Exhaustion pipe not really hot

Dear all,

I am very happy because today we could finally see our Rocket mass heater finally burning successfully with good draft. We did another one in the garden before and then we decided to start build the real one. Everything went fine but we noticed the temperature on the exhaustion is not that hot, I would say something about 40 and 50 celcius (sorry I don't have a thermometer) but perfectly bearable with my hand, the rocked was burning for about one hour and I could put my hand in any point of the exaction pipe. The top of the barrel was very hot, I could not touch it. I am wondering if anyone can tell me what I can do to improve my system.

I am very glad to have started this thing as here in Uruguay nobody does anything that is diferent.

thanks a lot for this great idea and any help will be very much appreciated.

our best wishes

Carlos and Nara from Uruguay.

Carlos & Nara : First, Welcome to the PERMIES Forums, And Congratulations and a big WELCOME to Permies Rocket Stoves Forum/Threads ! Second, nothing may be wrong !
Did your flame start burning sideways,from the Feed Tube,and down the length of your Burn Tunnel, disappearing out of sight with a nice throaty roaring sound?

If you have followed the typical pattern and built your Rocket Stove With lots of Cob, and have done the same with your Thermal Bench, you have to dry out all that huge
mass of Cob before you will see much in the way of Elevated Temperatures. Lets hope that you are one of the lucky ones that got it right the 1st time around !

In order that you can use the same description words,and have some basic understanding of their meanings and usage, please let me direct you to Rocketstoves.com where
you can upload your PDF Copy $15.oo U.S., of Jackson's and Evans' Great Book " Rocket Mass Heaters "! There is no other book that contains as much Rocket Stove
information in any language!

In the mean time, any pictures that you could share with us of your stove as it is now and/or pictures of it being built would help us greatly ! Did you follow a set of plans to
create your Rocket Stove, and if so, Whose ?

Here at Permies we generally talk about the Cross Sectional Areas, or C.S.A.s of the various parts of our stoves generally ending up with round stove pipe going into our
Thermal Mass. We can talk in inches/feet or in MMs or Cms and Meters/metres,and everyone here will make an effort to switch from one to the other without too many
mistakes !

It seems as though you are telling me that you have a length of stove pipe coming out of the base of your Rocket stove that is not covered in Cob, due to the temperatures
you are describing, I believe that you have most of the rest of your pipe running horizontally through your Thermal Mass, well covered with cob !?! Are you getting a steady
stream of condensed steam out of the end of your exhaust pipe !?!

Finally what is the diameter of your pipe in your Thermal Mass, And how long is the total running length of your Exhaust pipe and how manny elbows !?!

(everything we do here is-) For the Good of the Craft! - Be Safe, keep warm! PYROLOGICALLY Big AL _ as always all questions/comments are Encouraged and Welcome! A.L.

Well, 40 50 celcius seems a smidge low, but not much. My workshop one doesn't go much over that and this is with no mass, but a long barrel and a bellish thing which slows down the flow to extract heat. I'm usualy in the range of 60/67/68, never seen it hotter. If you have mass, 40 could be normal before complete drying.

Carlos : Just in case Satamax and I weren't clear, just continue to heat-up your Stove as weather permits, and answer the questions as you have time !
Again you may be one of the lucky ones with no problems but to make new insulating cushions for your Thermal benches ! For the good of the Craft !
Be safe, keep warm ! PYRO - Logically Big AL - As always, your questions and comments are solicited and are welcome ! A. L.

Hey Allen and Samatax,

Since I wrote my original email and you answered back I continued customizing my exhaustion pipe as for the first fire I use a window as an exit. You're totally right about the water contained in the bricks and cob and now temperatures are slightly higher and I managed to have boiling water on the top of the barrel, despite the fact I have more than 8 cm between the end of the hitting tube to the top of the barrel, the sides of the barrel also irradiate lots of heat and the exhaustion pipe is almost unbearable to touch barehanded. No smoke in the house at all, and yes Allen, fire goes horizontally into the burning tunnel and the roaring noise you referred is always there. I did not start to build the bed yet as I am still arranging the exhaustion pipe I want to test it on its final position before starting to fill the gaps with cob and other debris. Here in Uruguay and specially where we live which is far from the main city there is a lack of supply specially tubes and when you find it is very expensive.
I think, Allen, we are lucky for having being able to build the heater just watching videos and reading descriptions in internet and still no smoke in the house.

