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Results of the 8" batch box thingy at the Innovators Gathering

 
Peter van den Berg
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Sunday morning at 11:00 am Matt Walker came up with the idea to build an 8" batch box mockup, outside the auditorium at Richsoil. Nearly everybody was working their socks off at the workshop higher up the mountain so we couldn't ask it would be allright to use the fire bricks of Ernie's 10" J-tube mockup. We tore the thing down, cleaned the bricks and I started to calculate while Matt dry stacked the bricks.

It turned out we could manage to come very close to the scaled up calculations. So after a lot of clay-and-sand mixing, laying bricks and nicking the superwool riser of the soon-to-be dismantled 8" j-tube inside the auditorium we managed to end up with a usable batch box and riser core. The thing looked huge, the first run appeared to be going very well.

After dinner we started the thing again and while it was getting dark more and more of the people gathered around the fire. Beforehand, I'd brag about the thing would growl like and angry bear while shooting one foot of flame out of the riser end. It turned out the growling sounded more like a whisper, but the promised flame was there. Well over two foot long, lasting for half an hour during the top of the burn, very impressive! Some people made pictures of that, maybe they are willing to share those here. Late that night some guys stayed around the stove and swapped the calcium-silicate top for a piece of ceramic glass. This looked fabulous, to say the least.

At Tuesday morning Jeyte, Taylor and me cleaned the bricks again and moved all the materials inside. We dismantled the remains of the J-tube there and started to dry stack the stove to a new layout with a slightly shortened firebox. Firewood at the premises were at a standard length of about 16", so a space of 18" would be sufficient. The coupling to the existing gravel bench of 30 ft threw up some difficulties too, but in the end we managed to find a solution. This figuring out lasted until dinner so the build commenced at Wednesday. In order to extract enough heat we used three 55 gallon barrels plus the existing bench. At the mean time Rick was busy building a proper chimney which happened to be in the pipeline anyway.

Thanks to Rick Edwards, Tim Barker and Tim Wheaton we managed to install a P-channel and a new piece of glass on the top of the firebox. Thanks to Ernie for the advise how to fix the barrels together and on top of the stove, Jesse and Jason to lend a hand when we needed it the most.

This is what we've been building:



For those who are interested here's the layout of the fire bricks, organised in layers.















And here's the complete layout of "the thing", the third barrel is coupled to the bench.



That 3rd barrel was later converted to a mass container in such a way that the internal surface area more or less remained the same.



This setup has been tested as well, my analizer turned out to be not happy with the first full run. The purple line is presenting the CO level which went completely haywire.



We'd figured out this was caused by burning out part of the binder in the riser duct, the refill turned out to be one of the cleanest I've ever seen.



In order to be sure this wasn't a run of 1 out of a million and repeatable I did another run with a cold start the next day.



This concluded it, this thing is really something. Several times when run the circle of people around it got wider and wider as the stove heated up.
Last but not least: the complete SketchUp file for anyone who's interested in this type of stove.
 
Alexandre Harpin
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Hi! Nice work! Does it mean that a bigger system burns cleaner or is it specific to this particular build??
 
Joshua Myrvaagnes
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Hey pyromaniacs, This looks really cool and I'm really glad it's measured too, congrats on innovating and contributing to sustainable warmth for all!

Can you put this in layperson's terms? how does this compare to the regular wood stove? and what does batch mean in this context? what is the device specifically for, just heating or is it for cooking, kiln, driving a yellow submarine? what does the weird-looking n on the graph mean? Thanks!
 
Julia Winter
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So, it's really huge, and it can heat a large space quickly with all that radiant heat from the double barrel? I would love to see a picture of the flame shooting out.

I'm not clear on the third barrel, what that is doing (but I know nothing about rocket stoves, really).
 
allen lumley
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Joshua M. : Thank you for your questions, We here at Permes.com have become a little complacent in watching others innovations, nodding our heads,
and except for working with new materials, building J-bend rocket mass heaters with very little change from Ianto Evans' basic Design!

You are speaking for a larger group of us rocketeers than most of us realize ! I specifically mean the innovators,hand several more vocal members who may
have more readily grasped the need for and affect of these changes ! Failure to change is a failure to Grow !

