Stratification/bell bench for rmh

First of all a thank you that this forums exists, allowing to ask questions <3

I am not planning to build the actual rocket stove myself, but are hoping to buy a Gamera 7 from Bulgaria.

My questions are in relation to the bench I wish to attach. Apologies if this has been covered, but I have been searching here and elsewhere for answers, and could not find any.

I came across Matt Walkers discussion on flue versus bell benches, and as much as I love the idea of cob (and got plenty of clay) - I have dogs (and not just 1 or 2 >.>), and I know the bench will be claimed by them. This being Ireland, there is a lot of rain involved and moist fur and paws, which worries me using a cob bench. Also, I will not be able to double the piping back on itself, so it would be a single 6 inch pipe running through the mass of only 3 meters length, due to space restrictions (and going around a corner). So additionally to the worry about recreating mud back out of the dry cob.. I fear a single pipe might not create enough heat to allow me to keep my cottage warm for the hours when the stove is resting.

However, while I love the idea of the bell bench, I am a bit scared of fumes possibly leaking into the living space. How much of a risk does this pose?

Also, I have been trying to see what stone slabs I might could buy for the bench top, and the most common on offer (and cheapest) seems to be limestone. When I researched limestone, it says it gives off CO2 when heated, as well as it can form cracks. So maybe not the most ideal to use? What would be the best stone for the top of a bell bench? I am not adverse to concrete, but for a smooth concrete surface, I fear it means sealers that might not be healthy to heat either? (sealed concrete for the easy of cleaning due to the dogs)

Would slate paving slabs be a good alternative? Would slate store heat well?

Should the sides be build from fire brick or will normal brick do?

The floor is concrete with tiles - should I remove the tiles where the bench would sit, or can the tiles remain?

There is also the problem of one wooden beam going up (and it supports ceiling, so can't be removed). I would build brick around it, also creating a gap, maybe filling it with some added material to protect the beam (and a thermostat to make sure the temperature reaching the beam is not dangerous). Cob might be less of a worry in this case, so I could also say I create the bell bench, but then it leads into that corner with the beam, and have a flue pipe for the shorter part of the bench, assuming this would be far less hot, as the gases going through the flue would have already cooled from heating the surface of the bell bench. Would mean less warmth in that last part of the thermal bench, but could be safer? (and I could construct it so that the dogs would not be able to use that cob part for sleeping on)

Would a bell bench with stone slab top, 2 meters long, be enough thermal mass to keep 60 sqm warm? (as the 1 other meter of bench may would not get very warm at all, if it's a flue in that part)

Or should I use cob and flue for all of the bench, but could still use a stone slab as the top, or maybe tiles?

Sorry, so many questions, I do apologise. The bench would run along an inside wall, build from solid rocks, covered in plaster.

Hi Aine;  Welcome to Permies!
I'll do my best to answer your questions.

I say a brick bell would be much preferable to a piped mass.
I have one of each and the piped mass is temperamental in the early season.
The brick bell with a bypass works well every time no matter the outside temps.

Will your bell leak exhaust into your room?  
Partially that depends on how tight you build it.
The rest of the answer is no it will not leak. Once warm there is negative pressure inside the bell.  
Any tiny leak will suck room air into the bell not exhaust out into your room.

Roofing your bell)  The temperatures in a separate bell will be low enough to not cause cracking.
Given a choice between limestone or slate, I would choose slate.
Temps inside the bell itself will be under 200F surface temps will be much lower.

No firebricks would be needed at all if using the Gamera stove.
Regular clay bricks can live in a 200F-300F environment with no problems.

To avoid wet dogs, you do realize your "bench" can be a brick box that dogs can not get on?
Maybe you're wanting to give the dogs a warm bed?
No need to seal the slate but even if you did, the surface temp would not be hot enough to off-gas any sealers.

No need to seal or remove the floor tile inside the bell, the bottom of a bell is just warm never hot. (The hottest temps are at the top.)

As to how well this will heat your house, that depends on home construction.
A well-insulated home will be fine.
An old drafty stone cottage with single pane windows ... not so well.

@ Thomas Rubino

(phew, the forum saved what I typed despite power cut, as in rural Ireland the electric poles are held up by the cables, not the other way round, and it is windy outside >.>)

Thank you for the welcome and also thank you so so much, this is such valuable information!