On the other hand while burning I noticed in the connections of the exhaustion pipe (in the vertical segments) a brown liquid which is condensation but I am curious about the nature of this color, do you think this might be from the kind of wood I am burning or wood not totally dry, I guess it is dry but cannot say for sure. I am burning local pine.

Allen, you asked about the diameter of the pipe, it is 15cm (6 inches) and yesterday I had 9 meters 27 feet of pipe, today I will try another setup for the pipe and I guess it will end up with about 11 meters 33 feet, 5 90 degree joints and 1 180 degree joint.

Allen, yes for your question about getting steam out of the exhaustion pipe and the temperature of the steam is bearable bare hand.

Another question is, because of the difficulty in the pipes down here I am thinking on making up a hole into the bed using bricks but no metal pipe, this way I can save the pipes I have to portions where I have to have it. Does this make sense? what do you think?

Guys, thanks for your replies and for you time reading this long email and sorry for the delay in answering.

temperature today dropped to 3 Celsius, I guess we have an early winter this year.

Best wishes

Carlos and Nara from Uruguay

Carlos, some would say it's pushing it to put 11m behind a six incher. (150mm is close enough) Even more if you don't have a chimney stack.

Carlos : I too find your expectations as to how far your Rocket Stove can push your Hot Exhaust Gases thru your Thermal Mass unlikely! As a general rule we count every
Elbow as being the Friction loss equivalent of ~ 5' ~ for each 90 degree elbow. Elbows that are more open than a true 90 degrees are calculated only a little shorter. Adding
in your Elbows, you are attempting to double the length of pipe you are trying to flow your exhaust gases through! Not Knowing the piping layout you are trying for I can not
tell you how many Clean outs/inspection ports you are going to need for cleaning but for every elbow you replace with a more expensive 'tee' fitting and clean out cap you
add to your friction losses! Generally the entire tee should be oriented horizontally to make using it for cleaning easiest !

We can increase the distance you can flow your exhaust gases three different ways ! The first one is to close the gap between the top of the Heat Riser, and the inside of the
top of the barrel, to 1 1/2 ''- 2'' . keep the distance between the outside of the Heat Riser and the Inside of the Barrel a minimum of 5cm all around.

The Second way to create more push to flow your hot exhaust gases farther through your thermal bench is to raise the height of BOTH the Heat Riser and The Barrel up as
much as 30'' more. this will definitely create more 'push' and more 'flow'.

The third way is to raise the height of the Exterior chimney ! Here due to problems with local weather patterns, and directions of prevailing winds, you may be required to
raise the height of your Exterior chimney at least 3' above the tallest part of your roof , we will leave this until last !

You are going to want to insulate your Rocket Stove very well just to get a little more push! Keep all of the walls of the interior plumbing as smooth as you can make them
for the same reason. Always pick the cleanest, smoothest sides of individual bricks to face in towards the interior spaces of the Burn Tunnel and base of the Heat Riser!

This will be the first time that I Post to you about the Transitional space between the bottom of the barrel and the Horizontal pipe leading into your Thermal Bench ! Here is
where you will want your 1st clean out ! The hot exhaust gases should flow out of the barrel into as large an opening as you can create,turning 90 Degrees in a big sweep-
ing turn before being funneled horizontally in a straight run through your first clean out ! You should have the walls of your transitional space as smooth as finish plaster !
If you have hurried through this part of the build, you should give some strong consideration to redoing this section, it is one of the most likely areas of system failure and
can eliminate all of the potential gains we mentioned above ! In order to create as large a cavity to flow the gases, and make the 90 degree turn as sweeping as possible
we may need to raise the entire height of the Rocket Stove base by the thickness of one (or more ) bricks ! For right now just be aware that this is a possibility based on
present rocket stove performance and desired improvements !

For the good of the Craft ! Be safe, keep warm ! PYRO Logical Big AL - As always your questions and comments are encouraged and are Welcome ! A. L.

