Advice needed. My rocket won't draw!

My rocket mass heater in my new greenhouse does not work. I have documented the build ......
http://www.youtube.com/watch?v=2bOhbPySnJs


I would b very grateful if someone has an idea what the problem is.......

J

Highlander A. : Welcome to PERMIES !,,,,, And a BIG Welcome to Permies Rocket Stoves Forum/Threads! You have documented on video that you are a great
intuitive thinker ! Your mind is clearly capable of great leaps forward, thinking inside the box actually does not come easily to you ! It will be very interesting to see
what your future builds will be like. It is no exaggeration to say that people like you are the future of Rocket Stove development ! After you get a few fundamentals
and your first build under your belt, your only limitation will be the boundaries of your imagination!

It seems most likely that no one has invited/advised you to go to Rocketstoves.com to instantly download your PDF copy, $15.ooU.S., of Evan's and Jackson's
great seminal book " Rocket Mass Heaters ". There is no other equal source of Rocket Stove information in any language ( And I don't make e'on a ha'penny )

If we can start out together reading off of the same page, I am sure that together we can create for you the first of a whole fleet of future Rocket Stoves, Remember
inside every Rocket Stove build is a wee small dragon ,only needing a few feedings of Small very dry wood to grow and create the magic that turns a house into a home!

If you choose to except this offer, just let me know that you have indeed order'd 'the book' and with the attached map we will follow an unmasked trail to success !

May you be in heaven a 1/2 hour be fore the devil knows you're dead !!! For the good of the Craft! Be safe keep warm! PYRO Logical Big AL !

As always, all comments are solicited and welcome ! A.L.

Highlander, welcome.
There are indeed a couple of restrictions and flaws in your implementation. I have to agree with Allen, buy the book of Ianto Evans and Leslie Jackson, read it carefully from start finish and back again, preferably several times.

Now the flaws, since you are using decimals I will keep on that track:

Throughout the stove a constant cross section area should be maintained. The tunnel should be the tightest part of the system, nothing should be smaller than that. Here you slipped badly, feed, tunnel and riser are 238, 314 and 227 cm2 respectively. The tunnel is far too large here, riser and feed are within tolerances. Moreover, in your video you showed the riser and tunnel part, there's another, higher part in the tunnel as well working against the draft.

Method to calculate the length of the different parts is subject to debate. The best method I have come across is this: take the lenghts in the heart of the openings. Following this, the feed should be measured from the top to the middle of the tunnel, the tunnel from middle of feed to middle of riser and riser from middle of tunnel to end. The best ratio would be 1:2:4, still counting in downstream direction. I calculated your stove and came up with 20.75, 50.5 and 61.75 cm. Feed and tunnel lenght would be OK, riser waaaay too short. Remember, the tunnel should be as short as practical, the rest all related to that.

The top gap, the headroom above the riser should be at least the same as the riser cross section area. This is to be calculated as the riser c.s.a. divided by the circumference. Resulting in 4.25 cm as a minimum value, so the 3.5 cm used in your stove is also too tight.

Another point which is very prone to flaws is the connection between the barrel and bench pipe. This pipe should be the same as the rest of the system's c.s.a., by the way. You would think the connection would be alright being the same as system size, but it isn't. The gases are not streaming straight through the opening, but from the top and the sides instead. The bottom doesn't count as opening because in your case it is blocked by the bottom of the barrel. Assuming the pipe is the same as the riser size, the gap between barrel and riser container can be calculated as follows.
The c.s.a. of the pipe should be divided by 2/3 of the circumference of the same pipe. This will result in the minimum gap you need at that spot. For your stove: that should be at the very least 6.38 cm. Anything smaller and the stove won't run as healthy as it could. A wider transition pipe, like one of 20 cm to 17 cm diameter would result in a smaller minimum gap: it's still the system size c.s.a. divided by 2/3 of the circumference of the larger pipe this time. Your stove could do with a side gap of 5.4 cm in that case. Even better: make it a lot wider combined with a clean out port to remove fly ash.

