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!!! Advice on a RMH build in Hokkaido Japan

 
Posts: 41
Location: Toyoura Hokkaido
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Hey guys,

Looking to get ideas and advice on a RMH build and a room fit out.

My wife and I have recently moved to the mountains of Hokkaido Japan. We have a piece of farm land at the base of some foothills about 10 minutes from the ocean near the southern coast. We have been here since late June and have been working on the old 2 story Japanese farm house that's on the property. We are living in it now and plan to spend the winter here. This will be our first winter in the area. Although it is Hokkaido we have been told, because we are near the ocean, the winter is rather mild compared to other parts of the island. Average winter temperates of around -4C to -8C with moderate snow fall.

We are the first people to live in the house in about 5 years. The house is a Japanese pier and beam foundation with mortise and tenon construction. The foundation is questionable in places and I plan to jack it up where needed in the Spring. The house has been fit with aluminum siding and roofing. (no leakage from the roof that I can see) Fiberglass wall insulation is old and sagging for sure, so will need attention at some point. Thinking of retrofitting with neutral material in the future.

My focus for the next few months, will be getting the house ready for the winter season. At present there is no heat source in the house besides a small portable kerosene heater. I am thinking of installing a Rocket Mass Heater in the center room to serve as our main heat source for the winter. I have no prior experience building them, but have researched and watched most of the content on Youtube and feel I understand the process of the build fairly well. Have read Rocket Mass Heaters by Ianto Evans Leslie Jackson and plan to buy The Rocket Mass Heater Builder's Guide, to use as a reference if I go ahead with the build.

As mentioned above, the house is set on a pier and beam foundation so the floor in the room is above a low crawl space. My idea is to remove the tatami mats and the floor joists in this one room and build directly on the ground. Thus making the room a step down "sunken" room. This will alleviate the issue of weight from the RMH and allow for a stable foundation to build on. The room is located in the center of the house with only a small portion of its Northern wall being a directly exposed outside wall. I plan to level the present clay heavy soil under this room and then lay the fallowing: (in order from bottom to top)

1. Tamped and leveled road base gravel 6cm-8cm
2. Tamped and leveled pumice stone 4cm-6cm (for insulation)
3. Old carpet (protect the moisture barrier)
4. Tamped and leveled builders sand 2cm
5. Waterproof pond liner as moisture barrier (still debating if this is necessary)
6. Another old carpet (protect the moisture barrier)
7. Tamped and leveled builders sand 2cm
(The above numbers are rough estimated calculations based on information I have gathered from other builds with similar requirements.)

On top of this I plan to build a L shaped RMH that follows the edge of two of the walls. (See attracted drawings and photos for clarification)
The rest of the room will be finished with a Japanese Tataki style earthen floor (rather small area). The space that is left on the other two sides of the room, where the floor has been dropped out, will be filled with salvaged cinderblocks and cob to seal off the gap in the crawl space and create the step down for the sunken room.

I plan to build the finished floor once the RMH has been installed and create a seamless connection between the two. I will using the heat from the RMH to help with the drying process.

Few more points
- I have access to the materials and tools I believe that I need for the build start to finish.
- I will be doing this mostly on my own, with help from wife when needed.
- The space is relatively small (270cm x 360cm) Hight from ground level to original floor about 60cm
- I can devote all of my time to this project and I feel confident that I can complete the bulk of the work before it gets winter cold. Snow flies end of December
- I have tested the soil and made test cob bricks coated with hand-made lime plaster from burnt scollop shells. No visible cracking or damage after 10 days drying.
- I have consulted with a local Japanese Architect, who feels my idea will work, seeing that I am not planning to alter the structural integrity of the building.
- I plan to follow the standard 6" feed tube build layout

Questions and points that I would like guidance on:
- Does this solution seem reasonable or will it create potential issues in the future?
- Provided I have all of the needed materials can this be accomplished in a month and a half by one person?
- Should I be looking to do the RMH in the traditional cob bench and ducting style or should I use a bell style bench for the build? (Looking to use this as the main heat source for winter for myself, wife and two dogs. Might sleep on it if needed.)
- As the RMH will be built in a relatively confined area, what are the potential fire hazards and what kind of distancing do I need to take into consideration to insure a safe environment inside the timber framed walls?
- How should I plan to incorporate an air intake, to feed the RMH, so that it does not suck all of the cold air in through ever crack in the old house?

These are my initial concerns at present.
I am open to any ideas, and hope to get a clearer picture of how to approach the project from those with more experience.

I have added a few photos of the room I am planning to build in, along with initial rough sketches to help clarify.

Thanks in advance, Peter
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pollinator
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Hello Peter,  Welcome to the  WWRS  (Wild World of Rocket Stoves)!  
I would say by your description and comments that your good to go for launch Houston! Building a RMH is certainly a labour of love (with perhaps a little crying too) but if mistakes are seen as learning lessons then you won't be disappointed and just carry on.

Some quick points I can offer:
I'm sure you designed it with some kind of idea in mind but to me all I can see is how the bench breaks up the room in half with no walkway to get from one side to the other.

-The barrel seems quite close to the wall which would have to be protected somehow. The RMH Builders Guide covers safe distances to combustables for your barrel with of course many options to decrease the distance if some kind of heat shielding is used.

-Ducting vs Bells.... If you hav'nt already done some research, I would suggest these two: Bell Theory       Flues vs Bells
Once you've decided, come on back and we'll discuss your findings.

-Air intake is an interesting topic. See here for a good discussion on the subject: (Video at the end)    
RMH, fresh air intake, why suck out warm air from inside?

- Your going to need to have some form of insulation under the stove and mass. Not sure about your decision on the pond liner in the floor....

Hand made lime plaster is something I've always wanted to make. Good on you! Perhaps when my time comes, I'll be posting back to you!
 
Peter Sedgwick
Posts: 41
Location: Toyoura Hokkaido
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Hey Gerry,

Thanks for the response.

The idea here is to make the room recessed, therefore there is no walkway. You will have to step down to get into the room, much like a sunken livingroom. Similar in design to the attached photo (minus the man napping on the sofa) Also see new attached drawing for further clarification.

The placement of the barrel in my perviously attached drawings is just to show general layout of location of the RMH in the room. Barrel in the far right corner, with the "L" shaped bench/day bed fallowing the far back edge of the room and turning 90° to fallow the left hand edge of the room. I will read up on clearances to combustibles before deciding on exact location of each part of the RMH unit. Drawings are again just to give a general layout of placement.

I will have a look through the links you have included. The flue vs bell design will also play a large part in calculating a workable configuration for the exhausting options for the chimney. I feel venting though an outside wall would be most ideal if possible. The snow can sit heavy on the roof in this area of Hokkaido and has a tendency to take out stove pipes when it slides. Snow tore the masonry chimney right off the neighbor's house here last season. Still laying in the front yard. This is an area I would love your advice on a bit later on in the process if possible.

The idea of the pond liner comes from an article I read by Tony Sirna at Dancing Rabbit article link as well as a few other builders who worked in similar clay heavy soil situations. No vapor barrier is necessary even if I am putting an earthen floor directly on the ground?

I was thinking that the pumice stone would create insolation across the whole floor base. I am more than open to other ideas and any suggestions regarding the materials I use and the order and thickness in which they are laid.

Made the lime from burnt scallop shells i got for free locally. More than happy to share my experience and any insight that may help you. Lots of fun.

Thanks again for your help, Peter



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Peter Sedgwick wrote:Japanese pier and beam foundation with mortise and tenon construction



TRADITIONAL MASS-STOVES IN JAPAN

Your great timber framed house is perfect for a traditional Japanese mass stove floor plan. Surely you can design your rocket stove to fit the architecture, considering how these timber-house types were usually heated originally. I've written small introductions to links below.

