relationship between the end of the riser and the top of the barrel.

this is my first post on these forums and im not great with forums . but I shall try to do my best .
quick story . so im building a greenhouse . a winter greenhouse , temp gets as low as -5 . after researching , it'll be sunken with insulated back wall . so I figure it'll need heating . as I researched heating I hit early on Paul Wheaton rocket mass heater you tube vids and bang that's the design for me . so I spend time soaking up all the info I can find about rocket mass heaters . so now im at a stage where I understand how it works , what drives it and how it all fits together . the better designs and more impotently the fails . so I get all that .
but there is one thing that im not getting......... so the air gets sucked in heated up and comes out of the top of the chimney into the barrel . what is the relationship between there and the top of the barrel . how does having a larger space above the chimney effect the mass heater / all I can think of it that by having a larger space increases the cooling effect . is there something more to it then that ? is my question .
I want to build and try something different to the barrel design . I have planned what im calling an Avalanche rocket mass heater .  I plan on replacing the barrel for a chamber that slopes down and round the backs of the seating and then under the seating , down deep to the channel that will lead off the the mass. so think of a corner with the rocket part sunk into the wall in the corner and coming out the top of the wall (thing of a triangle with a circle balancing on top) . so I cover it all (leaving space for some metle cooling) and then down the sides of the slope . down to a point where it exits . I hear the barrel gets too hot to sit next to sometimes , but if the cooling is going on above head level and the seat cob is thick enough the seating will act like its own mass. but the heat will be even through out the whole thing.
the question is to design enough cooling to make it work , but not to much cooling , because the more heat I put into the mass and the less into the air around me the better. I want the mass to heat the air after all . now the kicker here is ill be building it all out of cob with a touch of cement . I think I can make it work without the metal . with the metal its all about small area that can cool fast . cob does not cool fast , but if I increase the area of cooling so that the whole tops of the seats are all cooling , maybe itll work and if it don't I can just sink a metal plate into the top to help .
I also figure I can make the rocket out of what I call washed clay. I take clay mud from my garden , mix it with water till all I got is muddy water , take away what's floating on top and what's laying at the bottom and just let the muddy water evaporate back to clay. iv e been watching these vids where these peeps are working cement by hand and I can use the same methods to make the rocket part of the heater.
I got it all planned out . but the true reason im typing in a forum , is that I don't know what I don't know .  I may think I have it all figured out , but how could I truly know. so I open it up to the people that may have heard all this before and say someone tried that and it didn't work or advice to make it better .
so I start this humble thread in the hopes of not making lengthy mistakes that cost time and money fixing . thank you for your time and look forward to hearing any ideas about this.

So what you're really asking is less about the gap between top of riser and top of barrel/enclosure, and more about an alternative enclosure to a steel barrel.

The short answer is yes, it can work, depending on the details. I would want the cobbed-in space to surround the riser, it can be just a couple of inches of space in front and back and sloping out to the sides. This will act like a bell, and allow the hottest gases to stay at the top and the cooler gases to settle to the bottom and flow to the chimney. The seat backs will be by far the hottest part of the surface, with the bench getting warm last. You would probably want most of the back to be very thick, 8" or more, so it absorbs heat and doesn't get uncomfortably hot while the bench is still cool. A bell system has design rules, principally the amount of interior surface area. It needs to be the right amount to absorb the useful heat, but not so much that the exhaust is too cold to make a draft.
Bell sizing
See the previous section, Bell theory, for more on how and why this works.

Your idea is conceptually and functionally similar to a rocket-fired masonry heater Peter van den Berg built at an MHA workshop a few years ago: Bell with two benches

You are probably overthinking the amount of clay preparation you need to do. If your soil straight from the ground makes bricks that are hard and at least somewhat durable when dried, you may be able to use it as is. You don't want pure clay, you want around 2/3 or a bit more sand and gravel. For mass construction, even stones up to golf ball size are not a problem, rather they increase the density and heat capacity of the clay. For surface finishing, you may need to refine your clay some.


I wouldn't bother putting any cement into the mix. If you use some straw, that will reinforce it well to minimize cracks. In a greenhouse, you probably will want some sort of stone, tile or brick facing to protect the cob.

How deep are you thinking of for the exit channel? There is a limit to what you can do and maintain draft, and especially a deep dip may make it hard to start. It will work best if the chimney can rise near the core, to be warmed a bit as it leaves. This also allows a bypass to be inserted, so the fire can be started easily, and then diverted to the full mass route when it is going well.

How big of a system are you considering (chimney diameter, which should be about the same as the core interior cross section)? The bench and seat back setup you describe may take all of the heat, leaving nothing for an underground channel. How are you thinking of routing the exhaust - distances and configuration?


To answer your specific initial question, more gap between top of riser and top of enclosure principally makes flow easier. If you have a steel plate there, closer is better for a concentrated hot spot for cooking if that matters, otherwise I would give it a few inches minimum. Also, if you make a cob enclosure, you would be well advised to put in an access panel where you can get to the riser for inspection and maintenance. This will also serve as a bit of instant radiator, but much less than a whole barrel.

wow , some great comments and so fast , thanks Glenn .
please let me just say im in the digging phase now . after new year I will be digging, bagging and building. I cant see me working on the inside till late spring/early summer. not to get into it ,but im somewhat disabled , but I am stubborn in equal measure . so plenty of time for planning . but just for peoples mind eye , the plan is for a  greenhouse to be 8m x 4m with a slope to the north and 1.5 m to 2m below surface . So I plan ether run the gasses the length of this and possibly back again . So the seating and rocket will be 2m x2m , then up 4m and 7m to 8m back to the heater some way . I hope to make as large a cavity as deep as I can/should . Failing that I may send it through the north side slope. Hence why im here .

“I would want the cobbed-in space to surround the riser, it can be just a couple of inches of space in front and back and sloping out to the sides. This will act like a bell” . I figure the top of the seat will act as one large long bell , Dissipating heat . But I am with you on the thickness of the cob around where people sit . It will be think , but I had not thought it may steal to much heats and leave little for the green house. I hope I can tune the flow better by how thick and high up on the seat I cob. But I may conseed to an inspection hatch on top .