My understanding is : This unit is bigger to the eye AND generates more BTUs. Batch means just that a load of wood is loaded all to once, and needs much
less tending, as this tower of barrels Gives us the additional Time, Temperature, and Turbulence to live up to the legacy of clean high efficiency burns !

Originally made as a front loader, the new glass top shows clearly where the hinge is and how it has been modified here to be a J-bend type stove (I Think)

The third floor level barrel can certainly be used as a cooking surface, though I do not know what Temperatures were or were not recorded !

In short, This new ''to most here at permies'' collection of designs needs a whole bunch of schooling to bring the unintentional laggards up to the level of
those Peers for whom these changes were intuitively grasped !

And, though it pains me to say it- We must find a way to pay for the privilege, or accept that we will always be building one model from the 1970s

For the GOOD of the craft ! Big AL Late note : at those %s it has to be the Nitrogen
 
David Bennett
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Awesome sketchUp file - great resource for learning and great that you've shared it and the test results.

Some questions (most yes/no):
  • are the diagonal bricks in the feed area fastened in any way?
  • have you knocked them by accident when adding feed stock yet?
  • is the fuel fed in through the top of the feed area?
  • ... by removing the ceramic glass cover?
  • ... that constrains the dimensions of the feed stock to longer (say 16") sticks, right?
  • the opening to the riser is tall and thin and instead of the usual long low burn tunnel - what is the reasoning behind that?
  • the flange on the bottom of the riser is there to direct the gases upwards, right?
  • seeing as the burn doesn't have to be at the bottom of the feed area (due to exhaust leaving at almost any height) - does it stay there?
  • there is a secondary air intake behind the ceramic glass top, right?
  • is the front "free-standing"?
  • ... and made of metal?
  • ... doesn't it get crazy hot?
  • what temperatures are you getting on the top of the third barrel?
  • are you welding the connecting tubes (between the barrels)


  • Cheers!
     
    Joshua Myrvaagnes
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    Thanks Big Al! And can you tell me about how much wood this saves, or what the advantage is to this design ? is it just for heating bigger spaces or does it just burn more efficiently? thanks!


    allen lumley wrote:Joshua M. : Thank you for your questions, We here at Permes.com have become a little complacent in watching others innovations, nodding our heads,
    and except for working with new materials, building J-bend Rocket mass Heaters with very little change from Ianto Evans' basic Design!

    You are speaking for a larger group of us rocketeers than most of us realize ! I specifically mean the innovators,hand several more vocal members who may
    have more readily grasped the need for and affect of these changes ! Failure to change is a failure to Grow !

    My understanding is : This unit is bigger to the eye AND generates more BTUs. Batch means just that a load of wood is loaded all to once, and needs much
    less tending, as this tower of barrels Gives us the additional Time, Temperature, and Turbulence to live up to the legacy of clean high efficiency burns !

    Originally made as a front loader, the new glass top shows clearly where the hinge is and how it has been modified here to be a J-bend type stove (I Think)

    The third floor level barrel can certainly be used as a cooking surface, though I do not know what Temperatures were or were not recorded !

    In short, This new ''to most here at permies'' collection of designs needs a whole bunch of schooling to bring the unintentional laggards up to the level of
    those Peers for whom these changes were intuitively grasped !

    And, though it pains me to say it- We must find a way to pay for the privilege, or accept that we will always be building one model from the 1970s

    For the GOOD of the craft ! Big AL Late note : at those %s it has to be the Nitrogen
     
    Bill Bradbury
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    Your combustion analyzer is a bit different than my Bacharach, but it looks like the little n is % efficiency, calculated using stack temp and gas volumes, not measured. A typical non-induced draft gas furnace will run around 82% as an average, so the amount of heat being absorbed out of the fire is very high, about the same as the latest hi-efficiency furnaces. The disconcerting # is the ppm CO. This is looking good when the heater is up to temp and burning fully, but can be dangerously high when not running perfectly. BPI standards require me to disable any unit with CO above 500ppm. Can you change the scale on your unit? It is very hard to get a steady state reading on CO with the current range.
    Where did you take your readings? 150F is a very low stack temp, thus the high %eff.
    Did someone try and close down the air intake on the 2nd run? The free O2 sure dropped and spiked the CO.
     
    Peter van den Berg
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    Alexandre Harpin wrote:Hi! Nice work! Does it mean that a bigger system burns cleaner or is it specific to this particular build??

