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james manning
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How's this coming? I've heard mention of it on the podcast and was wondering what the difficulty is... Is it scale? If there were enough interest we could have saint gobain make a custom SiC core about a 3/8 inch thick that could then be insulated with ceramic fiber wool... The SiC is expensive (relatively) but is specifically made for extreme heat (its strongest over 2200 f), thermal shock, and corrosion. The fiber is the best insulator you can buy for these temps. The whole thing should be less than 25lbs and should last for years.
 
Brian James
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I'm working with a company that makes vacuum formed ceramic fiber shapes to have a one piece rocket stove core produced. I already got them to make ceramic fiber risers (the thread is https://permies.com/t/53413/Inexpensive-vacuum-formed-ceramic-fiber .)

It will be made of 2600• F ceramic fiber with rigidizer where necessary and the firebox will be lined with split thickness fire brick. The tooling, molds and minimum orders cost multiple thousands up front, so I'm launching a Kickstarter campaign next month to hopefully finance it. We have a very successful prototype and the 3D CAD drawing of the core is being submitted to the ceramics manufacturer next week.

Keep your fingers crossed, and if you're the praying type, please offer some prayers that this succeeds.

I lost my entire business as well as my home due to 4 strokes in 2016 but I've had a remarkable recovery and spent my time for the last year designing this core and building prototypes as my own personal "rehab." I'm literally, desperately depending on this effort succeeding.
 
james manning
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Hey Brian, I hope that works. There is a castable version of IFB (soft brick refractory) called Greenlite (they have different grades, the increasing number corresponds to tougher stuff) A monolithic interior should last longer and ship easier. I do wonder if this may end up being a more cost effective version than the Silicon Carbide? The advantage of the SiC is that is non-porous and more resistant as a whole to the erosion/abrasion of combustion gasses in regards to the flow (think wind erosion) and chemical attack (wood ash has a high alkali/alkaline content). When do you expect a prototype? I work with a company out of the Boston area that has a fast turnaround time... Have you thought about building it outside and running it nonstop (sleep depending) in order to ascertain lifecycle? A shared google sheet with all owners could allow an aggregation of data (spall, hot face wear, cracking) to be tracked over time to factor in the price of the riser vs life and factor that into the overall efficacy... How much does one cost?

Regards, James
 
Brian James
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james manning wrote:Hey Brian, I hope that works. There is a castable version of IFB (soft brick refractory) called Greenlite (they have different grades, the increasing number corresponds to tougher stuff) A monolithic interior should last longer and ship easier. I do wonder if this may end up being a more cost effective version than the Silicon Carbide? The advantage of the SiC is that is non-porous and more resistant as a whole to the erosion/abrasion of combustion gasses in regards to the flow (think wind erosion) and chemical attack (wood ash has a high alkali/alkaline content). When do you expect a prototype? I work with a company out of the Boston area that has a fast turnaround time... Have you thought about building it outside and running it nonstop (sleep depending) in order to ascertain lifecycle? A shared google sheet with all owners could allow an aggregation of data (spall, hot face wear, cracking) to be tracked over time to factor in the price of the riser vs life and factor that into the overall efficacy... How much does one cost?

Regards, James

Hi James,
I'm currently working with a local company I dealt with before for vacuum formed ceramic fiber risers. These risers and their ceramic fiber board insulation hold up well enough when directly exposed to the flames and temps of a rocket stove core that I'm not too concerned about erosion due to combustion gases. I could be wrong but the leaders in this field have been using ceramic risers successfully for years.

I would be happy to submit the 3D drawing to the Boston firm to get another set of estimates. I do NOT know the per unit or tooling/molding costs yet.
 
J.D. Ray
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I designed a two-piece core that's meant to be castable.  If the single-piece core thing turns out to be too expensive, perhaps a two-piece would be less so, even if an extra mold is needed.  I had an idea that I could turn my design into a cottage business, but the reality is that I have too many things on my plate to get there.  So PM me if you're interested in what I've got.
 
james manning
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I don't think think the expense is in the casting. There shouldn't be any reason why the draft angles to make it in one or two pieces would get in the way. It's really about spreading the cost of setup, design, and tooling over enough units to bring that cost down. Additionally, my thoughts for SiC were that people use it in wood fired kilns over 2600 f for decades and they're still serviceable. That's why I'm curious to track life vs cost/ energy required to fabricate. My thoughts are that a SiC core insulated with ceramic fiber would out last an IFB core by an order of magnitude of thousands... My basis for this is that no one uses soft brick in anything wood-fired because the alkalis degrade it very quickly (wood firings typically go to over 2500 f and will stay there while accumulating caustic ash deposits for hours) while SiC lasts in these conditions for decades. That being said, if the short run time of a rocket stove limits exposure at temps that melt ash maybe it's not an issue, but then wouldn't said ash be a particulate concern?
 