“Your idea is conceptually and functionally similar to a rocket-fired masonry heater Peter van den Berg built at an MHA workshop a few years ago: Bell with two benches “  so looking at that design , so standard Wheaton down , across and then up the chimney . The top of this shall be ground level and as far into the corner as the across will let it. So above ground shall be the bell that separates  like your link pic ether side into an L shape with the rocket in the corner . Then I hope  to have enough cooling so both sides join as one and flow down a slope between ground and cob to the opposite corner to the rocket then off down the mass and back . I working on the pricable that gas moves like water and have all that heat fall down the slope , cooling all the way till bell becomes seat . This is how I see it in my imagination. I haven't seen anything like it to show you a picture off. Why im trying to make it this way is that later I want to add a water radiator and hook it up to a water mass and a flat slope works well for that . Later plans.

“You are probably overthinking the amount of clay preparation you need to do. If your soil straight from the ground makes bricks that are hard and at least somewhat durable when dried, you may be able to use it as is. You don't want pure clay, you want around 2/3 or a bit more sand and gravel. “ as a comedian once said , a cunning plan , failing only in two points . I don't have any sand and I don't have any gravel. LOL . In truth I am too poor to buy it and too disabled to find it . What money I had for this has gone on bags for walls , 2 clear tarp for a roof and a couple of much needed digging tools. In fact im hoping Santa will bring me a bag of cement .

“I wouldn't bother putting any cement into the mix. If you use some straw, that will reinforce it well to minimize cracks. In a greenhouse, you probably will want some sort of stone, tile or brick facing to protect the cob. “ the cement will be for the pillars between the cob and the slope . But the main reason is to make a strong caverty underground to run the gasses through . If I make it out of cob also , I fear the moister in the gases will break it down . A coating in cement will seal that up for me.

“How big of a system are you considering (chimney diameter, which should be about the same as the core interior cross section)? “ as I have typed above as to full size . But the info is that the opening at the first hole has to be the same as the exit of the chimney . I would say the diameter of a plastic downpipe for waist on a house . Make a circle with your hands and put an inch between thumbs and fingers and you got about the size of it .  So I want to make it out of just clay so I can work it as it dries to make a twist in it to help with the cyclone effect in the chimney. But I will take you up on the cob idea as the wall of the chimney gets deeper . The difference here is normal the chimney is a tower inside the barrel . I plan it to be solid and built into the ground .

“The bench and seat back setup you describe may take all of the heat, leaving nothing for an underground channel. How are you thinking of routing the exhaust - distances and configuration? “  this is something I had not thought on . But thinking now , this is the good thing about cob. I build it with minimal cob , maximising cooling and then I build it up thicker and higher up the slope , tuning the heat and flow , till I get it just right.

“To answer your specific initial question, more gap between top of riser and top of enclosure principally makes flow easier. “ that's the thing . So the bigger the space under the bell the better the draw . But the gap top of chimney to top of bell does not need be large . That works out well for me as I would not have much space from ground to tarp above it . Very much thinking on the access hatch in top . I figure an old frying pan upside down would work just fine. Just cob it in after I have a look down the chimney I guess as you can never really know how the thing will hold up over time.
I'm not a fast reader and a slower typer . But I got there in the end , one pizza , one beer and two smokes later .

Hmm... you're talking about a 5", or would it be 6"?, J-tube system. Just so you know, the smallest system that is known to work reliably for most people is 6" diameter, and for the size of greenhouse and the bench/underground combination run, an 8" system would be more likely to work for you.

I think you would get much better results warming your greenhouse if the whole core and bench arrangement goes in the center, or at least on the center of the long north wall, so there is not a long underground run to worry about. Slightly off-centered near the north wall would make it so that no part of the greenhouse is more than about three meters from the mass. With the seat backed into a corner, half or more of the heat would be going into the earth rather than the greenhouse. Do you anticipate the bench regularly being used for seating of more than just the person tending the fire?

You spoke of separating out the clay in your soil; what else is in it if not sand/gravel? How much organic matter is there after you remove the topsoil? Is there a lot of silt? That is not necessarily fatal, as long as there is enough clay in the mix to make a sturdy brick. I have built small pottery kilns with native clay which has a lot of silt; it is not very strong, but strong enough for mass structures.


Twisting the riser to try to make cyclonic flow has been shown to have no beneficial effect. The kind of turbulence you need for mixing happens from the sharp angles in the flow path, vertical feed to horizontal burn tunnel to vertical heat riser.

Glenn Herbert wrote:Hmm...
Twisting the riser to try to make cyclonic flow has been shown to have no beneficial effect. The kind of turbulence you need for mixing happens from the sharp angles in the flow path, vertical feed to horizontal burn tunnel to vertical heat riser.

That is an interesting opinion, not something I can accurately dispute but I believe a well formed vortex can make a difference.
In theory a spinning volume of hot air will take longer to travel up the riser and might allow a shorter riser to still be effective?
I have also read that a vortex will very effectively draw in secondary air and feed it into the centre of the riser where it is most wanted?
I have done a fair bit of testing on my own rocket stove but until I build “mark two” with a purpose designed vortex, I can’t really say if a vortex will make any “real time” difference.
However I have followed several Facebook  builds that use vortex designs, not surprisingly the builders believe their designs to be more efficient!

First off , thanks . Its good to have someone to talk to , where I don't have to explain what it is first so they can understand what im talking about. Not that im great at explaining . Still .

Glenn , dude , you must have small hands LOL . 6 to 8 inches sounds about right . Maybe I just got giant monkey hands he he he . Something that's been nagging me about it was the heat coming off the riser(that's the chimney part right, see learning) will be sinking into the ground around it soaking it up and insulating the riser . But being in the southern corner the heat would go out to the sides and up through the ground.  I thought I would be maximising the growing space to the north. But now you mention it . I should be storing as much of that heat to the centre . As for seating , I started thinking loads of seats , but then I don't know loads of people , Doh . so I figure one for me , one for a guest and maybe space for a 3rd to just squeeze in . As I am typing I am now contemplating the idea of moving it to centre north slope or one side , north slope. No centre would be better .
(quick pause of contemplation)
so I had a smoke while looking at my hole . Weighing up to too's and throws and I figure your right  , the riser would be better of to the centre of the north slope . I did have my hart on underfloor heating . But fact , the heat is best stored in the slope where there is most insulation . So it come out the riser , down the slope under two seats , then curves back underneath at floor level back into the hart of the slope where ive made a large open space the length of the greenhouse slope . Just one large empty space . Sort the exit from the chamber later . It would make it much more effective and probably less work .  

