Breaking "all the rules", and looking for input

Hello,

Let me first apologize in advance for such a long post. This system is far from ordinary,” breaks all the rules”, and is not shared as a completed project, but rather a proof of concept prototype.

I wanted to share here in hopes of getting some critique, especially about low burn temps, ash, creosote, safety etc… as well as getting ideas for further development. We’ve been running this system for just over a week now, burning less than 1 square foot of wood per 24 hour period and maintaining our indoor temps between 70 and 73 degrees, (It’s below 30 outside here this morning.)

I’ve spent many months reading through many websites, watching countless you tube videos (the good, the bad and the ugly), and reading through several books, including “The Book”… (Still reading.)

Brief Background: 25+ years as a professional designer and prototype developer with projects ranging from toys for Mattel & Hasbro, to deep sea diving equipment for the Discovery Channel, wind tunnel models for Northrop/Grumman, (background in aerodynamics), UAV design, designing & building three human carrying ultralight aircraft, two world land speed record vehicles and much more.

A few months ago, I built a 34” X 75” “zero pass” style, aluminum screen, solar heater and when the sun is out, it brings our indoor temps up to 70 degrees for only 21 watts (computer fan), while outdoor temps are 25. This doesn’t happen though when it’s super cloudy or raining or at night, so I decided to try and design a system using our existing fireplace a rocket stove.

My priorities included not having it be “visually or spatially invasive” to our living room (I did not want to use a large “barrel”!). I wanted a radiating heater as well as “some” mass heat storage

I am very aware of the issues using metal (especially using stove pipe for my burn chamber!), I’ve read countless threads focused on this very subject and have seen the photos of corroded Stainless risers and burn tubes. I plan to “evolve” this concept into a high-temp refractory final version, so please, any “positive input” is desirable, but I’ve read so many “wrist slapping” posts provided to those who have gone the “metal route”… This is a functioning, “proof of concept” model only, operating at lower temps (1,000 degrees at the burn tube)

I do some amazing mold work and plan to re-visit this concept using high temp refractory mixes to replace components in this system. I’m already experimenting with high temp silicone poured into platinum based silicone molds to create true sealing gaskets between refractory and metal components that won’t leak, will hold up to temps and contact and expand without cracking refractory components.

Regarding safety and operating this first generation rocket stove heater in our home: Before moving up to Oregon, I was a firefighter for LA County (experienced too many needless tragedies!). I purchased two digital Carbon Monoxide alarms just for this project (different brands and models in case there was a “defect,” in one, I didn’t want to discover the same defect in my ”back up” alarm). I am obsessive about safety, which is also an important reason why I’m sharing this here, looking for feedback and more information to work with.

I built and tested this basic design in my shop and was surprised by its performance!!! Especially while breaking so many “rules,” I was really surprised!

I built this “proof of concept prototype” design using 6” black stovepipe in less than one week. (I already have LOTS of improvements and changes I want to make and I’m thinking of many others as part of the development process.) It cost me under $400 for everything and that included all the “incidentals” (firebricks, stainless screws and fittings), and also included about $100 for two digital Carbon Monoxide alarms (We already had smoke alarms in every room of the house.) These alarms were “extra”: One in the living room closer to the insert than recommended (I’m fine with false alarms, especially while just starting out with this prototype, but so far, nothing.), the second, is just outside our bedroom.

Changes I already plan to make include building an angle iron frame for the current loose, vertical stacks of firebricks to prevent them from tipping over, screwing that frame into the existing white masonry ASAP. I fabricated aluminum standoffs, screwed into the white original fireplace bricks, and used SS hose clamps to secure the vertical pipes a few inches away from the existing white masonry. They are very secure!

I’m also researching creating cast j-tube systems and other components, possibly eliminating the bricks. This will probably raise over all temps through the system allowing me to burn hotter and cleaner but I have to see how that would effect heat transfer (radiant and mass), to our interior. I’ll be testing any high temp cast components/systems outside first!) Right now, indoor temps remain constant for about 3-4 hours after the last burn goes out… I’d like a little more (5 to 7 hrs?).

I’ll also be building a heat shield (perforated stainless sheet metal supported by angle iron frame), over this or any future horizontal radiating pipe, if it stays in the final system… I do like the instant, radiating heat, but I’ve already burned my forearm when I tried to support myself getting up while feeding the stove and operating the lower damper (I wasn’t thinking!)…. Nasty 2nd degree burn across my forearm!

I’ll be adding a second ash clean out at the bottom of the right side down tube for this temporary build… molded/cast, later on.

Right now, I’m burning a mix of hardwood (Madrone and Walnut, combined with pallet pine). Removing the side Tee cap where the bottom side tube damper is located, I sweep out 1 to 1-½ cup of super fine ash/dust before lighting it up each morning. (Last night, we burned primarily Madrone and I swept out even less than that.) After one week of using this system. I removed the top, cross tube to check for ash build up and emptied about 1-2 cups of fine powdery ash. I need to be able to burn at higher temperatures to correct this.

NOTE: I have NEVER experienced ANY smoke, blowback, smoky smell, or flames creeping up the feed tube! Ever! Flames are straight and horizontal going toward the riser.

After a week of use, I’m getting the following temps: (These are averages, depending on wood type, intensity and duration of burn.)

Bottom of Tee at burn area: 780 to 1,000 degrees I doubt it’s getting over 1,200 but my IR thermometer just reads “high” after 1,000, which I sometimes get… I’d say the average burn tube temp is about 750 to 950.

First riser (on left), 200 to 400 (Average is about 300)

Cross tube: 200-300 (I have a separate temp sensor that shows that the wood mantle (above the cross tube) never gets above 110 degrees.)

Down tube (on right): 200- 250

Additional ducting tubes towards back of fireplace: (175- 250)

Last vertical exit duct into existing chimney: 140 – 200

Height of vertical riser (from floor in burn tube to top of cross tube/first elbow) is 42”. Length of cross tube (along top) is 48”. Height of feed tube (Top opening to bottom of 6” Tee), is 18”.

I’d say draft is excellent. I get straight, horizontal flames like a jet engine afterburner and we can hear a nice “rocket roar” (Well maybe not a loud roar, but we can hear it from across the room)… Nice comforting sound for us!

All ducting is new black stovepipe. After I cut and fit the entire system together, I disassembled everything and baked all the components in our BBQ to about 800 degrees (Checked with IR thermometer). After the black stove pipe paint stopped “fuming”, I baked the parts some more until the black color turned to a flat, dark gray, then I baked it for at least 30 minutes more for extra measure. We’ve had zero paint fumes.

Our original fireplace damper was wide and narrow, so narrow, that I could not feed the 6” stovepipe through it. I used a piece of “backer-board” and created a “ceiling/roof” inside the fireplace, just a little lower than the original damper to seal it up. I cut it to be fairly tight fitting (1/8” to ¼” gaps to help bring it in and place it). I used 1” angle to support its weight and then sealed the gaps with 600 degree Hi-Temp silicone. The exit ducting has its’ own hole to extend through the backer board and the edges between the exit ducting and backer board were sealed using more hi temp silicone.

A great feature is that I can shut off our central heat system and leave the fan blowing. Its’ air intake is about 12’ from the fireplace and with a small fan (Seen just to the left of the top elbow), blowing air across the top tube towards our central heating air intake, our central air system sucks up the heat and distributes it evenly throughout the house! We’re averaging about 70-73 degrees inside, evenly and everywhere!

I still have a lot of general questions about acceptable amounts of ash, possibilities of leaking duct/elbow joints (So far, I’ve found no leaks (which goes against my prototype development and firefighting experience, but I’m still testing!), exit duct temps and concerns about Creosote build up and Carbon Monoxide production (especially burning this system, at much lower than the “classic” firebrick temps/designs). (I’d also like to get a Co monitor that measures levels well below alarm levels.)