Hello Allen and Samatax,

After various attempts which included the rebuilt of the connection between the burning part and the exhaustion pipe as per the Allen's advice to pay attention to this part and smoothing a bit more few parts that were made by cob and, also per Allen's advice closing the gap between the top of the barrel and the upper part of the heating riser, we manage to have a pipe setup that fits our needs (I will try to describe the pipe after) and is functional. When I say functional I meant it worked as it should but needed first of few minutes of heating as at first it was pushing smoke back into the house. After 3 or 4 newspaper full pages it started to work nicely and kept burning and drafting for 4 hours by now.

As I mentioned before the pipes are 6' (15cm) and I have 4 meters right after the burning chamber with a 180 degrees turn (2 meters and then 2 meters) then I have another 90 degrees elbow
and the pipe starts going vertical for 2 more meters (into de house) then another 90 degrees elbow and the pipe starts going horizontally for 3 more meters then it exists the house and there is another 90 degrees elbow that makes the pipe to go vertical again outside the house which I think is our stack that going up for 2 more meters and overpasses the roof by 50cm. Did all this make sense? on the top of the stack I have one gallon can which I made to turn with the wind, this was a last minute project and needs to be improved but it works for the time being.

The portion of the pipe that is going to be the bed is still to be covered and although we still have a lot of water to burn from the cob the pipe is a bit hot, I guess something about 60 to 70 Celsius.

I will continue to test this setup for few days and decide whether to cover or try a different layout.

Almost forgot, Allen I understood what you said about the tee's being horizontal, but this is something I will have to make by myself as there are no Tee's available nor flexible pipes.

And finally I have a question, what you suggest as a creosote and other liquids trap? is there a picture you can send me of something like this?

Thanks a lot for all the information you've been providing.

Best wishes,

Carlos and Nara

Carlos and Nara :W.O.W., a lot of good hard work ! ( and room to grow ) I wish that I could promise that you would never have any problems with Creosote!
I am willing to concede the possibility that, after your ceiling level pipe carries the gases outside and they cool a little you could have a problem with it there,
put a pinhole in your elbow down low !

Having problems with creosote is unheard of when one is able to get good hard wood and dry it for a year before you burn it ! Because you tell me that you
are burning pine I would suggest trying to always create the hottest fire you can, small and hot being better than lots of wood and just burning pretty good,
I would always be on the lookout for all the hard wood you can find, to include the hardwood found in old furniture that is being thrown out, its generally clean,
and unpainted, without varnish etc.

After your pipe makes its 180 degree turn and comes back running along the wall, of what material is that wall made, and what is on the other side of it !

Eventually we will talk about plans to install some thing called a bell just above the 90 degree Elbow that brings your pipe from the horizontal to the vertical !
When you are ready to cover the most amount of your pipe in Cob, plan on covering the whole first vertical pipe with Cob , here you could try a couple of
deep niches, for allowing the dough/unbaked bread to rise, this may be a great area to hang your outside coats etc. so that they are always warm and dry!

O.K. I understand that you are going to make your own 'T's, (and Cob caps?) Go to your hardware supplier and see if you can find a clear picture of a ''Draft
Corrector"! If you can get a clear picture of how to make a draft corrector ( NO You do NOT want one of these !) you could even make one that straps onto
and around your horizontal pipe, and a couple of sizes bigger to make it easier to get in there to inspect and clean, after all this is only a form to support your
Cob while it is drying ! This is a very good place for a some 2'' long pieces of straw in your Cob !

The two of you are the only people who can determine when you have an ideal layout, think about how you are going to open and close the doors while your
hands are full of wood, and where you will store a couple of days worth ! I have a very funny story of a minor coal gas explosion when my father went down
to the basement to 'shake down the fire' and provided extra oxygen to a pocket of hot coal combustion gases - it was a very minor explosion, more like a
small bang, but it blew the upstairs smoke pipe apart and my sisters were covered with soot !

Nothing like this can happen to you with the Rocket Mass Heater system you are creating. You may eventually have a slight drift of fly ash in your ceiling level
horizontal pipe, but that is all ! I just want you to have your ceiling level horizontal smoke pipe so well suspended from multiple wires that it can not fall even
if it were to become unhooked !