As for the mud , standard mud with high clay content. Lots of chalk and flint. I built a oven/BBQ out of it , I started with cob , but found I got a better quality of finish if I washed the mud like vie said and kinda paint it on think and let it dry each day , building it up over days of repeating. Once the thing was fired ,it was rock hard . I found if I cob up think , you get the cracks and then you cob over the cracks , but the cracks are still there under Neath. But by slowly layering up im filling the cracks in before they can form . Guarantee the mass would be solid , think and even with no impurities and I got a lovely finish to the outside and inside. So I figure it should be good for the finish on the inside of the riser.

As for the cyclone thing . I know im new to all this , but if I can chip in what I figure and maybe point out where you think im wrong . So gas moves like water , simplifying it . So I think there is no way of  keeping the gas in the riser for longer by making it cyclone for one reason . What is in the riser needs to be pushed out the way by the flow of gas coming after it. It would seen that it would stay there longer by spinning but in fact by spinning it you are making it travel faster , but the same pressure is there , the gas would have to travel out the top at the same speed at what it is coming in at. Lest you have a pressure build up. So I think  by spinning it would not make much effect then to just look pritty . Has anyone tried studs inside the riser to help mix it all up without spinning it I wonder.

fox James  I just don't see how . The flow is controlled by the pressure . What goes in , has to come out at the same quantities or pressure blow back . The pressure in the riser should stay constant . By spinning it , it does force it to travel longer , but the pressure then forces it to travel faster . So that what goes in also balances with what comes out . It has to balance , if it don't then you got a leak .

ill leave a pic i hope it uploads . but a pic of the area to give you better perspective .

The temp. in the riser is 1500-1800 F   studs would melt.

let me quick add . the hole corner behind the tree. its two meters from the wall and tw from the hedge to the leftand from that corner it 3 m across and 6 long . i hope to finish by slpoeing the sides out 45 degrees . im just moveing the topsoil to the right, so as not to put my best soil sequested away in bags to build up walls.the slab by the window is my resting seat where i have a cuppa and watch the birds.
but i fear this may be moveing off topic about rocket mass heaters.
*quick edit*
tom , yes i figure also . but a few low down in the riser may not get as hot as one higher up and haveing a couple of studs low down would help get it started . as is warming the riser .

The very hottest part of a J-tube will be the back of the burn tunnel, followed by the base of the riser. Studs would not last long.

The youtube experimenters do not have instruments to test efficiency; A few researchers who do have the right instruments (they cost thousands of dollars) have tried many different configurations and tweaks, and found that the standard J-tube without fancy bits in the riser, but with a few subtle modifications in the burn tunnel, gives the best results. Look up "P-channel" and "tripwire" for more info. The forums at http://donkey32.proboards.com/ have much research information.

A house drain around here is about 4" diameter, so I was influenced by that description. Yes, 6 to 8 inches should be fine.

It looks like you have an essentially flat area to build in, so you will have to create the berm to the north. Unless you move a lot of fill offsite, you will only have to dig down maybe 3/4 of a meter to get 1 1/2 meter deep around the walls. Good for you for locating the core near the center, I think you will find that works well.

BoBo, I am not sure at all about the effectiveness of a vortex for use in a heat exchanger. but I have read some convincing reports from a couple of builders.

I worked for many years developing and building C02 water reactors, theses devises used a vortex inside a 4” tube to spin water up through the 3’ tube.
A thin stream of C02 gas was directed into the flow and the indervidual bubbles of gas would spin around the tube obviously increasing the length of their path dramatically compared to travelling  straight up the tube.
The effect was the C02 would dissolve within the 3” tube but without the vortex it required a massive 10” length of tube!

I thought that if you push a volume of gas in a spiral it would take a longer path than going straight up but perhaps this is not the case?

What I have read on Facebook included a theory that the spinning gasses would form enough of a vacuum to draw in air to feed the far bottom of the burn tunnel directly below the centre of the heat riser.
However I have no personal everdance that this works.
I have tried a very basic vortex set up in my stove but it did not show any noticeable difference, but my exempt was just a temporary obstruction in the tunnel that caused a spin.
I now plan to build a specific vortex design with a central secondary air inlet.

It would be very interesting to see this kind of vortex/secondary air tested in comparison to existing designs, with a Testo for accurate readings. Peter van den Berg has said that a vortex did not give better results than his other designs. A vortex as such could not increase the time gas spends in the hot riser, but the faster speed might increase frictional turbulence. I wonder if the CO2 was rising through a contained volume of water, or if the water was also moving up through the tube? Gas bubbles in liquid would try to rise against the liquid resistance, and maybe the vortex lengthened the time a bubble spent in the tube?

Well I am certainly not trying to convince anyone that a vortex is a good idea but I definitely want to find out!
Yes the water is flowed from one point to another, the gas is added into the flow. ( the systems are used for growing submerged aquatic plants)
So what you are saying is... if there were a particle of ash in the flow,it would go straight up even thought the vortex is spinning?

No, the particle would spin same as the rest. It would spend the same amount of time in the riser whether there was a vortex or not, so the difference would be that turbulence is possibly greater. The question for RMH testing is whether the amount and kind of turbulence causes better mixing and combustion.

But the partial will travel a longer distance in the same time?
I built a model a few weeks back but I have now read the secondly air is fed in the bottom rather than the side....

From what I've read, the lowest point of pressure in the system is the Venturi port because that's where the gases are squeezed through the constriction.  Therefore anything happening past the Venturi must be at a higher pressure.  It's the draft that pulls the gases through the system.  But presumably there are relatively low pressure areas in the riser at the edge of the vortex at the boundary layer where the gas particles are moving the fastest.

Spinning the gases as a single vortex means heat energy of combustion is converted into kinetic energy inside the riser, and the gases spend more time in the riser for mixing to occur.  But having dual vortices, the rams horns, means even more mixing of the gases with secondary oxygen which leads to more complete combustion.  I've seen people choose a single vortex because it looks prettier, and because they want the flame against the bottom of the cooking pot.  Does the hot spot rise up the riser if you choose a single vortex instead of a double? I have no idea.

But Peter's testo testing shows that dual vortices leads to more efficient combustion.

I just be a noob in the land of knowledge here , but  fox you are right by saying that they travel a longer distance in the same amount of time . but to balance the equation it also has to travel faster . it still exits the same speed . remember the laws of angular momentom and the conservation of energy. We all know the skater bringing there arms in as they spin and they get faster. Arms out and slower , that is what I think you are basing it on . But the walls of the riser would stop the skater from opening up there arms . So spin away , but your not changing speed it stays in the riser .
Has anyone tried a cone shape for a riser . Th roughing that idea out there . Like just after the j meets the riser it widens and then the riser narrows to the same diameter of the j tube. A spinning cyclone in that may have the desired effect.
The way I see it is that there has to be a solid smooth pressure all the way through from start to finish in order to get the thing working best .

