Design advice needed

We are going to remove our inefficient, big-box purchased wood hog of a stove, and build a Dragon ! I've read Ianto's book, watched tons of YouTube videos, and haunted these forums for a while. Of course, I have questions I'd like to have answered. So, out of the shadows I creep. Any and all advice would be greatly appreciated.

Some background:

WHO - 43 year old family man. My wife and I have a 13 year old son, and a 2 year old. And no, we DONT get enough sleep ;^) despite the help from my sister in law who also resides with us. We care for an elderly gentleman with learning disability as well. Throw in a couple dogs, a mix of cats, and some chickens.

WHAT - 130 year old farmhouse in a constant state of remodel. We heat entirely with firewood. I have a large stove in the basement that heats via ductwork. We also have a small stove in the lining room on the main floor. This is the one I'm replacing with an RMH.

WHEN - soon.

WHERE - nw PA. Snowbelt. Surrounded by agriculture.

WHY - Comfort, reduction of wood consumption, safety, and satisfaction of building something ! I want a butt / back warmer I can enjoy once I fight for a spot from all other inhabitants. I use a huge amount of wood, with most of its potential floating out the chimney. I want to get rid of the burn risk of cast metal sitting where my 2 year old is constantly passing thru. It's constantly too hot, too cold, rarely just right. Also, I love the look of cob benches !

HOW - I have a number of interested friends, all eager to fill my house with mud ! I just need the confidence to go thru with it.


LAYOUT - I have a 7' section of wall, extending from a corner, that I want to build on. I have 25' of vertical triple wall stainless steel chimney to hook up to once the wood stove is pulled. It is 6" ID. I am pouring a reinforced footing, and installing a steel I-beam to handle the weight.

My biggest question at this time is regarding the ducting. I was going to do 6" all he way thru, based on my 6" diameter chimney. But, different things I've read make me wonder if I need 8" to get enough heat. Am I correct in understanding the 6" vertical can handle the "volume" of exhaust gases, since it will have condensed due to cooling after it's heat drawing off into the cob ?

Or, should I stick with 6", and try more lengths of horizontal run to pull the BTU's out ?

Thank you in advance for all advice.

Hello Robert, welcome to Permies!

Short reply to you question:

if you choose 6" ducting then you should design the rest of the RMH (J-tube diameters, barrel size, and maximum ducting length) with 6" in mind. This should be no problem if you are heating a smaller area say 600 - 1000 sq. ft. It will be a problem if you are trying to heat a large farm house. Since you are replacing a small wood stove with a small RMH I don't see a problem.

Make sure the floor of your house is able to support the weight. You might need reinforcements.

Personally, I would love to reuse the existing stainless steel chimney and not waste materials.

Thank you Brett. Yes, reinforcement of the area is planned.

I should clarify, I have no delusions of heating the whole home from this RMH unit, the home is too large and drafty for that. Last winter tho, we had such ridiculous cold, we ran both stoves. It consumed WAY too much wood, and made the dining room too hot for comfort. We used fans to try and distribute the heat further thru the house, adding yet more expense in electrical consumption . My wife would stay up to the wee morning hours keeping the fires going so it was reasonably warm.

The RMH replacing this will give us a more regulated warmth in this prime living space. I just wasn't sure if I could use 8" all the way till the 6" vertical exhaust chimney. I thought I saw somewhere that someone had success with a "throttled down" scenario like this, but can't find it again.

I will be using the stainless steel triple wall already in place, just pulling out the wood stove hooked to it.

Robert; Congrats on discovering RMH ! They really do work ! Unfortunately I don't have enough experience to answer your question about the 6" chimney , but my guess is it would work but.... wait for more answers from more experienced people .One question though ; could most of your 25' be replaced with 8" thin wall hvac ? pipe temps after leaving your mass averages 130 F. 5' sticks of that are $11.00 at home depot ,if you replaced most of your 6" with 8" I'm pretty sure you can go thru the roof with 6". What I can recommend is get yourself a load of clay and a bigger load of sand home now, before freeze up . A bale of straw not hay is used as well. locate a source of lincoln 60 fireclay, you'll need it also. If you haven't already, look (on permies) into building matt walkers cast riser & cast core. The cast riser using a burnable inner liner & the 16 gal barrel works exceptionally well.