* Examples of both the L-shaped and tatami-room heated floors are included in chapter-1 of the series "History of Radiant Heating and Cooling"

http://www.healthyheating.com/History_of_Radiant_Heating_and_Cooling/History_of_Radiant_Heating_and_Cooling_Part_1.pdf

* In a Japanese farm house, the burn chamber would typically be in one room, and the heated mass in the next room. The lower pounded-earth floored room would have the burn chamber and a high ceiling. This would usually be the farm-room kitchen and barn entrance room.  The stove's heated earthen mass would be under the floor of the raised room that had low ceilings for keeping heat in. The wall between the burn chamber and the mass would be made from a plastered wall or movable screens which could be adjusted for the season and privacy. This way occasional smoke would not enter the main sitting room so much.


https://ja.wikipedia.org/wiki/%E3%83%95%E3%82%A1%E3%82%A4%E3%83%AB:Kamado-M1685.jpg

https://proxy.duckduckgo.com/iu/?u=https%3A%2F%2Fs-media-cache-ak0.pinimg.com%2F736x%2F2d%2F7a%2Fa4%2F2d7aa4e66277c4369bde5af306116f0e--small-japanese-kitchen-japan-architecture.jpg&f=1&nofb=1

* Even the stand-alone kamado in the middle of a kitchen usually had some invisible chimney buried in the earth.

https://upload.wikimedia.org/wikipedia/commons/a/ac/Kamado4816.jpg

http://www.filtsai.com/japan/2002/18-JulyB/29-indigo-23.jpg

https://i.pinimg.com/736x/03/df/29/03df2929190b8dcc3b037a6418db9de3--japanese-interior-japanese-homes.jpg

https://proxy.duckduckgo.com/iu/?u=https%3A%2F%2Fi.pinimg.com%2F736x%2Fd7%2F5c%2Fbd%2Fd75cbd7c719f85ecd5453c88257f5176.jpg&f=1&nofb=1

https://proxy.duckduckgo.com/iu/?u=https%3A%2F%2Fi.pinimg.com%2F736x%2F79%2F02%2Fbb%2F7902bb2dcb9a8d7e229c483a310205c9--japanese-kitchen-japanese-house.jpg&f=1&nofb=1

* The raised-room floor might also have a sand-filled depression in the middle for keeping a pot warm with small charcoal. Architecture drawings often show this sand pit in line with the kamado in the next room. So likely that may have been directly over the buried kamado chimney.


https://en.wikipedia.org/wiki/Irori#/media/File:Kabuto_Kazari_-01.jpg

https://proxy.duckduckgo.com/iu/?u=https%3A%2F%2Fi.pinimg.com%2F236x%2F8a%2Ff5%2F20%2F8af520cfe8b6eb03a3d4dd6302633465--household-items-diorama.jpg&f=1&nofb=1

https://1.bp.blogspot.com/-on1PreCEUr8/U2VkEU-j2zI/AAAAAAAAO08/t4qpJjWonfg/s1600/P1020533.JPG

https://3.bp.blogspot.com/-W9tG1NRwTVo/U2VkiNlit2I/AAAAAAAAO2E/_Oaf51r2kRc/s1600/P1020608.jpg

https://tokyobling.wordpress.com/2013/12/18/irori-the-japanese-hearth/

* The heated table "kotatsu" evolved from those irori sand-filled floor pits.

https://nekohakase.tumblr.com/post/68208953171/kotatsu

Keep us posted Peter.

key terms: "traditional Japanese stove", irori, kamado, ondol
 
Gerry Parent
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Peter Sedgwick wrote: I feel venting though an outside wall would be most ideal if possible. The snow can sit heavy on the roof in this area of Hokkaido and has a tendency to take out stove pipes when it slides. Snow tore the masonry chimney right off the neighbor's house here last season. Still laying in the front yard. This is an area I would love your advice on a bit later on in the process if possible.


It is generally recommended to: 1) vent your chimney as close to the peak as you can for the very reason you mentinoed 2) To keep the outside chimney as short as possible (to reduce the more expensive insulative piping) while benefiting from a little extra heat radiating into the building 3) To be above the peak level so that the wind eddies don't cause problems with proper drafting. Lots of info and suggestions in the builders guide also.

The idea of the pond liner comes from an article I read by Tony Sirna at Dancing Rabbit article link as well as a few other builders who worked in similar clay heavy soil situations. No vapor barrier is necessary even if I am putting an earthen floor directly on the ground?

It really all depends on your soil drainage and how susceptible this area will be to water infiltration. A drainage layer is pretty much standard for an on-grade earthen floor to provide a capillary break for any moisture in the ground migrating upwards and could also include drainage pipe in wetter areas. Vapor barrier is particularly helpful if your going to be putting rugs or other objects directly on the floor as these items can block the flow of moisture coming from the ground and possibly cause mold. Pond liner seems a bit overkill to me...

I was thinking that the pumice stone would create insolation across the whole floor base. I am more than open to other ideas and any suggestions regarding the materials I use and the order and thickness in which they are laid.


Check out the forum if you havn't already :  Earthen floor
Also, I would highly recommend the book Earthen Floors: A modern approach to an ancient practice




 
Peter Sedgwick
Posts: 41
Location: Toyoura Hokkaido
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Thanks Gordon for all the links and info. This will keep me busy.

Gerry thanks for your insight as well.

Just ordered the builders guide from Amazon US today. Should be here by Friday.

Down on the main island for a few days and won't be back on site till later in the week.

I'll read up on the stuff that you guys have sent me in the meantime.

After watching videos and researching I feel like the bell bench would be the best option. Not a whole lot of info out there that I can find. Really going on Matt's explanation and the Sundog rebuild video for the construction tips. I've got access to tons of reclaimed cinder blocks. Thinking of using those, filled with cob, for the walls of the chamber then cobbing over and plastering with the same material I use on the floor. Maybe use paving stones for the top of the bench depending on how cheap I can get them. Other option would be to hammer out pieces of drum can like he did in the Sundog video. If anyone has other ideas I'm more than interested.



I'm looking into fire bricks now. Might have to buy new, but will save me time and energy. I want low density is that correct?
Assuming this info is in the book, but I'd like to get a head start as it's always a time consuming process to track-down technical materials in a foreign country.



A large part of this whole project is going to be dictated by what is actually under the tatami mats and floor joists in the room I plan to build in.
Until I tear it open and asses the situation I'm just theorizing based on the construction of the other room I removed the floor from. Who knows, maybe buried gold under the house.

Really appreciate all of your support and input. Will keep you posted... Peter


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Antigone Gordon
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Peter Sedgwick wrote:Thanks Gordon for all the links and info. This will keep me busy.



Yeah, sorry for such a large data dump, but I did select those links primarily for good pictures, and secondarily for prose content.  Perusing the picks should not be as daunting as that long list of links makes it look.
 
Peter Sedgwick
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Hey guys,

So we are back at the house and I have finished my homework.

Got the Rocket Mass Heater Builders Guide in the mail and started reading. Really easy to understand.
Had a think and did another preliminary sketch this morning to work out what could be possible in the space. (Drawing included in pictures below)
All of the info that you guys sent me in your last reply was really helpful. Thanks again.

Seams like a bell type stratification chamber system makes sense and will reduce lost hot air (that mixes in the ducting). Inlet of hot air from manifold high, outlet for cooler air to the chimney low. Makes sense and seems to distribute the heat more evenly over the whole surface of the bench top.

Was thinking of using Matt Walkers half barrel layout to create the benches.
The half barrels are cool, but they have to be cut in half and possible reshaped a bit. Also the barrels, unless completely flatted, create high and low points under the cob top. The middle of the barrel will sit closer to the flat cob top and the cob will get thicker as the barrel curves down and out. Hot in the middle cooler as you go out to the edge. "So why not make the top metal surface flat?"

This afternoon my wife and I took a ride over to the local scrap metal yard to see what we could find. Old barrels etc.
I thought. "Whats strong enough to support human weight and wide enough to span the dimensions of the daybed/bench.
Thats when I saw something that gave me a new idea. The scrapyard had a pile of metal scaffolding platforms with hooks on the end. Each platform is 42cm wide with a 2 cm gap in the middle. (See attached photo for reference)

My idea is to take two 42cm wide platforms, flip them over, and bolt them together on the side, thus creating a single 84cm wide piece. Make 2 identical. Then to make the "L" shape for the top to wrap around the room I will cut off a set of hooks from one end and bolt that end to the side of the other. That will create a strong connection and solves any structural issues. Then I will weld all of the seams with subsequent strips of metal to cover the gaps and seams. As a precaution I will then tape all of the welded seams with the silver chimney tape. Each platform is 17cm long + hooks

That whole piece will serve as the flat "under" top for our bench. I will cover that with the required thickness of cob to finish.