First and most important thing (over not suffocating -.-) - yes it has to be dog proof. The bench will take up much needed sleeping space. My lot ranges from the smallest of around 5 kilo, to my massive oaf at 46 kilo, to varying sizes in between (and yes I know I am mad). Also my fox terrier girl is getting older, which she will refuse to admit.. but she will love the warmth of the bench, and in my household everything goes to the dogs lol

The brick bell does all around sound so much more suited, so I am extremely glad to have your positive advice. Could I have it 80 cm deep (brick walls included)? I think I might be able to get 80 cm slabs (well, I hope so anyway), but should there be additional support for them? Like building some pillars from brick into the hollow to help the stones? What thickness of the slabs would be best?

And you say you would choose slate over limestone, but is limestone an option at all? Because I know I can get limestone easily, while having searched for other stone options, it either gets insanely expensive (granite), and slate funnily enough also does not seem that easy to come buy in the size I'd like. Black limestone especially is used for hearths around here, so it's common to get hold of.

The cottage is not draughty as such (well, aside from the dog flap leading into the yard ). I did invest into double glazing, but as a cottage with 80 cm thick walls build from rocks, it takes quite a bit of heat to permeate the walls enough to not have the walls counter any warmth from a radiator or so.

I was thinking of having a T junction on the pipe that would exit into the chimney, to be able to maybe burn small twigs there to warm the chimney before firing up the Gamera. Not sure how to create a bypass, would have to research how to go about that. It's all very exciting, but also scary!

oops, just realised I had asked that specific question about thickness already, scatter brain today...

They look like nice stoves, we dont get to hear much about their  long term use and there are not many youtube vids.

It looks like a nice stove, similar to the liberator stoves made here.
It will push 5 meters horizontally. It has a life expectancy of 10 years.
Cost is high but then so is everything else.

Aine;
No crazy dog lady thoughts here!  I love our four-footed friends and go out of my way to make life as comfy and happy for them as possible!
Having dogs as your best buds can be much less trouble than the neighbors or the inlaws can be.

As you are not using a conventional Rocket core, I'm not sure exactly how much "bell" you can have.
I would think you could have an 80cm wide bell, just not sure how tall that could be.
I will say that having a bypass is as "handy as a pocket on a shirt!"  You can make a balky system start drafting much faster and easier with one.
You need a smaller pipe (4") directly from the outlet of the Gamera 7 to your chimney with a way to open and close it.
Once your chimney has a draft then you close your bypass and send all the heat into your bell.

How thick should your limestone be,  I say if it is easily available I would get 2" (50 mm)
Adding a brick column inside would be a good idea as some of your doggies are rather large...
If you have not visited it yet, my website has good information.  https://dragontechrmh.com/

Hey Aine;
Here are a couple of posts showing a bypass install.
https://permies.com/t/155372/Installing-Bypass-bell
https://permies.com/t/159700/Retrofitting-Piped-Mass-Bypass-Install

I stumbled upon the Gamera while researching, and decided with my restricted space it would be the best option. Yes, it says a minimum life expectancy of 10 years on average use. We have mild winters, rarely that temperatures drop below freezing during day time and only around zero usually at night, yet darkness lasts for many hours, and the overall heating period extends to around 7 months. I definitely hope it will last me, as it is not cheap, but considering what I am currently paying for electricity, while having to wear a thick coat indoors all winter (or pay even more for electricity).. I should be saving massively regardless. My property borders forest, and I walk out there every day, already bringing sticks home to shred for composting. It seems ideal

Urgh, 5 cm sits slap bang in the middle of the slab sizes I have found so far (2.2 cm and 7 cm). Murphy's law lol, but I shall keep looking!

I will consult with the Gamera company on size of the bell, hopefully they will know. They are currently displaying their stoves at a festival and I am waiting for them to return, to order.

Not sure I can integrate a bypass. The stove will sit located away from the chimney. Not a great photo and my scribbles are terrible, but it gives a rough view (of the chaos). That corner cupboard will be taken out, and the exit into the corridor has been widened further (my daughter and I are very proud we took that wall out by ourselves, only needed help with last bit due to cables). My poor builder friend is living in fear of my newest adventure, but he has tentatively agreed to help me build a bench.

