Advice on a RMH build in Hokkaido Japan

Gerry Parent wrote:For the most part, I would agree Graham. The ISA would probably have a lot more influence on draft than mass ever would but..... after you tear down your heating system during a cold snap and have to make frozen cob out in the cold, you would tend to want to play it safe and proceed cautiously too.  :)

Sure

Definite change in temperature of the 20cm perlite filled exit flue on the second floor of the house. Like I said, I can touch it now continuously. To me that means the temp in the 15cm is down, gases exiting at a lower temperature. Gases also traveling the full length of the bench now. Cautious about the mass and how much heat it will extract from the gases now in contact with full ISA.

Don’t have a scale right now so can’t give you weight, but can give you volume. Burning a small box of wood, 25cm x 25cm x 40cm, in about an hour and 15 minutes. Assuming that is a rather fast consumption rate for an RMH. Of course we’re still massing and drying so that is to be expected. That said, is this consumption rate normal for a new 6”/15cm J-tube stove?

Thanks again Gerry

Peter

Graham Chiu wrote:

Peter Sedgwick wrote:No trouble. Just don’t want to over mass the thing and lose drafting and reliability.

Any thoughts on how to approach would be very helpful.

Cheers Peter and crew

My understanding is that you don't want to take heat away from the combustion chamber as that needs to be as hot as possible to burn all the combustibles but after that adding mass should not affect the draft.
If you're seeing some smoke past the initial burn that suggests that your fire isn't as hot as it could be ... unless you're actually still seeing moisture being driven out

Hey Graham,

Yeah
Super insulated in the front half of the firebox/feed tube.

Manifold side of the burn box is 5cm of CFB rated to 1400C

Might insulate the heat riser more.

Here’s some images of our feed tube insulation install.

Peter

thomas rubino wrote:Hi Peter;   Mass is everything.   It is your heat.  
The more mass you put over your barrels , the longer they will hold heat.

Thanks Thomas
Ok

Next step more mass. Drying each time between layers. Should fill in the back as Satamax suggested? It’s a deep space.

Peter

"Could the bench be too big, too long? "  So far, there doesn't seem to be anything that indicates that it is. Your external chimney temp is a good indicator of this. Keeping an eye on the exhaust temp with the thermometer can really be helpful to get to know your dragons breath and what it means. Other than lets say...."boy, it sure needs a tic-tac"
BTW, its getting pretty close to start thinking about how you want your dragon to look  as the rough mass can start to take the shape you want.
With you and your pit crew, I bet its gonna look awesome!   🐲    🐉

Peter Sedgwick wrote:Don’t have a scale right now so can’t give you weight, but can give you volume. Burning a small box of wood, 25cm x 25cm x 40cm, in about an hour and 15 minutes. Assuming that is a rather fast consumption rate for an RMH. Of course we’re still massing and drying so that is to be expected. That said, is this consumption rate normal for a new 6”/15cm J-tube stove?

Well, it really depends on the kind of wood it is. I remember you saying something about your wood...scraps from a teardown? Hardwood or soft? Any wood that is like in your recent pictures (smallish) will definitely get eaten up right away but of course produce a lot of quick heat. Bigger stuff is nice once it gets rockin' so you don't have to tend as often. By your description though, the quantity sounds about right. A baby dragon needs to be fed often. "Feed me Seymour"!

                                                           

Gerry Parent wrote:"
BTW, its getting pretty close to start thinking about how you want your dragon to look  as the rough mass can start to take the shape you want.
With you and your pit crew, I bet its gonna look awesome!

Thanks Gerry

Yeah working on the edges of the room now back near the front door. Stapling in chicken wire on the wood and MIMI is adding a layer of perlite/clay. Making a step down with shoe shelf under step. Get that worked out and then tie into the wrap around bench. Fill in and then start to find the shape as it evolves. Keep it organic and design around our utilitarian needs. Feel like these materials will work well with this approach. Will update as we progress.

So much thanks to you and everyone who have guided us through the process. Learning so much and seeing how much there is to learn. So many amazing things you can make with the “dirt” in your backyard...

Cheers Peter and crew

Peter Sedgwick wrote:

thomas rubino wrote:Hi Peter;   Mass is everything.   It is your heat.  
The more mass you put over your barrels , the longer they will hold heat.

Thanks Thomas
Ok

Next step more mass. Drying each time between layers. Should fill in the back as Satamax suggested? It’s a deep space.

