most of the heat before blowing out the exhaust in the air. I see also potential for growing foods like sprouts and micro greens outdoors where I am in spring and fall. Drying foods summertime. Drying fire wood..

It would need a roof and removable cover for snow and rain.


Edit: I read once more and see you actually mentioned an outdoor extension.

[tallgrass]

Thank you for the kind comments pyroman. This particular stove was designed only to cook with the goals in mind of
1) keeping a simple design constructed out of readily available material
2) Insulating the stove body to prevent it from working as a heating appliance
3) A clean burn that could be harnessed with efficiency emphasized for cooking with less fuel

These things being said, I do believe this stove, or a variation on it, could be made into a cook-stove/heating element in one. My initial thoughts would be to modify it by placing the cooking elements directly over the firebox and to decrease the use of internal insulation. Of course it is always important to insulate the heat riser and the firebox to keep temperatures high and clean, but the rest of the body would be made of a highly massive brick or earthen cob mixture to increase thermal heat storage. I would also create either a batchbox or increase the size of the firebox to use an 8" horizontal L feed. Less fuel could be used while cooking and more could be added for heating. An even simpler design would be placing similar pot-holes and sinking the cooking elements into a bell system. A hollow cavity is very easy to construct. The problem I see with that is that any cooking elements (pots, pans, skillets) installed would run at the same temperature (it would be hard to boil water in one pot for grain while simmering vegetables in another). If you are not limited entirely by what can be sourced locally, I would direct your attention to the walker riser-less heating and cookstove. donkey32.proboards.com/thread/1624/walker-riser-less-core

[pyroman]

Had not seen the "Walker Riser-less core" yet. Very impressive! And good for additional inspiration. 

A cast iron cooking plate is one of the modifications I was thinking of, yes. Also a cast iron piece in the front would be good for radiant heat. I can get these parts and they are not that big and heavy. Would fit in a back pack.

I'm into these sort of dwellings:

When covered with snow these huts keep frost out even when -30C or colder.

I too want use what's available on site. In my case that is granite, and hopefully I'll find some clay and sand nearby. Will need to carry up fire brick, some insulating material and maybe a bag of fire clay.

As for using a batch box instead of L feed, I imagine a batch box could be built in in the middle of the front, a bit above floor level. A J tube as well I guess.

The bell alternative you mention requires a core heat riser I suppose. But that would need to be a small one. I hear it's harder to get the small bells/barrels to work properly compared to the larger.
For now I'm likely to settle on the built-in batch box alternative. Also because these I understand to be more of a fire-and-forget solution

I may not fully understand the "bypass", and "directing of heat" you mention in OP. If you got the time and possibility could you maybe photo-shop a line into one of the photos and point out the direction of the heat flow, and how you would be able to do any directing? I do see a circuit but so far unable to figure out the "directing" part.
It does sound really useful to me if you're able to shut off the 2 cooking units to the left and direct the heat out of the building..

I did find and read Donkey's double dragon rocket cookstove thread. That thing may one day end up as an out of place million dollar artifact Definitely a masterpiece!
Donkey if you read this I'm interested in how effective your 2 cast iron cooking plates are compared to the other 3. Ever checked cooking time for a liter of water?


Edit: In the meantime I discovered the swing pivot. I was sure that "handle" was a masonry tool.
I see how it works now  
Also need to do some more homework on the batch box....    

[mkrepel]

Nice work! I love the innovation on this site.

I first thought your skillet and dutch oven were going to be removable, but it looks like they have become permanent parts of the installation. Do you cook directly on them or use some other pan on top of them? I suspect they would be a little difficult to clean properly if used directly, but that would be more efficient in terms of heat transfer to the food. I'm just curious.

[tallgrass]

Mkrepel- the elements are designed to be removed. I have simply burnished the earth tightly up against them and have been waiting to fire the system up again to let the skillet and oven, and kettle all expand with the heat to see how much space is left between the earthen frame and the cooking elements before removing them. It is my hope I won't need any other type of gasket to keep the flue gas inside the stove body while cooking, but it is possible I will need to wrap some ceramic wool or something around them. Any ideas for gaskets?