Glenn , I picked up the info some place that the north face needs to be thick to work well . So I figured into my plan to have a meter to two meters depth to the north wall . That is why after what you said about moving it to the centre and shove the heat into the slope and not the floor.
As for the studs . I'm sure its been tried before , but I may just try it for myself .  As you can see from the pic . It'll be a while yet before work starts on the heater. But its good to have a solid plan before I start .

Graham  . interesting idea , both spinning the same way and mixing together or counter to each other . I'm guessing the counter one . Did you never learn from the ghost busters “Never cross the beams” . I joke .

But what about this injection of air into the riser , to help combustion in the riser. Is that a thing everyone agrees on ?
*edit*
also while im at it , am i right in thinking the taller the riser , the stronger the flow . so too speak .
*edit 2*
i was outside haveing a smoke after writeing. as i sat there thinking on the subject of keeping gas in the riser for longer and i was drawn to a tesla valve . https://en.wikipedia.org/wiki/Tesla_valve . has anyone tried something like that for a riser . (https://grabcad.com/library/tesla-one-way-valve-1)

or even dimpals like on a golf ball . it works to help air flow over a golf ball . has anyone been there , done that and come back to tell about it ??

BoBo Jones wrote:this is my first post on these forums and im not great with forums . but I shall try to do my best .
quick story . so im building a greenhouse . a winter greenhouse , temp gets as low as -5 . after researching , it'll be sunken with insulated back wall . so I figure it'll need heating . as I researched heating I hit early on Paul Wheaton rocket mass heater you tube vids and bang that's the design for me . so I spend time soaking up all the info I can find about rocket mass heaters . so now im at a stage where I understand how it works , what drives it and how it all fits together . the better designs and more impotently the fails . so I get all that .
but there is one thing that im not getting......... so the air gets sucked in heated up and comes out of the top of the chimney into the barrel . what is the relationship between there and the top of the barrel . how does having a larger space above the chimney effect the mass heater / all I can think of it that by having a larger space increases the cooling effect . is there something more to it then that ? is my question .
I want to build and try something different to the barrel design .

Hi Bobo,

Welcome to Permies and the land of rockety heating and cooking.  I read your posts and the responses and I get the drift that you may be missing something basic which the answers you have gotten are adressing at a higher level.  I could be wrong and if so please forgive me.  The chimney as you call it is of course the heat riser as others have stated in their posts.  It is integral to a J-tube rocket stove and while the steel bell can certainly be replaced with other materials to do a similar function, I am not sure you actually want  to eliminate it entirely.  

The primary function of the feed area, burn chamber, and heat riser are to insure complete combustion of the fuel.  The entire assembly must be insulated to minimize heat loss and get the fluids hot enough to burn the highest flash point gasses and long (thus high) enough to accomplish said task.  Once you have a clean burning device now you can do what you want with the heated gasses as long as the design allows the oven to be lit with some ease and minimal smoke back and also cleaned out and maintained.  

As I believe Glenn mentioned, you can go with a masonry bell which does not impede the prime objective stated above, but does minimize the amount of immediate heating of the heated space.  The drum radiates the heat immediately whereas a masonry bell heats up slowly and acts as part of the mass.  From that point I believe all the others have fully addressed the issues.  

Again welcome and best wishes on getting the greenhouse and heater finished so you can get growing as soon as possible.  I also fall into the partially disabled category, but have the attitude that I can do almost anything, but I may have to figure out a way to do much of it sitting down.  So it just takes me longer.  Oh well.

Ralph thank you and I thank the others for the help that im getting here from your words . It reminds me of a vid by Paul Wheaton where he said that new people to all this , have great plans on changing the plan to do this and that , they will try stuff that don't work  , that's me right now .
So I picked the rocket mass heater , for that very same reason that is combust s most things cleanly.
This is my first try at this and even if I fail to start with ill have fun failing and grow a better understanding of it all .  The truth is . I want to try something slightly different and see if its better or worse for it . If I just copy a design from someone else . I am doing nothing to push understanding and ideas about it all onwards. Or if we all just went , “yep Paul . T hats the best we can get it and everyone just copy that “. so please allow this fool his foolishness in trying something different , then after I can tinker with it . W hats the point  building something if you cant play and tinker with it . Who knows , I may be an accidental guinius . Or just another chump that thought he knows better.

so after talking with Glenn , ill move the heater centre greenhouse. But the syphon(large empty space to store heat) , will be behind the heater into the earth . Ill have to make that first . Then build the heater in front of that  then the seats and feeder/batch box.

again Glenn has convinced me about the need for an inspection hatch/metal cooler. So ill had a smallish one , large frying pan size (don't let the wife know one of her pans may dissapear next year). Just enough to get the cooling effect.  The riser J tube I hope will all be underground with only the cooling hatch and entrance to show that its there. 2M X 8m squared  of mass (air+earth)should be enough to hold the heat in. but all plans change and all the dimensions can change . The one thing for sure is the size of the hole im digging 3 x 8m . im not 100% desired the thickness of the north wall yet. Between 1m to 2 m thick is the idea . I watched all these “cheapest greenhouse” vids on you tube. Then I went and priced up the different materials  needed to make a roof and walls . I fell on heavy duty rubble bags for walls and clear reinforced tar p , two the same size to make a insulating gap between them. I learnt early on . Its not about heating , its all about insulation. Compared to that the next cheapest material (plastic sheets) ended up over twice as expensive. I only had a spade and garden fork to dig with to start . I spent the last of my money on a mattock and a heavy hoe . Those two tools increased my digging speed 3 times over. I cant sing there praises loud enough .
But my point is that . I had a plan to build with . But then im thinking , what if I don't know something that I don't know , but need . So I came to the home of the rocket mass heater(so to speak) and bounce my ideas as best I can to a group that knows all about it and has probably seen many fools like me make the same mistakes many times. Just by this thread ive changed plan twice and will probably change again. Like that studs thing , I wonder lower down it may work . Glenn says that's where its hottest . I've learnt something. I asked about Tesla valve , if you can say someone s tried something like it or why it wouldn't work . But isn't that how we trial and error work out better ways .
“  I also fall into the partially disabled category, but have the attitude that I can do almost anything, but I may have to figure out a way to do much of it sitting down“.  My problem is that this all will take me a long time to make , slow and steady wins the race . But once its made , people not in the know may look apon it as a sign that if I can do that , im fit for work . When in fact it was an hour a day over a year to make. But im getting old and if I don't do this now , I wont be strong enough to do the work later . I have friends that can help , but im encountering the chicken that grew the corn to make the bread kids story. Where everyone has excuses why not to help ,  but everyone wants a taist of the bread.