I have been told and read many times that using metal is an absolute “No-No”… My expectations for this system as is, include replacing “at least”, the bottom “Tee” through the first two elbows and the riser tube within a year or two (at best)… I hope to design/develop a refractory molded replacement design before then.

With what I’m experiencing, I’m searching for a system design that produces radiant heat and stores heat in mass collectors. I want to go with “proper” high-temp refractory components for the burn chamber and a proper, insulated riser, but I’m concerned that any metal radiant tube across the top will give off too much heat.

My ultimate goals include keeping the visual design as intact as possible (aesthetics and not bringing anything into our living room like a bench or a barrel), burning at hotter, cleaner temps without elevating the heat in our living room too much, being able to store “some” heat (enough to last for at least a few hours, maybe up to 6 hours), and to insure safe operation.

I’m the type of person that thinks “outside the box” and willing to do the work, take the time to experiment, make mistakes (outside!), rebuild and do what it takes to reach a goal. (It’s what I do for a living…. And… the actual designing and building is what I live for as a favorite pass-time.)

Your feedback is very welcome!

Thank you!

Richard

Richard... Welcome. Can't offer you any help with the rocket-stove project - rocket stoves are fascinating and admirable, but I haven't built one.

But you and I did exchange PMs - so here is a link to another thread here at Permies, on the broad topic of tinkering, designing and building equipment of value for homesteaders and home-based self-reliance. https://permies.com/t/52575/gear/Online-home-making-homestead-devices#431513

You're off to a great start here with your photo-illustrated thread and in-depth technical inquiries. I hope you continue to post things here, and good luck with that RS project.

Hi Joel,

Please forgive my "memory cells" for not functioning properly... I'm embarrassed to admit that I don't remember your PM... This website?

My "day job" requires me to calculate, defy the laws of physics (My name appears on many patents that belong to clients as part of our contracts) and generally operate in a semi-scrambled state of mind. LOL! My brain is always over-loaded and operates on a "need to need" basis, based on what I "need to know" while I'm in the process of designing/building... My wife is always trying to get me to take a break and relax in between client projects, instead of designing and building a new one for our "Urban Homestead"... (God! I LOVE her!) =D

Richard

Just looked at the photo of the solar heater... This was taken BEFORE I added duct insulation... Anticipating remarks about the heat loss without it! LOL! Added a couple more too.

Richard

First i must say i think many of the things you do are outstanding and very creative.

i do want to refer to what you have said

I’d say the average burn tube temp is about 750 to 950.

Breaking "all the rules

you are not breaking any rules. do as thou wilt... are you saying that because you are using metal? at those temps there is no way you can call it a rocket stove so no "rules" have been broken and you will be able to use that system until the cows come home because there is no way you will be able to break your metal down let alone all the energy out of your wood.

i will tell you if you are in fact burning at those inefficient temps you will have creosote.

do you plan to brick it all in solid?

if you read the book then you known the reason for a rocket stove design is in fact the temperature in which it burns the wood so it may get the most out of the stored energy in the wood. at your average burn temp you state, you are not releasing any more energy out of the wood per pound than you would with that fire place. the reason you may be happy with those results you are getting, are because of your radiant heat off the pipes and a fireplace sucks all the heat up without radiating the heat very much. you could probably get very similar results with a few simple fireplace mods with less material and less work and in my opinion with your engineering skills you can do so much better as i can see your other ideas are anything less than amazing.

if you are seeking sub par energy extraction and storage then this is the system for you, but just as i stated with your superior skills you can do so much better with more attractive reflection of those skills.

in my mind obtaining wood is energy used and to waste my energy getting wood and extracting a lower energy potential out of the wood i get is a absolute waste of my time and energy. i desire as close to 100% energy extraction as possible and the only way to do that is to start with higher burn temps.

good luck with those skills my friend you do beautiful work

F Styles,
Thank you so much for your insight and observations!

I do hope to develop this "idea" into a "true" rocket stove burning at much higher temps. I know I can't achieve that with this system and I fully appreciate your pointing this out!

I'm still learning about Creosote... At these temps, am I collecting creosote in the ducting, the brick chimney I'm exhausting into, both? How much might I create burning like this for the next 2 to 3 months (Solar will kick in more and temps will rise within this time.) Just curious about what kind of damage I'm causing and where. If my exit exhausts are between 140 and 200, am I risking igniting what I've created? (The masonry chimney was clean when I started burning this system.) After reading your post, I'm planning on designing and completing a "proper" rocket stove heater this spring/summer, using our fireplace ("Somehow").

I haven't finished reading "The Book", so I might have missed or not gotten to this subject. (Swamped with completing current client project with a tight deadline, but I do see that I need to read it cover to cover!!) I have it as an e-book and it's hard for me to take time to sit with it here at my desk. I'll ask my wife to print it out at her work tomorrow so I can leave it by the bed along with highlighters, pad of paper and pen to take notes...! =D

I could also be asking the "wrong" questions: At what temperature and for how long (exhaust traveling from burn tube through heat riser), would I expect to eliminate creosote? Guessing this is a matter of height of the riser and burn tube temps? (I'm sure this info should also be in the book!) I ask as part of accumulating "parameters and equations" to design around. I want to burn hotter/cleaner, but concerned with producing too much heat for our living room and approaching from a place of designing each component correctly to burn at true rocket stove temperatures...

Especially with your comments regarding my not actually having a "rocket stove" (in this configuration), I'm formulating my next version using a refractory cast burn chamber, possibly fire bricks and building a proper riser (possibly having it enter a tall, narrow, vertical bell where the left stacks of bricks are, having the exhaust ducting exit the bottom of that vertical bell and then continue through a combination of mass storage (Cob) and some radiant heat surface (probably part of that vertical bell). (Am I using the term correctly thinking that "bell" and "barrel", provide the same function?).

Re-reading your post:
I hadn't planned on sealing up the fireplace. it brings me back to another DIY, rocket stove fireplace insert I saw (saved the thread). Wasn't happy with the look, but I appreciate his performance and open to following the creator's lead... (Just had a "light-bulb flash" regarding a possibility but will have to re-examine his build thread... Possibly running duct out of his metal plate fireplace closure and somehow bringing heat out into mass collectors and a little more radiant pipe. If I recall correctly, his rocket stove was built out of firebrick, completely enclosed in his fire place with a metal door sealing off a batch box... I need to look over his design again.

Whenever I approach a new project, even if I "think" I know what I'm doing, I eagerly dispense with ego and approach with an open mind as if I know nothing and in that way, making it easier to de-rail my "train" and start over.!

Thank you for your kind words about my work, my creations etc... For those reasons especially, I will not settle for any excuse to not have a system (hopefully, visually "resembling" "some of" this design (resembling referring to the space I'm using in our home/fireplace area, but totally open to completely redesigning how it operates and the materials I use to do this the right way!

"if you are seeking sub par energy extraction and storage then this is the system for you, but just as i stated with your superior skills you can do so much better with more attractive reflection of those skills."

You totally captured my mind and heart with this line! Your feedback is exactly what I was hoping for.... Not a pat on the back, and not getting blasted, but more of "Hey! for what you're capable of doing, why not do it the right way!?!" Great motivations to do much better!

I genuinely thank you for "de-railing" my project! REALLY! I don't use the term "de-railing" as a negative thing... and I'm not giving up! There are many times I follow a designer's lead with engineering suggestions he knows nothing about AND times even I think I know what I'm doing, and some of the BEST engineering solutions come from picking up the debris at a train wreck site! LOL! (I SURE HOPE you understand what I'm trying to share here!!! I really do love that what has happened just with what you've shared has had the power to help me disengage with ego or love of the "look" of this thing, to start over, study more, re-consider the rocket stove "events" that happen within a correctly designed and operating rocket stove system, and apply my creative juices to see what I can create from a solid foundation!

Again. I thank you!!!