Thanks Thomas for the welcome. I hadn't considered pulling the triple wall due to lower exhaust temps. Tho it would be safe, I'm going to leave it. We are subject to routine inspections by unenlightened cubicle dwellers with clipboards due to caring for an elderly man with learning disabilities. ( hopefully that was all politically correct so I won't get penalized )

They already get a frightened look on their faces when they see a wood stove, firewood, chimneys, etc. I have to jump thru a ton of hoops as it is. I'm willing to bet if I put something without a UL approved sticker on it for a chimney, I'll have to revive someone with smelling salts. I'm going to surround my barrel with brick or something artsy to make it look as little like a hobo heater from a city alley as possible =;^>

LOL Robert; I hadn't considered the bureaucrats sticking their noses into your business. I guess living in the wild west, I forget about small details like that. If you surround your barrel with brick make sure to leave plenty of air gaps for the heat to radiate into the room as well as to allow for cooling air to create the pull on your riser. I've included a pic of the barrel in our greenhouse heater. As you can see I left the top 1/4 black steel and cobbed the rest. The 2" tile sticks nicely to the cob and a mixture of red & black concrete color gives it a nice brick color.

I like that look Thomas. Is your barrel top removable, or do you have clean outs down low ? I'm thinking of using a barrel with lid and clamp for top cleaning.

Yup, top is clamped and I have a cleanout door at the horizontal transition area . I did not need to open it at all last season. I did a core rebuild this spring and removed maybe 2 gal of super fine fly ash from my low point below the start of the horizontal pipe. The removable top barrel is nice for riser inspection and if you have power, a shop vac will suck your seasons fly ash up without opening your cleanout door. Having a cleanout is important , with mine open and a bright light I can see down 11' of pipe to my 180 turn. I also could stick the shop vac hose at least that far in if i have a blockage of ash. Oh before you ask , I rebuilt my core because, being in a green house it gets run way longer than it would in a house. My original core & riser were a casting of fireclay/perlite and a little refractory. Performance of the core was awesome but the feed tube and (by the end of the season) the roof of the burn tunnel were wearing to much and I ended up with a feed tube hole the size of a 5 gal barrel and i had to keep it partly covered at all times to keep from smoke back. The cast riser however is the same one with no problems.

Robert D. GreatAdvice so far ! Sounds like you have the Floor bracing well in hand, here's some great help to help you determine your best way to protect your floor.
goto :::-->

www.youtube.com/user/villagevideoorg Right clicking with your mouse should get you there, or to a [google search] -so 2 clicks maybe !

At Village video's u-tube page find the topmost set of short video clips Labeled Rocket Mass Heater Scenes hover your mouses Icon just to that lines right !

You should see and click on a [> PLAY] button, sit back and enjoy, this excellent professionally made video shows the first 3/8ths of an upscale build by Ernie and
Erica Wisner (and is for sale in its entirety)

They are our Rocket and Wood stove Forum Moderators here at Permies.com. More information is available at ernieanderica.info/shop, the whole site is very
useful in setting up for a build, and following through without losing your mind ! Good Luck come back here often, with over 27,000 Fellow Members and our own
search engine feature you can come here 24 / 7 and expect to get knowledgable help from members whose different outlooks will stretch your mind as you stretch
ours!

Think like Fire! Flow like a Gas! Don't be the Marshmallow! As always your questions and comments are solicited and welcome ! For the Good of the Crafts! Big AL

I like your setup Thomas. I've not seen the "recipe" for your casted riser. Can you link me to it ? What's its advantage over a stacked fire brick riser ?

Thanks Alan. Working my way thru your linked info as well.

Robert ; go to youtube (scary) look under broaudio , this is matts page and you will find plans for his cast core as well as the cast riser (core part 2 ) As far as an advantage over fire brick ? Well not much really, round riser verses square, cheaper to build ? maybe , better insulated ?? probably.