I'm rambling . I should be outside digging but all I can think of is bacon sandwich.
Long and short of it is I am thankful for being here and even more so for the advice.

Experimentation is a wonderful thing, but experiments that start without a base have nothing to compare to and no way to know if they are better or even as good as the standard method. I would recommend that you build the combustion core "by the book" as that is the most critical and extensively researched part. It is highly unlikely that someone new will come up with a better design the first time; thousands have already tried. Experimenting with the shape, layout, or materials of the mass and gas flow channels is much more open to trial and error. One thing you really don't want to do, though, is bury the thermal storage mass in the side bank away from the greenhouse space. It will conduct much of its heat to the earth and away where it will do you no good. Keep the mass, whatever its shape, inside the greenhouse space.

but glenn. i may be that one in a million and if i dont try , how will i know . lol
i figure ill go with the standard J shape and size . maybe a longer riser then normal . but pritty standard all the same . but rather then the riser at the center of the barrel , i want it bury it into the slope of the north side. i want to put the heat from the riser into mass as well . leaveing just enough steal to do the job of cooling. a solidriser tube made of clay and cob. plenty of time to think about the cyclon and exstra air for the riser.
"One thing you really don't want to do, though, is bury the thermal storage mass in the side bank away from the greenhouse space". i was going to do that till you mentioned putting it to the center. if we say that the hedge is the closest point to the air (zero insulation).then ill have about two meters dirt insulation between the mass i heat up and the outside.so a meter all around the mass and you still wouldnt be outside. would that not be enough insulation ? truth is nothing is set in stone till ive finished digging and bagging and putting roof on.

Earth is excellent thermal mass, but not a very good insulator, especially if it is damp as the north bank will be all winter. If you try to store heat in a mass/cavity outside the greenhouse space (say a cube for simplicity), five faces will leak heat to the earth while one leaks heat to the greenhouse... not a very good rate of return. Put it freestanding somewhere inside the space, and five faces will leak heat to the greenhouse while one leaks heat down into the earth, and even that one may help heat the ground of the planting beds near it.

i heard that water sinks into the ground at a 45 degree angle in soil. so for every meter it sinks , it will spread a meter. so if the inside of the north wall is 2 meters think , then i can make a virtical line down two meters and that should be where the dampness should reach. i plan to go 1.5 m to 2 meters down.so i have a meter/sq into the wall . plus half underneath that. plus what ever i build as mass on the inside of the north wall. by my calculation i should have 12meter squared of mass to store in . but the J rocket and possable two seats will bite into that.not forgetting the meter think wall down the sides and those are planned to slope in . both tarps a 10m by 6m , so i got 2m thick north wall and a meter thick all, round also planned to slope inwards on the inside. if i have a virtical south inside wall , it would give me a spare meter also that i could add to the mass. i figured that if all walls below ground level were 45 degrees sloped inwards. then i would have dry mass for as thick as the walls are.
so good point to bring up glenn , but i think i got that covered would you not agree . this all will take a long time and ill keep taking photos and post them up as i go , so you can see how its comeing along and advice as i go . if it pleases the forum.

So you're talking about extending the tarps 2 meters beyond the greenhouse space on the north side.  You might get dry soil in that triangle, but I think it depends on the character of what is there, and potential water table or groundwater moving through. That is very site-specific and I can't give an authoritative opinion. Still, if your thermal mass is in there, you will get at best less than half of the heat conducting in useful directions unless you have some extensive and probably expensive waterproof insulation surrounding it on all other sides.

It also appears that you plan to have the greenhouse floor sloped down from the edge more or less all around, which makes sense for getting depth without (so much) structural walls. Are you going to be using that slope for planting? A sketch of proposed cross section would make it much easier to be sure we are talking about the same thing.

A greenhouse requires water, so I don't think you will have a lot of really dry soil which has insulative quality. The walls and floor of the space will affect the average temperature and dampen temperature swings, but are not mass that will store a noticeable amount of the RMH's heat output. The detectable effect will not reach more than about a foot from the nearest part of the interior cavity, judging from my RMH bell. The walls and ceiling are around 9" thick of brick and cob, and corners never get more than faintly warm even after long hard firing which makes the flat walls uncomfortably warm to the touch.

Hi BoBo,

You have two issues which are going to create a bad result for you in the end my friend.  Both of them revolve around insulation, and not about the relationship between the end of the riser and the top of the barrel.

You can choose to ignore me and Glenn and everyone else that is trying to help you but you will end up spending a lot of hard work and not have much to show for it when you are done.

The first bit of insulation is around the engine itself including the burn tunnel and riser.  By insulating the engine well and using the right ratiometric dimensions in the design the engine will produce a clean very very hot burn.  The riser provides a very useful part of that in the fact that when you use the correct ratios in the sizing of your engine, you end up with a tall tube spewing hot gasses.  Those gasses need to be harnessed.  The bell does this as well as heating the space nicely in the process while routing those hot gasses to a mass for storage.

If you plant the engine in the ground, how do you plan to insulate it?  How do you plan to feed wood into it?  Laying down on the ground and  dropping logs and sticks into it?  How do plan on cleaning out the ashes my friend?  Another problem is that if you extend it into the ground, the hole into the j tube will now be part of the gaseous fluid system.  This means that it effectively will make the feed tube longer relative to the height of the riser.

Second insulation issue is the mass itself.  You will be heating up the earth out in every direction, if you do not insulate it well.  You certainly can dig down around the mass (more diggin by the way) and create a floor and wall of several inches of perlite or some sort of foam insulation that the ground will not quickly degrade.  Then you will contain your heat into the ground where you want it.  Otherwise you will lose likely half of your heat.  I suspect the weeds around the outside of your greenhouse will be happy that they can now thrive year round.  

I have been an aerospace electronics design engineer and Registered Professional Engineer for nearly forty years now. One thing I learned early on was to "steal" (or adopt) sections of existing designs that have worked for others and of course any good engineer always wants to make everything he does better.  i had a boss who told me over and over again that he had to keep me off the production floor because each system was better than the last.  Unfortunately  that improvement process made it virtually impossible for field service to maintain the equipment.  I only bring this up to address that I understand your desire to innovate, but unfortunately you are trying to make your jet airplane fly faster when you have yet to get it off the ground.