Length of the pipe run should be a tad on the long side, but it will help a lot when you add a chimney stack, preferably about one meter above the barrel. When the greenhouse is installed this stack should extend at least 50 cm above the highest point of the roof.

All in all, these are a lot of corrections to make, try the easiest ones first and see what the difference might be.

regards, Peter

Mate, first of all, just remove thoses concrete chimney elements. Your gap is not big enough. You can replace that by a sheet of metal folded round the insulation. Keep the refractory elements thought. May be you could keep the bottom concrete blocks, where your burn tunel is, and fit the bazrrel above that. Sliding it on the metal tube around the insulation suggested above. Listen tou Peter for the exhaust to barrel connection, this has to have aplenty of room. What Peter hasn't suggested, looking at your thing in it's begining state with the big vertical opening, is to transform it in a horizontal batch rocket. You could narrow that port, which would become the venturi; with firebricks; and make a firebox in front. Easier to load. longer burns, less tending.

Ok
I am off to buy the PDF, will study and get back to you. Peter, many thanks for your suggestions, I am not sure I understand all of them yet but I will work through it and work it all out. Satamax, also many thanks, yep, the concrete blocks must go, I was interested in what you said about 'Horizontal batch rocket' I have not encountered the term before, will do a youtube search but if you have any links I would be most grateful. I'll get this thing rocketing yet!

Start there!

http://donkey32.proboards.com/index.cgi?board=experiment&action=display&thread=511

Highlander,
A large part of the development regarding the batch box rocket is done in 2012, so it's no wonder you didn't heard of it before. In fact, it is quite a different animal as compared to the rocket mass heater. Based on more or less the same physics but a very different implementation. It's a stove which can take a larger load and it will deliver a far greater yield in a short time. Maintaining the clean burning of a J-tube rocket at the same time. Given a good chimney stack in order to maintain high gas velocity.

The development is described in the thread Max is mentioning above.
In my YouTube channel there are some videos of this.
http://www.youtube.com/user/peterberg10

Peter and Satamax : Lets let 'Highlander' walk before we teach him to Fly! If we just help him to grasp the fundamentals found in Evan's and
Jackson's '' Rocket Mass Heaters ", within 6 months he will be showing us all how to build Rocket Stoves!!!

If we look very carefully at the video that he sent us, you will see a layer of 'heavy-weight 'Wool fiberglass' between the ceramic flue and the
Concrete blocks that he was trying 'to trim down to fit' when he asked for help ! I have seen several builds done here without any insulation
between block and ceramic flue by people trying to imitate the 'European Style' Even if some one is wrong lets take a second look to see
if we can learn something!

Highlander, There is an incredible amount of 'fertilizer' found in places like You Tube, probably 1/2 have been abandoned since being posted,
"HINT" If you only get to see the outside 'build', ignore everything you see ! Ignore 80% of the rest! You are on the right track, read, and re-
read 'the book' if you have any questions someone here can help you ! Just don't let them help you arrange the furniture on your 3rd floor until
they have volunteered to carry in a weeks worth of firewood !!!

For the good of the Craft! b.s.,k.w.! - PYRO AL - As always, your comments are solicited and welcome !

Et all : a perfect example of what I was just talking about !

See '' My first Rocket stove Video !'' ! These young men are the future of our Craft ! BIG AL

Hi guys
Upon first reading of 'the book' its obvious I have some challenges. My exhaust pipe is 12cm Diameter which is too small. Unfortunately it is already burried as I needed to get my grow beds in and get my vegetables planted. I still have access to the stove though so I am now faced with the challenge of re-building the stove to work with an 11 meter long exhaust with two 90 degree bends & which is of insufficient diameter to begin with.
So I will completely rebuild the stove such that the burn chamber is correct in relation to the cross sectional area of the exhaust and that everything else relates correctly to the burn chamber.
Allen, yes, there is a difference in types of materials available here & I have to work with what I can get cheaply or for free.

I will document the ongoing process & keep you posted. Unfortunately it will be a few days before I can continue tinkering, real life intruding upon my projects.

Many thanks to you all once again.