    This build is a scaled-up version, as close to the original testbed as possible. So it looks like it's because a larger system has a favourable volume versus surface area ratio.
     
    Peter van den Berg
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    Joshua Myrvaagnes wrote:how does this compare to the regular wood stove?

    In short: an average woodstove would be doing between 1500 and 3000 ppm CO, this one was some time very close to zero. When the carbon monoxide level is 4000 ppm or more there will be smoke. As it looks like now, this batch box is surpassing the standard 8" J-tube by a fair margin although there need to be done a lot more testing on both of the concepts. The most surprising part, also to me, is the stability of the burn, rock steady and no spikes in all of the lines.
    Joshua Myrvaagnes wrote:and what does batch mean in this context?

    There's a difference between semi-continuously fed like the J-tube and batch fed like a bog standard box stove. It is loaded full and left alone to run by itself for the next hour or so.
    Joshua Myrvaagnes wrote:what is the device specifically for, just heating or is it for cooking, kiln, driving a yellow submarine?

    The stove as it is has been specifically built for heating purposes of a large space in a a short span of time. The combustion unit is the front end which could be applied to a choice of back ends. The yellow submarine isn't one of those I'd think.
    Joshua Myrvaagnes wrote:what does the weird-looking n on the graph mean?

    That's the symbol for efficiency. From the top down: red is efficiency and in percentages, green is excess oxygen and also in percentages, blue is end temperature and in degrees Fahrenheit, purple is carbon monoxide and in parts per million. This graphs are spanning the complete burn from start to glowing phase, necessary to be able to compare those.
     
    Peter van den Berg
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    Julia Winter wrote:I'm not clear on the third barrel, what that is doing.

    More or less the same as the others, shedding heat as quickly as possible. The second test was done with the firebricks inside it to exchange some direct heat to slow release.
     
    Peter van den Berg
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    allen lumley wrote:Originally made as a front loader, the new glass top shows clearly where the hinge is and how it has been modified here to be a J-bend type stove (I Think)

    Sorry Allen, this is not correct. It's still a front loader, the calcium silicate plate is functioning as the door. What you think is a hinge on top is in fact the secondary air inlet also known as p-channel.
    allen lumley wrote:The third floor level barrel can certainly be used as a cooking surface, though I do not know what Temperatures were or were not recorded !

    Actually, I don't know either. The top of that barrel happened to be the only part that still had paint on it. No problem during the first couple of burns but it became a very hot surface with the brick liner inside the barrel. Ernie and Jeyte applied newspaper and clay slip in a hurry, burning their fingers and all. So in this last set up that top could be used as cooking surface, probably.
     
    Peter van den Berg
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    Joshua Myrvaagnes wrote:is it just for heating bigger spaces or does it just burn more efficiently? thanks!

    I would say both. The original 6" experimental stove did yield about twice as much power as compared to the 6" J-tube in any given time. Of course it will consume also twice as much fuel in the same time frame, BTU's can't be made out of thin air.
     
    Mike Cantrell
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    Fellas, it looks like there are quite a handful here on Permies who haven't encountered the background for what Peter's presenting here. Hard to blame you- it's kind of spread around the internet a little. Not something that's easy to say, "Gosh, everybody knows that, duh!"

    So here's where it started:
    http://donkey32.proboards.com/thread/355/small-scale-development
    and
    http://donkey32.proboards.com/thread/511/adventures-horizontal-feed

    Donkey32 is a forum like Permies, but strictly for rocket burners. Both stoves and heaters.

    The threads above span a period from 2011 - 2013, and will take you a couple hours to read. In it, Peter and Donkey (and other contributors) make a number of iterations where they start with the "J-tube" rocket, the type that you often see mentioned as a "rocket mass heater" or "RMH", and that usually gets built with a steel barrel and a cob bench, and they step-by-step rebuild it into a firebox that

    A) burns even more efficiently than the J-tube (which itself is more efficient than the newest woodstoves, and MUCH more efficient than older woodstoves)
    B) is loaded once and burns down to ashes, unlike a J-tube, which is typically continuously fed.


    The system eventually takes the name "Peterberg batch box", because peterberg is Peter van den Berg's screen name at that forum, and it's a firebox that burns a batch of wood instead of being continuously fed. Peterberg batch box. Sometimes even 'batchbox' with no space.


