Advice on a RMH build in Hokkaido Japan

I didn't bother to mention the p-channel, which should be a part of every J-tube build. It can be extremely simple and cheap as described here, or it can be a full steel feed shroud that preheats secondary air while cooling the top of the feed like the one I made.

Glenn Herbert wrote:I didn't bother to mention the p-channel, which should be a part of every J-tube build. It can be extremely simple and cheap as described here, or it can be a full steel feed shroud that preheats secondary air while cooling the top of the feed like the one I made.

Great thanks.

So it can just be cut in a “T” shape to the dimensions of the diameter of the feed tube, in my case 15cm? Then weld small nibs to one side to keep it from being pushed against the fire brick at the front of the feed correct?

Thinking of pouring custom bricks for this rather than getting them cut. Cost of refractory castable cement is probably about the same as getting the bricks cut. Any suggestions on minimum temperature tolerance for the castable cement. My CFB is rated for 1400 Celsius. Was planing to use that as a bench mark. Also any recipe suggestions? Cement to perlite ratios etc.
I’ll use a Reciprocating saw without the blade to vibrate the air out of the molds. Any other tips or tricks? Mold release? Cure time before burning?

Any insight would be much appreciated.

Thanks Peter

One more thing. Matt has given me the green light on my custom 15cm J-tube core design. Would just like to confirm with the rest of the Jedi Council that I’m not headed down a dark path with this one. Bit nervous before the big exam I guess, especially because these boards are $75 a pop with a minimum order of 4.

Please advise. Thanks Peter

The simple P-channel plate can just be cut 3/8" wider on both sides, and bent toward the burn tunnel to keep the plate the right distance away. I have heard about people making the bent tabs a bit oversize from the recommended, and trimming them down bit by bit until the fire hits a sweet spot...

Glenn Herbert wrote:The simple P-channel plate can just be cut 3/8" wider on both sides, and bent toward the burn tunnel to keep the plate the right distance away. I have heard about people making the bent tabs a bit oversize from the recommended, and trimming them down bit by bit until the fire hits a sweet spot...

Thanks Glenn,

Not sure I can exactly visualize what you’re describing, but this is what I gather as the general idea.

Peter

Peter,   That's it....or could be it... What Glenn was saying about the tabs you can see more clearly in these photos.
Sorry, don't have any cutting experience with CFB but I can say "May the Cutting Force Be With You!"

Came to this post because of the Japan tie in. Oh how I miss it. Also very smart of you to put your chimney out through the roof. We spent many winters at a farm house in Aomori where a lot of the rooms could not have their kerosene heaters turned on because the exhaust tube was completely covered in snow. You certainly want the exhaust tube far up enough that it's not going to be covered and kill ya.

It's a beautiful country. I loved it there. Steeped in tradition, which is both it's magic and downfall I would think. To go outside of the norms makes you an oddball for sure. Love watching your progress!

Super easy to understand. Thanks Gerry. Just out getting a few last bits. Will get into the core and casting bricks later tonight or tomorrow...

Cheers Peter

Hey Elle thanks for saying hi.

Yeah it’s a wonderful and nerve racking place at the same time. But to be honest when we’re at the house with no one else we could be anywhere in the world. Plus the people of Hokkaido are a bit more laid back than the main island for sure.

Making a custom welded chimney box to put on the highest point of the highest roof with a big metal “H” cap. Hopefully that can handle the Hokkaido winter. We will soon see.

If your ever in Hokkaido stop by. Welcome to pitch a tent and hang out. We’ve got a mountain and 13.5 acres, so plenty of room. 5 minutes from the ocean.

Every season is absolutely amazing.

Keep the dream alive, Peter and team

Thought I’d share how I cut my half barrels for the stratification bench. Took me a minute to come up with but think this works , is pretty accurate, and leaves you with half barrels that sit flat on the ground.

First find the diameter of the circle on the inside lip of your drum.

Draw a perfect square on a large piece of paper with that diameter.
Draw lines from each corner of the square to find the center. Then use a wire with a thumb tack and a pencil/pen as a compass to draw your circle. Good to put a piece of cardboard under the paper so the thumb tack has something to push into.

This gives you the inside circle of your barrel. Cut out the circle from the paper and fold in half. Take the paper and line it up with the straight edge of a piece of plywood/something. Trace the edge of your circle onto the plywood. Then cutout. I used a reciprocating saw cause that’s what I had, but I’m sure a jigsaw or router would give a cleaner cut. Make it as clean as you need to fit snug in the lip on either side of the barrels you want to cut.

Next bang out any dents in the rims of your barrels and try to make them as true to round as possible.