Best,
Richard

If your burn tunnel tee *surface* gets as high as 1000F+, you may be getting in range of full combustion inside at least part of the time. There are "three T's" in combustion: time, turbulence, and temperature. You need enough of all of them for full combustion. The gases have to mix well and stay hot for long enough that all the combustibles burn. As the "riser" surfaces are only 200-400F, i suspect you may not be getting enough time at temperature, and creosote is getting to the later flues at some parts of your burn. The problem here is when you have a really hot burn, and the first bit of creosote catches fire...

Granted that you are planning on replacing the metal with refractory, the flue path has what should be the heat riser passing through mass, when the riser needs to be highly insulated and should not give up much heat at that stage. With your goal of keeping the appearance of an open fireplace, I think you could achieve the general layout you show in a somewhat less obtrusive fashion.

I would start with two hollow brick bells at least four times the cross section as a 6" duct, or 10" x 12" inside and as tall as practical. Some discussion of bells and how they work:
http://donkey32.proboards.com/thread/1194/regarding-bells
http://donkey32.proboards.com/thread/1593/bell-theory

Set the feed tube right next to the left bell with a short burn tunnel and an insulated riser going up inside the bell. With burn tunnel and riser properly insulated, you will get full combustion. The gases then exit the top of the riser and move down in the bell space around the riser, absorbing considerable heat. This has about the same function as the typical barrel. You don't have space for thick masonry, so heat will transit fairly quickly (a few hours). You could even make one face of the bell metal instead of brick for faster radiation. For safety, making a 10 x 12 x 48 or so steel box faced with brick would more reliably eliminate leaks.

From the base of the first bell, run a channel along the floor behind the feed tube to the base of the second bell. The hot gases will rise to the top, stratify, and the coolest gases exit the bell at the bottom and head to the chimney. You would want a bit of divider at the bottom of the bell to keep the flow from short-circuiting directly to the chimney. This is standard masonry heater bell design.

I can see from the firebricks lining the back of the fireplace that you have a big deep box, known "affectionately" as an "ox-cooker". This design is appropriate for a country kitchen where big things were cooked in the fireplace and heat in the kitchen needed to be minimized; unfortunately, ill-informed masons built the same design in modern houses. A much more efficient fireplace design for heating is the Rumford style, which has a shallow firebox with sides angled in toward the center, to reflect heat into the room. You could easily brick in half of the volume of your existing box making the appearance of a Rumford fireplace, and gain yet another chamber for heat accumulation and hiding the flue going up to the chimney.


One feature of this layout is that there is no duct going across in front and above the fireplace. I think it would be a cleaner look.

well buddy i do speak my mind and the reason most of my friends that want a real opinion whether it hurts or not ask me. people either love me or hate me... i have seen most people that dont like an honest forward opinion seem to lean to the later but you know you can always expect the truth from me.

Glenn is a smart guy and im sure he has better links to batch box explanation than i do and you may want to take a look at a batch box design i think it would look sharp built into your fireplace area. clean looking, burns efficient and radiates heat well with a masonry bell.

that solar heater is pretty neat... you got any ideas for a solar water tank heater?

Glen: THANK YOU!
GREAT ideas! And thank you for the links! Read and bookmarked in a NEW folder in my computer: "Rocket heater, Version 2" LOL!

Tresa is printing the book for me today and this morning I went through 3 cups of coffee re-reading threads over at the Proboards website with pad and pen in hand (went through 6 pages of threads and 2 pages of notes so far!) Gotta get to work though!

How far am I willing to go to learn something? Some of what I do is design and fabricate remotely controlled aircraft (UAV)... I started back in the mid 80's and NASA/NACA had nothing pertaining to smaller Reynolds number aircraft design. At that time there were only two PHD professors doing work in this field. They were both German and their thesis papers were written in German. I purchased two technical German/English dictionaries and translated them all, word by word! I then had to collect some basic math books to understand their equations and graphs (I failed algebra in high school! (I ditched that class to attend another "math" class taught by a pilot. He applied the math to aerodynamics and I'm GREAT when it comes to understanding concepts which motivated me to "do the math". Since it was an AP class, I didn't qualify to get credit, but the teacher loved my enthusiasm...)

So, that's what I'm doing here... I glanced over the e-book version of the rocket stove book this morning and didn't find any hard numbers, but I'll wait until I get the paper version in my hands and read every page.

Glenn:
I don't know what kind of fireplace I have (built in 1951). There's a metal lined space (sides, back and top), that feeds out through the white masonry (vents), to bring hot air out into the room (pretty ineffective)... I'll measure the interior later when our solar heater kicks in (Burning current "wood heater" now) and create a drawing to post here later. (I don't know fireplaces, but I don't "think" the space is that large in there.)

I TOTALLY understand you idea of running more duct in back with some sort of mass "wall", to continue radiating heat after the burn. I LIKE that! A LOT!

I also like your idea of foregoing the top cross tube.... I do however LOVE how the small fan at the left blows hot air across and towards our central air intake!

To that end, (This idea and not thought out... Only an idea/concept:), if I have a tall narrow bell at left, I'm thinking I could cap it with a cast refractory piece and mold a "ducted fan" style tube through it running parallel with the white masonry. I could install a computer fan at the far left (heat issues will be taken into account). As I understand it, the top of the bell will be the hottest (I can make the base of this cap thicker to protect the fan from excess heat with some mass around the fan's exhaust tube). The fan would blow ambient air through the heated "ducted fan" tube and I'd get the same effect as what I have now, but without the top cross tube. (I might be able to attach a thermo switch so that the fan turns on at a certain temp, and shuts off at a lower temp.)

I'm also reconsidering leaving the fireplace open, or closed with a metal plate.

You both (Glenn & Styles), have totally opened up my mind to considering all sorts of ideas... I FIRST have to go back to the basics and FULLY understand the whole rocket stove system (performance, requirements, dimensions etc...)!!!

I would GLADLY weld up a rectangular bell (both for safety and for fitting/placement on the white brick platform (floor), extending forward from the vertical white masonry. On this subject, I'm currently focusing on ISA of bell (Please... I have a feeling I'm mixing up the term "bell", with "barrel"... Are these two one in the same?) Anyway, I believe there has to be a certain specific area between the riser's outside diameter and the inside diameter of the bell. The white masonry floor in front of the fireplace opening extends out 15-3/4". I really do not want to extend anything out beyond that. I'm thinking that I could connect a thinner mass between the riser and the white masonry in a way that there are no air gaps to utilize the existing white masonry for mass storage. That would give me more room in front to have thicker mass around the riser.

I think, creating a rectangular bell/barrel will help me hold both ISA and space between outer diameter of riser and inner diameter of bell/barrel while keeping it from extending beyond the white masonry ledge. The next question that pops up, is how much mass around that? What might I expect in terms of hours per inch thickness of mass(I'm pretty sure the answer will have to do with performance desired: immediate radiating, or slow build up mass as well as what kind of material for mass around bell.) I'm thinking I might want a slow build up mass heat, because another part of what I'm imagining is closing up the fireplace and running a separate duct system to enter/exit the opening covering plate and running a separate fan through it (starting at cold end), so that ambient air blows into the duct, travels back through the plate, gets heated up inside and blows hot air out. An alternative radiating idea would be to create a thinner wall metal plate mounted on standoffs from the thicker fireplace covering plate with a slightly curved outward bottom a few inches off the floor so that cold air would flow up between the rear and forward plates via convection.

I know what I've shared sounds like I'm "all over the place", but this is how my brain works and how I approach my prototype work... I pull out "cards" (ideas/questions), and spread them out on a table and look at them until something "pops out" as being possible (or part of), a solution. Sometimes, an idea will spark another.... I think "conceptually" first and then let the numbers or experimentation prove an idea worthwhile and keeping or discarding it. (Re-reading the book and the research I re-started this morning will give me more facts/numbers etc which will help me not waste time placing cards on the table that are ridiculous.