    Distinctive features of the batchbox design are:
    1) The "port". That's the surprisingly tall and narrow slot at the back, where the fire enters the heat riser. The point, if I understand correctly, is turbulence, and it does a heck of a job.
    2) The "P-channel", a preheated secondary air supply injected at the back of the firebox. Hot fresh air coming in at the port allows for a really complete combustion.


    Among other things, Peter et al worked out a set of ratios for making that batch box large or smaller. Heck, I just printed them yesterday, so might as well throw them in here for easy reference:

    Given: Heat riser DIAMETER = D

    Base B = D*.72
    Riser Height = 10*B

    Box Dimensions
    Width = B*2
    Height = B*3
    Depth = B*4

    Port Dimensions
    Width = B/2
    Height = B*2.2

    P-Channel Dimensions
    Width W = B/2
    Height (thickness) = ((3.14(D/2)^2)*.05/W


    Because these are being built both in the US in inches and in Europe in centimeters, you can imagine the advantage of working out the ratios to build a unit of any arbitrary size and making sure it works.

    Which brings us all the way to the purpose of this thread- Peter is sharing this 8" system because that's, in a word, huge. Most existing units are 6", and people find them plenty hot. An 8" batch box is a monster. And that's why it's worth sharing.


    Joshua Myrvaagnes wrote:Thanks Big Al! And can you tell me about how much wood this saves, or what the advantage is to this design ? is it just for heating bigger spaces or does it just burn more efficiently? thanks!


    "How much wood this saves" is a question no one can answer, because there's no starting point to subtract from. The batchbox design has been measured to produce temperatures approaching the theoretical chemical limit for combustion of wood. In other words, you pretty much can't get any more heat out of wood than this device does. "Can't" in the really firm sense of "can't", where we're talking about laws of physics. So if you're starting from an old woodstove that's just a cast iron box, and you switch to a batch box, and build a good system around to capture the heat instead of letting it out the chimney, you can expect to save a LOT of wood. On the other hand, if you've got a brand new top-end woodstove with secondary air AND a catalyst, and you build a batchbox in a sloppy heat-capture system.... heck, you might not save any wood at all.

    The 8" batch box in this thread is, like I mentioned, notable for being much larger than usual. So it would heat a larger space than usual. Just to answer the question directly.




    Last thing, I can't fail to mention that here on Permies, you may have seen this batch box design in the work of Dragon Heaters (www.dragonheaters.com). They licensed the design from Peter, and are selling batch boxes that are cast of refractory in three pieces (left, right, and riser). It's the same device, even though the one in the photos above was built of bricks. Edit: They're selling an "optimized J-tube". The J-tube rocket concept has been around for some time now. Peter's experiments have uncovered some modifications that can be added to a J-tube to increase its combustion efficiency. Dragon Heaters sells a "rocket mass heater shippable core" that's an optimized J-tube.
     
    Peter van den Berg
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    Bill Bradbury wrote:Your combustion analyzer is a bit different than my Bacharach, but it looks like the little n is % efficiency, calculated using stack temp and gas volumes, not measured.

    Yes that is correct.
    Bill Bradbury wrote:A typical non-induced draft gas furnace will run around 82% as an average, so the amount of heat being absorbed out of the fire is very high, about the same as the latest hi-efficiency furnaces. The disconcerting # is the ppm CO. This is looking good when the heater is up to temp and burning fully, but can be dangerously high when not running perfectly. BPI standards require me to disable any unit with CO above 500ppm. Can you change the scale on your unit? It is very hard to get a steady state reading on CO with the current range.

    Average gross efficiency for both of the nice looking diagrams is around the 93% mark. When stack loss, dry gas losses etcetera are taken into account then efficiency would be about the same as the gas furnace. Sure I can change the scale on the unit, but this scale is chosen when the figures were very different and readability not easy. I like to keep it this way in order to be able compare all the graphics. This unit is always running flat out by the way, and the third graph is representing a full run, starting from cold. Average CO during this run has been 312 ppm. I would say it's quite clear that the main part of the run, apart from glowing phase, is well below 500 ppm.
    Bill Bradbury wrote:Where did you take your readings? 150F is a very low stack temp, thus the high %eff.
    Did someone try and close down the air intake on the 2nd run? The free O2 sure dropped and spiked the CO.