Then set you wooden half circle template along the inside rim of your barrel so that the corner of the half circle lines up with the factory weld seam on the side of the barrel. Use your template to mark the center of the barrel across the top and mark the other corner of you template on the lip of the barrel. I used builders chalk.

Now repeat the process on the other face of your barrel using the same factory weld seam as your corner reference again.

Now use a long straight edge to draw a line connecting the two points you marked on you lip.
This will give you a pretty accurate reference line that will run parallel to your factory weld seam on the other side of your barrel.

Then just cut along the line all the way around with a cutting torch or grinder. The torch leaves you with a rough edge that I think may hold stronger in a cob footing.

Now you can use the template on endless barrels! Happy days and happy cutting...✌️🌞✌️

Wow! That's quite the process you have. Glad it worked out for you and thank you for your detailed documentation for others.
Love the "Burn Bitch" sign... :)

Since you've already dug up the floor, it may be not too late to consider sub floor heater rather than stratification benches.



Maybe Erica can tell us how it worked out ...

Graham Chiu wrote:Since you've already dug up the floor, it may be not too late to consider sub floor heater rather than stratification benches.

Maybe Erica can tell us how it worked out ...

Thanks for that Graham.

Had a look. Might have to happen a bit down the road, but will keep it in mind for sure. We are coming up on cold quick and we need to get this thing running. Will see how the stove works as a bench and take it from there.

Cheers, Peter

Gerry Parent wrote:Wow! That's quite the process you have. Glad it worked out for you and thank you for your detailed documentation for others.
Love the "Burn Bitch" sign... :)

Sure there are other ways to go about it, but always fun to share the thought process. Learning day by day.

Keep you posted... Peter

Here's where we are with the room. Working out these molds for the custom refractory bricks right now.

Peter

So here’s where we’re at with the homemade refractory bricks. Molds took a long time to make. I definitely Improved my lap jointing technique with hand tools and a circular saw. Also know that if you want to make decent molds in an reasonable amount of time you kinda need a table saw. Two days and three nervous breakdowns later we have something. Plan to leave the bricks in the molds for at least 24-48 hours. Then let them cure for another day or so. The refractory cement I used is good to 1400C and says it doesn’t need heat curing. Vibrated with a reciprocating saw for a good 20 minutes each until I didn’t see any more air bubbles coming out. Hope we don’t get cracks or an explosion. Anyone have any experience with these castables? Will build the core as soon as the bricks are good. Here are some images of my process. Made sure everything was square and all the surfaces were sealed with beeswax and vasaline. They are mounted on board with a layer of drawing paper and wax paper to give a flat surface and then leveled in place with a torpedo level.

Let me know if anything looks suspect.

Cheers, Peter

Nice moulds, did you add the directed amount of water to the refractory cement ?
I say that as you mention vibrating for 20 minutes... it is normally mixed very dry and sets in around 10 15 minutes.

Fox James wrote:Nice moulds, did you add the directed amount of water to the refractory cement ?
I say that as you mention vibrating for 20 minutes... it is normally mixed very dry and sets in around 10 15 minutes.

Hey James,

Yeah, followed the directions of the manufacture. Said the working time is between 30-45 minutes and doesn’t need heat curing. They also said to mix a bit wetter if casting as apposed to mortaring. At first a bit of water pooled on the surface when I vibrated, but that soon evaporated. Covered with plastic over night in an un-heated room. Never went below zero. Remisted in the morning. Still have plastic on now.

There are three sets of molds. Each one was mixed and cast separately, one at a time to makes sure each one got my full attention throughout the casting process.

1. One set for the back panel and bottom same dimensions
2. One set for the sides same dimensions with notch cut out for top front brick.
3. Top front brick.

I made a mistake and made the first set 2.5cm taller than originally planned, so just made all the feed tube bricks 2.5cm taller. Still shorter than the length suggested in the guide, but a bit taller than Matt’s PDF plans. Figured it was meant to be. Also gives the front brick a bit more volume and body to withstand heat. Either way will make a P plate soon to recommend specs.

Sure I was probably a bit to anal with the molds, but figured it was worth it, if the dimensions work well I will easily be able to duplicate for other builds or in case one needs replacement.

Mimi threw the excess cement, that was left in the mixing bucket at the end of the last cast, in some aluminum pie tins just for fun. They popped out of the molds a few hours ago. Easy release with no grease or mold release. No dusting or caulking. Bit of spider webbing on the mold side faces, but they hardly got the attention of the hero bricks. Any idea what would cause this?

Peter

Photos of test...✌️🧘🏽‍♀️✌️

So got a bit excited and took a few out of the molds now. Bit tight on the mold release. Need more “lube” if I cast again for sure. Overall intact. Baking sheet was a bad idea. Bunched up and went a bit wavy gravy on us. Cool for the top block if run upside down as an esthetic, but back of the side blocks are pretty extreme. Also small bubbles in places on sides and a bit of sediment separation on bottom of top block.

