My first Batchbox build, on top of Barcelona's mountain.

Hello permies, I'm Sara from Barcelona!
I'm happy to finally introduce myself, after some months of lurking around and absorbing every bit of knowledge all you nice people so kindly share!

I heard for the first time about rocket stoves and batch boxes this February. I was doing some research on masonry heaters to replace a useless pellet stove and finally solve
the heating of my home, and ended up in this forum. I tell you, for a couple of months all I could do was to read and watch every bit of info available on the subject!
As a person who's been almost my entire life living with fire stoves, my mind was blown up by the idea that most of the wood I've burnt in my life has been thrown away up the chimney.

Since then, I've been in a journey most of you people have already shared in so many useful threads. I've learned a lot, read about the pros and cons in many different options available, considered my needs and capabilities, and I'm finally ready to start planning my first build (*spoiler alert, it won't be the last!!).

Now I came to all of you with my ideas and plans and any question, contribution or correction you like to share will be much appreciated!

My needs

    - I live on top of Collserola, the mountain at the back of Barcelona, facing the sea at 411m/1.348 feet above sea level.
      Barcelona has really mild winters, average temp. 10ºC/50ºF, and what we can call winter goes from November to March if we are lucky.
     
    -My home is an open space plan building 92 m2 with 3m ceiling ( 301 square feet / 9'8 feet)
     My exhaust pipe runs through the old chimney 2,45m outside the building, straight from the ground, only the last 30cm are exposed pipe ( 8ft. / 12in.)
     Old building with 40cm. thick masonry walls (15'7 inch.) and the whole north wall is below ground level.
     Most of the ceiling is insulated by 6cm/2'36in. extruded cork slabs, and the dorm has a 10cm/3'93in. insulated sandwich panel roof.
     Only 3 old sized windows with double glass in the whole space.
     Last year the house was empty and cold, and inside the temp hasn't dropped below 14ºC/57ºF.
     Ideally would love to be around 22ºC/71'6ºF when living there.

   -I spend my day on my workshop next door, so my idea is to build a system that allows me to light one fire a day and forget about it until the next morning.

Considering all of the above, I believe I can manage with a 15cm/6"in. batchbox, but would love to hear the input of the rocket scientist
community, cause all I have are ideas : )

For the building, I've enrolled my father, who's a skilled craftsman and an experienced builder, I've learned a lot being around him, and
I'm a skilled craftswoman myself. I'm quite positive we can manage to do a great job with our skills and your guidance on stove making, and we already
plan to build another system at his home further on. In fact, if this works as I'm sure it will, I plan to build more for family members who already have expressed
interest : )

So far, I have made several decisions on materials and design that I would love to share and get your ideas on.

- Batchbox right sidewinder core to adapt to the shape of the space I have, with a single skin bell, a mass bench bell on the right and a hollow small bench to the left, to store
wood under and link the different levels of the space.

-Secondary air chanel through the floor of the firebox with RA330 metal tube.

-Heavy firebricks for the firebox and riser (VITCAS 60% Alumina), and IBF to insulate it (VITCAS Grade 26). Heavy firebricks for the top of the bell and DPB (Dry pressed bricks) for the base of the bell and the bench. Vermiculite board to top the bench.

-Gray concrete blocks to make the base of all the build and make a 20cm/7'8in. open air chamber to insulate from the floor and have an air flow from below. On top,
a layer of mortar with some insulation as the foundation for the whole system.

-Clay and sand render for the finish layer.

-Bypass to help start the fire when the stove is cold or when the temp outside is not that low, but you still want to heat the inside of the house (these days we're having below 22ºC/71'6ºF at noon but at night it can drop to 8º/46'4ºF).

My idea is to make a build that won't need repairs in a foreseeable future, I'll plan to be busy making the next one for my father, probably a small one for my workshop later.
An eventually replace all the wood stoves me and my family have around. No more throwing heat up the chimney!

Ok, I believe that's all for my first post, I can't wait to hear your inputs, corrections and thoughts, and I'll come by with new questions and dilemmas.

Best wishes to all of you wonderful people around the globe!






 
   

P.S I forgot to mention that we have a wet saw!
     And that to bind and seal all those bricks we'll use clay and sand, refractory clay for the high temp. areas and regular on the rest!