    Readings has been taken 4 ft above the floor in the single walled chimney pipe going up to the ceiling. I didn't close the air intake during the run, although we had some problems during that last run with leakage around the make-shift door which also shrunk and warped a bit. The 6" unit at home showed a much lower excess air figure coupled to about twice the CO. Not much time to test all the possible wrong doings so I left it running without altering the air intakes at all. We pushed it quite hard to see what would trip the thing I have to admit, all of the fuel happened to be coniferous and loaded full, moisture level less than 10%. Very dry in Montana.
     
    Peter van den Berg
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    Mike Cantrell wrote:you may have seen this batch box design in the work of Dragon Heaters (www.dragonheaters.com). They licensed the design from Peter, and are selling batch boxes that are cast of refractory in three pieces (left, right, and riser). It's the same device, even though the one in the photos above was built of bricks.

    Thanks for the clarification Mike, a native speaker has its advantages.
    The above quote is not entirely right, though. Dragon Heaters licensed an optimized design of the J-tube from me. This is not the same device as the batch box. No offence intended.
     
    Robert Dearborn
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    Thanks for the explanation and links, Mike Cantrell. Thank you Peter Berg (and cohorts) for the R&D. This stuff amazes me. The only thing I'm still a little fuzzy on, is what exactly defines a "p tube". I'm having trouble visualizing it, despite pics. Any chance a labeled sketch can be added for Noobs like me ? And the term "tripwire" also has me confused.

    I'm in planning stages of a rocket heater with cob bench, but this batch heater seems like it has promise for my needs in my workshop, when done. That's a ways down the road, tho.
     
    Peter van den Berg
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    David Bennett wrote:
  • are the diagonal bricks in the feed area fastened in any way?

  • Only with clay/sand mortar at the wall and floor side.
    David Bennett wrote:
  • have you knocked them by accident when adding feed stock yet?

  • No.
    David Bennett wrote:
  • is the fuel fed in through the top of the feed area?

  • No, from the front because it's only fed lengtwise. No criss-crossing or campfire style at all, so the firebox can contain quite a big load.
    David Bennett wrote:
  • ... by removing the ceramic glass cover?

  • The glas is staying in place during loading or whatever. It's a translucent top, that's all.
    David Bennett wrote:
  • ... that constrains the dimensions of the feed stock to longer (say 16") sticks, right?

  • The mockup outside happened to be about 5" longer which wasn't really necessary when taking the fuel length into account.
    David Bennett wrote:
  • the opening to the riser is tall and thin and instead of the usual long low burn tunnel - what is the reasoning behind that?

  • This is one of the fundamentals: the port (or gate) is 70% of the riser diameter, so according to Bernoulli's theorem, in the opening itself the speed is higher and the pressure comparatively lower. The secondary air channel is right in front of the port so this lower pressure will feed air in automatically. Behind the port both the pressure and the speed do go back to normal which in turn causing a lot of turbulence. The flames inside the riser are forming a double ram's horn pattern, coming back onto itself and spiralling up, thus lengthening the time in the riser.
    For this phenomenon please see this video:

    David Bennett wrote:
  • the flange on the bottom of the riser is there to direct the gases upwards, right?

  • Yes.
    David Bennett wrote:
  • seeing as the burn doesn't have to be at the bottom of the feed area (due to exhaust leaving at almost any height) - does it stay there?

  • No, typically some time into the burn all the fuel will be on fire.
    David Bennett wrote:
  • there is a secondary air intake behind the ceramic glass top, right?

  • Yes, there is
    David Bennett wrote:
  • is the front "free-standing"?

  • It's a make-shift door, just to test the thing. It's by no means a complete stove.
    David Bennett wrote:
  • ... and made of metal?

  • No, it's calcium silicate board.
    David Bennett wrote:
  • ... doesn't it get crazy hot?

  • Yes, it does. According to Ernie, the end of the riser could make a forge and it is a reducing flame, whatever that means.
    David Bennett wrote:
  • what temperatures are you getting on the top of the third barrel?

  • Not measured, but enough to burn the paint off.
    David Bennett wrote:
  • are you welding the connecting tubes (between the barrels)

  • No, Matt made the holes half an inch smaller around and I'd bended and hammered a flange to achieve a very tight fit.
     