Robert D. : Thomas is being extra nice and giving me my usual place on the Soap box, to Warn you about The crap that you can see on U-tube !

U-Tube is hungry for content, it will take anyone Videos, and nether makes any judgement calls for commonsense or safety, and has no program
for Peer Review, it is actually SO Bad that after someone posts a video of a Flaming Unit of Death, 4 months later there will be a new crop of
Frankin-clones out there ! Let the viewer beware ! If in doubt ask here ! for the Good of the Crafts ! Big AL

I have another question guys.

As I'm doing projects around the house today, I'm in and out of the garage. A low watt bulb popped on over my head when I moved a bag of kitty litter. The ingredients - bentonite clay. Could these tiny chips be mixed up with water to make clay slip ? Could you mix portions of it, perlite, sand and water to make a pourable casting material ?

Sorry if it's been tried and discussed already. I'm BUSY today and too lazy to search the forums.

Thanks, and have a great weekend.

Robert; In short, NO ,kitty litter clay is not suitable in a casting . I wouldn't even use it in the mass. You want fireclay for your casting and hopefully free clay for your mass.

Rob D. : Fire clay gets its name of course because at the very high temperatures it takes to make china Very little of the china is lost to cracking !

A Few reasons for this good effect in china ! 1) Fire clay has VERY LITTLE expansion with heating or contraction as it cools ! 2) The type of sand,
and how much of it there is, the sand sits between the clay particles and reduces further the amount of Expansion or Contraction, some clay like Kaolin
is perfect clay as it comes out of the ground, and some clay already has perfect sand in it! 3)we add stuff in with low expansion rates, this material as a
group are called Grog! Bone China, which most people who know next to nothing about china Know is good China (!), is one example of a superior grog !

Sorry, There are few clays in this world that can be considered to be poorer clays for building than Bentonite ! Big AL

Thanks for the info. I figured it was probably unsuitable, that being why it was sold for cat port-a-johns ! I' ll do some reading up on clay before I retire for the evening.

So, the fact that perlite has a low expansion ratio and high melting point, along with high refractory properties makes it a good additive. Proper clay has good binder and thermal storage, and sand serves as an aggregate, am I correct ?

Robert D. : There are actually two units of Measurement for Determining how good the Heating qualities are of any Rocket Mass Heaters RMHs Thermal Mass
(or Any Thermal Mass)! An RMH made of just Cob can be improved on !

The two units of measurement are 1) Heat Capacity : which is related to a given materials Density, generally we say the heavier the material the more heat
it holds ! 2) Thermal Conductivity : this is more closely related to how the atoms or molecules are stacked within the material ! short version most 'rock' does
a better job in capacity AND Conductivity.

Generally a well made Russian Masonry Heater is expected to have a high Percent of very dense Rock. The RMH can be made to match the Masonry stove,
If you want to create an equal to the Masonry stove, one of the additional duties of Cob or actually pure clay slip is to 1st coat all of the potential contact areas
to prevent voids, voids equal a lack of mass to hold heat, and voids equal an area that heat 'flows through' very slowly!

A second place that is often seen with problems with voids is where we are using 'Urbanite' or recycled concrete! Here the rough edges and porosity of the
surface of the 'Urbanite' also require a coating of clay slip, and the careful bedding in of the chunks of Concrete, an important goal is to use mostly Rocks for
a greater amount of heat energy Capacity, and heat energy Conductivity. An additional goal is to use mostly rock to reduce the amount of Cob being used.

Cob as already said, is not the best material to use, and making cob is a labor intensive material, so that the less cob made -equals saved time on initial build,
and saved time and saved fuel with a shorter drying time, a more efficient Thermal Mass can be smaller !

You probably have noticed that there is no mention of a perfect ratio of clay to sand, this has a lot to do with the type of clay and the amount and type of sand
that is commonly found in mixed amounts found with 'natural' clay

I hope this is both helpful and timely, For the Good of the Craft ! Big AL

Indeed Al, helpful and timely. But, it also invokes more question - sorry, I'm one of those people who will keep going till I feel I understand all the angles sometimes.