For the Good of the Craft ! Be safe, keep warm ! PYRO AL - As always, your Comments and Questions are solicited and are Welcome ! A. L.

Carlos, how you gonna cob that one?



Well, it would be better to cob that one, as well as the first vertical one. The second vertical is outside? If yes, to avoid creosote problems, insulate it with rockwool or something.

Carlos and Nara : Don't wrap the vertical pipe in anything, the insulation will get wet and work against you! Insulated
pipe or triple wall, is very expensive here, and very high down there ? Insulating the last part we will put in the
hands of God ! With just a little Devine disinterest we can forget about it, and never worry about it again!

Carlos,how did you pick that point to exit out the house with your Exhaust Pipe ! was it just because the builder put
a hole for a smoke pipe there ?

Mom Wisdom ' If every one of your friends jumped off a cliff would you jump too?!' - Where have your neighbors
Exhaust pipe exited out of their houses, is it on the lee side, or generally out of the wind? does the chimney get any
direct sun ? These are things to worry about ''tomorrow'' !

About making ''T''s, we have very heavy cardboard tubes which are normally used as forms to fill with reinforcing
rods and concrete, and used to make support columns, around here they are usually sold under the brand name
sonnotubes! With acouple of these, and a good pattern from a "T" or the big strap-on part of a ''Draft Corrector''
you can ether cast your ''T" in place, built with Cob with Straw, and then reach in with a Utility Knife and score it
heavily and then burn it out, or cast the whole Part as a separate piece of cob to manhandle into place. ( I don't
Know HOW to do the last one its only a suggestion! )

As a third choice you could wrap lots of cardboard around an undersized form to make up your "T"s, build with clay,
and 'pick your form apart' after your Cob dries!

Let your friends and fellow members here at Permies know how you are doing, and send lots of pictures ! Remember
when in doubt, Don't lower the barrel, raise the Heat Riser/Interior Chimney !

For the Good of the Craft ! PYRO Logical Big AL - As always, all Questions/Comments are solicited and Welcome! A.L.

Dear Allen and Samatax,

Please let me use parts of your original posts to organize the following text.

I would always be on the lookout for all the hard wood you can find,

Allen, we have eucalyptus here which is harder than pine, it is hard to cut too but I will try to get some when I have a chance. People don't throw old hard wood furniture away here, actually down here people throw away only garbage.

After your pipe makes its 180 degree turn and comes back running along the wall, of what material is that wall made, and what is on the other side of it !

Allen, on the other side we have our living room, the wall is made by clay bricks and concrete bricks as it was the outside wall. This part of the house where we are installing the Rocket is a room that we added to the house.

On the subject of the 180 degree turn, we decided 3 days ago to go single pipe under the bench and simplify the project therefore we exist the Rocket then 2 meter of pipe then 90 degree elbow toward the sky inside the room. We will accept and implement your idea of a coat hanger in the vertical pipe inside the house which we will cover with cob. Then this pipe climbs about 3 meters and turn 90 degrees to be horizontal again just to cross an outside wall then turn 90 degrees again toward the sky outside the house.

We tested this design and it worked nicely. I guess this answers the question provided by Samatax on how to cob the horizontal pipe that were formerly running into the house. We are not.

install some thing called a bell -

Allen, do you have any picture of the bell thing, I am curious about it.

When you are ready to cover the most amount of your pipe in Cob, plan on covering the whole first vertical pipe with Cob , here you could try a couple of
deep niches, for allowing the dough/unbaked bread to rise, this may be a great area to hang your outside coats etc. so that they are always warm and dry!


Allen,Those are great ideas I am going to implement them.

Carlos,how did you pick that point to exit out the house with your Exhaust Pipe ! was it just because the builder put
a hole for a smoke pipe there ?

No, I did the whole where we thought might be the right place.

Mom Wisdom ' If every one of your friends jumped off a cliff would you jump too?!' - Where have your neighbors
Exhaust pipe exited out of their houses, is it on the lee side, or generally out of the wind? does the chimney get any
direct sun ? These are things to worry about ''tomorrow'' !