    Robert Dearborn
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    Do you have an estimate of the square footage of the building this was in ? Did I read correctly that temperature of the building began to rise within minutes ?
     
    Peter van den Berg
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    Robert Dearborn wrote:The only thing I'm still a little fuzzy on, is what exactly defines a "p tube". I'm having trouble visualizing it, despite pics. Any chance a labeled sketch can be added for Noobs like me ? And the term "tripwire" also has me confused.

    This p-channel is short for "Peter channel", a name given by some people at donkey's forum to a secondary air tube which was introduced by me some years ago.
    The trip wire is a projection at the top of the burn tunnel that creates a turbulent condition. The term trip wire is a kind of "term of art", as there's no actual wire. The surface ramps into the burn tunnel space slightly before terminating in a sharp edge or "bluff body". It creates turbulence which should improve fuel/air mixing.
     
    Peter van den Berg
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    Robert Dearborn wrote:Do you have an estimate of the square footage of the building this was in ? Did I read correctly that temperature of the building began to rise within minutes ?

    Square footage might be something like 200 sq ft, just a quess. And yes, the temperature began to rise within minutes.
     
    Mike Cantrell
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    Peter Berg wrote:
    Mike Cantrell wrote:you may have seen this batch box design in the work of Dragon Heaters (www.dragonheaters.com). They licensed the design from Peter, and are selling batch boxes that are cast of refractory in three pieces (left, right, and riser). It's the same device, even though the one in the photos above was built of bricks.

    Thanks for the clarification Mike, a native speaker has its advantages.
    The above quote is not entirely right, though. Dragon Heaters licensed an optimized design of the J-tube from me. This is not the same device as the batch box. No offence intended.


    No offense taken, certainly. I evidently misunderstood, and I'm glad to have the correct information.

    (Also, my reply is timestamped after yours, so it looks like I was restating or clarifying what you wrote. What actually happened was, I began before your replies appeared, so I thought I was answering the questions first. Took me a little time write it all out. )

    I've considered spending some time putting together an accessible summary of the entire batch box project from beginning to end, because there's currently not an easy way to go from zero to understanding. (And I've tried short, quick explanations on Facebook, here just now, etc.) The information is spread across the different threads, the formulas are elsewhere, the most recent sketchup files are elsewhere again.

    In any case, when I do get around to it, I'll be happy to have my facts straight.
     
    Rick Howd
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    Please refer to the attached pic. Is this an intentional air intake or an oops in the sketchup? Because of this layer I'm confused about your air draw into the draft chamber and I can't tell if it's dual height, super wide or single height.

    In your picture with the bricks laid to provide mass in the 3rd can, is there a reason not to fill the central core area? It's still mass that would then radiate outward and retain any heat that they were provided. I wouldn't fill it too tight as the air wouldn't move as well, but I think there is a long term, low temp gain to be realized, as the air is pretty worthless.
    8 inch layout5z.jpg
    [Thumbnail for 8 inch layout5z.jpg]
    8" Layout5a question
     
    Peter van den Berg
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    Rick Howd wrote:Please refer to the attached pic. Is this an intentional air intake or an oops in the sketchup? Because of this layer I'm confused about your air draw into the draft chamber and I can't tell if it's dual height, super wide or single height.

    No, the only thing you see there is two pieces of two-third bricks that are a little bit too short. There are only two air inlets, the main inlet in the door and the p-channel at the top of the port.
    Rick Howd wrote:In your picture with the bricks laid to provide mass in the 3rd can, is there a reason not to fill the central core area? It's still mass that would then radiate outward and retain any heat that they were provided. I wouldn't fill it too tight as the air wouldn't move as well, but I think there is a long term, low temp gain to be realized, as the air is pretty worthless.

    No, it's not worthless. The reason to stack the bricks this way is to provide mass. It's also an attempt to keep the heat extracting surface as large as possible and at the same time the space inside much wider than system size. This way the gases are slowed down and will be allowed a longer time inside the barrel and give off more heat. In the mean time there's nothing to stop you from doing things differently though. Please build one, I am very curious what the experiences of other builders will be.
     
    Robert Dearborn
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    One feature im unclear on from the sketches and the podcast - is there a heat riser inside the barrel above the heater ? What is its proportion ? Im assuming it doesnt reach to within 2" of the underside of THAT monster barrel !
     