My questions are:

1. In this scenario would it work if I use earth bags for my supporting walls for the above described metal top?
(I was thinking to use cinder blocks but they seem too unstable.)
I would stack the earth bags with barbed wire and then cob the inside of the cavity before placing the metal top on, and then cob again over the whole thing. Are earth bags a problem that close to the flu gas chamber if the are covered in cob?

2. How should I approach clean outs for something like this?

3. Would earth bags be an issue against the edge of the raised wooden foundation? I will lay drainage gravel first.

4. Having a hard time finding insolation options here other than foam insulation board. Pumice is proving difficult even though we are on a giant volcano. Any other options?

5. At what layer in the "sandwich" do I add the insolation?

6. Will I still need some drainage gravel on grade if I'm using earth bags?

7. Am I totally nuts?

I was also thinking to use the earth bags around the "Non RMH" portion of the rooms perimeter.
Then I thought, why not just infill the whole room with earth bags and bring the earthen floor closer to the hight of the original room?

So the RMH "L Shape" day bed/ lounge will sit flush with the bottom sill of the sliding doors that run around the perimeter of the room and the non heated portion of the floor will be filled with earth bags to compensate for the difference in hight between the grade below and the hight of the door sill. Then finished with tamped road base and earthen/tataki flooring. Theoretically, the RMH will be "embedded in a new solid mass earth bag floor.

Here is a few photos of the room with sticks laid out to represent the placement of the metal platforms measured to exact size.
Black hose on the floor represents the placement of the barrel, with allowances for clearance from flammables (18"). i.e. wood posts and wall panels etc.
Builders Guide represents the feed tube:)

Other Points:
I will follow the books standard construction for a 6" J-tube configuration using firebricks for the feed tube, burn tunnal, and heat riser. Regular bricks and cob for manifold.
Chimney will go more or less straight out the roof near the peek.

Think that is a good place to stop.

Let me know if any part of this is unclear. Happy to elaborate or draw more images and references if needed.

Thanks again in advance.

Cheers, Peter





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Gerry Parent
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Peter Sedgwick wrote:
1. In this scenario would it work if I use earth bags for my supporting walls for the above described metal top?
(I was thinking to use cinder blocks but they seem too unstable.)
I would stack the earth bags with barbed wire and then cob the inside of the cavity before placing the metal top on, and then cob again over the whole thing. Are earth bags a problem that close to the flu gas chamber if the are covered in cob?

2. How should I approach clean outs for something like this?

3. Would earth bags be an issue against the edge of the raised wooden foundation? I will lay drainage gravel first.

4. Having a hard time finding insolation options here other than foam insulation board. Pumice is proving difficult even though we are on a giant volcano. Any other options?

5. At what layer in the "sandwich" do I add the insolation?

6. Will I still need some drainage gravel on grade if I'm using earth bags?

7. Am I totally nuts?


1. From my understanding, cob heats up approximately 1" per hour. If you use earth bags which are like 18" (or so) wide (minus the rendering), that would take 18 hours of burning before you felt any heat on the other side of the bag. Yikes!  There have been many people who have had much success with building their bench supporting walls with standard size brick (3.5-4.5" wide) with no strength issues. So that equates to around 3-4 hours of burning before the heat transfers. A lot more realistic (to me). Also, the sides of a bell doesn't transfer nearly as quick as the top will.

2. Cleanouts: Just make sure you can get to all areas of the bell comfortably without too much trouble with a shop vac, your arm, a scooper or broom etc.

3. Depends on how you answer question #1

4. Insulation: Perlite is another possible option. A quote taken from Earthen Floors by Sukita Reay Crimmel and James Thompson page 118-119:  "To install perlite, keep it in the plastic bags it comes in and place these tightly together on top of the vapor barrier. Compact the bags with a hand tamper or plate compactor. Important note:Regardless of the type of insulation, the finished layer of an earthen floor should never sit directly on insulation. There needs to be a dense structural layer of concrete, poured earthen basecoat or compacted gravel between the two, to create a firm, stable base for the finish layer."

5. The order is: Grade, Drainage rock, vapour barrier, insulation, compacted road base or concrete

6. same as #3.

7. Absolutely!  But that's a good thing because you probably wouldn't be even starting this project if you were'nt a little....er..... 'different'.  :)

Other Points:
I will follow the books standard construction for a 6" J-tube configuration using firebricks for the feed tube, burn tunnal, and heat riser. Regular bricks and cob for manifold.
Chimney will go more or less straight out the roof near the peek.


One thing to look into is a 5 minute riser: 5 minute riser
 
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Peter Sedgwick wrote:
After watching videos and researching I feel like the bell bench would be the best option. Not a whole lot of info out there that I can find. Really going on Matt's explanation and the Sundog rebuild video for the construction tips. I've got access to tons of reclaimed cinder blocks. Thinking of using those, filled with cob, for the walls of the chamber then cobbing over and plastering with the same material I use on the floor. Maybe use paving stones for the top of the bench depending on how cheap I can get them. Other option would be to hammer out pieces of drum can like he did in the Sundog video. If anyone has other ideas I'm more than interested.



Hi Peter,

You can find my videos from a recent bell build on my youtube channel.
https://www.youtube.com/channel/UCXqH6W1oen_2hWeTuhqKpcw/videos

Thanks
Dan
 
Peter Sedgwick
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Thanks Gerry!

That was really good info.

I found an explination for the "5 minute riser" in another permies thread. (screen shot attached below)
So basically, all I need to do is find this Morgan Superwool Plus material in 1" thickness and fit it into a chimney pipe with and 8" ID so that the final ID is 6" is that correct?
Not sure I understand what the stainless wire they mentioned is for.
Also I think I will use full and half fire bricks for the feed tube and burn tunnel while fallowing the layout instructions in the Builders Guide.
Not sure exactly how to connect the "square" exit on the exit of the burn tunnel to the "round" 5 minute riser. Can you explain this connection a bit? Maybe I missed something.

I had a think about the points you made and have revised the stratification chamber design using half thickness cinder blocks on the chamber wall that is closest to the middle of the room. AKA where we want more heat to resinate. The blocks are 10cm (4in) thick and should fit the bill. Laid a few out on the floor this afternoon and determined that I would only need about 5-10 of them depending on the final hight of the bench/bed and how much vertical space the base layers of gravel and insulation eat up. I don't want the bed/bench any higher that the bottom sill of the door. Otherwise, as you mentioned before, it will become a design problem and a trip hazard.

Here is a new drawing of my plan for layout in cross section. I will use salvaged metal sided refrigeration panel insolation in two staggered layers. The top layer will cover the seams of the bottom layer. Because I will use this material I thought I might not need a vapor barrier. Any thoughts on this?

Everyone seems to differ in opinion on this subject. It is heavy clay soil and the house is not set up with the best drainage, however it is a small space in the middle of the overall foundation footprint with only a very small portion exposed to an outside wall. (Maybe about 2.6` wide space exposed to outside wall) All other walls adjacent to the build room are internal. (See reference drawing)

Cheers, Peter



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NEW LAYOUT IN CROSS SECTION
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MATEL CLAD INSULATION
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5 MINUTE RISER
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HOW TO CONNECT?
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SMALL EXTERIOR EXPOSED WALL AREA
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MIMI LEARNING TO WELD:)
 
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With your round peg, square hole question, the square is 6” the pipe is 8” so it sits directly on top.
In my case, I used 50mm of ceramic fibre wool (not come across Morgan’s super wool) inside a 10” pipe and it simply self supports it self over the 6” hole.
36D450F5-05CE-44F9-AF90-E87FCA8AAEB9.jpeg
[Thumbnail for 36D450F5-05CE-44F9-AF90-E87FCA8AAEB9.jpeg]
 
Gerry Parent
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Peter, I think we should keep you changing your plans all the time because your pictures are totally awesome!!!  ...and please have Mimi wear gloves next time while she's welding....Ouch!  
 