Peter

Yes, definitely! It is not that much! Let say, 45 in height for the finished bench, 35 cm width at half the barrel's height. 4 barrels long?

86x4 344cm

344x45x35 541800 cm3 0.5418m3  


Let's count the weight of your cob and stones at about 1600kg m3  That's about 866kg. This is not much mass. I would say, a 6 incher can support a good two tons, two and a half ton.

Mind you, if you don't want to transfer the heat to the surounding walls, and to the ground, it would be clever to put a little insulation where the end of your tape is, and onto the ground.

Satamax Antone wrote:

Peter Sedgwick wrote:

thomas rubino wrote:Hi Peter;   Mass is everything.   It is your heat.  
The more mass you put over your barrels , the longer they will hold heat.

Thanks Thomas
Ok

Next step more mass. Drying each time between layers. Should fill in the back as Satamax suggested? It’s a deep space.

Peter

Yes, definitely! It is not that much! Let say, 45 in height for the finished bench, 35 cm width at half the barrel's height. 4 barrels long?

86x4 344cm

344x45x35 541800 cm3 0.5418m3  


Let's count the weight of your cob and stones at about 1600kg m3  That's about 866kg. This is not much mass. I would say, a 6 incher can support a good two tons, two and a half ton.

Mind you, if you don't want to transfer the heat to the surounding walls, and to the ground, it would be clever to put a little insulation where the end of your tape is, and onto the ground.

Thanks for that. Yeah, that exactly what we’ve done. Made a processing station out side with a few buckets.

1.Clay dirt processed to a thick chocolate pudding and strained of rockets. Then mixed that with perlite until it’s basically a spreadable rice crispy treat.

2. All the rocky left over waste from the clay pudding mix was then added to road base and mixed to a consistency of rough pavement.

Used those two buckets of mix throughout the room. Alternating between insulation and mass. Stuck as many golf ball size dense rocks in the road base mix as we could. Will add more large dense rocks as the present layers dry.

That sounds reasonable?

Few points to mention.
We have been burning as we build all day to promote drying. Hot gas can be seen leaving the chimney but no smoke. Just the wavy thermal effect you see on hot tarmac in the summer time. Have had a pot of water on the top of the burn barrel to use to melt clay. Not once has it simmered or boiled.

Thoughts there?

My thermometers are useless and they didn’t sell anything worth picking up at the big home center in Sapporo. Will have to order online.

Thanks again Satamax.

Peter

I think 350c on top of the barrel is pretty good and above average for a 6” j tube with added mass and a long exit... but that might not equate to 350 inside your saucepan!
I bet if you sat an empty pan on top and took a reading it will be a lot lower temperature.
I realise my fire is different to yours as I have only a few hundred kg of mass and a much more direct route out of the chimney and I also have a larger fire box and a shorter riser.
However when I built my first version it had very similar dimension to yours and would soar up to 500c on the top.

The recommended amount of insulation around a “5 minute” heat riser (on this forum) is 1” (25mm) but I used 2” and I also used 4” all around the fire box. (Picture on first page of this thread)

I think it might have more to do with the draw because the route  out of my barrel is so direct, I also wrapped the chimney in  titanium heat wrap (exhaust wrap)

In your case there might be a bit more efficiency to be had with more insulation  around the riser and firebox but I suspect you might need more air flow to get higher temperatures?
Another way to gain more heat might be via a small electric fan to improve the airflow?

I am sure you will work out how to get the very best from your fire, I wonder if you could work out a way to isolate the mass to see just how much heat you barrel will radiate  then?
This might be an advantage for you once you mass is warm if you could then isolate the mass and get more radiant heat from the barrel?

Interdentally my new fire which is primarily for cooking has a 4” hole cut out directly above the riser so I can seat a pan directly over the heat, I can get a thin metal wok glowing red hot in 10 minutes or less.

Peter Sedgwick wrote: Have had a pot of water on the top of the burn barrel to use to melt clay. Not once has it simmered or boiled.

Thanks again Satamax.

Peter

That's weird! I would expect at least simmering.


May be chuck something like this on top of your barrel.


https://www.ebay.com/itm/Magnetic-Stove-Pipe-Chimney-Thermometer-Metal-Temperature-Gauge-For-Wood-Log/202807135377?hash=item2f383f4c91:g:yuMAAOSwsR9c7JYw

https://www.ebay.com/itm/Magnetic-Stove-Pipe-Chimney-Thermometer-Metal-Temperature-Gauge-For-Wood-Log-B/392187930456?hash=item5b5038e758:g:d8sAAOSwDFZcBQXJ

Satamax Antone wrote:

Peter Sedgwick wrote: Have had a pot of water on the top of the burn barrel to use to melt clay. Not once has it simmered or boiled.