Hi Sara;
Welcome to the wonderful world of rocket science!
Oh, and Welcome to Permies!

It sounds like you have a good understanding of how to approach a new build.
An overall good plan, of course, there will be details that will need clarification.

I do suggest buying an RA253ma stub for your secondary tube, rather than the RA330.
I have used both and sold both, but the RA253 has proven itself to be as impervious to the internal batchbox temperatures as the RA330.
I have stopped stocking the RA330 and now only stock the RA253, as it is that good.

With a heavy brick core and riser, it will take a bit to reach working temperature, but it will retain that heat far longer.
All my cores are heavy brick, but for the riser, I use Morgan Superwool and create five-minute risers for them.

Especially with your climate, a good bypass is essential for enjoyable operation.  

thomas rubino wrote:
It sounds like you have a good understanding of how to approach a new build.
An overall good plan, of course, there will be details that will need clarification.

Hi Thomas! so nice to finally talk directly with you, after so many hours spent reading all the knowledge and experience you so kindly share : )
I'm here for the details, as they are the key to the success of any project.  With so many possibilities and variations to adapt to every specific project, I have a storm of ideas in my head, and I need to start making decisions.

thomas rubino wrote:
I do suggest buying an RA253ma stub for your secondary tube, rather than the RA330.
I have used both and sold both, but the RA253 has proven itself to be as impervious to the internal batchbox temperatures as the RA330.
I have stopped stocking the RA330 and now only stock the RA253, as it is that good.

This will be my first detail to settle : ) The idea of getting the RA330 came from this encyclopedic and enlightening thread on donkies
https://donkey32.proboards.com/thread/3909/firebricks-refractories-fail-silica-flux  
Doing my simple math ( I'm an arts girl myself; my science teachers would be over the moon to see me devouring chemistry and physics threads in my forties!) I concluded that if burning metal accelerates the degradation of the materials inside my building, I should get the metal that degrades the least in contact with the fire.
This way, I'll have a longer lifespan for my build, right?

thomas rubino wrote:
With a heavy brick core and riser, it will take a bit to reach working temperature, but it will retain that heat far longer.

When you say it will take a bit, considering I'll be burning mostly hardwood bought from  cleaning forests, kindling will come from the garden where I have an endless supply of soft and hardwood, does this mean the stove will reach working temperature within the first load? Or maybe when the stove is cold, I will have to make a couple of loads in a row to get it going?
I don't mind if this is the case, when you start the heating in a home, it takes a while after the place gets warm. I work next door so if necessary, I can give more attention to the stove for a while, I've been attending two unefective stoves (home and workshop) for a while now, still sounds like heaven.

thomas rubino wrote:
All my cores are heavy brick, but for the riser, I use Morgan Superwool and create five-minute risers for them.

I've considered the use of ceramic fiber, but after reading another useful thread on donkies, I'll try to keep it only in unavoidable places like gaskets and expansion joints, and away from fumes as much as possible.
When this dream come true eventually requires some maintenance, I would like to be able to work with as little precaution as possible handling the repairs. I recognise it is a super useful material but I'll go for a slower rocket that goes far away ; )

I've find a supplier for this manufacturer Izospar in Spain,  and I'm wondering if the ring B150/100 could make a good riser, and maybe a second layer of some of the other bricks (I have still to figure out the math) for good insulation.

thomas rubino wrote:
Especially with your climate, a good bypass is essential for enjoyable operation.  

On that point, first of all, I wonder if experience with lightning fires in stoves and open fires does help in this subject of starting a rocket stove? Because I can set a fire going in any condition, I've been warming my home like this since I can recall. I don't know if this gives me any advantage?

Anyway, another detail I still have to figure out, is where exactly to locate the bypass. I want to keep a straight exit draft to take advantage of the 5m/16ft. chimney I have, and with my floor plan that's on the back corner of the stove.
I have to find a way to make the bypass operable from the front of the bell.

As you can see, I still have a lot of things to figure out, but every question brings me closer : )

Good night from Barcelona!