Brian James
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Thanks JD. I looked at a two piece core, to make assembly easier, but then I would have had to pay for two sets of tooling and molds instead of one and had a shiplap where the two halves meet so it would seal well, once again raising costs.

So we've settled on a design that only uses one piece for the walls and roof. The floor will be separate and simply made out of ceramic fiber board insulation.
 
Brian James
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james manning wrote:I don't think think the expense is in the casting. There shouldn't be any reason why the draft angles to make it in one or two pieces would get in the way. It's really about spreading the cost of setup, design, and tooling over enough units to bring that cost down. Additionally, my thoughts for SiC were that people use it in wood fired kilns over 2600 f for decades and they're still serviceable. That's why I'm curious to track life vs cost/ energy required to fabricate. My thoughts are that a SiC core insulated with ceramic fiber would out last an IFB core by an order of magnitude of thousands... My basis for this is that no one uses soft brick in anything wood-fired because the alkalis degrade it very quickly (wood firings typically go to over 2500 f and will stay there while accumulating caustic ash deposits for hours) while SiC lasts in these conditions for decades. That being said, if the short run time of a rocket stove limits exposure at temps that melt ash maybe it's not an issue, but then wouldn't said ash be a particulate concern?

There is a high rate and temp of gas flow and turbulence in a properly functioning and insulated rocket stove that leads to complete combustion of volatiles and particulates. The ash content left behind is a comparatively small amount, and I doubt the ash content in the rapid  gas flow itself is enough to be concerned about during the relatively short (compared to a kiln) burns.
 
james manning
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Brian,

I hope you're right! I don't mean to sound like a negative nancy... I've just worked with these refractories for years, please note I'm not saying an IFB/ fiber core won't work (they're great insulators) rather I'm just curious as to the lifespan vs the cost of an IFB/ fiber core vs the lifespan vs cost of an SiC/ fiber core. For shits and giggles I've fired a soft brick next to a hard brick in a wood kiln a few years back... the soft brick eroded by half its volume in one firing, while the hard brick was slightly bigger from an accumulation of melted ash without having worn away or eroded. I am still interested in this project though and would be interested in helping track the life cycle and total run hours of any configuration as I believe that we will do more with data to push UL standards and bring this tech into the mainstream.

P.s. have you checked out Kacheloffens/ Masonry stoves? They seem like the big brother to rocket mass heaters but prettier!

P.P.s if the cost is less than 50 bucks count me in on your project.
 
Brian James
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james manning wrote:
P.P.s if the cost is less than 50 bucks count me in on your project.

LOL!

If the cost was less than $50 someone would have already done this!

(The only reason I was able to source the vacuum formed ceramic fiber risers so cheap is because when they gave me a formal cost per unit, they forget to add the tooling/molding set up costs and I had already placed the order when they realized their mistake. That mistake cost them a good bit but they honored their offer and it's the only reason I've been able to continue experimenting and get to this point. If I had had to pay the initial costs for the tooling and mold for the ceramic riser up front I couldn't have afforded it and none of this would have happened.)
 
Thyri Gullinvargr
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You mentioned something about doing a Kickstarter for this, if that paid for the tooling and mold how much would each core be? Do you know yet?
 
Brian James
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Thyri Gullinvargr wrote:You mentioned something about doing a Kickstarter for this, if that paid for the tooling and mold how much would each core be? Do you know yet?


No idea yet. A Kickstarter campaign, to the best of my knowledge, will help cover the startup costs for tooling/mold fees to go into production, but usually there are "incentives" that an "investor" expects in return for their investment, and there are numerous other costs to trying to start a business from scratch. Bottom line? Per unit costs for each core still have to cover the initial tooling/mold costs to make this endeavor financially feasible. The Kickstarter simply provides start up capital without which the business couldn't get off the ground in the first place. (Of course I'm relatively new to this concept, and if I'm in error, I would invite and appreciate constructive criticism.)
 
Thyri Gullinvargr
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It depends. Paul just ran a Kickstarter that was something like 1400% funded (goal was something like $6000 and final amount was over $80,000). A bunch of that went towards stretch goals, but I think that's because the whole point of the Kickstarter was to give people something they were asking for. You might find the Kickstarter podcasts he did after useful.

Part 1: https://permies.com/t/65954/kickstarter-part
Part 2: https://permies.com/t/65976/kickstarter-part
Part 3: https://permies.com/t/65992/kickstarter-part

The thing is is that if it's for something people really want and they know about the kickstarter you may get than you're expecting. It could go anywhere from not getting funded to getting funded much more than you thought you would.
 