No building standards are being followed here, each one has a different way to have their chimneys. I understand the Mom wisdom here we don't follow anybody, I actually think this heater is the only one in the whole country. We are currently thinking on building a tire house which will be also the first on the whole country.

Yes the chimney gets direct sun as the whole house confronts the North, so we have sun all year round. Is this important? why?

To finish this long email, I have two new questions please let me know if I need to open new topics,

First one is about smoke leakds, I guess if I have small wholes on the metal pipe I can cover them with cob, right? and I also guess that in doing so they will be air tight right? please correct me if I wrong.

Second is about the bench, I have a lot sand here, as I live 2 from from the ocean, not really ocean as technically speaking this is a big river mouth and the ocean is about 50 miles down the river, but there is plenty of sand, what is your opinion about filling part of the bench with sand provided I did a contention wall to receive the sand. Of course not all the bench will be sand but only parts of it.

again, thanks a lot for your time and information.

Best wishes

Carlos and Nara

Carlos and Nara : I'll try to answer a few of your questions, I have time issues just now ! I will be back ! about the barrel oil it just like you would a cast iron skillet!
It will get more beautiful every day ! In a perfect world the wind would blow from one direction only, and your chimney could be on the 'Lee' side of your building !
Just because every one exited their chimney in one place would not have made it right ! Smoke leaks can be dealt with by burying in Cob! Sand has tiny air spaces
and is insulating. Use as much Cob as you need to completely cover your pipe, the vertical parts will have to be built up ! The heavier the material that you add to
your Cob the more heat it will hold and the faster it will transfer the heat from the horizontal pipe out through the Cob and warms buts and your whole house ! I
hope that we can impose on Satamax to send you a link to a clear picture of a bell, I believe he will be able to explain it better too ! For the Good of the Craft !
PYRO LOGICALLY BIG AL As always, your comments are Welcome and solicited ! A. L.

Hi everyone, this is my first post in permies forums.

I am also interested in finding more about what temperature have the gases as they leave the barrel into the horizontal pipe, the one usually covered with cob for mass heat transfer.
I'm interested in it because I suspect that between the max 600-800 centigrades (or more?) in burning zone down to the 40-70 centigrades at exhaust, the most significant drop is inside the radiating metal barrel. That would make the rocket more of a direct heater stove instead of a mass heater.

One simple way to increase the temperature of gases entering the benchis to simply reduce the heat lost through the barrel, by using a smaller barrel and/or covering it partially, at least after the room is hot enough.

All other sizes being the same, the 8" flue will draw almost twice as much combustion air, and fit twice the wood in combustion zone as the 6"... that means twice the power. Shouldn't the exposed convective metal surface (barrel surface) be half size too for a 6 inch pipe?

regards,
cezar

cezar blimpyway : Welcome to Permies, and a Big Welcome to the Permies Rocket Stoves/ Rocket Mass Heaters Forum Threads! You will always remember your 1st
posts here !

This is where I ask all New Rocketeers and Members Of Permies to go to rocketstoves.com to pick up your PDF Copy $15.oo U.S.D. of Evans' and Jackson's
Great book - Rocket Mass Heaters . There is STILL no better collection of 'Rocket Stove Family information', in any language * (I don't make a dime ! )

Each Rocket Mass Heater R.M.H. is an Individual Thing, As is the Dragon that lives inside it ! The design plans from this Book for a 8'' R.M.H. are a proven build that
will produce a R.M.H. with very similar traits every time ! This is an Excellent design for a First time build - My personal Strong recommendation would be to live with
a new R.M.H. for about a year before modifying a working Rocket, or attempting further experimentation.

Said another way, it IS MUCH BETTER to have 12 months experience with a Single R.M.H., Than 1 months experience with 12 Rockets !

Due to both the joys of Personal Creation, and the pleasures of playing with Fire, some people go on to create multiple R.M.H.s without learning their Dragons temper-
ament first, and often get frustrated by planned or unplanned design changes that reduce the R.M.H.'s performance.

An R.M.H. with the Heat Riser / Internal Chimney set with a close air gap to the underside of the Barrel will deliver a lot of prompt heat causing the top of the barrel to
glow orange, so easily 1/2 of your max temperature !