Thanks again Satamax.

Peter

That's weird! I would expect at least simmering.


May be chuck something like this on top of your barrel.

Yeah. Cool

Burning now for about an hour tonight and inferred thermometer is reading 306C on the top of the barrel. Also took all the big rocks and cob bricks, I had on top, off the burn barrel. Burning bigger pieces of hard wood mixed with off cuts of relativity dry timber.

Could that be it?

Peter

Fox James wrote:

In your case there might be a bit more efficiency to be had with more insulation  around the riser and firebox but I suspect you might need more air flow to get higher temperatures?
Another way to gain more heat might be via a small electric fan to improve the airflow?

I am sure you will work out how to get the very best from your fire, I wonder if you could work out a way to isolate the mass to see just how much heat you barrel will radiate  then?
This might be an advantage for you once you mass is warm if you could then isolate the mass and get more radiant

Hey James!

Thanks for the tips. Numbers are better than this afternoon I feel. Just let her go out now. Will keep adding mass tomorrow and keep drying. Thinking of adding more insulation to the heat riser and other half of the fire box soon. Fire box on the inside of the manifold has 5cm of CFB heat riser only has 2.5cm. Planning to take off the barrel and change the wire ties, i have on the CFB heat riser now, to stainless. Could wrap in chicken wire and perlite clay then. Roughly 2.5cm/1in extra will make a difference? Think it will help to fill/seal the gaps in the CFB as well. Interested to see what the inside of manifold and riser look like after a few days of burning. Will keep you posted.

Peter...🏔✌️🏔

Has it stopped smoking from the outside chimney now that you're using drier/harder wood?

Graham Chiu wrote:Has it stopped smoking from the outside chimney now that you're using drier/harder wood?

Hey Graham,

In general no smoke at all now. Occasionally a few wisps of white smoke here and there, but mostly just heat waves coming out the chimney now. Softer wood be have  is definitely dryer. Hard wood sticks and logs bubble a bit of moisture/sap from the end sticking out off the feed tube. Will get more/different wood soon.

Will keep checking and reporting our findings. Realizing how much I can learn from watching the fire box and moving burning sticks.

All and all it’s burning pretty well I think. But, again, I have nothing to gage against, other that previous campfire and wood burning stove experience/experiments...

Peter

Quick update on the perlite/clay double barrel insulated flue chimney system we are using. Working like a charm as far as we can tell. Three hours into the burn on a half finish bench and I can touch the insulated portion of the 20cm exit flue. No danger of over heating and zero fire hazard I feel.

Our chimney build was a bit complex cause we put a 45 degree bend in the middle of the vertical run to get the flue to run out the highest roof in the house. However if you were just doing a straight flue with a double pipe it would be a super easy an inexpensive way to insulate your chimney through the roof.

We just used 15cm spiral air duct for the gas flue portion and 20cm spiral air duct to hold the insulation in place. Infilled with perlite and a bit of wet clay “soup” mix to weight down the perlite and avoid static electricity issues on installation.

Doubt it will pass codes in places that they apply, but seems good to us and thought we’d share our findings so far.

Pictures and more installation information in previous posts.

Feel free to comment or ask questions if you have any.

Happy days...Peter and the people of Hokkaido 🏔🛢🏔

Gerry Parent wrote:Peter and Company....  I encourage you to watch this guys videos. They are all fantastic and his style reminded me of you The Nito Project

Hey Gerry,

Yeah thanks for that link. Have watched that one before. Like his series of videos. Well shot and well edited. Mimi says she use to make these balls when she was a kid. Great textures for sure. Will get into some of those finer details, hopefully in the coming weeks.

Right now trying to dry things out evenly in the room. This is my solution to combating cold, snow and a late build start. Don’t try this at home...🧱🔥🧱

Cheers, Peter

Innovation Peter !   I love it !

I would recommend moving the rock closer together and more of them in your bench unless you want it this way. The cob doesn't hold the heat as long and the best part about it is that you don't have to mix as much.