(Geeze! I know I had more questions to share, but after typing away in "free thought", I forgot them! LOL!


Styles:

I again want to thank you deeply for your truth! If you can't tell from what I've shared here, I'm walking around a most wonderful "train derailment wreckage", gathering what I can and eager to continue creating another new track! :)

(Solar water heater: Go visit the "Simply Solar" website! TONS of great info including people doing testing and evaluations using thermo imaging!) I've been researching compost water heating and because of our intensive gardening activities here, we need compost. Our current system works great, but we're only getting compost... We could also be harvesting heat to pre-heat water entering our water heater! :)

I'll continue sharing here, including drawings of ideas and specifics for further evaluation. I hope you will both (actually anyone willing to contribute positive ideas including those you may think I "don't want to hear"), will join me?

I seem to get email notifications of additional posts to this thread. IF you don't see me here for a while, don't read anything into it. My prototype work is super demanding and many times I'm working 18+hr days trying to meet a deadline. From here, if I'm not pre-occupied with work, I will be READING anything I can get my hands on!

Since I keep talking about my "day job", I'm going to post a few photos of what I do.

Thank you again!

Best,
Richard

Only allowed to post three images and I didn't include "toys". These days, probably 80% of what I create are toy prototypes, from rough proof of concept prototypes to "looks-like/works-like models (there are used over seas to scan with a laser to create CNC programs to machine injection molds.

I like what you do Richard, i am also an outside the box thinker like your self. my kids may have even played with some of those awesome toy designs.

i am the type that looks at all issues to solve that other have not and then creatively approach them and that is what i did in my rocket stove design.

wow, great idea with the rectangular bell. that would fit rather nicely into your brick layout and look attractive. yes the bell and barrel are the same.

this is my rocket stove build. https://permies.com/t/52316/rocket-stoves/Rocket-stove-heats-water-pics

i heat my house, cook on the top, bake with it and heat my water with my rocket stove. i plan on another water heating upgrade and oven upgrade.

i am also going to try an incorporated a crude oil and fuel cracking add on to my system.

i like your rectangular bell idea... awesome. if i had the money i would build a rectangular bell system like the one i have.

That's some pretty cool stuff you've been involved with! With all the movie props, do you perhaps know Chris Gilman of Global Effects? (He's in LA.)

Your fireplace is a Heatilator style (I'm sure there were other brands too). We had two of them in the house my parents built in the late 50s. I remember playing in the box the second one came in as a small child.

"Bell" has a fairly specific meaning in the art, as a chamber that is large enough that entering hot air can rise to the top and stratify there, while only the coolest air falls to the exit at the bottom. The first chamber around the riser, whether custom or barrel, is more of a downdraft chamber; even if it has enough area, the strong draft of the riser probably doesn't allow any stratification. It has a fairly similar effect, as the air is generally moving downward and cooling before it exits. The second bell in your situation would be more of a true bell.

Technically, there is supposed to be a minimum of 2" space around the riser to the barrel, but it will still function as long as there is sufficient overall circulation space. With just under 16" of depth to work with, you would need to lay facing bricks on edge to get a 2 1/2" or 3" thick front and side face which would leave sufficient internal clearance. 1 1/4" thick firebrick splits against the back would leave a maximum of 12" clear, which would just do for a 6" riser with 1 1/2" of insulation. This would be a good place for a ceramic fiber tube riser (6" diameter with a 1" wall) similar to ones in use in Europe. Another member has just located a company that will make them in the US for a reasonable price.
https://permies.com/t/53413/rocket-stoves/Inexpensive-vacuum-formed-ceramic-fiber

Glenn,

Thanks for the kind words and more info!

Don't know Chris, but there are a LOT of people in that industry! LOL! Surprisingly, I've met a few FX artists up here in Oregon, that I've either worked with or we each knew of each others' work! LOL!

OK... More questions:
IF I use the existing firebricks around my "bell" (And thank you for clarifying the term for me! LOL!), I'm "thinking" that I would want to fill the air space in between the inside surface of the bricks and the outside surface of the bell for more direct contact and transference from the bell to the mass heat storage (like a cob bench?)? (As well as using refractory mortar to seal up gaps between the bricks to create a more solid mass collector?) Also curios if I fabricate my bell in a rectangular configuration, can I make up for any minimal clearance to the riser (front to back), by having it wider (side to side)? Any studies regarding internal airflow in that kind of configuration?

Ironically, I just read the thread about the ceramic heat riser tubes this morning and bookmarked it! Does it still need to be insulated?

I need to print out your post regarding your suggestions for my "new" design... My memory cells are just not that great anymore! (I'm sure I damaged a few in my younger "wilder years", and I'm sure old age (61), doesn't help much! I'll re-read it and draw out what I think I understand about your ideas, post it here and see if I'm understanding correctly.

Thanks!


Styles,
Thank you too for your kind words, AND for sharing your build thread! I read over it (a little... bookmarked it for further study.)

Your feeding system of larger logs burning for longer times brings up a HUGE question/decision I've had: feed tube or batch box? I too tire from splitting wood down to "sticks", but like the vertical feed tube regarding safety (keeping embers etc from spilling out the front of a batch box. Also inconvenient is having to constantly feed the feed tube. I "think" my highest priority is to burn as little wood as possible while creating the most amount of heat. This system as it sits (6"), is actually serving our needs pretty well... I'm "Wondering if going down to a smaller CSA (like 4") would help in many ways? Less fuel used? More space for my bell,riser and mass storage around it? More ducting running back and forth at the rear of the fireplace? I've read a LOT that smaller systems are harder to make operate correctly which is why I stated with a 6".

OK... Client emails awaiting after sending them update photos... Hopefully, good news!

Thank you both so much for your time! You've been such a great help!

Best,
Richard

Ah! Another question! (Good news from my client: Time to ship for them to test... This is a GOOD thing!)

Running at my current low temperatures, I haven't been too concerned about clearance between the side of my brick stacks and their proximity to the wood back cases on both sides. They extend forward 3" from the vertical white masonry. Will running at new higher temps change this? Would I need to insulate them from the heat of the mass I surround the riser with?

Thanks!

OK... gotta go pack up the project and ship.

i cant speak for anyone else but i would not suggest a 4" system. i barely have 1000 sq ft in my house and 6" is minimum for my drafty home and i have a full mass bench running through most of my house.

the main things i have come across over the years of research i have noticed that same complaints repeated from the owners of rocket Stoves over and over as follows:

1 less than easy [cold] start ups.

2 inconvenient maintenance and clean out.

3 baby sitting start ups and tedious short feeding intervals.

4 limited wood chunk sizes. having to split tiny wood pieces is boring let alone more work.

5 copious amounts smoke back.

6 once installed its difficult to move especially if you change your mind.

7 no restarts and short burn times.

8 unattended burns are out of the question.

9 limited work load [mostly just heat home].

this list is not all inclusive and may not be what every single rocket stove owners has or feels is an issue that needs to be addressed.

It would be hard to say which of the issues was the most important to address or my favorite that i did address may have to be the very large feed chamber since i do NOT have to split as much wood and thank goodness because i am not getting any younger. Although the wheels are a really nifty feature. if you have seen my videos you will see i can put a maximum of a 10.5" x 18" full size round log in my rocket stove and it will last 8 hours. i do have to admit that very thin split chunk do burn faster, hotter and more efficiently than a 10.5" log and i have admitted that size was only to test its max size and not practical. 8" full size round log is the best of both burning hot and plenty efficient enough to last a good amount of time and not have to baby sit the fire feeding with many hours of good heat.

Richard you sound like a good business man and know time is money and i believe that having to spend all day splitting tiny pieces baby sitting my rocket stove just isnt in my schedule.

you mentioned building a brick layer around your bell? that will be good for heat storage but you will lose some instant radiant heat. if you like the instant radiant heat of the pipes you have now, you may want to expose a bit of the rectangle bell to radiate into your living space.

i am sure if you did build a unit like mine it would look much better since you not only have talent but the resources to build it to your desires as i had to work within what i had laying around.