Please take this in the spirit intended.  Also I know you are tight on funds because of what you said in one of your posts about purchasing a mattocks.  If one of the coordinators on the site can arrange it.  I will pay for a copy of the Wisner's book and the coordinator can arrange for you to enter your shipping address of where to send it.  The first 30-40 pages should clear up most of your misconceptions and they have lots of helpful tips throughout.

Best Wishes on your project

The first premise that you made was that you will need heating for your winter greenhouse.  I presume that you will also need appropriate lighting as that's where the plants get their energy to grow from.

As an alternative you might want to look a methods of growing in the winter greenhouse without additional heating and lighting.  Eliot Coleman addresses this in his book the Winter Harvest Handbook.  Heat is achieved by covering the plants with plastic inside the greenhouse, so it's a double layer of insulation.  Of course there's more to it than that.  Coleman has his own youtube channel.  Maybe that might be easier if the aim is to grow winter greens.

This is a good point, depending on exactly what you want to grow. You mentioned possible lows of -5... if that is Celsius, it would not be a huge deal to keep the interior from freezing. I would still totally agree with an RMH to make it more comfortable, and if you want to grow plants that need more warmth.

I do get the impression that the J-tube core would be built on interior ground level, not in a hole inside, so those issues are probably moot.

Glenn ,
so I plan on sandwiching the tarps between two layers of earth-bags , so at the very top two layers of bags then a layer of tarp , then another layer of earth bags , then another tarp , then bags all the way below that down to ground level and I plan the tarp to be a meter into the wall all round. Making a sealed layer between the tarps . I also plan to have some 2 by 4 beams covered in copper pipe insulation . I was going to have two of those under each tarp to help support it , also sunk into the walls a little and then two more beams on top to help stop the tarps from lifting up in the wind. The tarps have got rings in them and I plan to use them also to stop anything moving. .
 no worries about ground water . I live on top of a chalk hill . Plenty of drainage.
“It also appears that you plan to have the greenhouse floor sloped down from the edge more or less all around, which makes sense for getting depth without (so much) structural walls. Are you going to be using that slope for planting?”   no that's all heat sink baby ! He he .  I like to grow  buckets and tubs and im gonna try bags this year. I like the ability to move the plants around to get the best spot for them and not blocking other plants. I plan to build the heat sink , then the heater into that heat sink , then what I end up with as a slope I will them make steps onto (not into) it and then place my plants on that . I may have to water proof the top layer . That brings me to cement . I hear talk about all that come out of these heaters is CO2 and water vapour . So if I build the syphon(heat sink tunnels) out of cob , it'll fall apart fast. But if I put a thin layer of cement . It should seal it against dampness .  It sure would help if I could draw a picture for you . I spent 3 hours trying to draw what I had in mind and it still came out , ill say bad , but you know I want to say a stronger word in its place. Ill try a sort something out to clear up any confusion.

Ralph , let me say , I am so pleased for the help im getting . I may be a bit of an old fool . But im not fool to think I understand all of this , even when I think I know all about this . Before I got here I was like all the rest , with big ideas and way to make it better. Glenn is like “no , standard J plan “.  
now that's part of the plan . Like it or not we are on this road together now . So hold on LOL .
Ill try and knock up a picture , even if I have to draw it and take a picture of it with my phone. But to address your comment . The J tube will be standard size buried into the mass , with as long a riser as will fit and work. The bell will have glenns inspection plate in it and the rest made of cob. I hear if you make the top of the riser 45 degrees and not flat then ash cant build up there and block it. So I want to use that 45 degree angle on the riser facing outwards and the slope that the hot gases fall down to get to the syphon . *(Sod this for a game of solders as the saying goes here . I'm off to find a pencil and paper)* ive just sketched out the idea .


Understand this is  a quick sketch by a poor artiest , so the dimensions are a bit sqiffy.
So the J tube entrance will have to be sunken into it a little . But that should help with dropping fuel into it . Standard J set up . Hits the inspection hatch , cools , then drops down the 45 degree slope under the seat. (I know your gonna say it'll be hot there , but thick cob and some tin cans should I hope solve that). Down the slope and falls into the ash collector pit , next to the cleaning hatch. Then back into the mass to an empty chamber inside and then some how to be desired out and up a chimney. As for seats , just two small ones will do , enough to get comfort and snooze . Earth bags , tarps , you can see what im kinda thinking. As for the arrowed lines , its where I think the damp will be. So if the bottom most part of the pic is say 2 m down , then the damp should reach two meters under the wall at 2 meters deep. So if I place the syphon 2.5 to 3 meters from the outside wall . It should have at its dampest/closest part to the syphon should be at least half a meter at its lowest part. I have plenty of space to the south I could move it all another meter away from the north wall.

Getting back to what you were saying Ralph . “create a floor and wall of several inches of perlite or some sort of foam insulation that the ground will not quickly degrade “ perlite , the battle cry of the rocket mass army .. he he he .  Joking aside . I don't got no perlite dude . That's for the rich dudes . I is poor … yes im still joking .  I'm lucky to have a bag of cement . With out going into the whys and where s of it . I'm disabled and don't work, this is all coming out of my pocket , not the family money. I'm not like “ give me a dollar mister” poor . just keeping it together, kinda  poor. As I said in my post before bags , tarps , tools and im skint(no money left). Plan for the worst , hope for the best . Still perlite would be good .
“but unfortunately you are trying to make your jet air plane fly faster when you have yet to get it off the ground. “ . you know it . I'm not the only spirited fool to pass these part  . Ralph . Its all good . I'm lapping this all up and enjoying a few giggles along the way . Show you a pic so you know im not a troll or something and we are away. Thank you so much for the offer of the book . But somehow learning from a book isn't as much fun as chatting about it and learning how not to fail . That and I am the kinda chap that would feel in your debt , even after saying it was free. See haw we go . I think we are doing OK . Plans are changing for the better the longer we are chatting. Now if you would like to come over here and dig a bit for me , I wouldn't turn you down . LOL.

Graham . No lighting needed , but for me not to bump into stuff. i had given it some thought . my first idea was solar garden light(LED's) . then i thought of a peltier power generator (https://en.wikipedia.org/wiki/Thermoelectric_generator) connected to LED's. apart from that a couple of candles would do. im not trying to grow plants under lights. wife stopped that idea , when we talked about the electric bill. As for heating . Its natural heat will work for most of the time , only in deepest darkest winter would I need to fire it up . That and when im showing it off or when im escaping from the wife . in truth i want the greenhouse , but also a place i can sit in peace, away from family. im looking at less time infront of me then behind and im not getting any younger . so nows the time to do this or not have a greenhouse at all . im not going to be able to afford one and the wife turned down a large poly tunnel as sticking out to much. i try my best not to argue with her , so sunken greenhouse it is.

