Brainstorming our next rmh - shorty core? multilevel?

Having successfully built our first rocket mass heater in our own place, it's time to start brainstorming designs for my son's place next door.

The house is old, and mostly stone built. It's been partially renovated since this photo was taken, with a new roof amongst other things. My son, Alan,  lives in the top and back parts of the house, accessed by the little door up the bank into the back of the house. The lower room, which used to be for animals, is due for renovation and will soon have a proper floor and some rendering on the walls. Maybe even a window! There are no stairs, it's a completely separate space, and the plan is for it to become a sort of 'man cave' which can double as visitor or emergency accommodation if ever anyone is brave enough to want to cope with our kind of crazy.  



In our own place we've built a Matt Walker tiny cookstove, which is pretty much perfect for our needs. But this one will need to be a bit different.  No cooktop is needed, as he will be cooking up in his own kitchen while we want the rmh to be down in the man-cave. Also, the walker cookstove has a rather small firebox which in colder weather will need refilling occasionally. It will be much better if we have one with a bigger firebox that can stocked up with all the wood likely to be needed that day and then left to get on with it.

We're also thinking of maybe having a heated bench up in his main room upstairs. In our house enough heat works its way up the stairwell to keep the whole house heated well enough, but there isn't one in my son's place so we want to make sure he stays warm enough without over-heating the man-cave.

Thomas Rubino has recently built a rather awesome looking masonry dragon based on the new shorty core and I'm wondering if this would be a good fit?

And if so, where do I find the plans for building it?

And then we have to figure out about how to get a heated bench upstairs to work...

Let the brainstorming commence!

Hi Burra;
So, my quick thoughts.
Shorty would be ideal in the mancave alone (it would be a workshop for me).
However, I do not think she is correct to try and sufficiently heat a stone room and a bench upstairs.
Shorty requires hand-casting large slabs.
Peter has reduced her Isa compared to the first-generation Batchboxes.

I suggest that  a 6" traditional Batchbox would be easier to build and be strong enough to supply a bench upstairs.
Perhaps, a smaller Isa downstairs with a "hot" exhaust chimney (hand insulated) going upstairs and into a stratification bench?

Burra -

Have you seen any of the Russian "transit" stove layouts?

A single burner on the lowest level, with sliding blast gates to control the flow of stack gasses through one or more bells (single or double) on each level above.  Thus, one fire (firebox) heats the whole complex.  I'll see if I can find a graphic or two for you.

In principle, there is no reason one of the bells couldn't be in the shape of a bench.

The firebox could be a batchbox or J-tube or whatever - but a clean combuster of wood, in any case.

Kevin

Burra -

Attached is a schematic of multilevel heating from a single firebox, from Shkolnik's "low rise heating" book, and a series of section drawings, showing an implementation (same source).

I think I can come up with some more extravagant versions than this two-story implementation.

Many of the multi-level stove Shkolnik shows have separate fireboxes.

Kevin

Kevin,

In the cross section on the last image, I have counted 86 bricks, so it would result in the height of 86x65 mm = 5.6 m.
Building a thin walled structure this tall would not be easy even for an experienced mason.
Also, Portugal has experienced earthquakes in the past.

Burra -

Here's a schematic of a 3-storey transit stove, from Kolevatev's "new stove designs" book.

Per usual, Kolevatev doesn't use true bells, but instead has lots of projecting bricks poking into what amounts to a larger cross-section flue to increase the internal surface area and thermal mass.  Russian testing has demonstrated that Kolevatev's setup is less thermally efficient than a true bell (as you'd expect), but some, especially non-professionals, find them easier to build.  A true bell stratifies the stack gasses, and only relatively cool gasses are allowed to pass out of the bell.  See, for example, the comparison here (https://www.youtube.com/watch?v=nfpTXI6j6tY ) at about 5:27, where you can see that the Kolevatev stove of a notionally similar size and intended use both gets hotter more quickly, but also loses heat more quickly, than the equivalently sized stove from Kuznetsov.

If the heat exchangers illustrated were true bells, the blast gates (labeled 7) would be lower in the central stack (just above the inlets, labeled 3) and the outlets (labeled 4) would be just above the relocated blast gates.  In practice, 3 and 4 might even be able to be adjacent to each other if the blast gate can be inclined or vertical, rather than horizontal as shown, but the vertical separation of the inlet and outlet channels is straightforward.  A bit of internal baffle to prevent any tendency to short circuit the bell (flow directly from inlet to outlet) might be helpful.

Here's a video from another Russian stove mason who constructs a two story transit stove:
https://www.youtube.com/watch?v=zZ2Nf_XeWiQ
At about 9:30 you can see his sketch of the upper heat exchanger - also not a true bell, but several vertical channels.  This video is part of a multi-video series on his YT channel documenting his build of the stove.