Hi Styles,,

Thanks for sharing your thoughts regarding downsizing to a 4" system (From what I've read, I would be strongly inclined to agree with you... just had to ask and it comes from my desire to control the amount of heat emitting into the house I share more about that below.).

I LOVE your "list" and it had me laughing out loud being able to identify with some of them... Fortunately, mine starts "instantly" & consistently, I've never had any smoke and partial diss assembly for weekly clean outs is pretty easy. For daily morning clean outs, the lower side damper cap just slides off (I first place a paper plate under it to collect the ash. The ducting size at the Tee/feed tube allows me to insert a small, narrow hand held "broom" where I can just brush the ashes into the paper plate. Re-starts are super simple, especially if I still have glowing embers... I just place small pine sticks on the glowing embers and open the side damper. The air rushes in and the sticks ignite, sometimes with a few seconds, maybe as long as a minute. I then go back to the hardwoods. I'm not thinking about lightweight (Concrete floor/foundation) and I don't worry about having to move it... Whatever i build, it's staying right there! LOL!

However, two issues on your list are things I want to correct!

Frequent "feeding" of wood. Fuels is cut to about 16" long (Unfortunately the Walnut I now have a stock pile of averages 7" to 12" long... But it was free, already split into quarters or smaller and I can't see getting rid of it... Sometimes I'll stack one on top of each other (Two-up still doesn't come passed the top of the feed tube. Longer pieces of Madrone that I have (17"), burn between 40 - 50 minutes (Which for me is an acceptable time between feedings). With the Madrone, after flame-out, I'm left with a really hot bed of glowing coals. I place a couple of sticks back in and it ignites pretty quickly... Just repeated the re-lighting steps I mentioned above... 1.5 minutes from coals to full rocket sound.

Having to split wood down to tiny pieces. (I don't mind splitting a log down to quarters, I can use "some" exercise which I dearly lack!) LOL! But I'm also getting tired of it... been studying some of the smaller, manual splitters and thinking I can design something better and faster... just need to discover how much force (in tons), I'll have to design to... (I LOVE designing and building "better mousetraps!) You should see my "Gophernater"! (Actually I'll post a couple of photos... I welded a fitting to the muffler on our chipper. I connect a copper nozzle to it using semi-flexible auto exhaust tubing. The nozzle goes into the gopher hole, the adjustable choke on the shredder gets set to "rich"... No more gophers! (Before this, we researched everything imaginable from traps 9variaous types and how they were st, flooding with water, chewing gum and even once tried poison, but we don't want to do that for fear that birds of prey or other critters would eat them and become collateral damage. I don't think our new method is legal in California, but here... at our "Urban Homestead"... NO MORE GOPHERS! LOL!

Regarding building up mass around my bell, wait until I come up with some concept drawings to share some ideas about still having some radiant feature options while increasing out current mass heat to last longer into the night after our last burn (No matter how safe a system can be, I will NOT be burning when we go to sleep! Firefighting history and experience......

Right now, I have to keep the burn temps down (75- 850, intermittent burns), or the house just gets too hot for me... We had the room up to 86 once when we first started! I'm "thinking" that if I'm burning at much higher (proper rocket stove), temps, I can use that additional heat more effectively collecting heat in mass (extending our night time heat supply), while still being able to provide some radiating heat. (With the idea of a ducted fan on a cast bell cap, we'll still be "radiating" heat by virtue of the fan blowing through a pre-heated tube that stays warm... that warm air goes into our central heating air intake and will be dispersed evenly through the house as it does now. The sketches will be concept only to explain "ideas" and the amount of mass and the amount of radiating surface will be "numbers" I'll have to play with "guessing" what ratio will work for us. (DON'T ask Tresa though!!! She LOVES it nice and toasty! LOL) Sitting in the living room listening to the "rocket sound"while wiggling her toes, has become one of her favorite "coming home from work" pastimes! LOL!

OK... I can see that I really don't want to leave this website... It's becoming anew 'second home" for me... And I still have so many other forums here to explore! (I need to win the lottery so I don't have to work anymore!)

Thanks again!

Richard

Re: Splitting Fuel Wood

I surmise the greatest advantage of the rocket design is to efficiently burn very small diameter wood [such as from trimmings or or blow down or slash off a tree dropped for timber or hugels or such] at an extremely high temperature.

One thing I would like to ask you guys, how well does a cage J-tube feeder work for extending the height of the feed tube without creating a competing draft? I'd like to use a metal ring type design to be able to easily put in 3-4 foot long sticks.

Hi Kyrt!

I laugh out loud here (not at you!), but at my having wondered (and still wonder about), the SAME THING! Design wise (if it would work aerodynamically), I should think that the vertical wires/rods, would need to have supporting rings around the outside of the vertical basket to help prevent snagging and improve longer pieces chances to slide down as you're thinking...

My next thought, would be that I would "think" (I really don't know), that any object extending beyond the top of the feed tube might act like a "chimney" of sorts providing a path for smoke to draft upwards.... Logic behind this thought: When you stand a way from a campfire, the smoke doesn't hit you (unless you are downwind)... As you step closer, ever notice that the smoke is "attracted" towards you? I "believe" (again, I don't know), that your body acts as a sort of laminar flow type draft inducing chimney to draw the smoke towards and up your body... Again, just "thinking" without any hard facts to support them.
I wonder if any extension of longer pieces of wood extending upwards beyond the top of the feed tube would act the same way?

I would LOVE to hear responses from others who are more knowledgeable.

I have thought of your idea (enough to have already figured out the physics and requirements to help the wood slide down without getting snagged!), as a way to reduce the number of times (frequency), of having to feed my feed tube!

Good luck and waiting to learn more!

Richard

Richard is right you can cause the wood to creep up if you dont have perfectly straight pieces and have them extend past the top of your feed tube and that was a consideration of mine when i built my rocket stove so I chose to build the feed chamber wider and with a lid so if it did smoke it would not come out. the air mixture has to be right and one of the reasons there is a man that invented the peter channel that allows the air to flow even when the feed tube is full. i dont need a peter channel since i have a front access port that delivers perfect air across the bottom of the wood were it desires it and its never blocked i just put my designed spark screen over the front access port and it always has the perfect air intake.

sorry to add more things for you to look up. "peter channel" dont kill me. thats only if you want to use a feed tube instead of a batch box or large feed chamber with a lid then you wont need it.

Hi Styles,

Thanks for responding,

In your last post, you wrote:

"the wood to creep up if you dont have perfectly straight pieces and have them extend past the top of your feed tube"...

Did you mean that the smoke and flames would "creep up"? (Just wanted to be clear.)

If so, I'm wondering about other solutions for longer burns without such frequent feedings of fuel into the feed tube (I'm using a J-Tube).

In my current system (burning at much lower temps than a "classic", insulated burn tube and riser), I can see a marked difference in temps and thorough burns depending on how packed I have my feed tube: Less fuel (especially with hardwoods), there are times where the flames go out and I'm left with un-burnt wood still sticking up into me feed tube. In a "proper" burn tube with riser, do the higher temps resolve this?

Reason I ask is, in your system you claim to be able to burn whole (and much larger logs than mine), for a longer burn time. (I think, that's what Kyrt is trying to achieve (I would too!). I understand burning enough to know that when you have smaller pieces surrounded by even small amounts of air, you get a hotter burn that is self-sustaining and all the wood burns, leaving only ashes, where, with a larger "log", the burning can go out, leaving un-burnt wood.

(I haven't read your thread thoroughly yet to fully understand how you do this in your system. I'll be reading it this morning)

Tresa printed the book for me last night and I'm already up to page 70! Great stuff!