Multiple Choice Questionnaire:
1. Should I try to skim coat the backs?
2. Recast?
3. Leave as is and continue building?

Let me know your thoughts as this is the first time I’ve cast refractory cement blocks. Any advice is much appreciated and want to avoid doing anything dangerous that could have been easily avoided.

Thanks in advance, Peter

Don’t know if it’ll work, but it looks pretty cool. Thanks middle school geometry...
✌️🙏🏼✌️

I would choose answer #3. Leave as is and continue building. Seeing as its all an experiment anyway, your looking at function over fashion. No sense in re-making the perfect block only to find out it majorly cracks or falls apart similar to Erica's shippable cast core that went temporarily into the tipi at Wheaton Labs. I don't think its like a pottery cup that can explode in the kiln if there are any air bubbles in it. Just for safety though, maybe wear a football helment when you fire it up?

A few links that might have some useful info:
castable-burn-chamber
Rocket-mass-heater-tube-bell

Thanks Gerry!
Something like this?
💣🧘🏽‍♀️💣

Here’s a quick look at our earth bagging system. Used Japanese military flood bags for the whole thing. Pretty cheap on the net and think black will look good in our bunker style sunken room.
First course is filled with large road base and a bit of cement to stabilize. Second and third course are split bags. Hand sewn using heavy duty nylon kite string, also black to match the bags. One half is filled with perlite pellet and clay soil mix for insulation. Other half is filled with smaller sifted road base. Added barbed wire between all courses. Probably didn’t need cause it’s not very high or overly load baring, but added just for good measure. Corners were keyed like finger joints to avoid insulation gaps. Plan to put cob on top that will transition into the floor.

Most likely will only be able to get the cob on the bags and tamped road base this season. Getting colder each day. Finish floor in spring. Puppy’s think the room is outside and have a tendency to dig holes and poo poo etc in the room if they get the chance. With that in mind, might it be a good idea to use a small amount of cement in the road base layer before tamping to create a “soil cement” working floor that is puppy proof? Area under fire box and half drums will be clay and perlite. No cement. Is there a recommendation on perlite to clay ratio for this type of application?

Peter  

P.S. Matt said not to be overly concerned about the cob on the barrel being hot on top. No need to insulate. Heat distributions works itself out naturally.

Peter Sedgwick wrote: Area under fire box and half drums will be clay and perlite. No cement. Is there a recommendation on perlite to clay ratio for this type of application?

Just saw a thread that Thomas answered that addresses your question: perlite-RMH-cob-bench
The question actually revolves around insulating under the bench but can be done too under the core. Because the core gets so much hotter than the bench does though, I would be more inclined to want to use the perlite instead. If you do go with the perlite, I would think a similar amount of clay would be used as the same rule applies: The more clay, the less insulative the perlite becomes.

The helmet is perfect, just make sure you get one for Mimi, Chimi &Changa too!

Thanks Gerry. I’ll check that out. Matt says you don’t need any more insulation if you use the ceramics fiber board, but it doesn’t hurt to have more.

Just put the chimney box on the roof and sealed. Now will work backwards through the ceiling to get it into the room. Once in place with the 15cm pipe, covered in the 20cm pipe from the 2nd floor up, I’ll back fill the cavity between the two pipes with perlite to insulate.

Recheck my numbers and cut the core now.

Helmets in the mail... cheers, Peter

Here’s a few shots I took of the firebox as I pieced it together yesterday. Nothing is pinned yet. Just wanted to see if all the parts fit together and the math worked out. It came out clean with 15cm square internal dimensions through out.  Will leave like this, with bricks holding the sides on, when we test fire in the front yard tomorrow morning.

Also will do a follow up on our build process and how we handled the ceramic fiber board in a future post. Not much else I can say as of yet, being a first time builder, who has never lunched a rocket into space.

Will share more as it comes…

Galaxy out, Peter

Awesome work Peter!   Looking good.

Are you planning to use a peter channel in the feed tube ?
How about a trip wire in the burn tunnel roof ?

Your chimney cap is a style I've never seen before. Is it a common cap in your area ?

Please keep up the great coverage of your build it helps inspire other first time builders!

Second the motion! Nice to see it all coming together after all the virtual planning. Just let me know what time (-/+ 12 hour time zone difference) so that I can get my binoculars ready to watch the launch!

thomas rubino wrote:Awesome work Peter!   Looking good.

Are you planning to use a peter channel in the feed tube ?
How about a trip wire in the burn tunnel roof ?

Your chimney cap is a style I've never seen before. Is it a common cap in your area ?