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Peter Sedgwick wrote:So basically, all I need to do is find this Morgan Superwool Plus material in 1" thickness and fit it into a chimney pipe with and 8" ID so that the final ID is 6" is that correct?
Not sure I understand what the stainless wire they mentioned is for.


That's about all there is to it! But..... if my memory serves me right, I think I remember Thomas pointing out, knowing exactly where to cut it (so very little is wasted as its expensive stuff) so that when fitted in the pipe, the two ends meet nice and tight. A little math should help here. The wire I believe was to act as a backup to help hold the pipe together.

Not sure exactly how to connect the "square" exit on the exit of the burn tunnel to the "round" 5 minute riser. Can you explain this connection a bit? Maybe I missed something.


You could either make a transition piece to help join the two together but I think I remember the consensus was not to worry about it - The irregularity adds to the turbulence and the corners of the square burn tunnel don't get a lot of air movement anyway (the main stream is down the center) which is why a round heat riser is a more efficient use of ISA than a square heat riser. Correct or not, I've used this logic on my stove and its worked just fine for years.

Here is a new drawing of my plan for layout in cross section. I will use salvaged metal sided refrigeration panel insolation in two staggered layers. The top layer will cover the seams of the bottom layer. Because I will use this material I thought I might not need a vapor barrier. Any thoughts on this?


I certainly can't stamp your drawing with a certified, "PASS" but to me it looks good. In my shop I have an earthen floor with no vapor barrier and havn't run into any moisture issues. There is absolutely no clay in my sub soil however. What it says in a few books I've read is that without a vapor barrier, sometimes moisture (migrating upwards) collects under carpets, table legs, cabinets, etc ...places that can't naturally breathe and should be inspected from time to time.
 
Peter Sedgwick
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Gerry Parent wrote:

Peter Sedgwick wrote:So basically, all I need to do is find this Morgan Superwool Plus material in 1" thickness and fit it into a chimney pipe with and 8" ID so that the final ID is 6" is that correct?
Not sure I understand what the stainless wire they mentioned is for.


That's about all there is to it! But..... if my memory serves me right, I think I remember Thomas pointing out, knowing exactly where to cut it (so very little is wasted as its expensive stuff) so that when fitted in the pipe, the two ends meet nice and tight. A little math should help here. The wire I believe was to act as a backup to help hold the pipe together.

Not sure exactly how to connect the "square" exit on the exit of the burn tunnel to the "round" 5 minute riser. Can you explain this connection a bit? Maybe I missed something.


You could either make a transition piece to help join the two together but I think I remember the consensus was not to worry about it - The irregularity adds to the turbulence and the corners of the square burn tunnel don't get a lot of air movement anyway (the main stream is down the center) which is why a round heat riser is a more efficient use of ISA than a square heat riser. Correct or not, I've used this logic on my stove and its worked just fine for years.

Here is a new drawing of my plan for layout in cross section. I will use salvaged metal sided refrigeration panel insolation in two staggered layers. The top layer will cover the seams of the bottom layer. Because I will use this material I thought I might not need a vapor barrier. Any thoughts on this?


I certainly can't stamp your drawing with a certified, "PASS" but to me it looks good. In my shop I have an earthen floor with no vapor barrier and haven't run into any moisture issues. There is absolutely no clay in my sub soil however. What it says in a few books I've read is that without a vapor barrier, sometimes moisture (migrating upwards) collects under carpets, table legs, cabinets, etc ...places that can't naturally breathe and should be inspected from time to time.



Great Gerry,

Thanks so much. I will take all of that into consideration.
So the round hole of the pipe just sits on top of the square hole and the corners of the round hole don't get in the way because most of the draft is centralized seems like.
I'll keep you posted.
Glad you like the drawings. They help me visualize what I need to do.
I would love to get a pair of gloves for Mimi, but looks like we're gonna end up spending all our money on this Superwool, so bare hands for now:)
 
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Dan Hatfield Ii wrote:

Peter Sedgwick wrote:
After watching videos and researching I feel like the bell bench would be the best option. Not a whole lot of info out there that I can find. Really going on Matt's explanation and the Sundog rebuild video for the construction tips. I've got access to tons of reclaimed cinder blocks. Thinking of using those, filled with cob, for the walls of the chamber then cobbing over and plastering with the same material I use on the floor. Maybe use paving stones for the top of the bench depending on how cheap I can get them. Other option would be to hammer out pieces of drum can like he did in the Sundog video. If anyone has other ideas I'm more than interested.



Hi Peter,

You can find my videos from a recent bell build on my youtube channel.
https://www.youtube.com/channel/UCXqH6W1oen_2hWeTuhqKpcw/videos

Thanks
Dan



Thanks for the link Dan.

Watched the long version. Well done.
How do you feel about the open stratification style chamber now that you are using it?
Any advantages or disadvantages you see when compared to a traditional flu duct bench build?

Overall thoughts on the way it delivers heat.

Would love to hear your experience.

Cheers, Peter



 
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Fox James wrote:With your round peg, square hole question, the square is 6” the pipe is 8” so it sits directly on top.
In my case, I used 50mm of ceramic fibre wool (not come across Morgan’s super wool) inside a 10” pipe and it simply self supports it self over the 6” hole.



Thanks James,

Think my drawing made the question even more unclear.
Was really ask about the joint of the square hole ID on the lower potion of the riser and the circular ID of the round pipe. My concern was the flow of air will be clipped in the corners of the square as it transitions to the circular pipe. (See attached drawing) Think Gerry has cleared this up, saying that it really doesn't effect the drag.

Your photo was helpful.

Cheers for that, Peter
IMG_3088.jpeg
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Fox James
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Yes my photo was more to point out that the riser is just self standing and in fact shows the riser  temporarily placed over the feed chamber!
This is because when I took the photo is was to show how I made the transition from square to round.
However as others have pointed out it is probably not important.

 
Peter Sedgwick
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Hey folks,

Thanks for all the great info and ideas.

Here's the latest drawing of how I am think of approaching the "bell bench"

BASE:

Thinking of laying out a course of drainage gravel filled earth bags around the inside perimeter of the room and then either infilling the remainder of the area inside that with drainage gravel or more gavel earth bags. (See detail in attached drawing.) I thought this would be a good base to work from as I don't want the gravel to exert any extra force on the foundation beams if it spreads. Could use rammed tiers, but then I have to work to the depth of the tiers. I only have 45cm between grade and the lower sill of the sliding door. Want everything to sit at sill hight if possible. (See attached image of adjacent room for clarification).

I will lay the base insulation on top of the tamped drainage gavel and then a layer of road base.

Plan to build the RMH bell bench system on top of these layers.

Questions:

1. Does anyone have any suggested depths for the tamped drainage gravel? (It will be on grade, dense clay soil)

2. Tamped road base depth?

3. Do I need additional insulation under the firebox, bell bench chamber?

RMH:

I have been studying the Rocket Mass Heater Guide for the metric 6" system but I still have a lot of areas that are unclear to me.
I am trying to source ceramic fiber board to build Matt Walkers version of the core, but still not finding anything that doesn't require me to but 5 sheets of the stuff at ridiculous prices.
Also working on Superwool for a 5 minute riser option if the ceramic fiber board doesn't pan out. I might be forced to do the whole thing in fire bricks.
If so here are a few questions I have:

1. Fire bricks need to be resistant to at least 1300°C (2400°F) correct?

2. Is there any suggested metric dimensions for full and split bricks that I should be looking for?
There are various sizes available here in Japan, but finding full and splits with the same hight and width is proving difficult

3. Can I build the manifold with regular masonry bricks and cob fill?

4. What is the required ID for the exit and chimney pipe coming out of a 6" system?
Can't seem to find a definitive dimension in the Guide

5. How do I determine if my proposed bell bench interior volume is appropriate for the 6" core system I am planning to make?

6. Will I be losing a lot of heat storage mass by using a bell instead of a traditional flue system?
Should I make up for some of that by adding towers inside the stratification chamber?
I have large concrete parking blocks, will those work?