As I mentioned, I was thinking to work with a T junction, where currently the little wood stove is located, leading up and into the chimney. I could then light a small paper or stick fire in the T junction to warm the chimney up? I love the bypass idea and would buy that gadget you developed in a heartbeat, just not sure how I could get a bypass going with the locations involved, and my builder friend is stressed out enough already, poor man, I think he is beginning to curse ever having crossed path with me lol

Thank you again for all the help, it is invaluable, truly, and appreciated beyond what I can express! Bookmarked your site ^_^

Hi Aine;
About the limestone, use whatever size is easily available, the thinner ones could be used, just have spares on hand.
If they start cracking then either add a second layer on top or just upgrade to the 7cm.

I would be very surprised if the Gamera people will have an answer.
They may even tell you that it will not work.

Looking at your drawing  I have reservations myself on how well it might work.
I think you might need a pipe that runs from the Gamera inside the bell to the far end.

How were you thinking of making your connection to the chimney?
Coming down the outside of the bell and entering at floor level?

If so, to start you'll need an enlarged entrance to feed your stove pipe.
If your pipe is 15cm then you would want a 25-30cm exit from the bell that then reduces to 15.2cm to go up the chimney.
In combination with an open-ended pipe bringing hot air to the far end and the enlarged entrance, it might be enough to not need a bypass.

A T-junction would certainly work to get warm air flowing.
My concern is every junction in a chimney pipe is a potential leak.

Sitting here looking at your drawing, I see what I would build.
Directly in front of your current hearth, I would construct a medium-large brick bell.
Maybe as high as the mantel and 3'or 4' deep
A 4" or 5" batch box is built into that bell.
One might even build a Walker riserless core and have no riser to be concerned with.
The exhaust would come out the bottom back and go right into the existing chimney.

I don't feel confident to build the actual burn unit myself, and my builder is petrified of the thought. I mean I would give it a go (what can go wrong? *cough*) but I really like the idea of immediate heat, as well the storage in bench form.

I had thought about building a brick tower to run the pipe from inside the bench to where the chimney exit is now. So basically straight downwards from its current opening, with the upper bend visible, and a T junction built into the brick tower near the top. Then the bottom opening inside the bench to take the gases.

I am not really sure what is at the bottom of the chimney. I fear it was concreted closed in the past. Right now the small woodstove connects to another flue inside, which then runs up the chimney. This was done 2 years or so ago, for safety reasons. Before it was just the brick chimney.

Sincere apologies for my drawing, not easy to draw with a mouse >.<

Hope it makes some sense. The bench would be a L shape, minus that part where the wooden beam runs. The first/longer part of the bench (2 meter part) connected to the Gamera, would not reach all the way into that cupboard space. I'd remove the doors and open that area, but would not make that space part of the bell all the way into that space.  It would look part of the bench, as the bench top would reach into it, but it would not be part of the hollow.

I could of course give up on the long part of the bench, and instead place the Gamera sort of where the electric radiator is now, then just have it lead into the remaining bench part, but that would only give me outmost a 2 meter bench overall (if I'd extend the currently shorter bench part closer to the second wooden beam), losing what right now would be the bigger part of the bench.

Or would it help to just shorten the L shape? To for example cut from the bench part that I marked as 2 meters in the drawing? I am worried I'd lose too much of the heat storage /cries

Do you mean to just extend the pipe that would lead from the Gamera into the bench, towards near the end of the first (marked as 2 meter) bench part?

Or maybe to opt for a flue system after all, with an infill of cob or gravel, not too thick above the pipe, and the thinner limestone slabs on top?

I know it is a tricky space My whole cottage is a tricky space >.>

I can not tell you how grateful I am for the time you are granting me. I truly can't. I might end buying a bypass, even if I can't use it, just to repay you.


bad_drawing , on Flickr

There are a few videos on youtube made by Uncle Mud, he used to be a regular poster on this forum but not so much now, however he is active on facebook rocket stove pages.
I think the stove is a 5” J tube but it works with a shorter riser than we might build one with, never the less it seems to work pretty well.
I am a bit dubious  about a 10 year life span without  some replacement parts, as much as I love vermiculite, I doubt if it would last 10 years although it might be a standard replaceable part?
The guys who manufacture the stove seem to be on the ball and doing a good job.

Hi Aine;
Right now is the scariest part of your first RMH build!   PLANNING IT!
It is so very easy to become overwhelmed.  It all seems confusing and difficult.
It really is not!

I can assure you that once you have completed this build you will wonder why you were worried.
I built my first 8" J-Tube with a piped mass in 2013... I was a wreck... It seemed so daunting, to do things I had never attempted before.
Remember, in 2013 there was one book available and there was Permies.
I wrote many posts asking questions... unfortunately, there were not many folks with experience to help guide me
Like anything I do, I just dove in and got dirty.
I contacted Matt Walker directly, this was before his success with the Walker riserless core.
He was wonderful at encouraging and teaching me how to proceed.