Kevin

Cristobal Cristo wrote:Kevin,

In the cross section on the last image, I have counted 86 bricks, so it would result in the height of 86x65 mm = 5.6 m.
Building a thin walled structure this tall would not be easy even for an experienced mason.
Also, Portugal has experienced earthquakes in the past.

Cristobal -

I didn't mean to imply that Burra should build exactly this stove, only that this is a Russian example of a multistory heater fired by one firebox on the lowest level.  I would think connecting the lower floor stove to an upper story bench with a lightweight double wall stovepipe or fabricated chimney should also be possible, and better suited to seismic areas.  Blast gates for the chimney pipe to direct the flow may be more difficult to find/purchase for fabricated chimney than are the rather standard masonry heater sliding blast gates, however.

Most immediately, I intend to run a fabricated insulated double wall chimney from my ground floor ceiling, though the upper floor and attic and out through the roof deck to daylight in a chase.  But, I think it will be possible to later create a brick bell the height of the upper floor, such that this brick mass can be heated when the stove on the ground floor is fired, then a blast gate near the upper floor ceiling can be closed to stop the standby draft and slowly radiate the stored heat from the brick bell into the upstairs hallway and bedroom (opposite sides of common wall).  I may need to "suspend" this bell by constructing a truss or two in the attic, so this is a project  for "later".

Kevin

Lastly (and I'll shut up about this!), here is a link to Kuznetsov's discussion of multi-story stoves:
http://eng.stove.ru/stati/mnogoyarusnyie_pechi

For 180mm batchbox the bell could have internal circumference of 3 m, so at the height of 2.55 m, the ISA of 7.6 m2 could be created.
Assuming (by looking at the house image) the height of the first floor to be 2.4 m, the ceiling to be 20 cm and positioning the chimney exit at 50 cm above the first level floor would result in heating "stub" on the second floor sticking 65 (50 + 2 layers of bricks + flooring) cm above the floor.
The bell skin could have buttresses added on the outside to reinforce it.
180 mm batchbox could be too powerful for the small area of 36 m2, but at the same time it could be fired only once per day.

Burra Maluca wrote:Thomas Rubino has recently built a rather awesome looking masonry dragon based on the new shorty core and I'm wondering if this would be a good fit?
And if so, where do I find the plans for building it?

Building plans for the core aren't a the problem, I could provide you with one. All I need to know is the size of available firebricks. It can be any size, within reasonable limits, straight core or sidewinder. I do this regularly, mainly because it's a promising core and it isn't on the batchrocket.eu site as yet. The Shorty core seems to be fitting for a lot of purposes. She's really a friendly dragon.
A design for a complete heater is an entirely different animal.

But... I don't understand the connection between the ground floor and the top floor. Not the physical connection as such, but the different ways the spaces are used. For a permanently inhabited space a mass heater is fine, personally I wouldn't want it another way. But a man cave is occupated just now and then, mostly not even on consecutive days.
So, if the above is the situation, you want quick heat downstairs and gentle, long hours radiation on the top floor. It might be possible to achieve with a single heater, although the culprit could be that when the occupant of the top floor wants heat he need to go down and light a fire. And waiting for several hours in order to get the heat upstairs.

In short: what's the idea?

Peter van den Berg wrote: I don't understand the connection between the ground floor and the top floor. Not the physical connection as such, but the different ways the spaces are used. For a permanently inhabited space a mass heater is fine, personally I wouldn't want it another way. But a man cave is occupated just now and then, mostly not even on consecutive days.

So, if the above is the situation, you want quick heat downstairs and gentle, long hours radiation on the top floor. It might be possible to achieve with a single heater, although the culprit could be that when the occupant of the top floor wants heat he need to go down and light a fire. And waiting for several hours in order to get the heat upstairs.

In short: what's the idea?

It's a bit complicated, and delicate.

We have a long-term visitor camping on the land. He's elderly, disabled, a recluse, and in failing health. There is a very good chance that at some point he'll have to be brought indoors so he can be cared for properly. Not that he's going to agree to such a thing unless he's very much in need of it because he's about as stubborn as I am. Nevertheless, it is a VERY real possibility. I'd say even a likelihood. The man-cave space is currently completely un-renovated but there are plans to put a floor down and render the walls at Christmas-time. Then I'm pushing to turn the space into a cozy man-cave that all the boys will gradually make friends with. A place where they can hang out, make booze, cure meats, sample booze, put the world to rights, that kind of thing. Then if and when the time comes, we rearrange the furniture, slap a suitable bed in there, and I have a place where I can provide appropriate nursing support and hopefully it stills feels like a man-cave so he won't hate being in there so much. At that point it will need gentle, long-term heat with as few visits as possible so I'm not intruding too much except when actually needs care.