7. Do I have to worry about towers creating drag and slowing down the thermal siphon etc.

8. Could the system melt the earth bags under the road base and insulation?

9. I plan to use cob to cover the inside of stratification chamber. Will that be sufficient for the inside?

10. What would be the proper metric hight of a "5 minute riser" if I decide to go that route?

11. Based on my count from the metric 6" core illustrated in the Rocket Mass Heater Guide a full brick core requires at least 75 full fire bricks and 16 split bricks. Any suggestions on how many to buy or how to calculate?

COB:

I have done the jar test on my soil. Unclear as to percentages. Used a small amount of hand soup and in the water. The jar in the attached image has been sitting for 3 weeks.
I can make donuts, I can make snakes, I could probably even throw a pot on a pottery wheel. It seems to have a good amount of clay in the soil.

I have made test cob bricks and coated them with homemade lime plaster. That are not cracking and have dried well in the past 2.5 weeks.
See images below for reference.

Is this enough testing or do I need to continue testing?
I have mixed at a ratio of roughly half sifted clay soil and half builders sand
Used dead grass in the test bricks, but plan to use rice straw for the actual build as it will be available soon with harvest.
Added biochar to mix. Good or bad?

All knowing permise people please advise. Thanks, Peter

Disclaimer: I'm kind of an artsy fartsy type. I have watched almost every video on RMH. I am not trying to win the science fair on this one and the coefficient of π divided by the pythagorean theorem is starting to make my head spin. Just want a viable option to keep myself, my wife, and my dogs warm for the winter in an old Japanese farm house. Happy to tinker and adjust as the winter progresses and I become more comfortable with the system:)













Does anyone have
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REDESIGN BELL BENCH
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EARTH BAG LAYOUT
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METRIC CALCULATIONS FOR 6" SYSTEM
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JAPANESE ROAD BASE
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JAPANESE DRAINAGE GRAVEL
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ADJACENT ROOM REFERENCE PHOTO
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PARKING BLOCKS
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WET CLAY SOIL FROM LOCATION
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SOIL TEST JAR AFTER 3 WEEKS
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HIGH TEC PROCESSING FACILITY
 
Gerry Parent
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First and foremost, (even though I'm repeating myself - complements never get old right?) your drawings belong in a wiki or book as a RMH builders guide!

Peter Sedgwick wrote:1. Does anyone have any suggested depths for the tamped drainage gravel? (It will be on grade, dense clay soil)
2. Tamped road base depth?
3. Do I need additional insulation under the firebox, bell bench chamber?


1 &2 are taken from Earthen Floors by Sukita Reay Crimmel and James Thompson
1. 4-8" over compacted subsoil.
2. 3-6"
3. A clay slip/perlite mix can be used under the firebox for sure to keep the heat in the firebox rather than being drawn down into the Earth. The bell should have some insulation also but doesn't need to be as thick. Others here may have more specific depths for you.

RMH:
I have been studying the Rocket Mass Heater Guide for the metric 6" system but I still have a lot of areas that are unclear to me.
I am trying to source ceramic fiber board to build Matt Walkers version of the core, but still not finding anything that doesn't require me to but 5 sheets of the stuff at ridiculous prices.
Also working on Superwool for a 5 minute riser option if the ceramic fiber board doesn't pan out. I might be forced to do the whole thing in fire bricks.
If so here are a few questions I have:

1. Fire bricks need to be resistant to at least 1300°C (2400°F) correct? Yes

2. Is there any suggested metric dimensions for full and split bricks that I should be looking for?
There are various sizes available here in Japan, but finding full and splits with the same hight and width is proving difficult
The dimensions of a split are usually 9 in × 4 1⁄2 in × 1 1⁄4 in (229 mm × 114 mm × 32 mm)

3. Can I build the manifold with regular masonry bricks and cob fill? The heat at this point is much less but cement products may still be susceptible to the heat over time. Clay bricks are often recommended. The cob should be fine.

4. What is the required ID for the exit and chimney pipe coming out of a 6" system?
Can't seem to find a definitive dimension in the Guide. Everything is kept to system size throughout....so 6" however, the transition should be 4-5X system size.

5. How do I determine if my proposed bell bench interior volume is appropriate for the 6" core system I am planning to make?
Bell Sizing

6. Will I be losing a lot of heat storage mass by using a bell instead of a traditional flue system?
Should I make up for some of that by adding towers inside the stratification chamber?
I have large concrete parking blocks, will those work? There is a fellow working on his bell system right now. Satamax is helping him out with sizing and pillars. Perhaps you could get some helpful hints from this thread: Bell-Chamber-Mass-Questions

7. Do I have to worry about towers creating drag and slowing down the thermal siphon etc. See above

8. Could the system melt the earth bags under the road base and insulation? Probably no earth bags under the stove core but the perlite insulation should do its job

9. I plan to use cob to cover the inside of stratification chamber. Will that be sufficient for the inside? Glenn Herbert in another discussion mentioned the following:
"You do want a double wall for the box if you can, for safety in case there is a crack in the wall. A layer of bricks on edge, or a smooth layer of a few inches of cob that is separated from the stone & mortar layer by say a sheet of cardboard, would be ideal. At the least you need to not have any stones going all the way through the wall, as any crack in the bedding would leak. A good chimney will give enough draft that you will have negative pressure inside the bell except perhaps at startup, reducing risk further."

10. What would be the proper metric hight of a "5 minute riser" if I decide to go that route? If you are going with the barrel over the heat riser there is a minimum gap to leave (at least 2" for cooking but more if you are just using for heating) as this is an area that can cause restrictions in your system from ash buildup. Generally, the taller the heat riser (to a point) the more draw it will give you. So 122cm for a 6"system is a standard minimum. See page 8 in the builders guide

11. Based on my count from the metric 6" core illustrated in the Rocket Mass Heater Guide a full brick core requires at least 75 full fire bricks and 16 split bricks. Any suggestions on how many to buy or how to calculate? Not exactly sure of your question?

COB:
Is this enough testing or do I need to continue testing? Sounds like your all set. The proof is always in the pudding though....meaning, you may get really good results in a test batch but may show up a little different in the final product. I'd say your at a great place to start and because cob is so forgiving (compared to cement) you can always make small modifications along the way.
Added biochar to mix. Good or bad? If your planning on growing something in your cob then that would be great!..... just kidding. From my understanding, biochar is filled with little holes and would think that it would make a better insulator than a mass material which should be heavy and dense materials..

 
Peter Sedgwick
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Just spent two hours writing a detailed response and the photos got stuck in upload. Lost it all. Ouch...

Glad you like the drawings.

I’ll try to keep this short and sweet, probable better.

1. Does anyone have any suggested depths for the tamped drainage gravel? (It will be on grade, dense clay soil)
2. Tamped road base depth?
3. Do I need additional insulation under the firebox, bell bench chamber?

1 &2 are taken from Earthen Floors by Sukita Reay Crimmel and James Thompson
1. 4-8" over compacted subsoil.
2. 3-6"
3. A clay slip/perlite mix can be used under the firebox for sure to keep the heat in the firebox rather than being drawn down into the Earth. The bell should have some insulation also but doesn't need to be as thick. Others here may have more specific depths for you.


Followed these suggested depths and made a new drawing with the drainage gravel dug in 15cm below grade. Could this create a pooling of unwanted water at the bottom below the tamped drainage gravel?

2. Is there any suggested metric dimensions for full and split bricks that I should be looking for?
There are various sizes available here in Japan, but finding full and splits with the same hight and width is proving difficult
The dimensions of a split are usually 9 in × 4 1⁄2 in × 1 1⁄4 in (229 mm × 114 mm × 32 mm)


Noted! Length and width should be the same on both full bricks and split bricks for ease of layout I would assume.

3. Can I build the manifold with regular masonry bricks and cob fill? The heat at this point is much less but cement products may still be susceptible to the heat over time. Clay bricks are often recommended. The cob should be fine.

OK, Most likely do a half drum manifold at this point. Any suggestions on size of hole that goes into the bell chamber if I’m not using ducting? Bigger is better here?

4. What is the required ID for the exit and chimney pipe coming out of a 6" system?
Can't seem to find a definitive dimension in the Guide. Everything is kept to system size throughout....so 6" however, the transition should be 4-5X system size.

Noted. I’ll see what sizes I have available here and likely consult again.