    Peter van den Berg
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    Robert Dearborn wrote:One feature im unclear on from the sketches and the podcast - is there a heat riser inside the barrel above the heater ? What is its proportion ? Im assuming it doesnt reach to within 2" of the underside of THAT monster barrel !

    Your assumption is spot on, there is a riser inside the barrels. It's reaching up to about 3 to 4 inches below the top of the first one, so the top gap is one barrel plus 3". The riser is an 8" ceramic fiber tube, it could be shorter but it is being used as a whole.



    The space around the riser and the firebricks is filled in with a perlite/clay slip in order to fix it in place.



    The barrels happened to be open-top types. Ernie adviced to fit the lid around the riser and cut open the bottom end of both the stacked drums. It is even possible to extend the tower with yet another barrel. The gap between the riser and the hole in the lid is stuffed with superwool, of course.



    When cutting, one inch of the bottom has been left around the perimeter, this way there's a better chance the barrel would stay circular.

     
    Alexandre Harpin
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    Julia Winter wrote:So, it's really huge, and it can heat a large space quickly with all that radiant heat from the double barrel? I would love to see a picture of the flame shooting out.

    I'm not clear on the third barrel, what that is doing (but I know nothing about rocket stoves, really).


    This one is not by Peter but I think it can give a good idea.

     
    Josh Tinley
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    Peter Berg wrote:
    Robert Dearborn wrote:One feature im unclear on from the sketches and the podcast - is there a heat riser inside the barrel above the heater ? What is its proportion ? Im assuming it doesnt reach to within 2" of the underside of THAT monster barrel !

    Your assumption is spot on, there is a riser inside the barrels. It's reaching up to about 3 to 4 inches below the top of the first one, so the top gap is one barrel plus 3". The riser is an 8" ceramic fiber tube, it could be shorter but it is being used as a whole.


    How durable is an 8" ceramic fiber tube as oposed to using firebrick for the heat riser? Are they easy to come by? They sure look easier to assemble.

    Thank you,
    Josh
     
    Peter van den Berg
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    Josh Tinley wrote:How durable is an 8" ceramic fiber tube as oposed to using firebrick for the heat riser? Are they easy to come by? They sure look easier to assemble.

    As far as experience goes, these tubes are quite durable. At first, during the first full run the binder in the inside of the tube will burn out. This will show as some light smoke, with a caramel-like smell about it. This burning out won't go deep, estimated 1/4" to 1/2". After that the inside of the tube is quite soft but extremely insulating and this will protect the rest of the structure. I've used one like that in my workshop for one season, pushing it hard at times. The last time I've checked the thing it looked and felt like nothing had happened in the months before that.

    I don't know where to buy these tubes in the U.S., you could google "ceramic fibre tube" or ask Ernie and Erica.

    And yes, those are very easy to assemble. Of course you have to fix it in place and connect the short pieces together but that's not a big problem.
     
    Erica Wisner
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    Peter Berg wrote:
    Robert Dearborn wrote:Do you have an estimate of the square footage of the building this was in ? Did I read correctly that temperature of the building began to rise within minutes ?

    Square footage might be something like 200 sq ft, just a quess. And yes, the temperature began to rise within minutes.


    I measured out the shop last year, it's about 50 feet by 30 feet in the main room, with about 2" insulation along most walls. So about 1500 square feet / 140 square meters. There's another room alongside the main room, about 10' by the full 50'. So about 2000 sf total, or something under 200 square meters.

    -Erica W

     
    Erica Wisner
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    and thank you, Peter, for the course-by-course detail and sharing the data. This success was definitely a highlight of the week!
    I am already having ideas about other possibilities that open up from this design.... will use a separate channel, though.

    Yours,
    Erica W

     
    Satamax Antone
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    Erica Wisner wrote:and thank you, Peter, for the course-by-course detail and sharing the data. This success was definitely a highlight of the week!
    I am already having ideas about other possibilities that open up from this design.... will use a separate channel, though.

    Yours,
    Erica W



    Erica, that huge batch sure opens up possibilities! A little insulation around the bricks and a lip or two into theses to put grids at different levels!

    With my little six incher



     
    Peter van den Berg
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    Erica Wisner wrote:I measured out the shop last year, it's about 50 feet by 30 feet in the main room, with about 2" insulation along most walls. So about 1500 square feet / 140 square meters. There's another room alongside the main room, about 10' by the full 50'. So about 2000 sf total, or something under 200 square meters.