Imagination = Possibilities

Sometimes infrared thermometers can't read temperatures accurately if the surface they're looking at is shiny or reflective.  So you may want to put something on the surface and then read its temperature.  Pile of sand, different colored rocks, etc and see what temp they read.

When you're not getting water to boil is that possibly because you're using it and replacing the hot water with cold so it has to keep heating it up?  Sorry if that's a bit on the obvious side...

Gerry Parent wrote:I would recommend moving the rock closer together and more of them in your bench unless you want it this way. The cob doesn't hold the heat as long and the best part about it is that you don't have to mix as much.

Imagination = Possibilities

Thanks Gerry!

Big rocks on top, in the photo, are just there to dry off and thaw out before they find a home. Are you referring to the smaller rocks on the front?

Right now I’m making a mix.
Unsifted clay soil with rocks + road base

It’s lots of gravel and as little clay as we can use that will still stick to the bench sides.

Then “paint” that on and stick more rocks in the surface.

Can’t think of another way to get “more” dense material on the surface. Has about 3-4cm on the surface now. 🤔

Burned all day yesterday, but surface of the half barrel bench never got dangerously hot. The builders guide says 4-6 inches of mass on top of bench for safety and comfort. That’s like 15cm of mass on top. We don’t have anything close to that and we can sit on the bench now. It is uncomfortably warm for long periods in places, but don’t feel like it’s going to burn us.

The numbers in builders guide are for flue style benches. Do the rules change half barrel stratification chamber systems?

No smoke out the chimney, no drafting issues. Entire outside of manifold is cover in several centimeters of perlite clay insulation. This thing is eating up tons of wood. It is warm and comfortable while it’s “on” and yesterday before we went to sleep.

6 hours later and the bench and house are cold again. Hoping it’s the fact that there is not enough mass. Fearing it is a loss of heat through the floor.

Am I over analyzing it?
Already calculating that I’ll have to do a full rebuild when the weather gets warm again. More insulation in floor under bench.

🏔🏔🏔🏔
🏔Peter🏔
🏔🏔🏔🏔

P.S. Mimi did a google search for RMH in Japanese. Here are a few of the cutting edge, and extremely safe looking, “RMH” designs here in Japan.
Hummmm....🚀☠️🚀

You're over analyzing it!

Your mass is nowhere near dry! When it will be , you'll notice a real difference. And if you want heat for long, mo mass!

Mike Haasl wrote:Sometimes infrared thermometers can't read temperatures accurately if the surface they're looking at is shiny or reflective.  So you may want to put something on the surface and then read its temperature.  Pile of sand, different colored rocks, etc and see what temp they read.

When you're not getting water to boil is that possibly because you're using it and replacing the hot water with cold so it has to keep heating it up?  Sorry if that's a bit on the obvious side...

Thanks for the advice Mike.

Drew on the flue ducts with magic marker as Gerry suggested.

Do like your pilling idea. Will try.

Water was in a pot for a fair bit of time. Wasn’t my main focus at the time. Just noticed it wasn’t boiling. The pot we were using had a plastic handle so it was on the edge of the barrel and not directly in the center of the barrel top. Will find some with no plastic and try again today.

Nothing is ever obvious, until it is...
✌️🤓✌️

Peter

No problem!  You may want to try a piece of masking tape on the pipe.  The marker could be just as shiny (infrared wise) as the underlying metal.  I'm not sure, just thinking out loud...

Satamax Antone wrote:You're over analyzing it!

Your mass is nowhere near dry! When it will be , you'll notice a real difference. And if you want heat for long, mo mass!

Thanks Satamax

Nice to have a sounding board for reassurance.

What is the best way to infill the large area between the bench and back door frame? Dry rocks and roadbase? Should it have clay soil mixed in to fill air gaps and voids? Avoid trapped air/insulation.

🤖Peter🤖

Peter Sedgwick wrote:Big rocks on top, in the photo, are just there to dry off and thaw out before they find a home. Are you referring to the smaller rocks on the front?
Right now I’m making a mix.
Unsifted clay soil with rocks + road base
It’s lots of gravel and as little clay as we can use that will still stick to the bench sides.
Then “paint” that on and stick more rocks in the surface.
Can’t think of another way to get “more” dense material on the surface. Has about 3-4cm on the surface now. 🤔

Those big rocks are where its at man. Use lots of those! The little baby ones can just be used sporadically to fill in gaps. Think of it as a dry stacked rock bench fitting them as close together as possible then just filling in all gaps with clay/sand. Like 95% rock (or other dense stuff) 5% mortar.