5. How do I determine if my proposed bell bench interior volume is appropriate for the 6" core system I am planning to make?
Bell Sizing

Read this, Thanks.
Think it's saying to measure the mass of the sides and the top. No idea as of yet. Really trying to find out if there is a minimum hight on the bell bench. How much room do I have to play before the volume effects the system? Is an ID for the bell bench hight at 20cm (obituary number for now) going to create issues.
Trying to keep the hight of the bench to sit flush with the sliding door sill and there is only about 50cm from grade.


6. Will I be losing a lot of heat storage mass by using a bell instead of a traditional flue system?
Should I make up for some of that by adding towers inside the stratification chamber?
I have large concrete parking blocks, will those work? There is a fellow working on his bell system right now. Satamax is helping him out with sizing and pillars. Perhaps you could get some helpful hints from this thread: Bell-Chamber-Mass-Questions

This is the tread that got me thinking. Will keep following.

7. Do I have to worry about towers creating drag and slowing down the thermal siphon etc. See above

8. Could the system melt the earth bags under the road base and insulation? Probably no earth bags under the stove core but the perlite insulation should do its job

Roger that:)

9. I plan to use cob to cover the inside of stratification chamber. Will that be sufficient for the inside? Glenn Herbert in another discussion mentioned the following:
"You do want a double wall for the box if you can, for safety in case there is a crack in the wall. A layer of bricks on edge, or a smooth layer of a few inches of cob that is separated from the stone & mortar layer by say a sheet of cardboard, would be ideal. At the least you need to not have any stones going all the way through the wall, as any crack in the bedding would leak. A good chimney will give enough draft that you will have negative pressure inside the bell except perhaps at startup, reducing risk further."


Super clear

10. What would be the proper metric hight of a "5 minute riser" if I decide to go that route? If you are going with the barrel over the heat riser there is a minimum gap to leave (at least 2" for cooking but more if you are just using for heating) as this is an area that can cause restrictions in your system from ash buildup. Generally, the taller the heat riser (to a point) the more draw it will give you. So 122cm for a 6"system is a standard minimum. See page 8 in the builders guide

Was asking more about the length of the independent “5 minute rise” minus the hight of the portion of the riser from the bottom of the burn tunnel to where it transitions to the pipe.

11. Based on my count from the metric 6" core illustrated in the Rocket Mass Heater Guide a full brick core requires at least 75 full fire bricks and 16 split bricks. Any suggestions on how many to buy or how to calculate? Not exactly sure of your question?

Guess a better question would be:
The 6” Empirical brick layout on page 96 of the Builder Guide is completely different from the 6” Metic layout on page 98. Should I follow the brick course work for the Empirical layout if I am planning to use a half drum manifold?
Then adjust the Empirical dimensions to fit metric?

How much extra of each brick type is suggested when buying fire bricks in bulk?


COB:
Is this enough testing or do I need to continue testing? Sounds like your all set. The proof is always in the pudding though....meaning, you may get really good results in a test batch but may show up a little different in the final product. I'd say your at a great place to start and because cob is so forgiving (compared to cement) you can always make small modifications along the way.

Great

Added biochar to mix. Good or bad? If your planning on growing something in your cob then that would be great!..... just kidding. From my understanding, biochar is filled with little holes and would think that it would make a better insulator than a mass material which should be heavy and dense materials..

Made a bunch of bio char and crushed it into powder before adding. Could add to finishing plaster instead. Thought it might stop the chance of mold etc. Interesting article. https://www.biochar-journal.org/en/ct/3


Thanks so much for taking the time to walk me through this. Much appreciated, Peter
IMG_3244.jpg
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NEW DRAWING WITH DRAINAGE BELOW GRADE
IMG_3248.jpeg
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VISUAL OF THE BELL SPACE VOLUME
IMG_3240.jpeg
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EASY DIG IN CLAY SOIL UNDER SUBFLOOR
 
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I've just been following along to enjoy your experience vicariously (and to feel all nostalgic about a home I lived in like that a lifetime ago in Japan) but I sure do hope that you illustrate/publish books. Your drawings are delightful.
 
Peter Sedgwick
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Tereza Okava wrote:I've just been following along to enjoy your experience vicariously (and to feel all nostalgic about a home I lived in like that a lifetime ago in Japan) but I sure do hope that you illustrate/publish books. Your drawings are delightful.



Thanks Tereza,

It’s been a wild ride and an absolutely wonderful experience. So luck to have the opportunity to do this with my wife, Mimi and the puppies, Chimi and Changa. Glad you’re enjoying it as well. I’ll do my best to keep it interesting and try not to lose my mind in the process. Stay wild... Peter
3C799AB7-DEAC-4A4F-B293-EE51CB35EB63.jpeg
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The madness of trying to work this out in my head.
9E2B4668-23C9-428D-9650-3E601D4FBCBE.jpeg
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Chimi and Changa trying to stay warm cause with have no stove yet...(working on it)
4EF679AE-5323-4E13-86E5-CE8CAD0F38C1.jpeg
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One of my drawing in collaboration with Chimi
EED7A884-2A92-4D4C-98FF-289D7A3E05E5.jpeg
[Thumbnail for EED7A884-2A92-4D4C-98FF-289D7A3E05E5.jpeg]
New coffee table decoration by Chimichanga
 
Gerry Parent
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Peter,
- If you feel concerned of water pooling below the tamped drainage gravel then there is the option of putting in a drainage pipe (french drain).
- The hole coming out of the manifold half barrel is a bottleneck area so yes, keep it as big as you can. Transition areas like this should be designed to minimize friction on the exhaust gasses as much as possible.
- A bell works better when it has height rather than length for a given Internal Surface Area. When you want to make a bench or bed though, we compromise but it can still be done at the expense of some efficiency. I'm no expert at bell making (only one under my cap) so I am still learning about them too.
- A good discussion on the 5 minute riser: 5 minute riser
Once you get your core complete you will then know how long to make your riser so that it still leaves a top gap that you've decided on (the space between the top of the barrel and the top of the heat riser). This is another one of those bottleneck transition areas to watch out for.
- You know I never did the conversion on the two 6" sample combustion units in the builders guide but I do see that they are different dimensions. Perhaps they were trying something different/ experimenting or the client wanted it a certain way in each case.
- From my experience, firebrick is quite uniformly built with only the occasional one that is either cracked or mis-shapened. I wouldn't go overboard on extras but certainly would have maybe half a dozen extra on hand for good measure.
- Inside the bell, sometimes when the inlet and outlet are close together, a little pony wall is put in between them to help keep the hot gasses from short cutting to the outlet.
Keep up the great work!  Gerry
 
Peter Sedgwick
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Thanks for all the info and advice.

Still work on souring materials. Good chance that we are going to be building the core in full fire brick including the heat riser. Ceramic board is too expensive from what I've found so far and you have to buy 25 meters of Superwool. Most of this stuff is sold exclusively to contractors and construction companies from what I can gather. Am able to find MG Board 080 Rockwool board, that is 1" thick (2.5cm roughly). Claims to have a fireproofing good to 600°C (1112° F)

Can I use this to:

1. Act as an insulation layer and base plate to build the fire brick foundation pad for the core?
Figured it would be better to have a solid base of insulation, placed on the tamped road base layer. That will stabilize the foundation of the core, make it easier to level and keep level, and allow us to dry run the bricks and make location markings on the Rockwool board before committing to final clay slip layup.

2. Use as an insulation layer around the front fire bricks of the feed tube.

3. Use to insulate the outside of the fire brick heat riser.
Would cut panels that would fit together and incase the riser. Using an offset clockwise configuration, pinning together and wrapping with wire.

See silly drawing for details

Sourcing chimney pipe now. Standard sizes are much too small here in general. I am able to source stove pipe that is:

ID 15cm
6"=15.24cm

It is 2.4mm smaller than what is suggested. Will this crate an issue with drafting.

The chimney will be a straight run right through the ceiling, through the attic and then the roof near the peak of the roof line.

See attached photo for reference.

We'll keep plugging along here and keep you posted on our progress.
Planning to cut some barrels and weld the scaffolding frame work tomorrow.