    Ah, there's my error. The bench is about 9 meters, not 9 ft, mixed up again. That happened several times during the week at richsoil, source of laughter many times. Also mixing up of English and Dutch, when the others showed puzzled expressions I had to recap what I've said just before.
     
    Robert Dearborn
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    I measured out the shop last year, it's about 50 feet by 30 feet in the main room, with about 2" insulation along most walls. So about 1500 square feet / 140 square meters. There's another room alongside the main room, about 10' by the full 50'. So about 2000 sf total, or something under 200 square meters.

    -Erica W



    Wow. And obviously a tall ceiling. An 8" would be such overkill in either of the areas I was wanting to build. How well does this scale down with the 6", to keeping the ridiculously high efficiency that was observed at the innovators conference ? I mean, 20 ppm I carbon monoxide is unreal ! You probably exceed that burning a candle, right ?
     
    Peter van den Berg
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    Robert Dearborn wrote:How well does this scale down with the 6", to keeping the ridiculously high efficiency that was observed at the innovators conference ? I mean, 20 ppm I carbon monoxide is unreal ! You probably exceed that burning a candle, right ?

    A candle is doing much, much more CO, that's true.
    The 8" version was upscaled from the well known 6" version. Its very well possible to reach this same efficiency and low carbon monoxide levels running a 6" version. But such a system is rather critical in contrast with the larger one, which appeared to be rock steady right out of the box without the usual tweeking.
     
    Rick Edwards
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    Ok folks.
    Here's the first video of the beast as a prototype outdoor mockup. I'll get more pics and videos up soon. Also sometime soon I'll do a training burn for all hands at wheaton labs and be sure to video that as well.

    A side note about the box. Per Peter's notes, wood never goes inside the vertical port to the riser, not above the P-tube and not within 2" of the front door. So there is always 3-4" of free space above the full batch of wood and always a 2" gap between the batch and the front loading door.

     
    Julia Winter
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    That is so cool! Thanks for posting the video.

    Although, it makes me dizzy - is that your phone and you were just sort of waving it around??

    I want to know where I can get some fire safe glass.
     
    Rick Edwards
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    Yes it is and no problem.

    Yes it is and not intentionally, but it was very exciting times. We were all standing there enjoying the brand new never before seen innovation, then as genius collaboration in the moment goes, between about 5 of us, it went like this:

    " 'be nice to see what's going on in there.

    "I know, right!

    "You know there is a piece of wood stove glass about the right size in that truck right there. (Kinda kidding)

    "That'd be cool

    "Yeah wouldn't it

    "You know we could do that

    "Your right we could (walking to the truck)

    The rest is history and shaky phone ensues

    Btw. This is what happens when the magic combination of multiple innovators and all the attendees can stand around enjoying two innovators work while other innovator's materials are on site and a bunch of interested laypeople and innovators alike wish to see what's going on inside. Without events like this, who knows how long untill glass topped viewing batch boxes were on video.

    You can get the glass at most glass shops. It's pretty pricey though. That piece cost us $150.
    Ask for wood stove door glass or boro-silicate glass I think (someone correct me please). Our glass shop called it neo-ceram, a brand name I assume. Call around though, the shops vary a lot on price.
     
    allen lumley
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    for the last several years we have been happy with slow gains in the craft, or a kind of Creeping Status Quo! While we do not see a for profit organization
    behind this momentous change, this should open our eyes to the fact that We "Should " (and yes I mean We Should! ) expect to pay for this increase in
    our knowledge> Thank yopu everyone ! O. K., scare me a little how much for the glass and we still can have the J- Bend if we want it right ? Big AL

    Late note There was a little cross posting ! $150.oo does not sound to bad and a mirror slanted above it will let your mind get lost in the flames ! !!! A.L.
     
    Rick Edwards
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    Peter. I've been following your information on Jesse's thread about his 8" batch box. It has been pointed out that the transition from barrel to duct is important and needs to be larger than the duct itself.

    The design here has a short 8" duct between the bottom of the first barrel and top of the third. Would it have been better to have that larger on the first barrel side or is there a reason that it works in this system? Or is it or should it be at the output of the third barrel?

    Thanks for the great work here at the lab and here at the forums.
     
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