Also attaching an image of a licence plate I've had hanging behind where I sit to do my work in the studio... Seems appropriate for this forum! LOL!

Thanks!

Richard

yes the flame and smoke can creep up if conditions are right. that is why the air flow has to be perfect.

I'm sure you have dealt with a welding torch or Bunsen burner where you have to adjust the air ratio to get that perfect flame... well its the same for a rocket stove. imagine the burn chamber inside as the flame tip of a torch of a welder or Bunsen burner. fuel air mixture is absolute key and when you don't have it properly supplied you get inefficient burns, smoke back and even flame creep.

that is why i designed my "enlarged J burn chamber" to accommodate for many of those things. my stove wears multiple hats. i can put tiny sticks in with very rapid burns and extremely high temps or i can shove in very large logs and allow it to burn and settle on its own going through different burn efficiency stages... let me explain. once the fire is going good i can put in very large logs with out splitting and it will start very hot efficient and as it burns through its stages it will get hung up at times and more air will get in and the heat from the coals sucks off the wood gas continuing to burn the gases until the wood basically turns to charcoal and then settles for the final burning of the charcoal for a super efficient hot burn and that entire process from efficient to less efficient back to efficient again takes many hours to complete and it has to do with my powerful draw, extremely large feed chamber and the lid. its an unintended phenomenon i have but love how it works.

awesome license plate if i had one i would tack it near my rocket stove

OK... finished reading your thread and if I understand correctly, Your "J-Tube" is actually an "L" with an extended horizontal feed tube ("Magazine"), where you can place a longer log?

Not sure, but is the diameter of your feed tube wider than your 6" system? (I've read in the book and elsewhere that the entire system should use the same diameter CSA.) Have you experienced any issues/problems with this configuration?

For safety concerns, I'd like to stay with a vertical feed tube, not wanting to risk sparks or burning debris spitting out. Even in mine, I did have one instance where a hot ember was thrown up and out of the feed tube (guessing there was wet wood in there). Since then, I've created a fine wire mesh cap to use when I want to burn without my adjustable damper cap (They're interchangeable.)

One concern that arose for me (after reading in the book), was "code" requiring 18" from "stove"... I'm "guessing"; hoping, that this safety measurement applies to the burn tunnel and NOT the riser (enclosed in the vertical bell/barrel. )(BTW: Your photos, looking down into your heat riser helped me understand the riser/barrel concept much better!

As I see it now, the super heated air/flames are INSIDE the riser and NOT coming down the interior of the barrel, cooling at the top where the super heated exhaust exits and works it's way down the interior of the bell. With mass material molded around that, I would think that a vertical bell (replacing my left stack of fire bricks), would be MUCH cooler... If you look at the photo showing my entire system, you will see that there is not much space between the left hand (outer) surface of my fire bricks and the edge of a wood, built in bookcase. My concern (especially if I want to "pass code", or at the very least make sure that I've done as much as possible to ensure safety), is the temperatures I'd expect to experience with a super hot, insulated heat riser, encased in a metal, vertical bell and that being encased in some sort of mass (Cob, refractory, regular cement, other?)...

OK... back to reading and shipping out my project.

I will work on concept drawings for version 2 of this system with more questions regarding the details I'll illustrate.

Thanks!

Richard

Aside from ensuring adequate air supply in a full J-tube feed, the p-channel has beneficial turbulence-inducing properties when installed correctly. You can find all the details of this and its accompanying feature called a "tripwire" at Donkey's forum (I think it's the "small scale development" thread).

A batch box tends to deliver the heat from a load of wood faster than the same amount of wood in a J-tube system, so with more radiator than mass, this might not be ideal for you. However, the latest batch box designs in development by people at Donkey's, as I understand, have some ability to control the burn rate, at the cost of more finicky construction and adjustment. For average people, this may be more trouble than benefit, but your skills appear to be easily equal to the task.

Thanks Glenn! (So grateful that you keep visiting here. I'm planning to post quite a few drawings to "journal" concept development for this project)

As I keep thinking about this project, I'm re-visiting the metal plate covered fireplace rocket stove insert over at Donkey site... Reason: The design seems to keep everything IN the fireplace rather than out. I'm starting to look at this long term including potential building inspectors, passing insurance inspections etc... (This would also answer my previous concerns about book cases on both sides of the fireplace and anything that "might be considered hazardous", NOT being in proximity to those book cases. (Still LOTS to consider and design to.)

I REALLY do like the "J-Tube" rather than the batch feed. I " believe" a batch box would expose our interior to fire hazards. I also do like the idea of being able to control interior temps by gradually feeding fuel rather than starting a large batch fire and finding our interior space becoming too hot and not being able to cool it down after a batch fire is started. So, I would tend to agree with you about a "J-Tube feeder" probably being better for our needs.

IF I do go with an entirely different design by closing up the fireplace (either with a bell inside or using the fireplace as the bell), I see where I can run a separate (isolated from the gasses within), duct, from the outside of that plate, into the fireplace to gather heat and then run back outside, using a small computer fan to blow heated air towards our central heat air intake (we REALLY like being able to heat the ENTIRE house by utilizing that air intake and existing home heating ducting!!! Keeping this feature as part of any new design is now a major priority! So glad I built this version to find how it interacts with heating the entire house! I've learned a LOT just from experiencing this "feature"! =D

I might be a little confused about the term/purpose of the "P-Channel" and "Trip Wire".... For the longest time, I "thought" that an actual "wire" was inserted into the system to create turbulence. As I understand it correctly, I've viewed cross section photos of refractory cast burn tunnel components where the "trip wire" was actually a molded in piece that comes from the top to divert rocket flow in a way to create turbulence... along with a "back tail" (?) at the far/back end of the burn tunnel to further turbulate the flow before entering the riser.

As I understand the "P-Channel", it's a way to separate the wood in the feed tube from a small "slot" where additional air can be sucked into the burn chamber/tunnel to help create hotter burns? IF I have this all correct, Can/is the "P-Channel" adjustable to provide correct air/fuel mixture to obtain correct temps and burn rate?

SO MUCH TO LEARN!!! =D I'm enjoying it though, especially knowing that I have the "spring to design it, and the summer to test, mold, cast, build and install the next system!

Thanks for your compliments and confidence regarding my skills etc, but, I know enough that unless I have to, avoiding anything "finicky" might be the best route to go with so much I want to accomplish with the new system! LOL!

I'll go over to Donkey and search for that thread.

Thanks again!

Richard

Hi Glenn,

I found the thread and read ALL of it! SO MUCH information, my brain hurts and I think it's going to burst into flames!!! LOL!

Found some great images and now thoroughly understand the P-channel, the Trip wire and the theories behind changes in Peter's development process... Enough to lay out and draw up my won feed tube/burn tunnel... I set in measurements in the drawing following Peter's work (I need to thank him personally).
I created this drawing just to visually follow the 2 pages of notes I took while reading that thread... Still a LONG way off from actually drawing up anything close to a final drawing!

Whew! learning so much about the inner workings and dynamics of these systems is exhausting (oops... pun not intended! LOL!) I find it TOO addicting though... Really hard for me to step back from the computer and stop!!! But at some point, I need to: Been feeding my system while reading and the flames went out twice! (Haven't split more longer pieces of Madrone and burning my much shorter pieces of Walnut. I can't see getting rid of it just because I have it, it was free and it's already split into pieces I can split down further to fit into my feed tube... I have less than 1/4 cord left, but all this feeding sure brings up another priority to not have to feed so often!

I "think" having hotter burns with more mass to collect the heat and longer (17"), pieces of hardwood will help me move towards that end.

Can't say I won't be back momentarily, but for now, I need to take a break! LOL!

Thank you again!

Richard

OK... finished reading your thread and if I understand correctly, Your "J-Tube" is actually an "L" with an extended horizontal feed tube ("Magazine"), where you can place a longer log?