Hi Sara;
Nice to meet an aspiring rocket scientist like yourself.
You certainly have the right attitude to accomplish this!
I'm looking forward to seeing your future builds.

So, I have two Batchboxes in un-insulated buildings.
This is northern Montana, we get cold here...
These stoves burn back to back batches all day long.
Much more than any indoor RMH would.
I call them extreme burning batchboxes.  If something is going to fail, this style of burning will quickly identify it.
Carbon steel stubs lasted 6-10 weeks in my extreme batches before they began to spall badly.
RA330 was introduced to the RMH world by Matt Walker, using it on his cook stoves.
I bought and tried the RA 330; it works as stated—no spalling after two years of hard burning.
I became a dealer for rolled alloy and sold dozens of RA330 stubs at $90 each; they were not inexpensive.
I researched other Rolled Alloy high-heat products and discovered RA253ma, which is listed as only 100°F less than RA330.
I gambled and purchased enough to offer them for sale at $60 each.
Meanwhile, I removed my RA330 stubs and installed RA253ma in its place.
Multiple years later, I can confidently state that the RA253ma is a lifetime purchase; they have proven themselves able to withstand extreme burning with no wear.

One load in a batch is enough to heat the core and riser to operating temperatures.
However, except for the steel door area, you will not feel the heat for several hours.
If you burn two loads, you may find it quite warm and start opening windows.
Heating with bricks is quite different than heating a steel box...
As I say at Dragon Tech, once you go brick, you'll never go back!

Morgan Super Wool.
It is sold as a non-ceramic, fully bio-soluble (Safe) alternative to ceramic blanket.
After heating, it becomes hazardous, similar to fiberglass insulation, and can cause life-threatening problems.
The thing is, you have to breathe in the dust.
For me, it is relatively easy to wear a mask, lift a used riser off the core, and place it safely out of the way.
Treat a used riser with care, and avoid sticking your face over it, makes common sense.

Insulated firebricks (IFB) make the best risers, usually wrapped with rockwool.

You want and need a bypass.
If you have a bell, there will be a way.
A smoke-filled house does not make for happy spouses!

Hi Sara,
the plans for your RMH sound very good. What an exciting project. Also with the outlook of building more for your friends and family.

I will be in the area probably in July and then again in November to build a J-tube RMH for a costumer close to the french border.
I would be very interested to see your rocket.
If it works timing wise, I also would be happy to help in the build. I haven't built a BBR yet and it would be a good opportunity for some first hand experience.

Hi Thomas,

I'm glad to be a freshman in the Rocket science academy so far, hoping to graduate before next winter! I can't wait to see how it's going to turn out myself ; )
I have some ideas for the finishings too, more details to settle!

Certainly, at the rate you burn your fires I can get an idea of what mine can stand in decades : ) RA253ma sounds like exactly what I'm looking for.

I'm going to have a bypass for sure, just have to figure out how's it going to look like. Could it work to add a T section on the tube, right before exiting the bell?
We could open the short side of the T, allowing hot smoke to get out right after exiting the riser.
Would it affect the function of the bell to have a thin metal bar up there? It would cross from the front of the bell to the back corner, where it would open or close the lid of the T. And can be coated with something like VITCAS Zircon Paint Coating to protect it from the heat?
Also, how tight has to be this bypass? Is it important that it can be shut airtight or can be a metal disc slightly smaller than the tube it has to block?

As for the cold start, I'm comfortable with the idea that it will take a bit to warm up the beast. Once the season is on, it won't happen often that it stops for many days in a row. And when it eventually happens, I know for a fact the thermal inertia of the house will play in my favor.

Morgan Super wool, the fact is my concern is not just about the moment to handle it when doing repairs, but how to dispose of it afterward.
We're a small territory highly polluted due to industrial activity, and this type of residue is a nightmare to get rid of.
Unless it's completely unavoidable, I'll go for other options, and I'm willing to handle the inconvenience these can carry.
If I have a stove that will take a bit to light and warm up, I don't mind tending to it a little bit when necessary.

On this subject, does any sense to make a IFB riser, and make an outside layer of IFB also to insulate the riser? Am I making any sense? How can a riser be well insulated if not using Super wool?

I'm hoping to have some time this week to start some drawing, see if I can come up with something that can show you more what I have in mind!