Brian James
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Thyri Gullinvargr wrote:It depends. Paul just ran a Kickstarter that was something like 1400% funded (goal was something like $6000 and final amount was over $80,000). A bunch of that went towards stretch goals, but I think that's because the whole point of the Kickstarter was to give people something they were asking for. You might find the Kickstarter podcasts he did after useful.

Part 1: https://permies.com/t/65954/kickstarter-part
Part 2: https://permies.com/t/65976/kickstarter-part
Part 3: https://permies.com/t/65992/kickstarter-part

The thing is is that if it's for something people really want and they know about the kickstarter you may get more than you're expecting. It could go anywhere from not getting funded to getting funded much more than you thought you would.


Thanks! I guarantee that if I get results even a fraction like that, any "extra" money raised will go towards making the rocket heater core more affordable. On the other hand, when I organized the group buy here for the vacuum formed ceramic fiber risers (https://permies.com/t/53413/Inexpensive-vacuum-formed-ceramic-fiber ), the price of the risers was ridiculously low, a fraction of that for any available similar product and often considerably less that the cost of packaging and shipping. Frankly I lost money on that group buy. But I needed others to join in because I needed to meet their minimum purchase point and wanted to create a reasonably priced source for these (the company said they've subsequently sold a number of these based on the info I posted on that thread), experiment with them myself, and I was employed full time otherwise.

Now I do need this to be "successful" from a business perspective. I don't want to get rich doing this, I just dream of it to being the backbone of what I hope will become a full time rocket heater supply company online. Even if I'm the only employee,
 
Brian James
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james manning wrote:I'm just curious as to the lifespan vs the cost of an IFB/ fiber core vs the lifespan vs cost of an SiC/ fiber core. For shits and giggles I've fired a soft brick next to a hard brick in a wood kiln a few years back... the soft brick eroded by half its volume in one firing, while the hard brick was slightly bigger from an accumulation of melted ash without having worn away or eroded. I am still interested in this project though and would be interested in helping track the life cycle and total run hours of any configuration as I believe that we will do more with data to push UL standards and bring this tech into the mainstream.

The experts have been using vacuum formed ceramic fiber risers in their rocket mass heaters for several years with good results. Apparently they are holding up satisfactorily. More on the thread at Donkeys forum: http://donkey32.proboards.com/post/20469/thread
 
Dina Herrington
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Is it too late to get in on the group purchase? My only concern would be shipping to AZ
Thanks
 
Brian James
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Dina Herrington wrote:Is it too late to get in on the group purchase? My only concern would be shipping to AZ
Thanks

I assume you're referring to the risers? Unfortunately this group buy was about 1.5 years ago. I don't currently have any extras but they'll be available once again when I get the vacuum formed ceramic fiber shippable cores in a couple months as the cores still require a segment of these risers. The price per riser will go up some because it's no longer a group buy but an attempt to start a small business as a rocket stove supply company online. I want to be honest here; I did the group buy in the past when I was still working but now I'm unemployed due to a recent serious illness. My health has returned but I can't afford to do a group buy anymore.
 
J.D. Ray
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More power to you, and good luck.

I'm very interested in buying a well-made ceramic core so long as it doesn't cost a huge amount of money.  I have no idea what your expected production costs are, but (for me) two or three hundred bucks for a core and riser seems about the upper limit of what I could justify.  The $36 riser linked above in the group-buy situation seemed almost inordinately cheap; I'd happily pay double that for a riser.

Cheers.

JD
 
Brian James
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J.D. Ray wrote:More power to you, and good luck.

I'm very interested in buying a well-made ceramic core so long as it doesn't cost a huge amount of money.  I have no idea what your expected production costs are, but (for me) two or three hundred bucks for a core and riser seems about the upper limit of what I could justify.  The $36 riser linked above in the group-buy situation seemed almost inordinately cheap; I'd happily pay double that for a riser.

Cheers.

JD

Thanks. When people see how simple we've designed and made it to have a full power, incredibly well insulated and light weight 6" rocket stove heater with this core, I expect it to be somewhat popular. It's a rather unique design, that most people who are somewhat handy can assemble in a day or two.

I'm registered for the Innovators Part II of Paul's Rocket Stove Jamboree and Paul invited me to assemble one and run it while I'm there. It will be a good test of whether it's actually "shippable" because I'm going to have to ship the prototype core out to him, fly out, and assemble it on site. Hopefully someone there will have a Testo and will let me use it to test emissions while I'm there.