Well, don't dismantle everything yet. I have a six incher exhausting into a 11cm pipe. Thought my heat riser is longer théan usual, at 123cm iirc. And i have a kind of bell just behind.

I'm pretty sure you can make it work with a good chimney stack at the end of your 12cm pipe. High insulated chimney stack, to counteract the Friction encountered in the pipes. Make your rocket part work well first, then you'll see.

Highlander Anderton wrote:Upon first reading of 'the book' its obvious I have some challenges. My exhaust pipe is 12cm Diameter which is too small. ...

So I will completely rebuild the stove such that the burn chamber is correct in relation to the cross sectional area of the exhaust and that everything else relates correctly to the burn chamber.

From this, you clearly see there's no point in starting a build without the right knowledge. That's exactly the reason why I am writing at permies, starting with the right information yields a better chance of success first time.
And yes, when there's no possibility to change the exhaust pipe you have to change the stove itself.

Glad to be of any help, best of luck.

regards, Peter

Peter, I disagree.
While thorough research & preparation are a good (sensible) way to go. Nothing beats trial & error. Having started (and failed) this way just gives me the motivation to keep going & get it working. It took me half hour or so to demolish the stove ready for a 'from scratch' build. Most people waste more than that on watching tv on a daily basis. My failures Just give me a stubborn motivation to keep going and get it right, Which is then fuelled by you guys and your assertions that it can be done. i am enjoying this project very much (I think I have caught the rocket stove 'bug'). Future projects are already forming in my mind- Interested in the rocket stove sauna stove idea & I can't help but think along the lines of making a rocket stove on a big scale............I have access to a grain store, circular, made from old hand made bricks....5.5meters diameter.......heat riser?
Anyway, thanks for your support. I have turned down the offer of work this week so I can get this stove rocketing so updates coming soon.

J

Hello again
Starting the rebuild & I have a question the answer to which I cannot find in the book.

My new build will have burn tunnel with dimensions 9.5cm tall, 10.5cm wide, 49cm long. I am trying to decide on the height of the heat riser. If I use Peters 1:2:4 formula my measurements would be 17.25cm : 34.5cm : 69cm. I would like to take advantage of the barrels I have. As an outer barrel I can use a barrel I have which is 96cm tall. This would give me a significantly longer heat riser. I can, of course, cut the barrel down but I get the impression that the longer the riser the better. Is this really the case or is it only true within certain limits?
The book, page 34, says that "The height in the specimen 8 inch system shown is 33 inches, but could be anywhere from 25 to 50 inches" This seems to indicate that there is an upper limit, if so then how does one work out what that upper limit is?

J

Highlander A.: Just a quick bit of review before I take my best shot at an answer ! What were your original plans for the work load you were hoping this would carry?
I smallish inglenook, Or a big old barn ? In any case, all of our stoves develop their own characteristics some times showing themselves quick/prompt heat sprinters,
Others slow and plodding but in there pulling on the load for days !

We learn our Dragons tempers, and with luck, and similar materials we can come close to duplicating performances in nearly similar environments!

If we try for a truly long Heat Riser we may speed up the flow of gasses to the point that too much heat is finally lost because we didn't get the gasses slowed down
enough for a decent contact time within the Thermal Mass.

We do have several ways of dealing with this, but they too have problems ! We could move the Thermal Mass further from the Rocket stove base. Add air restrictors in
the piping, or add a 'Bell' or two, In one or more locations. This last one would allow the heat to be radiated out to the air saving it from going up the chimney, but not
storing it within the Thermal Mass.

Hows that for a whole bunch of slippery wordage that refuses to be pinned down ! If you just wanted to warm a wee little corner you wouldn't want a very tall Heat Riser.
If you were trying to use a big Thermal Mass, to temper the heat in a big old barn and found that all the heat was radiating from the 1st 15 ' and not getting to the other
end of your 50 feet long Thermal Bench, you might try adding height to your Exterior Chimney to see if that would help before you tore into your barrels and Heat Riser
to get just a little more velocity into your hot exhaust gases !