Thanks again for being so helpful.

Cheers, Peter and the team:)








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ROCK WOOL BOARD PLACEMENT DRAWING FEATURING EXCITED BRICK MASON
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FREE URBANITE
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CHIMNEY PLACEMENT IMAGE
 
Gerry Parent
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Hi Peter,    I don't have any experience with your MG 080 Rockwool board. I know a company called Dragon heaters has used a vermiculite board for their heat riser (without a firebrick liner as your intending) but then switched to ceramic fiber product as it was much less fragile. They said: "Most of our original customers were furnished with a heat riser made from vermiculite board. Vermiculite board is fragile and disintegrated easily." I have the most experience with perlite/clay slip and know it holds up quite well (still not as good as ceramic fiber products though but much cheaper and readily available at garden supply shops) but many people have gone away from it due to it being much more labor intensive and needing twice the thickness to insulate properly. Perhaps someone else with experience could comment on this product.
- Your 15cm pipe should be just fine.

 
Peter Sedgwick
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Gerry Parent wrote:Hi Peter,    I don't have any experience with your MG 080 Rockwool board. I know a company called Dragon heaters has used a vermiculite board for their heat riser (without a firebrick liner as your intending) but then switched to ceramic fiber product as it was much less fragile. They said: "Most of our original customers were furnished with a heat riser made from vermiculite board. Vermiculite board is fragile and disintegrated easily." I have the most experience with perlite/clay slip and know it holds up quite well (still not as good as ceramic fiber products though but much cheaper and readily available at garden supply shops) but many people have gone away from it due to it being much more labor intensive and needing twice the thickness to insulate properly. Perhaps someone else with experience could comment on this product.
- Your 15cm pipe should be just fine.



Thanks for that Gerry.

Mimi found it on line for a decent price. Here is what the website says. https://www.rockwool.com/products/comfortboard-80/?selectedCat=comfortboard%E2%84%A2%2080%20downloads Seems like it's almost as fireproof as the refractory ceramic board.

Wouldn't build the entire core out of it right? "Non-combustible with a melting point of approximately 1177°C  (2150°F)"
Not a hight enough temp?

But can use as I was planning to insulate the outside of the heat riser, front of the feed tube, and under the core base I think.
Anyone have any thoughts on this stuff?

25 x 605 x 910 mm 1 case / 16 pieces * glass without ¥ 11,200 ($100 USD)

Pretty good price for a bunch of it. Sure I can find lots of spots to use it.

Working on drum cans and a bit of welding. The owner of the scrap metal yard, Mr. Saito handed me some kind of high powered pneumatic chisel to cut off the tops of the drum cans. Works like a charm. Takes about two minutes each can and leaves a really clean edge. Highly recommended if you have access to one on your own builds.

Will keep you posted as we progress.

Cheers, Peter




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Pneumatic Chisel Demo
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Drum Cans
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Mimi with gloves
 
Gerry Parent
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Here's what I found about Rockwool at:  https://rti.rockwool.com/applications/marine-and-offshore/firesafe/
"ROCKWOOL stone wool fibres can withstand more than 1000°C without melting, whereas the binding agent is lost at temperatures in excess of 250°C. When the temperature rises above 250°C, the binder will evaporate in the zone which is exposed to 250°C or more. But the fibres will remain intact as their inbuilt cohesiveness and layering will keep the fibres together, ensuring that the material will retain its rigidity and protect the material beneath it from being affected by the fire.
Since mineral fibres are highly resistant to temperature variations, ROCKWOOL mineral wool can be used under conditions of very high temperature, provided that it is installed in such a way that mechanical stress will not alter its shape when the binder evaporates."

So from this description, without a binder to hold it together, the product would probably crumble under its own load, not to mention the weight of the heat riser its also supporting. So to use it alone is pretty much pointless. Besides, 'melting point' is certainly different than 'working temperature'.

Have you seen this video? RMH Autopsy He said in the video that it was rated for 2000F. There is always a reason why certain materials are not used for any kind of longevity and of course safety!

Side note: At the end of last year, I replaced my loose vermiculite surrounding my firebox and replaced it with Rockwool batt insulation. I don't know how its making out as its sandwiched between the firebrick and cob. It was an experiment and won't know until probably next spring when I tear it apart to see how it made out.

Just for your info on plans for a core: Walker ceramic fiber core
A build using the Walker plans (a long thread but the pictures show the core well) RMH Build

Those steel nibblers look pretty nifty. It reminds me of when Thomas used one a while back for his barrel Cool Tool

The picture of Mimi wearing gloves (even though their not leather...or perhaps her hands are as tough as leather?) made me smile :)  Thanks Mimi !!!
 
Fox James
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I am surprised you can’t find and ceramic fibre products, I live on a tiny island and I can now find it for sale.
Perhaps there is a trade name in your area as it is a very useful product for many industrial and domestic uses.
 
Peter Sedgwick
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Fox James wrote:I am surprised you can’t find and ceramic fibre products, I live on a tiny island and I can now find it for sale.
Perhaps there is a trade name in your area as it is a very useful product for many industrial and domestic uses.



Hey James,

Can find, but at this point my research has found products that require us to buy in bulk, much more than we need for the present build. That comes with a price. Working on it though, and may have a new lead. Will see if it pans out in the coming days.

Thanks for the support. Peter
 
Peter Sedgwick
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Hey Gerry,

Thanks for that.

I am currently in contact with Matt directly regarding his 6" Ceramic Fiber Board core.
Have a lead now for a Japanese guy, here who handles Refractory supplies, and waiting to hear back from him next week.
If we can get build site off-cuts that can be spec'd for Matt's template at a reasonable price I would love to go that route. (Not brake the bank)
Looks like the fastest and simplest way to get from "A" to "B".

Still a bit unclear with a few things. Trying to get my head around it. Apologize in advance for my lack of understanding.

In the case of a full fire brick core build you are going to need, "1" 2" of sturdy, noncombustible insulation below the brick floor pad" Quote page 75 of Builders Guide.

This also holds true for a full Ceramic Fiber Board core build? Or can you just put the Ceramic Fiber Board core, centered on a pad of fire bricks to act as base insulation?
(Maybe I should confirm with Matt on this if we go that route.)

"...wrap entire fire box with soft material insulation: rock wool, ceramic blanket, perlite with clay..." Quote page 98 of Builders Guide.
What "Rock Wool" product are they referring to?

"Fire Box" and "Feed Tube" refer to the same portion of the core, is this correct?
I see the terms used in similar situations and just wanted clarification.

Are there definitive minimum temperature resistance benchmarks for:
1. Insulation under the fire brick floor pad?
2. Insulation around the feed tube?
3. Insulation around heat riser?

It seems like the layout/build scenario and materials/insulation necessary for the core build are dependent on the style you chose to use. A lot of science, and a bit of alchemy.

Typhoon today, but the sun comes out tomorrow, so we plan to start ripping out the present floor and getting started on the gravel foundation portion of the build. Feel it is best to get this portion of the project under control and decide the details of the RMH as more core material options are confirmed. Winter is coming, and we're not interested in sleeping with the White Walkers this year...:)

Told Mimi the "Powers That Be" suggest an up grade to leather gloves. Safety First...

Thanks again, Peter
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BUILDER'S GUIDE PAGE 75
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BUILDER'S GUIDE PAGE 96
 
Peter Sedgwick
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Quick up date.

Tore up the floor and started in on the dig. Taking longer than expected, due to heavy clay under the room.
Taking it all out in the earth bags we got 20 at a time and piling it up to process for the cob in the bench build. About 7 meters away in the corner of the driveway, next to the pile of builder sand we have. The dirt pile is bigger than the sand pile at this point, which makes us think we have probably removed about two tons of dirt at this point. Cool thing is, we are not really moving it anywhere just changing and rearranging the materials that were already here.

Big pockets of clay in spots. Decided to separate some of the big pockets to refine for slip and perlite mix later. Drying the clay now.
Any tips on how far we should refine the clay to add to the perlite would be great. Thinking of making a wood box frame and pouring a clay & perlite slab to go under the core for insulation. Any thickness suggestions here?

Feels like I'm standing inside my drawings at this point, funny.