So as turnabout is only fair, I have made it a priority to help newbies work thru their build.
If Matt and the few Permies available were there to help me then I can be here to help you.
I would not sell you a bypass you do not need, just to thank me.
You can thank me by having a successful build and then spread the word far and wide on the emerald island, about how totally awesome RMHs are!
In a few years (or less) I would love to hear of more new builds that were inspired by you!

Remember it is not Rocket Science (although I call it that) it is playing with bricks ,sand, and clay.
You can do this!

Looking at your (much better) drawing.
Yes, I suggest bringing a pipe from the Gamera, down the length of the longer bell, and ending it with a 90 bend pointing it down the short leg.
That should get enough hot air to the far end of the bell.
As I mentioned earlier, you will want an enlarged opening for the chimney.
Sharp corners and small openings create a stall point.
The idea is a smooth flow of gasses that naturally want to flow up and out.

@ Fox James - Yes, that's how I came across the Gamera but indeed, there is little else to find on it, unfortunately, but I assume many just do not post videos, unless they run a youtube channel for such purposes, and I bank on if people would have been very unhappy with it, there would be more to be found. For longevity.. I sort of keep my fingers crossed and hope the company has some experience by now to state such figures. Really really hope they do.


@ Thomas Rubino

Oh, believe me, everyone I know is already hearing plenty about rocket stoves, I have been told I am obsessed.. lol, but there is also a  good amount of interest in the principle. If I could get mine working, there might be others to follow, but even if not - I got two houses on my property, one occupied by my daughter brat, and I already told her we need to see how we can get a rocket stove installed for her as well

And I am so relieved to read what you typed there. I was seriously worried it might not work at all. Did not sleep too well.. but now I can rest easier, it seems, yay! Yes, the planning is definitely stressful...

When you say it must have a wider opening, do you mean the 90 degree piece at the bottom? To have that at 8 inch to take the fumes out of the bell, up the vertical (as the Gamera has a 6 inch outlet, I think, and so does my own current exit into the chimney), and to then narrow it on the way up to 6 inch before the 90 degree exit into the chimney? Did another terrible drawing, hope makes sense enough to show how I understood it so far.

And I wanted to additionally make sure I know if it would be ok to have the whole pipe inside the bell (drawing B), or rather to have it as a hole in the bench brick wall (drawing A), so the pipe would be outside and behind the bench going up. Either should be possible for me to build, just when it would be outside of the bench, that part of the L shape bench would become a lot more narrow.

Can't even imagine how scary it must have been at the beginning with these builds, must have taken a lot of experimenting and bravery for you and everyone else.

Hi Aine;
Ha Ha you definitely have RMH disease!  
A sure sign is talking to friends, neighbors, and complete strangers about how cool RMHs are.
Overthinking your project is another.
Losing sleep considering how to proceed...
The list goes on.

You are now officially an Apprentice Rocket Scientist, Congratulations!
Your Lab coat, pocket protector, and certificate will arrive just as soon as we have such things.

Your artwork may not make it into a gallery but it works fine for me.
I like your 8" reduced to a 6" pipe idea.
If possible, I would put a handmade sheet metal  "scoop or funnel inside the bell directing the gases into the 8".
The smooth flow of gases is paramount to good performance.

A couple of questions.
Does your chimney draft well all the time or are there certain winds that blow backwards?
Are you building this with clay mortar or using cement?

Hahahaha yes, I am sure my builder friend is definitely sick of me talking about rocketstoves (he catches the brunt of it). I am certain I have caught him rolling his eyes... LOL

It's just such fantastic technology, reducing and utilising, which I love. Can't even remember how I first stumbled upon it, true chance, but the moment I saw it, I was hooked!

My chimney generally draws well. It is a traditional old chimney, rock, like the rest of the house, but also repairs with brick, possibly, I would say, of about 5 meters height. There can be certain days when it feels to draw less, but never to the point that I have experienced a blow back of smoke. Woodstove always starts fine, just some days it seems to take a bit longer to get it roaring. It has a 'hat' to protect it from rain and birds nesting in it, and as I mentioned, a liner was fitted about 2 years or so ago, to make it safer. I was not involved as such, which I now wish I would have been fully, so I'd know better what is actually going on inside. I was told basically a pipe is running up inside of it now, with my current stove slotting into that new pipe inside the chimney.