P.S. Mimi did a google search for RMH in Japanese. Here are a few of the cutting edge, and extremely safe looking, “RMH” designs here in Japan.
Hummmm....🚀☠️🚀

Cute...and some scary, like what the heck were they thinking when they made these?! Maybe if you translate your posts to Japanese you'll come up in the searches too? Has your friend (the one you mentioned earlier in your build) seen your creation? Bet he's jealous...

Peter Sedgwick wrote:

Satamax Antone wrote:You're over analyzing it!

Your mass is nowhere near dry! When it will be , you'll notice a real difference. And if you want heat for long, mo mass!

Thanks Satamax

Nice to have a sounding board for reassurance.

What is the best way to infill the large area between the bench and back door frame? Dry rocks and roadbase? Should it have clay soil mixed in to fill air gaps and voids? Avoid trapped air/insulation.

🤖Peter🤖

I would say, two, three options.


A crude way, 100/120 mm rocks. No filler. The air in between moves by convection, and warms up the stones some. Not very efficient.

The same, or bigger rocks, like head size ones, infilled with cob. Better, flat stones, like scottish or irish dry stone walls, infilled with cob.



Pavers, over here they often go for cheap. And can be stuck with minimal cob. Stuff like this  https://www.leboncoin.fr/recherche/?text=paves%20autobloquant&search_in=subject i like the square ones which are not locking.

Satamax Antone wrote:

Peter Sedgwick wrote:

Satamax Antone wrote:You're over analyzing it!

Your mass is nowhere near dry! When it will be , you'll notice a real difference. And if you want heat for long, mo mass!

Thanks Satamax

Nice to have a sounding board for reassurance.

What is the best way to infill the large area between the bench and back door frame? Dry rocks and roadbase? Should it have clay soil mixed in to fill air gaps and voids? Avoid trapped air/insulation.

🤖Peter🤖

I would say, two, three options.


A crude way, 100/120 mm rocks. No filler. The air in between moves by convection, and warms up the stones some. Not very efficient.

The same, or bigger rocks, like head size ones, infilled with cob. Better, flat stones, like scottish or irish dry stone walls, infilled with cob.



Pavers, over here they often go for cheap. And can be stuck with minimal cob. Stuff like this  https://www.leboncoin.fr/recherche/?text=paves%20autobloquant&search_in=subject i like the square ones which are not locking.

Thanks for the images and ideas. We collected as many rocks as we could find in the yard and just started building. Filling in all gaps will roadbase cob. There’s a lot of rocks here. Gonna need a bit more, but starting to fill in.

Peter

Peter Sedgwick wrote:What is the best way to infill the large area between the bench and back door frame? Dry rocks and roadbase? Should it have clay soil mixed in to fill air gaps and voids? Avoid trapped air/insulation.
🤖Peter🤖

Now your amassing mass! Should fill in all your voids rather quickly too. Just be sure to not leave any jutting out past the point you want to put your finish plaster coat on.
Those pups are sure growing fast!

Gotcha! Will keep filling. Get back to you with more stuff later.

Thanks again...Peter

Peter, i saw all the rocks in the middle.

But that center area with the grey gravel, you're not filling it in?  You're staying at the gravel's level?



It's what i would do. May be with clay floor tiles on top, or something. Thick slates, may be.

Satamax Antone wrote:Peter, i saw all the rocks in the middle.

But that center area with the grey gravel, you're not filling it in?  You're staying at the gravel's level?



It's what i would do. May be with clay floor tiles on top, or something. Thick slates, may be.

Yeah! We agree. Not filling in the area. Planning on doing some type of earthen floor with maybe lime/clay finish . It will all tie in with the bench and have seamless transition.

Like the idea of using as many found objects and materials from the property and surroundings as possible. Bring a little piece of the outside, inside.

For me, right now, a house is just a warm extension of the outside with a roof...

✌️🤓✌️

Gerry Parent wrote:Cute...and some scary, like what the heck were they thinking when they made these?! Maybe if you translate your posts to Japanese you'll come up in the searches too? Has your friend (the one you mentioned earlier in your build) seen your creation? Bet he's jealous...

Yeah Gerry, I’m no rocket scientist, but they look pretty sketchy to me too. Got me thinking that there needs to me more accurate and up to date information about RMHs here in the local language.