My next question is, are you gaining enough thermal advantage by collecting and carefully utilizing real stone (dried properly, of course ) encased well in cob, leaving no cavities, or should old clay brick dipped in clay slip work as well, with it's more regular shape allowing easier building outweighing a nominal gain in storage mass ?

I also want to apologize in advance - if I ask the same thing in a different way, or re-ask something as a discussion progresses, please don't think I'm not paying attention or ignoring anyone. I have a lot of responsibilities and lines of study going simultaneously, in addition to a teenager and a toddler ! At times, I'm running on minimal sleep, maximum stress, and inhuman caffeine.

When interested in learning about things, such as RMH, I am studying numerous topics. I'm rereading Ianto's book, browsing numerous threads on these forums, following various links out to Wikipedia, YouTube, Adobe, clay, home made firebrick, refractory cement, DIY forges, passive solar heating, thermal capacity of various materials, AND following current infection rates of numerous near epidemics.

So, my mind is periodically a jumbled mess.

Thank you to all patient enough to help me learn and understand.

Robert D. : I have a smaller s.u.v. type hybrid with careful driving i average out at 30 mpg, once a week I am paid to go to a meeting that is 25 miles
and climbs about 900', I go to an old mining quarry and pick up about 100 lbs of Iron ore every friday.

My down hill run averages 33 mpg(!), I will probably do this for several more years, I will use these materials because they are better, free, and familiar

I am within 40 miles of good Potsdam Sandstone, which was Used for decades to line the inside of early american blast furnaces, this is a very dense rock
with good expansion and contraction hence durability characteristics ! No one is paying me to load and move this stone, and I do not have a place to get
it for free !

That day may still be in my future ! One Of the best small joys in my life is a good hustle. Opportunity comes from where you look for it ! Big AL

Late note : For the record there is a lot of crap on u-tube please be suspicious of all of the things you see there, You-tube is hungry for content, and the
whole thing is less regulated than a whorehouse on saturday nite in the old west !

Since you ask : goto :::--> traditionaloven.com/artiles/101 <--::: (Try a right click to save typing this in your address bar )

After you finish that article look for similar articles at the bottom of that page ! A.L.

Robert; After surrounding your horizontal pipes in cob , as Al said ,adding as much solid mass as possible holds the heat better than just the cob . Other than the weight, solid rock will hold more heat than clay bricks. I thought of it as a cob and rock lasagna.Couple inch layer of cobb ,layer of rock, more cob... patting the wet cob by hand compacts it and drives out the air pockets, similar to vibrating concrete. I would mix up a five gal bucket of cob outside & bring it in to make my lasagna in lifts , leaving it to start air drying as i worked my way down the mass. Easy really... sort of fun (note making cob is HARD) In my case we topped our mass off with rock but could have gone the last 2" as a cob bench .

thomas rubino: You have just been credited with the creation of the word phrase '' Cob and Rock Lasagna '' a very powerful phrase
that evokes a powerful image (the pictures weren't bad ether!)

It is definitely a Jargon Translator Thread-worthy Creation !Big Al

You had me at "lasagna" !

Is this a kiln firebrick ? 9" long, 4.5 wide, 2.5 thick, and heavy.

Are these durable in high heat ? Has anyone tried them ? They were house foundation blocks. 16" long, 6" square tube.

Robert D. : The 1st new picture is definitely fire brick, and the second is definitely terra cota, I am un-familiar with their use as foundation pieces, perhaps
as a form to fill w/ concrete for a small outbuilding For --- --- -- --- Craft ! big AL

They aren't super common , but we have a number of homes in this area with these foundation. I pulled these from a home that burnt down. How durable would these be to RMH temps ? I was thinking a heat riser application.....

Robert D. Now is a good chance to self test your ability to find Its constant cross-sectional area and determine which round stovepipe will match its C.C.-S.A !

Otherwise no ! for the crafts, Big AL

Robert, i would make a cut lenghtwise on one of the faces of each of thoses, with a diamond blade in the angle grinder, and try them. You make a temporary backyard rocket. Insulate thoses with rockwool, and see if they develop other cracks than the one you have created.