*late night edit*  question . what gets more heat into the syphon ? cooling it a lot , but push it in there faster or cooling it just enough to maintain a constent flow, but slower.   i think slow and steady wins the race . but by making it faster , more volume is passing through the system. but more volume would eat through fuel faster.  please help , i cant come to a solid conclusion about this.
As I say glenn . Its not till late November through to late February I should need extra heat. Being a greenhouse should be enough till then. I'm not wanting to grow tropical plants . I just want my plants to stop dieing each year. (im not a good gardener , but I enjoy it).

merry xmas to you all , i hope you and yours have a good one .

ive been thinking . is there a reason beyond size requirements that a riser can not just pump stright into a chamber above. like my picture , but move the triangle syphon over the top of the riser and do away with all the rest of it ?
i mean j tube stright into syphon above. if i bury the j tube deep enough i may well have space above to fit a syphon . seems logical to do so if i can , but i may well be over looking something about doing it that way.

Yes, you can totally do that. It would be known as a "bell": a hollow masonry box, with the outlet near the bottom so only the coolest gases exit to the chimney. It doesn't need to be just above the riser, but can be any shape and full height from the greenhouse floor so you don't need to sink the combustion core deep into the ground. All you need is a few inches, or as much more as you want, of clear space above the top of the riser for good flow. You can shape it with a seat-height bump-out (cavity and walls) at the base so you have a nice sitting spot.

i see a vid on the mass heater bell thing . made of bricks built as a closed arch suround , instead of a barrel . i think it was the one with the see through pan lid for a door to batch box . so i know what you mean by masonry bell . i am simply working from an efficent angle , thinking if i moved the syphon above the riser there would be no need to cool to the room in order to get it to drop down the outside of the riser . this way every bit of the heat will be going to mass and not the room . what is it that say " heat the mass and let the mass heat the room ". this way i bury the whole thing deep with plenty of dry mass around it all . should work proper good.
ive got a few ideas about how to get the start of the j tube deep , yet still be easy to clean out .
next question for you glenn me old chum . j tube , down , across then up . at that up point where it changes from horizontal to vertical . what say you that we make a space the size of a soccer ball(its called foot ball but i dont want to confuse you colonial types). like a kind of mixing chamber . i hear people pipe more air into the riser to get a reburn of left over gasses . why not make a chamber to do this in and them send it up the riser into the syphon . a bit like a funny shaped hour glass.

nearly finished digging the hole . then ground work around the hole . then it'll be digging and bagging/wall building. so right now i would like some help on bagging before i start . would it be ok to talk about it here do you think or should i make a new post over in the greenhose part of this forum ?

you still here Glenn ? sorry fella if ive been ignoreing this thread . its just all go over on the greenhouse section . just wanted to say ive been giveing it a lot of thinking and come up with some ideas . now dont laugh . i mean it . but i want it all . i want the heater , i want a kiln(to bake bricks tiles and such) , i want a small oven and a place where i can make charcol and im crazy enough that i think i can have all of those .
ok heater aside , if i vent the riser into the syphon directly and build the syphon with a part wall theat can be brocken down and rebuilt . i can place clay stuff inside to bake. if i happen to leave them in then they are just added mass till i get round to taking them out. the thing with this idea is that ill need a good draw from the venting outside .
the oven is , just a hole in the mud with a door that gets hot.
as for making charcol , that is a much more dificult to exsplane with words . but ill give it a shot . so you got your standard J tube . at the turn up on the corner i make a space the size of a kids football(its called football, foot , ball . soccer is something you put on your foot before you put your shoe on lol).  about the size of a football . you got the riser going up , the fire coming in the side.  now under this ball sized space is anothing hole , not large or long . just enough to restrict the flow. this hole drops dow to a open space that has an opening large enough that wood can be put in and taken out.
so what im expecting to happen here and you can point my errors out . if the space underneath is sealed up , then the botten hole acts like an ash collector. ajust the amount of air coming through the bottem hole and you have an secondry air injector. but fill the bottem space with wood , set light to the wood and the heater . then seal up the bottem space so air cant get in and the riser is taking the air out and i figure ill be rolling in charcol . then i can mix the charcol with the soil and its party time for all the little worms.

i know the riser will not help venting the gas , so ill have to suck the gas out of the syphon . i see a vid where a guy had this metal part to his vent and built a way to have a candle heat the metal to increase the sucktion. all im saying is i know it will have to have good vent design . also i figure ill have trouble inspecting the middle of the beast . but if i have the riser vent into the syphon that big enough for me to get inside at a queeze i should be able to point my phone camrea down it. but i figure what ash i get will drop through the botem hole or into the syphon , both can be cleaned easrly.
ill hold my hand up and say all this working out is in my head right now and ill get to putting it down on paper somethime after we work out whats the best design to go with .
i am sure we can make this work and i have the skills to build it . i have to stop myself thinking about all this sometimes , trying not to get ahead of myself what with the walls and roof not even built yet. but i admit , the heater part of the build is for sure the more fun thing to imagine and plan.

Hmm, missed your previous question. Lots of parts... The RMH core can definitely get hot enough to fire pottery, but the space above the riser will not get hot enough. You would have to have the clay items in the riser, and then it wouldn't work so well. I have built kilns entirely of cob (English medieval style ones), so it can be done, but you need a purpose-built kiln for it to work.

People have done lots of experiments with various chamber and air configurations, and the best results come from what has become the standard: Square cross-section J-tube, right angle bends, P-channel and trip wire in the burn tunnel ceiling. (Look up those terms for more detail if you need to.) The P-channel injects air at the most useful point, top of the burn tunnel where it helps mix gases and ensures enough air supply. The trip wire in the burn tunnel ceiling gives beneficial turbulence, as does the sharp right angle from burn tunnel to riser.

A charcoal burning chamber sounds like a nice addition, not sure how you could get it under the base of the riser and access it for loading/unloading. It sounds pretty complicated to do something that will not interfere with the primary combustion goal.