My friend, Taka, has been over a few times now, and was the one who help put the barrel on for the first time with me. (think the band clamp idea is good btw) He’s planning to rebuild his as well in the near future. Probably give him a hand with it.

Peter

Been away since learning the floods didn't hurt you.  Glad you went for the barrels instead of flat steel smoke chambers.  Feels so good to see all your progress Peter.  Mimi is a hero!  

Antigone

Antigone Gordon wrote:Been away since learning the floods didn't hurt you.  Glad you went for the barrels instead of flat steel smoke chambers.  Feels so good to see all your progress Peter.  Mimi is a hero!  

Antigone

Thanks Antigone.

Yeah, we are past the floods and into full on winter here. Just snowed 22cm. House full of rocks and dirt, but we have fire so feeling pretty good. MIMI is a champ. Totally steppin up to the plate and knocking it out of the park. Letting her run with the logistics on stuff a lot. She pretty meticulous and picks things up super quick. A month ago she didn’t even know what perlite was. Now she’s a mix and application mater. Totally respect to the lady...

Will try to turn the pile of rocks into something. Right now I’m just tending to the fire, drying everything out, and trying to feel the space.

Sure it will tell me what it needs to become, where the next rock needs to go...

Peter and Mimi and two dogs named Chimichanga...

🏔🏔🏔🏔🏔🏔
🏔🌲🌲🌲🌲🏔
🏔🌲👩🏻‍🔧👨🏻‍🔧🌲🏔
🏔🌲🐕🐕🌲🏔
🏔🌲🌲🌲🌲🏔
🏔🏔🏔🏔🏔🏔

More massing and absorbing the space...

🏔✌️🏔

Oh my gosh!...is Chonga OK with that hatchet stuck in her head?  💥 🤣 💥

Starting to look like a real mass bench now with some serious rock in there..... Great Job Team Hokkaido!

Gerry Parent wrote:Oh my gosh!...is Chonga OK with that hatchet stuck in her head?  💥 🤣 💥

Starting to look like a real mass bench now with some serious rock in there..... Great Job Team Hokkaido!

Not sure. I’ll ask her.
Bit of cobbing around the feed tub. Lots more to do, but coming along...

Will keep you posted.

Team Rockaido🏔🔥🏔

So we are spending a bit of time with our heater these days. Temperatures outside have fluctuated a bit and we are up and down from +12°C to -5°C.
The bench is massed more or less. Have about 5cm, Matt's suggestion to start, on the top of the half barrels and a lot on the back side of the bench. Its a bit of a dusty mess, but I think I'll leave it like this for a few more days to let it dry more and evaluate the heat. It is starting to keep the room warmer for longer even after the fire goes out, but when we get up in the morning at around 5am the bench is cold again. First part of the bench closest to the burn barrel gets pretty hot if you sit on it for any extended period of time even with a quilted blanket folded over 4 times. Probably add a bit more to the mass there. Mass area near the wall never really gets warm at all. The whole of the bench is made of only dense large rocks and a minimal amount of clay and smaller rocks to hold it together. Will keep evaluating and sharing. Really impressed with the rocket aspect of the system. Really strong drag always and no smoke. Not so much with the mass storage yet, but still too early to tell. Want to remain optimistic.

Burned some kindling, I got from the neighbor yesterday, that has been seasoned for 10+ years. Dry as a bone and super light. Went up like matches in the feed tube. With in 3 minutes of lighting from cold the top of burn barrel was over 300°C. Wood has so much to do with performance I feel. Have only used wood and wood shavings in our stove so far, but feel that the claims that you heat your home with "twigs and berries" from your backyard seem a bit over stating the reality of it.

Update on the custom refectory bricks I made for this system. They have cured completely as far as I can tell. No further cracking and no new cracking. Using in conjunction with a P-plate made to Peter Van Den Berg's ratio specifications, for our 15cm square system. This my be helping, not sure. One modification to the custom brick configuration that I feel is worth making is making the inter-front brick in to a "T" configuration that interlocks with the two side wall bricks. This will help to eliminate a
excessive shifting durning the burn cycle. Believe the this brick wobbles back and forth a bit because it was cased thinner than a normal split brick, to maintain the same thickness as the CFB (ceramic fiber board) I'm using. (2.5cm thickness) Also sure that you lose a lot of insulation in these thinly cast bricks, but you can make up for that by adding additional layers of CFB off-cuts and perlite around the basic feed tube portion of the box. (See attached drawing)

Now seeing that it wall also be necessary to deal with the finishing configuration around the lip of the feed tube. The original design has the hight of the fire bricks and secondary CFB the same. This creates a "finishing issue if you want to have access to your fire bricks later on for repair etc, without having the brake through layers of cob finish.