Not sure, but is the diameter of your feed tube wider than your 6" system? (I've read in the book and elsewhere that the entire system should use the same diameter CSA.) Have you experienced any issues/problems with this configuration?

For safety concerns, I'd like to stay with a vertical feed tube, not wanting to risk sparks or burning debris spitting out. Even in mine, I did have one instance where a hot ember was thrown up and out of the feed tube (guessing there was wet wood in there). Since then, I've created a fine wire mesh cap to use when I want to burn without my adjustable damper cap (They're interchangeable.)

I designed it originally as a J tube 6" system all the way through but there were some concerns i did not mention and one of them was because of a rocket stove video i saw of a properly designed rocket stove having wood popping and spitting sparks and embers out of the top, especially if you put in longer sticks than your feed tube or stack pieces on top of each other to keep the fire continuing. so my feed chamber grew in size with a lid to keep the sparks from flying out and at the last moment i added the front L access port for precise air flow to the exact area of the burn needed and i get perfect burns every time with no p-channel. i designed a front access port spark screen that protects from any flying embers and i get zero sparks flying out with the lid and fireplace spark screen that is super fine.

I designed my system to be just as safe as a standard wood stove for all night burns if i so choose. i can burn as efficient as i want it to burn.

if you are interested in a p-channel, maybe you could design an adjustable p-channel so that you can adjust the air flow according to the amount or type of wood and burn you want.

Richard i just had an idea pop in my mind. you could design a square J tube and have a "P-channel Flap" the width as the ID of the square feed tube that hinges at the bottom that is gapped to about 1/8 to 1/4 all the way across at the bottom and is engineered so it leans toward the wood so it always has perfect air flow only allowing the right amount no matter how much wood you put in it. when its packed full it has the proper 1/8 to 1/4 gap and when it only has one stick it has the same flow. the metal P-channel flap could have holes in it to allow for when the feed tube is low and the flap is leaning all the way forward still allowing air through the holes. let me see if i can draw it and post it.

Hi Styles,

Thanks for explaining!

I LIKE your adjustable P-Channel idea....

Since I'm going to create a cast refractory base, I'd like have as MANY "options", separate components, adjustable items so that I can fine tune to achieve optimum results without having to go back to re-creating a plug, making a mold and casting a new base.

looking forward to seeing your drawing.

Thanks.

God, I'm still "overloaded" and just finished splitting more, longer pieces of Madrone...(Sure keeps reminding me of not wanting frequent feedings... The longer (16" to 18" pieces of Madrone, burn well up to about 45 minutes.... I may offer my much shorter Walnut up for sale on Craigslist for cheap and put that money towards longer/straighter pieces of Madrone! (Splitting and being distracted by making sure the dragon is burning, is just not working for me! "Novelty/fun" element is obviously wearing thin. LOL!

excuse the ms paint drawing

yup tired of spitting tiny pieces and if you stay with a 6" all the way through you will be stuck doing that PERMANENTLY!
I have always said necessity is the mother of invention and maybe you want a bigger feed chamber?

Thanks for the drawing!

Interesting.

I describe what I do professionally as a "Murphy Hunter"... You know, "Murphy's Las": If it can go wrong, it WILL go wrong"? Not in a way to create roadblocks, but to try and solve any unforeseen issues that might creep up (You'd be surprised at how many of these show their face in the line of work I do!)

So after just reading a ton of info about P-channels, all sorts of questions come up for me about your drawing... Creating a tapered entry from the top to the bottom of your P-channel; the holes in the plate and I just can't think straight after cramming my brain full of too much info! LOL!

I saved it and will look over again later with all the other stuff I just saved....

I really do like the concept and the intent of being adjustable according to the cross section of fuel! (Part of what I'm now experiencing, I believe is the lack of such a devise as this. If I fill the feed tube full, it burns great and hot, when it tapers down to just a few sticks, the fire goes out, even though there are 1 - 3 sticks of Madrone waiting to burn! Your "adjustable" idea may just do the trick!

Thanks again!
Richard

These drawings and questions are mostly for Glenn (Trying to understand the system you described), but open to anyone with guidance, advice etc...

I believe this system would be referred to as a "Double bell"?

My biggest question is: Can an "S" shaped burn tunnel work? (I'm trying to keep the feed tube and most of the burn tunnel inside the fireplace.) The darker lines represent the channels inside a hi-temp refractory casting. The top of he feed tube would be a replaceable metal tube. The base of the rectangular shaped metal bell would be refractory as well.

The red lines represent air flow:

From the feed tube (inside the fireplace... See photo for what I've done with my existing system), the burn tunnel goes horizontal before turning outward and out of the fireplace. It "might" need to turn again going outward from the center of the fireplace, before going up to an insulated riser. The bell would be welded steel (probably stainless if there were something to gain from using SS. The heated air goes up the riser and disperses downward. A welded fitting receives ducting that goes back into the fireplace, behind the burn tunnel and feed tube where it crosses the fireplace to traverse a second "S" shaped configuration to the go up a second riser. The air once again disperses and comes down the 2n3 bell to another welded fitting to more ducting that goes towards the back of the fireplace, crosses over, does a horizontal "U" turn the up a last 90 degree elbow to go up the existing masonry chimney.

IF this is correct, I'm guessing that I would want most of my mass (cob or other material), around the first (#1), bell? cob could then be used to collect heat for later use at any other point(s) in the system.

I'm guessing that the top of bell #1 would be the hottest point? I'm hoping to surround this bell with cob, etc and cast a hi-temp refractory piece for the top that will have a tube to accept a metal computer fan to blow heated air through and towards our central air intake to disperse heat through out our home.

I'm guessing that the ducting and base of second bell can be mass collecting cob rather than needing high temp refractory?

Any ideas on what I can expect at the duct exit at the first bell?

Hoping this will help further discussion on the new design.

Thanks!

Richard

what I meant with my last question was: any ideas as to what temperatures I could expect at the exit duct fitting at the bottom of the first bell?

additionally, I'm :guessing" that if I use cob (collecting heat and insulating that ducting) around the ducting exiting the first bell I would retain higher temperatures for the 2nd bell?

PS:

The existing fireplace is lined in metal: Sides, back and top. (I'm sure this is used to guide heat up to two existing vents on both sides of the fireplace (pretty ineffective when burning as a regular fireplace, but might help if I'm creating mass heat storage along these surfaces. The bottom floor of the fireplace is fire brick.

Richard Jarel wrote:what I meant with my last question was: any ideas as to what temperatures I could expect at the exit duct fitting at the bottom of the first bell?

additionally, I'm :guessing" that if I use cob (collecting heat and insulating that ducting) around the ducting exiting the first bell I would retain higher temperatures for the 2nd bell?

you can expect 300+ F exiting the first bell depending on burn chamber temps and insulation.

i can only assume that my system gets well over 2000+ degrees and i get 350+ F exiting my bell.

when can we expect some drawing designs of your system ideas?

Styles,

My "concept", "idea" drawing was included in my post (3 up from this one.).

This is based on Glenn's idea (as I THINK I understood it...

Right now I'm only going on theoretical basis. Once I get a general idea of what is possible within the constraints or our fireplace, temperatures at different points... (Example: If i cover the first bell with a "lot" of cob, etc... I think it will not only absorb the heat for later distribution, but "should" keep internal temps higher (?)... If I then cover the ducting going to the second bell with more cob (insulation), the heat drop from the bell # 1, should continue at a higher temp than if I left that ducting bare metal radiating....)

My goal is to have some radiating and some mass, finding the balance to create a hot spot source I can blow air over to spread towards our central air intake for distribution throughout the house... My idea of the mass on top of the first bell (#1), is so that that mass is molded in such a way as to mount a ducted fan that will blow the heat from the top of the bell towards our central heat air intake... Right now, I'm accomplishing this (WONDERFULLY!) with the small fan mounted at the top left side of my original installation. IF I can create a mass that will stay longer and design it to be aerodynamically efficient with a fan blowing through it, then the mass heat will continue longer while at the same time, allowing me to blow the hot air coming from it towards our central air intake...