Plan to finish the dig tomorrow. Do we need to be very meticulous on leveling at the bottom of this pit? Planning on having it slop a bit so the water runs away from the house.

All of the pillars in the foundation here are prefabricated concrete blocks that have been inset below frost line and embedded in a pored concrete hole from what I can tell. Seems stable and relatively level.

Ended up having to get large bags of perlite for the base insulation. Other panelling plan fell through. Looking to lay perlite filled earth bags on top of the tamped drainage gravel, after that a layer of road base. The RMH will sit on top of all of this. Dug down 70cm from the original floor hight so we have some room to adjust as we build. Hopefully this will give us enough room for the high of the bench.

Ended up using a combination of large blow torch while burning wood scraps in the drum cans to remove the paint. Didn't have a leaf blower, but did have a flame thrower.
Seems to have worked pretty well. Blasting the metal from both sides with heat simultaneously. Blow torch also helped get all the hard to reach spots around the rim and lip of the can. Probably finish with an abrasion disk on an angle grinder to clean them up and then oil.

Will ad some photos of the madness.

Cheers, Peter


 
Peter Sedgwick
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Photos:)
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PULLIN UP THE TATAMI AND FLOOR JOISTS
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MIMI DIGGIN FOR GOLD
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DIRT MOVING APPARATUS
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HEAVY CLAY UNDER HOUSE
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PAIN TO GET FROM ONE SIDE OF THE HOUSE TO THE OTHER
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PRESENT STATE
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MR. BURNS
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RICE STRAW
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DRYING THE RICE AFTER HARVEST TODAY (PESTICIDE FREE)
 
Fox James
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Great details and fun to read thread... I have found that laying a barrel on its side and rotating it will burn the paint far better than having the barrel standing up!
I wish you luck finding some ceramic fibre board as use this type of product is a positive step forward compared to brick or clay.  
 
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Peter Sedgwick wrote:I am currently in contact with Matt directly regarding his 6" Ceramic Fiber Board core.  Matt has been super helpful to not just his clients but to everyone. Yay Matt!


In the case of a full fire brick core build you are going to need, "1" 2" of sturdy, noncombustible insulation below the brick floor pad" Quote page 75 of Builders Guide.
This also holds true for a full Ceramic Fiber Board core build? Or can you just put the Ceramic Fiber Board core, centered on a pad of fire bricks to act as base insulation?
(Maybe I should confirm with Matt on this if we go that route.)  So the layers are your asking are as follows(?): Compacted road base, Fire bricks, CFB. If that's the case then there should be no problems.
If you look at LuAnne Welchs' build at picture "4-core-foundation.jpg" you will see the heat that gets to the base layer under the CFB. Not sure how much heat would get through the firebrick to the roadbase but to me it doesn't look like it would be much to worry about loosing too much heat to the ground....but I could be wrong. Matt may know and be able to answer you better.


"...wrap entire fire box with soft material insulation: rock wool, ceramic blanket, perlite with clay..." Quote page 98 of Builders Guide.
What "Rock Wool" product are they referring to? Rock Wool also comes in the form of batts. Home Depot


"Fire Box" and "Feed Tube" refer to the same portion of the core, is this correct?
I see the terms used in similar situations and just wanted clarification.  Their definition of Fire box includes: burn tunnel, feed tube, and heat riser. Some people also call these 3 parts a "core".


Are there definitive minimum temperature resistance benchmarks for:Do you mean thickness of various types of insulation needed in these areas?
1. Insulation under the fire brick floor pad?
2. Insulation around the feed tube?
3. Insulation around heat riser?


Typhoon today, but the sun comes out tomorrow, so we plan to start ripping out the present floor and getting started on the gravel foundation portion of the build. Feel it is best to get this portion of the project under control and decide the details of the RMH as more core material options are confirmed. Winter is coming, and we're not interested in sleeping with the White Walkers this year...:)
Not sure what White Walkers are...doesn't sound good though! We'll do our best to protect you and Mimi !!
Told Mimi the "Powers That Be" suggest an up grade to leather gloves. Safety First... smile....

 
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Peter Sedgwick wrote:Big pockets of clay in spots. Decided to separate some of the big pockets to refine for slip and perlite mix later. Drying the clay now.
Any tips on how far we should refine the clay to add to the perlite would be great. If you strain the slip through fly screen your good to go. Thinking of making a wood box frame and pouring a clay & perlite slab to go under the core for insulation. Any thickness suggestions here? 2" is a good thickness.
Feels like I'm standing inside my drawings at this point, funny. Ahhhh... the power of manifestation!
Plan to finish the dig tomorrow. Do we need to be very meticulous on leveling at the bottom of this pit? Planning on having it slop a bit so the water runs away from the house. Sounds like a good idea to me.

 
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I find some of the multi quote post quite difficult to read through so I may of got the wrong idea but I would definitely not recommend a full ceramic fibre board construction for the feed chamber.
This is the only part of the construction that receives hard wear and needs to be lined with something hard like split brick.
The only real disadvantage of using full brick for the fire box and heat riser is the amount of time it takes to heat up.

When I built my first stove I used a high mass construction including a high mass refractory cement riser, it worked really well but took two hours to get really hot.
My new stove makes use of a 1” thick cast cement firebox and everything else is insulating ceramic products, I can now see 500c in 20 minutes.

However.... my old fire worked extremely well and once up to temperature, the stored heat of the riser and firebox kept a more consistent heat for cooking on the hot plate .
Another aspect the high mass seemed to offer was the ability to burn larger pieces of wood (once up to temperature)
So high mass can have advantages ......
My new stove has some non standard design features, one thing that I have found a big improvement was building in small step from the feed box to the fire tunnel. In other words I made the bottom of the feed chamber 3/4” lower than the tunnel, I find this little step, stops the wood from falling into the fire tunnel and stalling the fire.

 
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Fox James wrote:I find some of the multi quote post quite difficult to read through so I may of got the wrong idea but I would definitely not recommend a full ceramic fibre board construction for the feed chamber.
This is the only part of the construction that receives hard wear and needs to be lined with something hard like split brick.
The only real disadvantage of using full brick for the fire box and heat riser is the amount of time it takes to heat up.

When I built my first stove I used a high mass construction including a high mass refractory cement riser, it worked really well but took two hours to get really hot.
My new stove makes use of a 1” thick cast cement firebox and everything else is insulating ceramic products, I can now see 500c in 20 minutes.

However.... my old fire worked extremely well and once up to temperature, the stored heat of the riser and firebox kept a more consistent heat for cooking on the hot plate .
Another aspect the high mass seemed to offer was the ability to burn larger pieces of wood (once up to temperature)
So high mass can have advantages ......
My new stove has some non standard design features, one thing that I have found a big improvement was building in small step from the feed box to the fire tunnel. In other words I made the bottom of the feed chamber 3/4” lower than the tunnel, I find this little step, stops the wood from falling into the fire tunnel and stalling the fire.



Totally understand. Yeah, I do get the need for the split bricks for durability in the feed tube.

Cool tips and things to keep in mind for sure.
Getting this foundation under control right now and should be able to get into the RMH later next week once I have a clear idea of what materials I can actually get.
Sure will have a lot of questions and be looking for advice then. Thing that is hunting the back of my mind is punching a hole in the roof and the whole chimney thing for sure.

Any suggestions on how to approach this would be much appreciated

Thanks again, Peter


 
Peter Sedgwick
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Thanks Gerry!

Are there definitive minimum temperature resistance benchmarks for:Do you mean thickness of various types of insulation needed in these areas?
1. Insulation under the fire brick floor pad?
2. Insulation around the feed tube?
3. Insulation around heat riser?



Thickness would be great to know.
Also each of the areas that require insulation have different top temperature that they must be able to withstand?

Peter
 
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Some more photos of the progress...:)
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TAMPA BAY
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FILLIN THE PIT
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ROOM FULL OF ROCKS
 
Hey, check out my mega multi devastator cannon. It's wicked. It makes this tiny ad look weak:
Dave Burton's Boot Adventures at Wheaton Labs and Basecamp
https://permies.com/t/119676/permaculture-projects/Dave-Burton-Boot-Adventures-Wheaton
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