Best,
Sara

Hi Benjamin!

It is as exciting as the night before Christmas : )
I don't have a clear calendar yet as we have to coordinate with my father and my work, but for sure you're welcome to see whatever there is at the time you're around.
And if timing is right, any help, especially of someone with more experience than us in rockets, will be much appreciated.
I'll keep you posted!

A riser built from one layer of IFB will give enough insulation, you don't need more. You would want to wrap the riser with wire to be sure it doesn't split over time, and a layer of rock wool (mineral wool) under the wire wouldn't hurt. This is much more durable and heat-resistant than fiberglass.

Hi Glenn, nice to meet you too!

All you frequent flyers have been my night reading for the past months, so nice to finally be digging in : )

So if the riser is made of IFB, it will have enough insulation on its own? That's good to hear! The wire to secure the riser should be coated to expand its life inside the bell?
Strips of mineral wool are a downsizing from a full sleeve for the riser to dispose when doing maintenance, so I'm getting closer to what I want.

I have found another manufacturer closer to home, from the Basque Country, that offers a wide range of IFB and other materials.
They're called LABELAN https://www.labelan.net/en/products/bricks and now I have too many options. My goal is to make a stove I won't have to worry about in a foreseeable future, which of these bricks would work better to build the riser and insulate the firebox?

-"Firebrick AL80
Dimensions: 230 x 114 x 64 mm
Maximum temperature: 1550ºC
Alumina: 79-82%
Format: Possibility of other formats
Characteristics:
High purity.
Low iron content.
Good mechanical resistance.
Excellent resistance to thermal shock.
Intended use:
Coating of industrial forging furnaces, heat treatment furnaces, boilers... especially screeds.

-"Insulating firebrick G-26
Dimensions: 230 x 114 x 64 mm
Maximum temperature: 1430ºC
Alumina: 56%
Characteristics:
Excellent insulating qualities.
Mechanical and temperature resistance superior to group 23 bricks.
High purity.
Thermal shock resistance.
Intended use:
First layer lining (direct exposure to heat source).
Second layer lining behind dense materials in forge furnaces, aluminum melters, etc."

They make also slabs, I'm wondering if these would work as the top of the fire box and the bell:

-"Refractory insulating slab G-23
Dimensions: 610 x 230 x 64 mm
Maximum temperature: 1250ºC
Alumina: 42%
Possibility of mechanisation.
Characteristics:
Excellent insulating qualities.
Low iron content.
High purity.
Intended use:
First layer lining (direct exposure to heat source) for heat treatment furnaces.
Second layer lining behind dense materials in high temperature furnaces (forging, etc)."

And if this will make a good ceiling for the bench?

-"BIO fibre plate 1000ºC 5-50 mm
Dimensions: 1200 x 1000 x 5/10/20/40/50 mm thickness
Maximum temperature: 1000ºC
Characteristics:
High insulation capacity.
Easy handling and cutting to make adjustments.
BIO product - Does not contain products harmful to health.
Intended use:
All types of insulation, both industrial (insulation layer against sheet metal), and for use in rocket mass heaters, home ovens, etc. In treatment or tempering furnaces they can be placed as a working layer."

For the lower rows of the bell and the bench I'm planning to use Compressed Stabilised Earth Block, made close from home. I'm trying to locate a translated technical sheet to share, but I understand they're made from pressed clay and sand and the stabilizer is less than 0'5% cement. Dry pressed.  

My idea for the whole build is to finish it with clay, sand and straw to seal it and aesthetics too. For the siting area on the bench, I would love to finish with ceramic tiles on top to have a resistant surface. Because it's going to be the favorite spot of my dogs besides mine, and those paws are like grinders.
This are the tiles: https://ceramicaferres.com/en/products/catalana/
And this is what the manufacturer says about them:
“  The base used is a mixture of clays from the area, giving them strength and unique properties
for extrusion and single firing. The wide range of colors is derived from the
clays themselves and from oxides applied together with a varnish unique for
its transparency and smoothness, which gives the surface an appearance and
texture similar to glass. The transparency of the surface and the unchanging
quality achieved by the colors at a temperature above 1000°"
I assume they're alright to place on top of the insulating slabs and the clay and sand finish.