The funnel you mentioned, would basically be a sort of half funnel, correct, as the 90 degree bend would be resting on the ground?

And yet another drawing, ouch, hehe

In 1), if the vertical pipe connecting to the chimney, could be inside the bell, then I could twist the bottom so it could face the horizontal pipe coming from the Gamera.

In 2) with the vertical pipe not inside the bell, but connected through a hole in the bench wall, it would not be able to have it face the horizontal pipe.

Will the bench still fill up fine with hot gases, if the vertical pipe would draw strongly into the chimney, from the horizontal pipe coming from the Gamera?

Someone in the village gave me the nickname 'the Fairy Godmother' when I moved here, as I live isolated up on this hill with all the animals.. and now I am gonna be known as the Fairy Godmother with a rocket!!!

Oh, forgot to say, I am not sure what would be better to use, cement or clay mortar? Do you mean for the brick walls of the bench?

Hiya Rocket Granny;
I am a big fan of clay/sand mortar.
It is user-friendly, and your hands will be nice and smooth.
If you need to make changes it taps apart and can be rehydrated to use again.
Concrete is neither...

The hottest air will always be at the top of your bell.
If it seems you are losing too much heat due to a fantastic draw, then you try shortening up the pipe from the Gamera.
You use a candy thermometer inserted into the stove pipe to monitor stack temperatures. (See the dragon breath monitor on my website)

Yes, the funnel would be 1/2 -3/4 or so.  You might not even need it but it will not hurt anything being in there.
I would come thru the wall straight and put your funnel facing the outer wall.
I do not think you would need a 90 there but you sure could put one in if you like.

LOL, the fairies in Ireland are a bit different to Walt Disney's or the Victorian's version... No granny nor Tinkerbell vibes lol. They were quite feared, 'the good folk', like the Banshee, an Irish fairy, Ban - woman, shee -mound, 'woman of the mounds', and I know grown men who don't make stuff up, who have heard the Banshee cry before a death occurred (in one case it was the neighbour being murdered, and all the family heard the Banshee wailing, without knowing what was happening at the neighbouring farm). I live on the slopes of a famous fairy hill, looking over the valley upon another famous fairy hill. Can just make out the ancient stone graves/mounds in the far distance. It's an area steeped deep in fairy myth, so I take it as a huge compliment they decided to lump me in with that ancient fairy lot, although I am certainly not feared, just seen as a bit.. unusual... but I have been well embraced by the people here, they are quite fond of unusual, phew! Wonderful lot

Clay/sand mortar it shall be then ^_^ feels better to me compared to concrete anyway.

I am still uncertain about whether I could have the pipe inside the bell, instead of the opening being a hole in the brick. It would allow me to have the bench deeper. If I'd have to create a cavity for the pipe to sit behind the bell, I'd lose a lot of depth from the bench. The depth of the bell could then only be about 40, maybe 50 cms, and that would include the two brick walls cradling the hollow within. Would that be enough of a hollow? I'd be happy for the pipe to sit behind, already got an idea how to make it all look nice, just yes, it would not be as wide.

Oh, and had a look at the thermometer. I wonder how long shipping from the States to Ireland would take? Any experience with shipping to Europe?

Do you think I should still incorporate that T junction, to have a chance to warm up the chimney?

Are you aware that your chimney pipe can come down and straight into the top of your bell, rather than the back?
A bit harder to seal and the doggies could bump it, but it is an option.

Remember we are dealing with a new configuration (the Gamera).
I'm hoping that the manufacturer has underrated how much push it has.
The US-made liberator will push farther than the manufacturer suggests, let us hope the Gamera is the same.

I liked drawing number 2, it shows a cavity for the chimney.
I'm not sure about your question... you did not supply a drawing...

Oh, my goodness;
Shipping that candy thermometer would be way too expensive.
I'm sure you can purchase a similar item locally.

I have shipped RA330 secondary air stubs overseas.  
They are not available locally.

If we build the "brat" a batch box RMH at your other home, I will sell you parts for it.

About the T-junction.  It would be simple to add it later if needed.

LOL, my head hurts from trying to draw it all...
Thought I could get away without embarrassing myself further with my none existing drawing skills!

But yes, that's what I had hoped I could do, to have it come down from the chimney bend into the bench That's where my idea of that brick tower tame into play first. To have the pipe run down within a brick tower, so to speak, to protect it from being knocked by the dogs.