Until that point, my son is quite happy to pop down occasionally to feed a dragon, though infrequently is obviously better than hourly trips. He works hard all day, outside, and spends several hours a day in the late evening on his gaming computer, which puts out 700 watts. That computer and his heated blanket are currently his only form of heating and he seems to be coping perfectly well like that. But then at the moment he's young and fit and physically active. Even so,  I'd really like for him to have some real heat in there!´

thomas rubino wrote:Shorty would be ideal in the mancave alone (it would be a workshop for me).
However, I do not think she is correct to try and sufficiently heat a stone room and a bench upstairs.
Shorty requires hand-casting large slabs.

OK, the hand-casting of large slabs is putting me off a bit. I have a vague sort of hope that whatever we build it can be of materials that are easily sourced locally and we can release the plans so anyone with the same size bricks can replicate it.

To give a better idea of the space, the man-cave and my son's main room above are both 4 metres x 3 metres (measured internally) with 50cm stone walls. aka 13ft x 10ft with 18" stone walls. The back bit is built out of blocks and is in need of major renovation. Currently two small rooms known as the 'bathroom' and 'kitchen' though they are rather hopeful sort of labels, especially the 'bathroom'. The upstairs floor is standard wooden tongue-and-groove floorboard on new, shiny steel box-section beams.

Peter van den Berg wrote:Building plans for the core aren't a the problem, I could provide you with one. All I need to know is the size of available firebricks. It can be any size, within reasonable limits, straight core or sidewinder. I do this regularly, mainly because it's a promising core and it isn't on the batchrocket.eu site as yet. The Shorty core seems to be fitting for a lot of purposes. She's really a friendly dragon.

Bearing in mind Thomas' comment, is shorty the right core?  It would be totally awesome if you could provide me with plans of whatever you feel is the best choice. I need to go and rummage in the heap of bricks downstairs and find an intact spare firebrick. I think some were thicker than others so I also need to double check with Austin that whichever one I find is a 'normal' one. I'll get back to you on this. And thankyou!

A design for a complete heater is an entirely different animal.

First we choose a core, then I get my head around designing the rest of it! Austin has learned a lot building Matt Walker's tiny cookstove and I think between us all, and Thomas' books,  we can gradually figure out the rest. I need to get my head around the stuff Kevin posted too. Though my heart is leading me towards a simpler stratification chamber like the one we haven't built yet to go with the walker cookstove.

Burra Maluca wrote:I need to get my head around the stuff Kevin posted too.

Burra -

My advice is to prioritize what others have said, over whatever I have posted here.

The others have much more true knowledge than do I.  Though I have tinkered a fair bit with conventional wood stoves, I have not yet built my first masonry heater.  So, whatever I "know" is - at best - second hand.  After getting a copy of David Lyle's book, I fell down the rabbit hole of chasing down references in his bibliography (and their references, and so on...).  Somewhere in this process, I reacquainted myself with rocket heaters (I'd encountered them years ago, when they were basically just the horizontal feed Lorena stoves - interesting, but not directly applicable to any purpose I had at the time).

So, give much more weight to what the rest of the gang says than to whatever I have posted.  Most of the time, I am more or less thinking out loud, and hoping it may be helpful.

Kevin

Heating both spaces with just one heater could be done. Using something that is called a double bell system. One downstairs with the firebox in it and another one on the floor above. The complicated part is how to serve these bells equally, bypassing the top bell for easier startup. It can be done but it'll cost quite some money to achieve this. Namely, the chimney parts.

Maybe, it would be easier to build two small ones, each with their own separate chimneys. In that case the two spaces would be independent for their heating requirements. I.e. not heating two spaces while there's only one occupied.

A couple of years ago, a small group was building and conducting workshops in Portugal. Most of them weren't Portugese, one of the builders was from the Netherlands. The group isn't active at the moment, as far as I know. Their website is offline but their Facebook page is still there. The first heater of the group happened to be a 4" batchrocket, specifically tailored to the Portugese climate. https://www.facebook.com/BatchRocketPT

As for the slabs that are required for the Shorty core (or any other core for that matter): there are refractory slabs available in Portugal, batchrocket.pt used two of them mortared together. As can be seen in some pictures on the Facebook page. I think I can contact the guy from Holland and ask him where he got the slabs from, if you want.

And last but not least: assuming two separate heaters coupled to relative cheap chimney's are the way forward, they could be built out of bricks and have mass or just a little bit of mass and generating lots of quick heat.

My thought was a small barrel on its side with the pebble stile like they have been building at Wheaton Lab would not be to heavy for upstairs.  They make a slip chimney pipe that is two layers so the sipping straw  could be one of those that rotates to open a window at the top of the barrel to bypass the stratification and reduce the stratification so reducing the heat if necessary.