I understand every layer of material is going to add thermal mass, but also delay the heat transfer. Is there a limit to how thick the walls can be? I'm not intending to over do with the clay and sand, but for what I know different layers have to be applied with different composition in order to achieve the effect I'm looking for.

Here you go, another round of questions, and I have many more to come!

Best from Barcelona to you all!

It looks like the G-26 IFB would be fine for the riser, while the AL80 firebrick would stand up to wear in the firebox and port.

I think the slabs would work for firebox and bell ceilings, though you don't really want insulation on the bell or bench. I would be concerned about the insulating slabs on the bench without clear indication that they are very strong. Simple concrete pavers (available in the US up to 24" x 24") work excellently as bench top structure, and transmit heat well. Any structural ceramic pavers should work.

Cob outer layers will work nicely for giving organic form to the heater and another layer of sealing assurance. I would not go more than about 10 cm thickness on bench and bell sides, maybe 15 cm total thickness including the CEB. I have a layer of bricks on their sides ( 2 1/2" or 6-7 cm) plus 6" or so of cob (15-17 cm) in my bell walls, and it takes hours for the heat to start to come through. If I had it to do again, I would make the cob an inch or two thinner. Corners give much more exterior surface for a given amount of interior surface, and even if rounded on the outside will be much cooler than flat areas. My bell corners never feel warm unless I am burning hard for several hours. I would make exterior corners with a radius at least equal to the total wall thickness.

The G23 sounds like it would work for the riser too, and sounds less "special" i.e. probably more affordable.
They don't have any prices on their website, please share the price if you get a quote.
So far I've only encountered big companies that don't sell to individuals around here.

And in general I found the insulating firebrick quite expensive. So far I've built a riser from dense firebrick with Rockwool insulation around and one "5-Minute"-Riser with SuperWool.

As a potter, I have occasionally come across old electric kilns that do not work, but are made of insulating firebrick. Each of these has around 50 to 100 firebricks which can be salvaged and used to make risers and other RMH parts with a little work.

Glenn Herbert wrote:It looks like the G-26 IFB would be fine for the riser, while the AL80 firebrick would stand up to wear in the firebox and port.

That's good news! I'm sure this IFB will be more expensive than the regular ones I've been seeing on oven and barbecue suppliers, but for this first stove I have a certain budget. Considering any other alternative to replace the innefective appliance I have now would be super expensive, and that there won't be labor cost because we'll be doing the job, I have room to invest in materials.
Let's say my first experiment on this one is going to be how to make an everlasting stove (considering the weather it's going to be up against).

I'm waiting for the quote from them, but on the website they specify they sell to craftsmen and individuals, and ship throughout Spain and Europe. They also sell this mortar,
I wonder if depending on the cost, it's something worth the money?

Mortar MH-25 Base raw material: Chamottes, clays and silica
Maximum temperature: 1450ºC
Alumina: 20-22% (wet) - 25-28% (dry)
Packaging: 25kg pots
High thermal resistance.
Fast hardening.
Supplied in a semi-liquid state.
Intended use:
Assembly of bricks, wedges and refractory slabs.
Approx. 200kg per 1000 bricks


So far:
Riser - G-26 IFB
Firebox and port - AL80
Firebox ceiling - slab G-23
And this way the firebox and riser are already well insulated and don't need a second layer of insulation? Just some wire to reinforce the riser.

For the bench ceiling, some slab with enough strength that is not insulating, but rather conducting.

Super helpful reference on the cob, as it's probably the area where we have less experience. My father did a cob oven some twenty years ago, and it's still standing and working. Considering it's completely exposed outside, it's a good beginning, yet it's always been rough in the corners. But I have my mind set on not just making a safe and efficient stove, but also a beautiful object that's going to be the center and heart of the home.
A cracked surface will be something I want to avoid, and if need be, repair, so any advice on this matter will be much appreciated. I'm much more confident in our brick laying abilities : )
I take note on the corners, it's super logical, but before you mentioned it, I didn't even think about it.

Also, repurposing oven bricks it's super helpful advice for further projects!

I'll come back with more, thank you for all your inputs!