Part of the "game" will be to devise a way to get as much mass needed, configured in such a way to provide heat to the interior of that ducted fan tunnel.

Another way, would be to direct as much heat as possible INTO the fireplace, surrounded by mass and have a separate ducting system with a fan on the outside, blowing air into and through that mass and then out with the ducting aimed ar our central air intake...

The "magic" of what I want is not to have a "bench" style mass in the living room that just radiates when you sit on it or into the living room, but a mass that I can "bleed off" that heat AND direct the heat via a fan/ ducting etc, blowing a stream of hot air 12' away and into our central air intake. My goal: to be able to do this for 6+ hours... (Again, I say "goal"... achieving a goal is a matter of compromise AND redesigning once more information and understanding is achieved in order to design within that information and understanding to get closer to that goal.


Question: Is it possible to run an "S" shaped burn tunnel? Are there any known consequences (Possibilities include but not limited to: good: tabulating air for more efficient, hotter secondary burn... Bad: not a long enough run of straight burn tunnel to achieve a high temp burn. etc... ) for me, these are unknown factors.


Question:
I believe that thicker refractory castings will help support hotter burns. Will they also act as part of the mass heat collector to provide heat after the burn?


Question: For my "concept" of having a cast ducted fan tube, component on top of the #1 bell (with the understanding that the top part of the bell will be the hottest point (next to the burn tunnel and riser interior), will refractory be a better choice (due to higher temp), or cob type... Will refractory cement retain heat as long as cob? more? less?

For this ducted fan tube casting, imagine an extension of the bell (including additional thickness (4"), in diameter extending upwards from the bell top as a vertical cylinder with a horizontal hole through it with the fan on one side blowing ambient room temp air through it to become heated...

More and more, I'm thinking that a greater amount of mass can be set up in the fireplace with ducting tube running through it to achieve the same thing while possibly lasting longer with regards to a greater mass holding more heat over time and the colder air blowing through the ducting inside having a slower cooling effect on that mass.

Just ore to think about.

Richard

im not sure how i missed that. im reviewing it now. looks complicated.

My biggest question is: Can an "S" shaped burn tunnel work?

it can work but I am always concerned with being able to get inside it for any type of maintenance that may be needed in the future. designing TEE ports to reach inside. i am not sure the downward burn chamber "S" will be as efficient as the straight horizontal burn chamber.

(Example: If i cover the first bell with a "lot" of cob, etc... I think it will not only absorb the heat for later distribution, but "should" keep internal temps higher (?)... If I then cover the ducting going to the second bell with more cob (insulation), the heat drop from the bell # 1, should continue at a higher temp than if I left that ducting bare metal radiating....)

the cob will indeed suck the heat away and will not act as a real insulator and will hold the heat but may increase restarts of your system. if i may give my advice i would build the first bell and insulate (with pink or yellow fiber) around the back and side of it so the front and top radiates heat and do not use cob on the first so the heat doesnt get sucked out too fast and design a access port in it so you can clean it out at a minimum or design it to be removed. i would then design the second bell with your favorite mass (cob, brick ect.) around it.

Thanks Styles...

The "S" shaped cast burn tunnel in this new design will be horizontal, (Not sure what you meant about "downward" other than referring to my existing duct transition from my burn tunnel to the first riser tube... My goal there was to begin the rise (height), in air flow as soon as possible while heading towards the vertical tube... Not sure if this part is what's causing it, but my draft begins immediately from start, never had any back flow/smoke.. ever...)

The "S" shaped tunnel starts as it comes out from the feed tube, straight until it makes a 90 degree turn out from the fireplace, then another 90 degree turn to head towards the first bell which I'd like to be off to the side on the brick shelf, then to a vertical 90 where it enters the heat riser. The reason for the first two 90 degree turns is to get the first Bell out on the brick shelf and away from the fireplace opening. (I'd like the inner surface (closest to the fireplace opening) to be flush with the fireplace opening. This means the inner vertical surface of the bell, plus the space between the outside of the heat riser and the inner surface of the bell being kept to correct dimensions. Still concerned about the effectiveness/efficiency of this kind of channeling. (I've not seen this done before.)

Regarding clean outs... I didn't include them in this drawing. I would mold two clean outs as hi-temp refractory plugs (kind of like tapered corks with a thick lip at the thicker end. One would be just to the right of the feed tube so I can clean out the primary burn area, the other would be where the second 90 degree turn is (clean out facing out), so that I can reach back towards the first 90 degree turn as well as to the right where the "S" shaped burn tunnel takes a 90 degree turn up to the heat riser tube. Each cast plug would fit into two lips molded into the main burn tunnel casting. At the main casting, the orifice where the 4" deep/thick plug would enter, the main casting would have a wider diameter opening where the end of the plug would nest into. That creates the first of two 90 degree lips to help solidify insulation and prevent flames/heat from coming out. At the outside of the clean out orifice, there would be a second lip The plug would have an even wider lip and again create a 90 degree seal for a total of two 90 degree sealing lips/ledges.

I'm going to have to study thermodynamics more to fully understand the issue of insulation around the bells and what that does regarding mass heat absorption and release as well as what it does "sucking" the heat out of the interior of the bell... I "thought" that by insulating the bell, the heat would be preserved and allowed to continue through the system to be shared at other places (2nd bell, additional ducting, possible mass collector at back of fire place.

Perhaps I'm confusing the properties of cob type covering of the bell with "insulation"? You mentioned using a pink or yellow fiber as an insulation... Are you referring to common wall fiberglass batting? or are there other materials used in rocket stove systems that I'm not familiar with? (I'm gathering that "air" in the "insulation" is what actually "insulates" rather than a solid mass like cob or refractory cement sucking the heat right out of it...?

If this is so, what protects the high temps in the burn chamber from being sucked out of the system as it burns using a thick refractory casting? Is this situation a matter of holding the heat within the burn chamber as it burns always generating heat within while the wood is burning, rather than trying to preserve heat as is flows through the system like the bells and/or ducting? Again, still learning, and rather being told what to do, I'm the type that wants to learn how and why so that I can better understand what's going on... LOL! Been like that since i was a kid... ("Why"? ..would drive my parents nuts!) LOL!

When you mention that the cob would suck the heat out of the bell, you also mentioned the possibility of "increasing restarts" in my system... Can you please explain what this is? (I'm guessing that maybe the reduced heat in the bell by having cob mass suck out the heat, reduces draft which might effect my wood burning to the point where I would need to restart due to lack of O2?)

Thanks for all you input!

This is the kind of stuff that opens up a path for me to learn all the stuff I don't know... And I'm sure there's a mountain of that between where I am now and when I actually build the next version of this installation...

Thanks again.

Richard

I meant to add, that I've been experimenting with molding high temp silicone in Platinum based silicone molds. (So far it works and separates using a special silicone-to-silicone mold release.)

My goal (especially for a bare metal sided bell), is to create a thick gasket with a molded slot to accept the bottom part of the bell and then have that thick gasket surrounding the bottom of the bell, slip deep into the cast refractory base for the bell. The seal would follow the bell a couple of inches up the inside and outside, with the gasket being 2" wide, the bottom of the gasket would slip into a channel molded into the refractory casting (maybe 2" deep X 2" wide), so that the bell is held firmly in place with a LOT of contact surface area to seal the connection between the metal bell and the cast refractory base. It also might be strong enough to keep it from moving side to side, but I'm also open to welding stand off mounts near the top of the bell to hold the bell firmly to the vertical white brick wall around the fireplace as I did with this first stove pipe only version.

If it works is should make for super easy removal for ash cleaning (and bell replacement if necessary), while providing a safe and secure seal to prevent any gasses from escaping.

Richard