The heat radiated off of the barrel here allows the creation of the 'heat pump', pushing the exhaust gases past 30 feet horizontally through the Thermal Mass, and must
be a planned part of the build. However if after living with the R.M.H. for a while the Owner can decide to cover the lower 1/3rd-ish of the barrel in Cob for more heat
storage in the Mass .

From a physics point of view the heat radiating off of the Barrel is interesting ! Due to the High Speed of the exhaust gas flow at this point, The over all contact time is
actually limited enough that most of the heat is delivered into the thermal mass ! Again there most be a large and prompt heat loss at the barrel to create the 'heat pump'
effect. A smaller drum MOST radiate the same amount of heat as a larger Barrel to create this effect ! It's a mass to surface area thing with the smaller barrel
having the smaller Surface Area !

This effect is most noted when your 3 year old wants to climb up in your lap for a cuddle, due to their High Mass to Surface Area, it's like having your own personal
radiator in your lap !

Heavy quilts, or Futon mattress-like covers are a common way of controlling the amount of heat radiating off of the Thermal Mass. With the 8'' system you can still build
smaller fires to regulate room temperatures on more temperate days ! Smaller fires will require some use of bricks or flat stones to cap off part of the top of the Feed
Tube to channel a reduced flow of air more directly past the smaller fire. Too much air will actually cool the fire and upset the 'draft' ! Hope this Helps ! With 17,000 +
members you can always get several answers to all your Questions !

* There are adaptations of 'the book' in French, Spanish, and (?) out there, for people who think better in their 'mother tongue' !

For the Future Good of the Crafts ! Be safe. keep warm ! As always, your comments and questions are always solicited and are Welcome ! PYRO - LOGICAL Big AL !

Hi, thank you Allen for the warming welcome.

My heating needs are quite low, it's a 150sqft, lightweight (litle mass in the walls), well insulated cabin, which could be easily kept warm with a 500-1000watt continous heat source.

I'm hesitant on just using an existing, proven rocket heater design since I feel the 8 and even 6 inch flue, full 50 gallon barrel with 2 tons of bench storage are too much - overheat and overweight - for such a small space.

From Janto's book and other good sources I found that the mass heater isnt easy to scale down but still, if most of the heat of combustion could go into mass storage then it might be usefull.

Finding how much % of the heat is imediately released through the barrel and how much of it goes into the mass storage is as simple as measuring flue temps in three points: combustion zone, the passage between barrel and bench and the exhaust from the mass bench.

I have found figures for combustion and exhaust temperatures, but not in between.

thank you

cezar blimpyway : You do have a problem, While there exists out there a few sub-6'' R.M.H. Systems that appear to work, This is a build that I have not even attempted!

We have to talk about laminar flow, for figuring gas flow thru a pipe we treat it just about like a liquid, a given diameter of pipe flowing material through at a given rate
has high friction losses at the pipes wall. Right at the contacted area of the pipe we go from a low flow to a no flow. This loss of working area ( my word choice ) is the
reason that a sub 6'' system is so problematic !!! In a straight section of pipe the hottest gases are in the center, even a slight bend in the pipe introduces a lot of
variables !

So - while we can gather true temperatures at the skin of the metal parts easily, most of what we think we know abut actual interior temperatures are actually just inferred

One could create an experiment placing a small target mass in the center of a pipe close to the start of the horizontal ducting, run the R.M.H. to a steady state of operation
and use a infra-red probe at a small inspection window to attempt to measure those temperatures !

Due to the high Heat Energy contained within the 'Latent Heat of Evaporation' , we need to know how much water vapor is in the Wood we are burning and being created by
the combustion of the Woods Cellulose Hydrocarbons ! -Or not ! This is over my head !

You really need to start a brand-new Forum Topic to address this specific issue! Piggy-backing on an old Forum Topic is an expected new member mistake which we nothing
to address except here and now by experience Again, with 17,000 + members we should be able to advance your knowledge on this subject !

With everything already said, I still would recommend you follow a Proven build for your R.M.H., Even if it means you are making it - for a friend !

For the Future/Good of the Crafts ! Be safe, keep warm ! As always, your comments and Questions are solicited and are Welcome ! PYRO - LOGICALLY Big AL !