The terra cotta pieces can stand the heat, but only if raised no more than 50°F per hour. Since a rocket heater gets hotter much faster than that, Santamax is recommending that you slit them and put some insulation around them for testing. The rockwool may or may not handle the temps making their way to the outside if used around the burn chamber of a j-tube. Ceramic fiber is the only thing which will definitely not disintegrate.

Cindy Mathieu wrote:The terra cotta pieces can stand the heat, but only if raised no more than 50°F per hour. Since a rocket heater gets hotter much faster than that, Santamax is recommending that you slit them and put some insulation around them for testing. The rockwool may or may not handle the temps making their way to the outside if used around the burn chamber of a j-tube. Ceramic fiber is the only thing which will definitely not disintegrate.

Cindie, you often speak out loud, but you still haven't tried rockwool? Protected by terracotta, it can handle whatever rocket you can throw at it!

Thanks Cindy and Max (and all other posters) for the info. Keep it coming ! It's really helping us advance our planning a dragon for our home.
I

Cindie, you often speak out loud, but you still haven't tried rockwool?

I said that it may or may not handle the heat because WEB4DEB has a pellet rocket heater in which he wrapped his metal heat riser with rock wool. In his autopsy published on 2/22/2013 at minute 1:36 he shows how the metal is long gone and the rock wool has deteriorated significantly.

We used rockwool on the outside of the firebrick in our kiln, so it is a material which is known to us.

You might also notice that in the rocket they built at the workshop in MT recently, they used ceramic fiber blanket around the feed tube and heat riser areas of the combustion system.

Cindy, i've seen that video! If protected by refractory clay tubing, or even thoses terracotta things, it should be perfectly all right!

You know my opinion on metal heat risers or fireboxes!

Metal is doomed!


And compared to kaowool or any other ceramic wool, the stuff is far cheaper, and can be found in nearly every skip in europe!

I have never said to use the stuff unprotected. That it you have me all crossed!

Edited, because i am nice!

YAY !!! I finally found a company ( 45miles away ) that has bags of fire clay and both kiln bricks and wood stove splits. AND they are a fraction of the price of the big box stores ! Saturday the recycle yard will be open, and I can get the 8" ducting. The cement company across the river has some old building bricks. Still after my steel drums, but I'm getting closer to building my heater.

I have a question. Not that I'm going this way for mine, but i see cast risers, they are mostly square shape, with the trip wire and upward slope molded in. They usually transfer to a circular heat riser ( I know not always )

The question is, why is the casting never made out of circular tubes ? Wouldn't that aid in gas travel , and turbulence ?

Well, it's harder to create turbulence in a round shape, the laminar flow effet being the same all around, while in a shape with corners, the flow gets slower in the corners, this is creating more turbulence.

Ok, so is it better then, to have a square heat riser as well then ? Aaaaaiiiiigh ! It's probably just the late hour and the cold meds, but I feel so confused. Every time I think I'm understanding where I want refractory, I read something that says, "insulation", and when I want circular laminar, then suddenly, maybe rectangular turbulence is better. =;^>

Oh happy dilemmas ! I just wanna get a successful dragon in my home for the winter, and spring to come again so I can play with experimenting for myself outside with different things designs for fun. Ok, I'm taking some Tylenol and going to sleep. Happy burning all.

Thanks for the reply, Satamax.

Any update on this project?  I'm located not far from you in Saegertown, PA and want to get going on making my RMH.  Looking for help and would love to see one of these in action.

Matthew

B Deereborne wrote:Ok, so is it better then, to have a square heat riser as well then ? Aaaaaiiiiigh ! It's probably just the late hour and the cold meds, but I feel so confused. Every time I think I'm understanding where I want refractory, I read something that says, "insulation", and when I want circular laminar, then suddenly, maybe rectangular turbulence is better. =;^>

 Oh happy dilemmas ! I just wanna get a successful dragon in my home for the winter, and spring to come again so I can play with experimenting for myself  outside with different things designs for fun. Ok, I'm taking some Tylenol and going to sleep. Happy burning all.

Thanks for the reply, Satamax.