But it's something that no one has tried before to our knowledge. It will make the rocket stove technology attainable for a lot more people.

Of course it's going to be marketed as a back yard/deck/patio/ice fishing hut/hunting tent and greenhouse/shed rocket stove heater/cooker/pizza oven/regular oven kit, but folks will be free to experiment with it once they see it however they want. And I suspect they'll really want to

By marketing it to this wider market we hope to bring the awareness of rocket stove technology to the general public, and eventually finance a home wood stove rocket heater model based on this core that can be UL certified.

(At least all that is the ad copy I'm writing in my head for the Kickstarter campaign...it's all well grounded and absolutely factual, but it's still vapor ware unless this Kickstarter is successful.)
 
J.D. Ray
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Put as much as you can into video production. Hire a professional; they're worth every penny.  And again, good luck.  If there's anything on the analytic or technology front I can help with, PM me.  Also, I do pretty well with SketchUp.

JD
 
Brian James
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J.D. Ray wrote:Put as much as you can into video production. Hire a professional; they're worth every penny.  And again, good luck.  If there's anything on the analytic or technology front I can help with, PM me.  Also, I do pretty well with SketchUp.

JD

Thanks!

A close friend does all the professional video production for a good sized website, is very familiar with Kickstarter, and is doing this for me as his contribution to the Kickstarter campaign. I do a little journalism on the side and I've been published internationally, so writing the script won't be too hard - if I can remember to "Keep it simple/short, stupid."
 
Brian James
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J.D. Ray wrote:Also, I do pretty well with SketchUp.

JD

Thanks for the offer. A friend, a retired engineer, is making a fairly detailed 3D drawing of the core on AutoCAD. Can Sketch-Up be used to view and manipulate AutoCAD files? I know the good folks at the Donkey rocket stove forum seem to prefer SketchUp. I might need it converted eventually. I'm pretty good with full scale paper and pencil drawings, but I've needed help making the 3D CAD versions.
 
J.D. Ray
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Importing AutoCAD files into SketchUp requires SketchUp Pro.  The good news is that Pro has a trial version that works for (I think) 30 days.  After that, you're relegated to Make, the free version.  The good news is that SketchUp Make is a very capable piece of software.

https://help.sketchup.com/en/article/3000165
 
Brian James
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Good news - the technical 2D and AutoCAD 3D drawings are done and going out to manufacturers for estimates tomorrow.

I downloaded FreeCAD software and was able to view the 3D drawings with that.
 
Brian James
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I posted a brief update on our progress at https://permies.com/t/69539/Shippable-cores-progress-report
 
Matt Walker
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James, I launched my shippable core yesterday.  I put an intro post in the RMH forum, it's here:

https://permies.com/t/69535/Walker-Stoves-Super-Hot-Shippable

 
Brian James
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Matt Walker wrote:James, I launched my shippable core yesterday.  I put an intro post in the RMH forum, it's here:

https://permies.com/t/69535/Walker-Stoves-Super-Hot-Shippable


Excellent Matt, congratulations!!

I've been inspired by your leadership and developments and while I'm a nobody in this field, I feel like I can heartily recommend your shippable core!
 
Brian James
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Brian James wrote:I posted a brief update on our progress at https://permies.com/t/69539/Shippable-cores-progress-report


I have another update posted on that thread with a good bit more info.
 
Brian James
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Progress
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Brian James
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Almost finished.
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Brian James
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Three hours into first burn:

 
Brian James
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I’ve been traveling and just got a chance to run another batch of the compressed sawdust fire bricks tonight. I lit it around 6:45. Barrel top temps were as follows. Firebox door was open about a half inch. It gets too hot too fast that way!
7:20 575•F
7:30 930•F
Closed firebox door
7:33 853•F

I wanted to see how hot the pizza oven would get so I placed insulation blocks to block the pizza oven door:
7:32 450•F (firebox door closed)
8:02 640•F (cracked firebox door approx 3/8” open)
8:07 700•F

At this point I figured I better check the barrel top temps, and it was over 1000•F on the laser thermometer and starting to glow red around the bases of the firebrick in the pizza oven, so I closed the firebox door and removed the insulation from the pizza oven doorway to let everything cool down.

Barrel top temps
8:16 960•F
8:24 812•F (closed air)
8:31 733•F
 
Brian James
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And at 10:45, four hours after starting this batch, barrel top temp is 445•F. It looks like there’s enough wood left in the firebox to burn another 1 to 1 1/2 hours, but I’m hitting the sack.

Edit to add:

Curiosity got the best of me, so I stayed up to check it at 11:45, five hours since lighting this batch. Barrel top temp was 340*F and there’s still enough fuel for about another hour in the firebox.
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