Sealing it should be the same, maybe even easier? If I could use a brick tower, which would be one brick wider inside the bell then above, so stone slabs could be made to rest on the extra bricks around the tower.
But it would introduce extra mass into the bell, which might interfere with the pull?

I honestly fear my drawings don't make much sense to anyone by myself o.O and I just had a long pvp session in ESO, so my head is double fried -.-

I did not bother to draw the T junction, which I'd also have sitting within the tower part, so to speak, to not confuse matters further lol, nor the thermometer.

Wonder if I am complicating matters all around this way, and instead should just sacrifice bell depth for the part of the bench, with the pipe staying behind the bench...

And the Gamera site says 5 meters of horizontal piping, while if I'd have all of this piped instead of a bell, I'd probably only have 3 meters, maybe 3.50 m, but of course it is a bell, which no doubt asks for more push, I assume?

Yes, daughter brat has more space to play with (typically, I let her have the bigger place lol), and a batch box would probably be more suited. Far taller chimney as well.

Not sure I could get a thermometer here, would have to inquire, else I could not imagine it being that expensive to ship?

And of course there is also still the ancient ancient cottage.. which I have been eyeing up to turn into a dwelling again, as we are currently in the process of securing it, as the rock walls have been looking precarious. My builder friend fell on hard times due to no fault of his own and needed a place to stay, and I own another cottage, not on my property , which had been rented out, but it had emptied just before he ended in a pickle. So I let him move in there, and he does not pay me anything (for 2 years now). Instead we swap apples for eggs, with him helping me with projects on my small holding here, which I love, it's a nice arrangement, no money, just practical swapsies ^_^

However, eventually I will run out of jobs, so I have been thinking if I restore the ancient ancient cottage (which would not cost much), I'd move in there, as I could make it a real quirky space, above all with a rainwater collection system, which I'd adore. Obviously - that would get a rocket stove too! While builder friend would get to move into my current cottage, making sure he has a roof secured over his head, should I have to sell the other cottage, not on my property.

3 rocket stoves! I'd have to rename my place to Kennedy Space Center...

Actually, I have just decided, it could be a great idea to leave that cavity behind the bench, and have the pipe coming in from behind, instead of going into the bell from above. Yes, it will make that part of the bell narrower, but the space behind the bench, I could turn into a stick storage. It should not get hot there, I'd work with a double layer of brick on that side. It would be a quirky solution. I'd still work with a brick tower to ensure the pipe can not be knocked, but all behind the bench. I think it could look nice, and still there is some thermal mass. Might also be better for the chimney draw/push of the Gamera, having the bell part narrower (hoping?)

We have come such a long way with this design, it is insane, again, thank you sooooooooo much!!! This has alleviated so many of my worries and headaches about this build It now really seems possible, instead of literally just a pipe dream haha

Aine Klein wrote:LOL, my head hurts from trying to draw it all...
Thought I could get away without embarrassing myself further with my none existing drawing skills!

I honestly fear my drawings don't make much sense to anyone by myself o.O and I just had a long pvp session in ESO, so my head is double fried -.-

I did not bother to draw the T junction, which I'd also have sitting within the tower part, so to speak, to not confuse matters further lol, nor the thermometer.

Wonder if I am complicating matters all around this way, and instead should just sacrifice bell depth for the part of the bench, with the pipe staying behind the bench...

In staying with Tom's comments (Dragon tech) Many have helped me, and thus I in turn enjoy helping others but in a slightly different way, It goes like this,
    If you supply dimensions of what you want to do, I can quickly draw this out, and calculate many of the "important" resulting dimensions, i.e.  Stove size-ISA- lengths and widths.  

    Now I am not saying, that I am going to suggest, "what is correct"  but rather, what it would look like according to your measurements.

   These are easily displayed as JPEG photos for this forum  Thus when suggestions are made, they can be directed to exactly the area, in question.

   Attached are just some example photos  (just some work, that was done, it may or may not have been employed.

   Absolutely nothing wrong with the "free sketchup" drawing thing, but it does make it hard for those not using it, when they see, "load this into your program and pull off some layers, and see how it is done"

   If you want, feel free to shout out,  

   Now for my reasons-  I am a very strong advocate, of ---  If you can't draw it, building will be harder yet --   If you can't show something with dimensions, others can't really KNOW your intentions.   Simple as that.

    Best of success.