At best, My answer reminds me of the old bit of folk humor - ''How do you catch a bird?" -''put salt on its tail!'' So my considered answer, subject to change tomorrow,
is sneak up on it , a little at a time and then you can get a chance to see if 'the salt' will help !

For the good of the Craft! Be safe,keep warm! PYRO-Logically Big AL As always all comments are solicited and welcome A.L.

Highlander Anderton wrote:I can, of course, cut the barrel down but I get the impression that the longer the riser the better. Is this really the case or is it only true within certain limits?

This could be found out by trial and error as I understand that's your favorite method, building and rebuilding the stove.
However, I am able to advise you, because I did the rebuilding etcetera already.

Of course, there are limits regarding the length of the riser. Depending heavily on the mass in there. In short, the less mass in there, the longer the riser could be without ill effects. In practise, when the riser is built out of fire bricks there is bound to be more mass for every inch of length. A thin-walled stainless steel pipe with plenty of insulation around it would be close to ideal: very little mass and very insulative. So, better to stick to a length that's been tried before.

Keep in mind, though, the recommended top gap above the riser is an absolute minimum. Stoves tend to be working better with a larger top gap, say 10 cm (4"), and even up to 150 cm (59") there seem to be no hampering of the system. When built up the same way as shown by your video, the top of the riser would be about 80 cm (31") away from the lower rim of the barrel, resulting in a top gap of 16 cm (6.3"), which ought to work with no problem at all.

I've spotted another possible bottleneck, however. The length of your ground duct is 11 meters plus two 90 degree bends. I am not sure this would work, because the recommended length for such a small system diameter is about 20 ft, which would be 610 cm. The stove itself should be really, really good, otherwise you're running the risk the gases will be cooled down too much and the chimney stack won't draw. I can't tell you more about this because I haven't tried the maximum bench length myself.

Ok.
The rocket is intended to heat my greenhouse which is 5m x 2.5m. Primarily to extend the growing season and also to give me a warm place for my morning coffee in the autumn & early spring when its chilly. However......If I discovered that my rocket worked well enough to heat the greenhouse through the winter then I would move my chicken hut in there in the cold season when there is no longer enough light here to grow in the greenhouse anyway, thus allowing me to keep the chickens year round instead of having to eat them once the temperature gets low enough that I cannot have them outdoors. Plus my greenhouse would benefit from chicken waste fertiliser.

But anyway, I have built the heat riser just a bit longer than the minimum and I will try it. I know that I am asking a lot with my 11m underfloor pipe with right angles but I am going to try. I have documented todays efforts and will try to upload a video this evening.

I am going to try something else though, let me know if you think this is a terrible idea but I want to add thermal mass to the heat riser itself. Currently it is made from ceramic chimney pipes with rockwool type insulation rapped around it but I am incasing this within part of an old water heater which gives me a gap between the insulation and the inside of this tank. I intend to fill this gap with sand, the idea being that heat can be stored here also for slow release after the dragon has gone back to sleep. I worry a bit about this extra heat source perhaps making the gap between the riser and the outer barrel to warm so that it competes with the heat inside the riser itself but I shall try it and see if it works.

J

Highlander Anderton wrote:I am going to try something else though, let me know if you think this is a terrible idea but I want to add thermal mass to the heat riser itself.

Not a good idea.
First, the sand will take up heat which isn't available for the ground duct anymore.
Second, because the riser is not very insulated the temperature inside the ceramic pipe will be limited to a lower value.
Third, after a longer period of firing the temperature difference between inside riser and inside barrel will even out. This will slow down combustion, perhaps even leading to backfiring again.

My advice: fill the space with perlite or vermiculite instead of sand, maybe even leaving out the rockwool altogether. The whole point of a rocket heater: maximum insulation around the whole of the combustion zone. The heat will inevitable come through however, the temperature difference will be enormous. The hotter the better, more heat using less fuel, the biggest bang for your buck so to speak.

Highlander A. : I totally agree with Peter here, what you want is insulation to 1) cause the Heat Riser to reach its highest Temperature - and soonest,
giving you a clean efficient burn, 2) The greatest difference between the Heat Riser Temperatures and the much cooler radiating surface of the barrel to
create the 'Heat Pump Effect'* - that makes it all work ! I think that you just had a "cant see the forest for the trees! '' moment, and really are starting to
get this! And yes we all have these moments !