My solution, to this issue, is to create an additional custom castable square "O" refectory brick that will sit on top of the original course of bricks. This brick will have the same ID as the rest of the feed tube and will be slightly wider than the lower course of bricks. This will make the brick span the top seam of the lower bricks and the adjacent CFB. Once set in place, the area surrounding the brick can be filled with your choice of material, thus covering/ protecting the fragile lower layer of CFB and giving you relatively easy access to the lower course of bricks if repair is required and allow you to use prefabricated fire bricks to cover the feed tube air tight. (See attached drawing)

Will keep updating.

Staying warm and hopeful that at some point this "mass" will deliver...

Peter and crew

Hokkaido Rocketnaido,    Your documentation, recommendations and illustrations are nothing short of wonderful and making an awesome contribution to everyone to pro or beginner. There are so many details that creep up that you couldn't possibly absorb on a first go and I'm sure will keep growing as you live with it for a while. Also, you get to see firsthand how much your preliminary ideas and dreams of them change that are based on other peoples claims or selling points. Which is another reason why your posts are important to future RMH builders - you give candid results, and not claiming a go cart be a ferrari when its not. So again, thank you for that.
The P channel for me also doesn't seem to do much for the burn that I can notice (without a Testo gas analyzer) but it does protect that leading brick from damage/excess heat and is much easier to replace so that's why I use it.
I love your description "square O". At first I was like: "What the heck is that?" Pictures are worth a thousand words.....no wonder why we have them!

Keep warm, Keep happy and keep updating!   ... (a pleasant picture to end on )

Gerry Parent wrote: Hokkaido Rocketnaido,    Your documentation, recommendations and illustrations are nothing short of wonderful and making an awesome contribution to everyone to pro or beginner. There are so many details that creep up that you couldn't possibly absorb on a first go and I'm sure will keep growing as you live with it for a while. Also, you get to see firsthand how much your preliminary ideas and dreams of them change that are based on other peoples claims or selling points. Which is another reason why your posts are important to future RMH builders - you give candid results, and not claiming a go cart be a ferrari when its not. So again, thank you for that.
The P channel for me also doesn't seem to do much for the burn that I can notice (without a Testo gas analyzer) but it does protect that leading brick from damage/excess heat and is much easier to replace so that's why I use it.
I love your description "square O". At first I was like: "What the heck is that?" Pictures are worth a thousand words.....no wonder why we have them!

Keep warm, Keep happy and keep updating!   ... (a pleasant picture to end on )

Yeah totally Gerry!

Just here to document and share our experience so that everyone wins. If you’re the only one at the party having fun then it’s not really a party.
Glad you enjoy the drawings. Just some quick fun sketches to illustrate some points that are often difficult to convey clearly in words.

I’m still convinced that I’ve under insulated the floor of my half barrel bench area. There’s probably about 4”/10cm of perlite and clay, but it might be a bit too clay heavy. Under that is about 15cm/12in of packed road base, then the perlite/charcoal insulated earth bag layer. Maybe just second guessing myself. Really need to wait for the mass to “stabilize” before we can draw any real conclusion. At this point just wish I had laid down a solid foot of packed perlite and super insulated under the half barrel bench, just for peace of mind. Would have cost nothing in perlite and no extra time really.

Really only using the heater to heat the space right now. Just dry all the rocks and dirt. Should get a layer of something on it soon so we can have a working bench/bed to document and evaluate. One things for sure, the locals are in ah of the thing. Can’t stop commenting on how amazing the draw from the flue is and most can’t understand the fact that there’s no smoke. I told them it’s sorcery and witchcraft...✌️🌞✌️

Will keep updating this thread and have a few other areas I’m beginning to consider as additional thread material. Things I don’t understand yet and that would be good to cover more clearly in the near future.

You mentioned wheat paste in another thread as a finish. Still debating what to do and this years version of the RMH might get a new insulated floor in the spring. With that in mind, what would you suggest as a “working finish” for our bucket of rocket?

Thanks again for all the support... Peter and crew

Hi Peter;
My mass although larger than yours. Literally took weeks to dry out and heat the far end of the bench.
It was solid rock and clay no 1/2 barrels.
Great Job !  Looking good!