Scott Weinberg wrote:/snip

Ah, thank you so much for the offer! I tend to be someone who just does, without much gone ahead planning. I just envision something and set upon it. I am sure my builder friend curses that at times.. but so far we have managed just with me explaining what's in my head (phew).

This project is a bit different of course, but there are not that many dimensions as such involved. Just a L bench, 2m x 1,8 meter outside measurements, and I have an idea now how deep I could probably make it outmost. Most important for me was to find out what materials to use for the bench, as in bricks, mortar and flagstones. I do not need worry about building the stove, as I am planning to buy a ready made stove, and I think I will have to just see if the bench dimensions will work with it, creating enough draw, and if not, to reduce measurements until it works. With Thomas having suggested to run a pipe within the bell from the Gamera towards the chimney exit point, this sounds like it might help a lot, so will definitely implement that

Aine Klein wrote:

Scott Weinberg wrote:/snip

Ah, thank you so much for the offer! I tend to be someone who just does, without much gone ahead planning. I just envision something and set upon it. I am sure my builder friend curses that at times.. but so far we have managed just with me explaining what's in my head (phew).

This project is a bit different of course, but there are not that many dimensions as such involved. Just a L bench, 2m x 1,8 meter outside measurements, and I have an idea now how deep I could probably make it outmost. Most important for me was to find out what materials to use for the bench, as in bricks, mortar and flagstones. I do not need worry about building the stove, as I am planning to buy a ready made stove, and I think I will have to just see if the bench dimensions will work with it, creating enough draw, and if not, to reduce measurements until it works. With Thomas having suggested to run a pipe within the bell from the Gamera towards the chimney exit point, this sounds like it might help a lot, so will definitely implement that

sounds good,   Some love to redo, if needed,(often with Peters help)  some love to figure out as close as possible to known working figures.. (of course that can still mean, a reworking, but hopefully much less)

I am in the latter group, but the builder community is diverse for sure.

Best of success to all.

About the draw in various configurations: The duct from the Gamera would be strictly to make sure hot air got to the far end of the bell space, and as such you would want it to be less than half the total length of bell so as to dump hot air into the middle of the cavity. As the exit will be nearer the far end, my personal opinion is that you would not need it at all or at most a short stub pointing downrange, with the hot air naturally spreading out along the top of the space helped by overall flow direction. Bells when built to spec (adequate cross section to allow very slow airflow and stratification) have next to zero friction and would give easier draw than ducts.

I believe you would get the best results from the chimney pipe rising straight from the bell space, extending down to a few inches from the floor with a "witches hat" shape ending. This will allow smooth airflow into the chimney from the coolest part of the bell cavity. Making this bit at the bottom movable so you can raise and lower it a bit (combined with an access port so you can reach inside the bell, a good idea in any case) will allow you to fine tune the heat extraction and draft. More heat extraction means cooler exhaust and weaker draft. There will be a position where you get the best combination of both. A horizontal exit from the bell is harder to adjust this way. This vertical pipe rising inside the bell from near the floor is called a "plunger tube".

I seriously suggest that the Gamera be placed where the existing wood stove is located.  (1) the bypass and chimney would work much better.  (2) you have an approved wood stove location established thee and would not have to build another.  (3) the way the bell bench works without flow restrictions the heat will gradually flow all the way to the far end of the L.  The hot stays up under the top of the bench and the cold flows along the bottom to the outlet by the stove where the outlet stays warm so cold air doesn't try to flow back into the bench.  As mentioned that keeps the bench at a negative pressure so any feared leaks go in not out into the room.

@ Scott Weinberg
I sort of think the problem is that the Gamera is a bit of a Wild Card, as I first have to see how well it will actually perform?


@ Glenn Herbert
I very much like the idea, but I am not sure how to build that, as a hole would have to be cut into the flagstone, and then how to give that support inside. The idea I had about basically building a brick tower, would provide support, beneath and above, but then I could not create it as a 'plunger tube'.


@ Hans Quitstorff
Problem is that the current woodstove there is tiny. The Gamera is wider and higher, and I can not relocate the two wooden beams. I  am worried the heat from the Gamera could cause a problem/present a risk to the two beams. Otherwise I'd love to have the Gamera there, but these concerns are the reasons why I decided it probably needs to go the far end. In the least I'd have to raise the shelf, but it does not become clear from the photos, there is a recess, which also includes a beam, and it will mean a lot of rethinking there and additional work, to get that possibly ready for a higher stove to sit underneath.