An oven in the bell chamber is quite feasible. You would probably want to put it high in the bell to get good temperatures, and it could be a black oven (with tight-fitting door that does not get opened during firing), or a white oven that you could safely open at any time. You don't want masses of super-hot gas coming out in your face instead of going up the chimney.

forgive my stupidity and this may well be a case where common sence lets us down here. but ill say it anyway . seems to me the heat goes into the riser and the riser heats up to a point where it isnt gonna get any hotter. the whole thing is insulated by the ground. if the riser is pouring out into the syphon. surely the syphon is going to heat up like wise. so long as i can insulat that heat inside the bell/syphon surly it should get hot enough to at least fire tiles ?? this is all guess work on my part . never built or uses a kiln before so ill bow to your exspirence.
so the space the size of a football i figure can be thrown out , but the fundermental is there. i figure ill have a space the size of a double bed . in this bed will be the start of the Jtube flushwith the top. then under the bed is a space i fill up with wood. i then put the cob door into place, leaving the right sized hole to let enough air into it. so i light the Jtube up and get it going . some time later . i open the cob door and light all the wood underneath and close the door. so now air is being sucked in, burning and then going up the Jtube . at a point of my choosing i block the hole in the cob door and the space becomes empty of air and cant fill up untill the Jtube goes out. seal up the start of the Jtube and the only place it can get air is by pulling it through the syphon.
it has the added advantage of me not haveing to clean the j tube out after each fireing. ash will ether go up the riser or fall down to the charcol area.

another crazy idea , what if i put the riser inside the syphon . would it get hot enough to fire clay then ? picture an upside down box with riser part of the J inside but the start of the J outside the box. so i use the syphon as the oilcan .
geez i tell you i keep on haveing thses ideas and they are the same ideas that everyone else has had , i know because im getting to all the same conclusions that other poeple have had. i mean as i try to inprove the design and it ends up looking like someone elses design.
thinking on it , i am 95% sure i can make a riser , if its contained by serounding soil. but free standing , im not so sure. confident , but not sure.

changing the subject . positioning . i know you said in the middle. but hear me out . in winter the north half at max will get light . so i figure half the greenhouse will be for growing and i can use the same space for the syphon. so the seating and heater will have to be in the other half . i will also need somewhere to walk up and down the green house. so seating and heating will have to be down one end , being as the door has to be on the west south corner. the seating can be in the east south corner , with the J tube being in the north west corner of the bed/seating. im calling it a bed but i mean a double bed sized flat area and pictureing a bed helps the imagination. if i build two seats , two people can sit down . build a flat area and more can squease up. not that im planing crowds in my greenhouse.

also got an idea for a water syphon. see what this guy is building , fast forward to get the idea .  https://www.youtube.com/watch?v=r3brwkoczRA
so i build something like this . so rain comes of the roof and into this thing. then i have the cleaned water collect into a concrete tank down the north inside. slap the hot gas syphon up against it and the water should heat up. plenty of mess to heat up . going through the filter should insulate heat flowing back and i get a water source at is moqueto free. ive been wondering what to do with the rain from the roof . this method would solve two problem in one.

plenty to think of there . ill keep throughing ideas at you Glenn and you deside what sticks and by the time it matters we should have a solid plan.

*edit*
so ive been thinking im not making myself all that clear . so to clear any misunderstanding . ive been drawing what i was thinking of making , in the fashion i was thinking . dimentions are way out of proportions  but you may better understand whats going on in my head .
good thing is i need never bother cleaning ash out of the Jtube . it all just get shuved down the tube and ether fall underneath or go out the riser , both places that i could get too . the riser feeds stright into the syphon , then gets sucked under the seat and up the vent someplace. the charchol bit will be deepest part but i can sort that out . maybe a hole next to the door i can crotch in and plank over the hole when not used . some how someplace i put a simple over in . not looking to cook full meals in there , but a baked potato stright out of the garden may be nice.
thing is if i dont have to worry about getting ash out of the J tube , the start of the J does not have to be vertical . standard is stright up to help with the feed to stop ash going down the tube and to stop you burning all the wood at the same time. as i understand it . make the start of my J at 45degrees  , it may burn wood a little faster , but it will let me build up a thicker wall between the riser and the seat. as for the kiln and the charcol . i may only use it a couple of times a year . so i can just cob it up the doorway and break it down when i want to use it . rig up some air flow control in the charcol door and bobs your uncle . it should all work first time .
i like this design , so later i can roof over the seat and turn into an alcove . then i can use the sapce on top for more plants .  my dream is sitting in my greenhouse , start feeling hungry and pluk something , maybe cook it and eating on inside my greenhouse. man , i gotta learn how to grow strawberrys .
so Glenn , forget all that gumf before . have a gander at the pic i drew and ask me some questions and ill tell you no lies . lol

happy spring time everyone .
did you get a chance to see my drawing glenn ? what did you think . i know it is still a long way off starting build . but i want all the planning out the way and all my crazy ideas put to bed, before im ready to start building . keep in mind in the picture that the kiln is not to size and can change size. its just a gist of an idea. a wouldnt it be good , rather then this is the way im doing it . rather then a bench or seats . i realy like the idea of a square platform to sit or lay on . i have it in the corner . i dont see anywhere else to put it . the whole left and back is for growing as that is where the best light will hit .remember the slopes will be 45 degrees sloped inside. so it takes it away from the walls somewhat by a meter or so and i could move it towards us in the picture. in my artists inpresion picture on the right , those steps i see covering everything on the left and back . even and very much the syphon/kiln. keep in mind with the kiln that im not looking for good grade pottery . so long as it comes out hard enough to resist water for a year or so and then cracks and i recycle it into something else. so im not looking for profesional quality here. all i want is a tile that lasts a few years and a drinking cup and plate i couldnt care less about smashing. i may end up smashing them , just to get out of the washing up lol.
i do very much like my design for the rocket heater part. more so the charcoal burner . it help so much with cleaning. but the design still needs work . i have to be able to get at the riser to reair it if needed. i have some steal buiscit/cake tins and lids i thought i may use in some shape of manner to do this .its funny or at least i find it funny that the very first part of the whole lot will have to be me building the exsorst outside. just an obvisation.
well look forward to any veiws on the matter. no idea is a bad idea , lets just find the better ideas together.

hey glenn , been a while . hope you and yours are good .
anyway trials and tribulations happening with the greenhouse. whole thing is on pause. but in the mean time ive been making myself a heated bench and having a lot of fun doing it.  im sure you would be shaking your head at my highjinks . but im just having fun with it. making mistakes and fixing them. ive kinda tring to do it different . build it my own way. the more fails i make and fix the more it starts looking like the standard mass heater. lol . truth is im just enjoying working it out for myself. well i could go on . but a picture is better then a few words . so i made a video of me building it. thought you may enjoy a look see.