There is some interesting information about a lady named 'Alice' who raised chickens in 'the understory*' of her green house even during greens production,
hopefully someone visiting these pages can give us a link ! Best of luck !

For the good of the Craft! Be safe, keep warm! PYRO - Logical Big AL All comments are solicited and welcome ! ( * my word choices )

Ok guys.
The new improved rocket is now done. 14.5 hours yesterday, finished in the dark. Now I will do a test firing and then I'll post the video. About the sand thermal mass, I suspect you are right..........but I did it anyway before I read your messages & I am going to give it a try. I can't help but question the reasoning just a bit despite the fact that you have far superior knowledge and experience here. The water tank is made of 4mm thick steel so it will heat up anyway, if it were filled with insulation then all of its acquired heat would radiate outwards while having thermal mass on the inside means that some of the heat will be conducted inwards thus reducing the surface temperature of the metal surface. Obviously if the rocket is heated for hours on end the temperature would eventually rise to the point that it would compete with the heat inside the heat riser but I should be able to learn how long I can heat it.

So I am probably wrong here but I'm going to try it.

The video will also show one other improvisation that I wanted to try, As Rocket stove purists you may not approve...............

Going out to do the test firing.

J

Comments?

Highlander A. : This was previously posted (in Part) to another gentleman who didn't understand where we came from, and thought we would tell him how to violate
All of the laws of thermo god damn ics for his pleasure !

Here I am just trying to re-enforce why we think insulation rather than sand ! Cheers,watch out for the Parmy bstrds ! >>>>> 20 yr history of Rocket Stoves ( RSs )

20-ish yrs ago RSs were made of materials that ''let'' RSs survive the high temperatures that allowed the incredible efficiencies their Unique Structure was capable
of producing !

Since then there has been the use of different materials that were lighter but still capable of surviving the high Temperatures. Due to less heat '' BEING LOST " to
heat energy Penetration/Absorption into its thermal mass the new RSs reached their extremely high operating temperatures much more quickly, further decreasing
energy lost to earlier 'cold' start-up inefficiencies !

The prototypes of tomorrows RSs are made from refractory/ceramic like materials, capable of of handling the Rockets extreme temperatures - with only slight heat
absorption, quickly glowing red hot and producing their high er/est efficiencies that much sooner!

With all the advances in RSs construction we can look forward to demonstrations of long term viability of RSs that can be batch loaded! Other developments will follow!

( But not from those people out there who always follow 'the rules ') For the good of the Craft! Be safe, keep warm! PYRO - Logically Big Al - All comments solicited /
welcome ! A.L.

Highlander,
The item you're missing here is the chimney stack. The stove is working as it should because it's outside. When the greenhouse is built around it, the game will change in the way that the roof of the greenhouse should be airtight, otherwise the stove wouldn't draw. Moreover, it will draw much better using a vertical stack.

Of course you should use insulation instead of sand, but it's your stove, you're entitled to make your own choices.

The vacuum cleaner is blowing a bit too powerful, I would say. Why not blowing from the top at a lower rate, you could refill without problems then. In case you would like to make a waist oil drip it's best to have something like a bunch of criss-cross large nails welded together as a bird's nest at the bottom. This way, the oil will have a large hot surface to evaporate on.

Peter Berg wrote:Highlander,
The item you're missing here is the chimney stack. The stove is working as it should because it's outside. When the greenhouse is built around it, the game will change in the way that the roof of the greenhouse should be airtight, otherwise the stove wouldn't draw. Moreover, it will draw much better using a vertical stack.

Of course you should use insulation instead of sand, but it's your stove, you're entitled to make your own choices.

The vacuum cleaner is blowing a bit too powerful, I would say. Why not blowing from the top at a lower rate, you could refill without problems then. In case you would like to make a waist oil drip it's best to have something like a bunch of criss-cross large nails welded together as a bird's nest at the bottom. This way, the oil will have a large hot surface to evaporate on.