Please keep up the great coverage of your build it helps inspire other first time builders!

Hey Thomas,

Thanks. Yeah Making a P-Channel now. The only way I could see a tripwire working in my CFB fire box is by somehow making a welded extension arm off the p-channel at the bottom.
Does this make sense or is there an easier way to do it that I haven't come across? (Drawing attached for clarification of whats in my head)

The "H" style cap is standard issue here in Hokkaido. Almost every house has some form of one sticking out the wall. They rarely use the roof for some reason.

Will do my best to document and share our build and findings.

Thanks so much for the support... Peter and crew

Gerry Parent wrote:Second the motion! Nice to see it all coming together after all the virtual planning. Just let me know what time (-/+ 12 hour time zone difference) so that I can get my binoculars ready to watch the launch!

We have liftoff captain. I repeat Elvis is in the building...:)

We believe the future burns sideways.

Here are some shots of todays test burn.
Everything except the heat riser held together with gravity. Thing started up without any real issue.
A bit of newspaper and some dry chainsaw shavings to get the party going. Used a rusty rod to hold the wood back and keep the airflow up.
Few small cracks in the bricks, but thats probable because we had a ragging fire inside for 3.5 hours straight. Took temp readings on inside and out.
My cheap point and shoot doesn't register over 592°C so it maxed out. CFB was so cool on the heat riser mid burn that a local spider decided to take a walk.

I feel pretty good with the results so far. Please have a look and let me know what you think and if you have any suggestions or see any red flags.

* Won't have big sticks coming out of the feed tub when we install and burn inside the house...:)

Cheers, Peter

You should really of done a few curing fires if you did not want any cracks in the cast slabs.
There will be moister trapped in the refectory cement and if that is turned into steam it will force its way out one way  or another.

Photos of burn:)

Few more photos

One more thing. Looks like a bit of mold in the cob we put down last week. Some sawdust, and probably some ceramic fiber board dust too, but pretty sure there is a bit of mold on the rice straw. Do we leave and keep building, let the heat from the RMH kill it all later or do we have a larger issue at hand?

Please advise...Peter ✌️🙏🏼✌️

Peter Sedgwick wrote:Thanks. Yeah Making a P-Channel now. The only way I could see a tripwire working in my CFB fire box is by somehow making a welded extension arm off the p-channel at the bottom.Does this make sense or is there an easier way to do it that I haven't come across? (Drawing attached for clarification of whats in my head)

Well, as you may know, the tripwire looks like the picture below, spanning the entire width of the top of the burn tunnel, so your picture wouldn't have the same effect that was intended. At this point in time though, I would say just get your system in and running to keep Mimi and the boys warm. You'll have plenty of time to make modifications like this later when the snow starts to fly.

Peter Sedgwick wrote:One more thing. Looks like a bit of mold in the cob we put down last week. Some sawdust, and probably some ceramic fiber board dust too, but pretty sure there is a bit of mold on the rice straw. Do we leave and keep building, let the heat from the RMH kill it all later or do we have a larger issue at hand?
Please advise...Peter ✌️🙏🏼✌️

A small amount of mold is common particularly when the temperature in the room is cool and the organic material is still wet/damp. This will go away when these conditions are eliminated but if you are sensitive to it then I guess you could spray something non toxic on it to control the mold. There are posts I've seen with recipes for natural and inexpensive mold sprays you can use.
Mostly though, I would say this is a sign and a good incentive to keep moving with getting your dragon inside so it can lower the humidity of the room and dry out your cob.
Love all your photos! Look forward to them and your discoveries every day!

Gerry Parent wrote:

Peter Sedgwick wrote:Thanks. Yeah Making a P-Channel now. The only way I could see a tripwire working in my CFB fire box is by somehow making a welded extension arm off the p-channel at the bottom.Does this make sense or is there an easier way to do it that I haven't come across? (Drawing attached for clarification of whats in my head)

Well, as you may know, the tripwire looks like the picture below, spanning the entire width of the top of the burn tunnel, so your picture wouldn't have the same effect that was intended. At this point in time though, I would say just get your system in and running to keep Mimi and the boys warm. You'll have plenty of time to make modifications like this later when the snow starts to fly.

Thanks Gerry. Yeah I didn’t know. Was only going on a few side view drawings and a quick explanation I read online from Peter I think. Good to see a real photo much easier to understand.

Will get the house warm as quick as we can. Frost on the ground in the morning now and snowing a bit up high in the mountains from time to time.

Actually it’s an all girl house except for me. Probably what makes it work. We have a new fury creature that just moved in to the attic. Not sure if it’s a boy or a girl, but time to figure out how to let them know they need to find a new home for the winter. Chimi and Changa are useless in this department...🥴

Modifications later for sure. 🤗