In my case the vertical chimney really made a difference ,it would smoke in bursts before , but when adding the chimney the draft stabilized and works very well, also i tried the p-channel mentioned in other threads and it also helps alot, seems like a turbocharged draft, the flame is more steady and strong.

Highland A.: Is that a clean out cap to the right of your Rocket Stove? I am Positive that you will decide to change that to bring it as close to your Rocket Stoves (RSs)
Base as posible, this is a number one location for the build up of Fly Ash, though if you insist on running 'your turbo charger' you will be blowing all that Fly ash into
the Horizontal Pipe! If you want to continue to use this, then it would be a good idea to have a second vacuum, as if the first one fails when the system is dirty,without
the boost your system can't handle the blockage1 and without a working Vacuum - - -

I freely admit that this is minutia, but you are teaching yourself a bad habit ! You should always load the thick end of your wood down, towards the bottom of the Feed
Tube. That way your wood should always feed into your Rocket without wedging together and hanging-up, You dont want to starve your Dragon with its food inches from
its snout, It wont like it and play tricks on you ! For the Craft! B.s.,k.w.! PYRO - AL , your comments solicited/welcome A.L.

Allen
I bow to your superior knowledge. You are without a doubt correct about the insulation/sand thing. It is done now and I am going to leave it and see how it goes, It will no doubt effect the burn characteristics but I'll see if I can get the hang of making it work well enough to heat this small space, should be interesting. This is my first rocket, there will be others I am trying to source the light insulation materials you have mentioned but have not yet found them.

Thanks for the tip on which way to load the wood. Its in the book but I forgot. As for the vacuum thing I do not really expect to use it on a regular basis, and I think I have about 7 vacuum motors so I don't think I'll run out.

It is indeed a clean out cap to the right of the rocket at about the 9 meter mark, however, during the rebuild I added another one immediately to the left of the stove where the exhaust leaves the barrel.

Peter
The stove is working with the short stack currently but I am heating it just for short periods each day to 'break it in' and slowly get out the moisture. Later, if it does not work so well I have a long pipe ready to try. But I think you misunderstood, the rocket is not outside, the greenhouse is already built.

Yes, the vacuum is too powerful but I could not resist giving it a try, I already have a nest of bolts welded up for the drip fed waste oil burner but this is really just an experiment. If it works then I will leave it installed just to give myself options, if I should at some point need to really quickly heat the greenhouse in a hurry.

Leonard
I have not seen the P-channel yet, can you provide me with a link?

Ok, I have found all of your help and encouragement invaluable & I will keep you informed how the stove operates. But I would like to ask your advise on my next project. Its not a rocket stove but it is quite closely related. I am renovating my house, when I bought it there was an old "drum-stove" it is a traditional design very common here which incorporates its own thermal mass. Very much like a very big heat riser (210cm tall, 70cm dia.) the fire is lit at the bottom, heat goes up the center to a second chamber at the top (gas burning chamber) and it then sinks all the way down and goes into the chimney at floor level. It was in bad condition & I demolished it & am starting from scratch. I have the original plans (dated 1898).
would you guys consider looking at the plans to see if you can suggest any modifications, using your rocket knowledge?

j

Highlander Anderton wrote:I have not seen the P-channel yet, can you provide me with a link?

Development of this feature is only about 2 years old, this is the link.

Highlander Anderton wrote:Its not a rocket stove but it is quite closely related. I am renovating my house, when I bought it there was an old "drum-stove" it is a traditional design very common here which incorporates its own thermal mass. Very much like a very big heat riser (210cm tall, 70cm dia.) the fire is lit at the bottom, heat goes up the center to a second chamber at the top (gas burning chamber) and it then sinks all the way down and goes into the chimney at floor level. It was in bad condition & I demolished it & am starting from scratch. I have the original plans (dated 1898).
would you guys consider looking at the plans to see if you can suggest any modifications, using your rocket knowledge?

This do sound like an early contraflow design. Would be very interesting to see how people implemented that more than a century ago.

Ok, here are a few images. the first is the outer shell of the drum, the second is the cross sectional views and third is the layer by layer building diagrams.

Very interesting. But... I've seen those drawings before, these are from a Swedish or Finnish design. Based on the original design of the kakelugn, a round Swedish contraflow heater of the 18th or 19th century. Of course they didn't use oil drums back then, but tiles on the outside. See this link how it would look like. The term 'kerros' meaning 'layer' is a Finnish word, even the title of the jpeg is Finnish. This is funny, some people used the drawings to incorporate the innards of the stove into a couple of oil drums. The firebox is very small, probably this stove has been used for heating a single small room.

Some posts back, you wrote these stoves were once common around where you live. Just to be curious: where are you located?

Unnecessary post, please ignore.

Highlander A.: This is, like Peter Berg says, a later day adaptation of an all brick model But, I Think that for many people it would a more esthetically pleasing than
the old 55 gal barrel on a clump of mud! That IS all that some people can see when they look at a modern Rocket Stove! A good working model like in your picture
should be preserved somewhere in a museum ! PYRO AL

Peter B. Nice pictures , Same as what I said before except, i would like to preserve one of these in my home ! Big AL

Well the word kakelugn actually means 'tile oven' so yes those are tiled but the version within a metal skin is still very common, certainly couldn't put this in a museum as I would say that perhaps 10% of houses here have them and companies are still producing the metal shells & colleges are still running courses in how to do the brickwork. The firebox is, I thought, quite big, spanning levels 6 - 13. Traditionally houses would have several of these, each in a different room but clustered around the chimney at the center of the building creating a large thermal mass in the heart of the house, in fact its even called exactly that 'talonsydän' house's heart. They work extremely well, usually you burns one 'pesa' (literally translated this means 'nest', fire box) every other day, even in the depths of winter which can be harsh here, -20 degrees celsius for several months, sometimes -30 and I have seen -40. Yes, Kerros means layer and the name of the Jpeg is indeed Finnish, I scanned the plans and named it Pönttö, these stoves are called 'pönttöuuni' (drum oven). I have also a diagram showing a variation from 1940 but there is no text or layer by layer breakdown. But back to the question. Can you suggest any modifications?

J

So you're in Finland then. I have been there once, when I was still young and foolish, hitch-hiking through Europe 44 years ago.

And yes, I can suggest some modifications. Keep the outer shell, complete with drums and skip the entire firebox/riser assembly. Replace this with a very recent development, the horizontal fed batch box rocket stove. See this link for the development process, please read it in its entirety if you are interested.

In short, the riser is then placed behind the firebox instead of on top, with a narrow 'port' between those two. At the top of the port a secondary air channel, the riser round or octagon shape. This thing, when running properly, will roar like a true rocket. Like one of those little Optimus petrol burners, only louder and at a lower pitch. About 5 minutes after the fire is lit, the smoke will disappear and will stay away as long as the roar is going on.

I could draw a stove sporting this firebox in SketchUp format if you are interested. To that end, I have to know what the dimensions of the metal outer shell are. And the size of the exhaust to the chimney. Scaling up or down can be done without problems.

Wow. that really is interesting. I am intrigued!

Yes, absolutely I would be interested in a sketch-up design so I can start to really get my head around this. I also have to admit that although I have now read the p-channel threads I still really don't understand what it is, can you explain it or give me a link that explains it to a novice like myself?

the pönttö is 208cm tall and the inside diameter is 70cm. The door is 42cm from floor level and measures 30cm wide by 32cm tall. the hole to the chimney is 13cm wide x 20cm tall and its bottom edge is 6cm from floor level (photo attached).

J

Highlander Anderton wrote:I also have to admit that although I have now read the p-channel threads I still really don't understand what it is, can you explain it or give me a link that explains it to a novice like myself?

This channel is part of a development done in 2011 merely on the normal RMH, you'll have to read this thread for that. In short, it's a secondary air channel of specific size which feed into the tunnel at a specific spot. Also the batch box rocket stove do use one of those.

Just wait a few days, I'll throw a drawing together which will make the principles clear. Scaled to the chimney of 13 x 13 cm, or 5" square. That would be on a par with a round pipe of 13 cm, airo dynamics -wise.

OK then, the drawing is ready, sort of. In fact, the batch box rocket is fitted with a firebox which can be loaded in the classic way. The difference is a kind of afterburner behind it. This implementation sports a bell setup to extract the heat. Look through the pictures, you'll see a riser behind the firebox, located in the center of the stove. From there, very hot gases are spewn up the bell. The shape of the stream is as follows: straight up from the riser until it'll met the ceiling, from there curling to the side and down all around, like the shape of an umbrella. The downward stream is coming down all along the walls of the bell, that's the reason to have the riser in the center. The hottest gases are at the top so that's where the majority of the mass is situated. Exit hole is at floor level at the back, but it could be anywhere around the perimeter, even at the front.

The last picture shows the inside of the firebox and afterburner/riser. The high and narrow port is 70% of system size, which in turn is the c.s.a. of a 12 cm diameter riser. It could be a little larger, but I estimated this as perfectly adequate for the size of the internal surface area, ISA for short. The octagon (or round) riser will be the cause of two vortexes, spinning in opposite direction. See the short video of that fenomenon.

This vortexes are in turn the cause of a very thoroughly mixing of the unburnt gases and fresh air, the last one provided by the p-channel, the black steel rectangle duct on top of the firebox. Main air inlet should be at the bottom of the firebox, comprising about 20% of system size, p-channel 5% of system size. This setup need to have an adequate chimney stack, this stove is depending heavily on a high gas velocity. The net result is a truly smokeless stove, running a very aggressive burn. Damping down shouldn't be done at all, this will kill off the excellent combustion properties. Any questions? I'll try to answer these to the best of my abilities.

Pete Berg : Thank You very much,Very Clear pictures, and definitely worth an APPLE ! However, this Information
needs the largest possible dissemination !

This needs to be re-posted as a whole brand new Forum Thread, not just buried here as just a follow-up
members Comment ! - this is just my opinion ! Pyro AL .

Peter
Excellent diagrams, fine work.
I already have a multitude of questions but I will study the drawings in detail and then ask everything in one sitting. Because of the nature of this build, with all the brickwork being done inside the metal outer casing and then the next section of the casing being lifted into place and the next stage laid within it, I really have just one shot at this thing so I have to get it right first time. Therefore I hope you don't mind that I am really going to pick your brains to make sure I am understanding everything perfectly. The chimney, by the way, is a touch over 10 meters.
Thanks again and I will post again shortly with questions!

J

Peter, this is superb. There's one thing different i would do. Make the base out of bricks, ok, filled with veminculite () But i'd go with two barrels on top, for the sake of easyness, and suround the barrels with brick latice or brick fins. I'm trusting more a barrel for being gas proof.

I quite like the way len does it



Or a nice brick latice



It's just another idea, which could speed up the build, still keep some mass, but also have direct heat. Yours is real nice, but imho, it would be complicated to make for some dumber like me.

@Allen,
The possibility of a separate thread didn't cross my mind, sorry. We'll see how this will go. After all, this design is specifically suited to a small stove and as much mass which could possibly fit inside. No direct radiation as such, I think the demand for such a stove would be small.

@Highlander,
When you are really interested, I can make the SketchUp drawing available. You have to have the SketchUp application to review this, but a free version do exist. Maybe you could ask questions about the main issues first, working down to the finer details along the way. Your 10 meter chimney stack is perfectly adequate I would think.

@Max,
This stove would be as airtight as any other, because the barrel is at the outside. Having the mass inside, directly in the gas stream has some advantages. For example, there wouldn't be a transfer from steel to brick, only from gas to brick. This way one transfer phase has been ruled out. The difficult part is de firebox/riser assembly plus door, the rest of it do consist of a lot of whole bricks, only the top is quite complicated. Maybe this could be done another way, skipping the 45 degree and just corbeling up. It would be interesting to see this one, built into two of those large salvage barrels, 400 liter a piece, equivalent to 106 liquid U.S. gallons. Using lime mortar to fill up the space between the bricks would add even more mass. Interesting...