-----
It's all a bit of a headache, but I have a lot more additional information/suggestions now, and will present it all to my friend, and see how we can best go about this, with the space we have available.
Thank you all so much for helping out with this, it means a lot to me to have found so much support here!

Aine Klein wrote:@ Scott Weinberg
I sort of think the problem is that the Gamera is a bit of a Wild Card, as I first have to see how well it will actually perform?

@ Hans Quitstorff
Problem is that the current woodstove there is tiny. The Gamera is wider and higher, and I can not relocate the two wooden beams. I  am worried the heat from the Gamera could cause a problem/present a risk to the two beams.

-----
It's all a bit of a headache, but I have a lot more additional information/suggestions now, and will present it all to my friend, and see how we can best go about this, with the space we have available.
Thank you all so much for helping out with this, it means a lot to me to have found so much support here!

what was:

directed to Scott---I am afraid, I have no idea how what I offered (drawings) , and what the Gamera have in common, but it sounds like you have a plan, so best of success.

Directed to Hans-- if your worried that the Gamera, could effect two wooden beams, thia would indicate that your thinking it is more of a space heater, rather than a heater of MASS, I don't think you likely could have both ( to hot for wooden beams, and still be hot enough to heat a lot of mass)  I might be missing something?

I suppose there are 100 definitions to "rocket stoves" but when you combine MASS,  it pretty quickly steers you to " a very hot efficient fire, with this excess heat collected by the mass (almost always stone-brick or heavy material, that can slowly release the heat."  Just my opinion.

@ Scott Weinberg

I think we might misunderstand each other, and like I said before, it is a lovely offer you made <3 It is just that I don't think there is much to draw. It is simply an L shape bench, with outer dimensions of around 200 cm by 180 cm. If I would pipe the mass and fill it with cob, it would have around 320 cm of horizontal piping, and around 80 cm vertical piping. It would have one 90 degree horizontal angle, then a 90 degree angle leading upwards, and another 90 degree angle attached to the vertical part, leading into the chimney (the Gamera can be build to specification with the exit at the back or either side, in my case the left side). As far as I am aware, the amount of bends I'd have is not beyond the limit for a flue pipe, so I could just make it a piped mass (which is what I had originally thought I'd do).

I came across the idea of a hollow bench though, which seems to me, would allow me to make better use of the hot gases created, compared to otherwise only being able to have a single pipe of about 320 cm horizontal, running through a cobbed mass.

The beams should not be a problem, piped mass or hollow mass, as the sides of the bench should only get warm, not near glowing hot. Most of the warmth, as far as I understand it, gets stored in the top of the bench, whether it is a piped mass or a hollow, and either method would not have the beams inside the bench, not even incorporated in the brick walls. The one beam mainly in question when it comes to the bench, would sit behind the bench wall, with some insulation as additional protection.

However, should I place the Gamera between the beams, due to the fact it is is even bigger than my now tinsy wood stove, in height and in width, I'd be worried about the sides of the Gamera getting far hotter than a bench side would get. My small woodstove gets obviously hot to the point it can not be touched, and I would think the same holds true for the Gamera. When in operation, my stove warms my wooden beams up by quite a lot, the beams being rather close to the heated metal. It is manageable, not to the point I am worried they'd suddenly combust, but still, I do not find it ideal. I honestly can not imagine a bench would get anywhere near as hot as a stove, and thus I decided it would be better to put the stove at the other end.

Additionally, if I'd place the stove where the chimney exit is, the stove unit would reach far into the room, as I have almost zero doubt that the old fireplace was concreted in, so no chance to just get an exit created lower in the chimney, unless embarking on a major undertaking. This then would create other space problems in the room.

Thomas's idea about a batchbox, basically masonry heater, would work in that space, again, as the sides should not get as hot as a metal stove, but I'd lose warm bench space, and thus definitely would prefer a bench.

My main 'issue' (aside from that I came to ask what materials to use would be best), is just if a hollow L bench with such dimensions could be worked, emphasis on L, I would imagine, and whether a stove that is said to be able to support 5 meters of piping through a filled in mass, would have enough push to fill a bench of such dimensions. Is an exit on the opposite end to the attached stove, to carry the cooled gases away, problematic in relation to the draw.
What depth would be advisable for such a bench, what height. I am not sure without testing, this can be found out, truly, reason I called the Gamera 'the wild card', as I don't think there is as much experience available to draw on, compared to people having built their own cores, and it also appears to me that most opt for piped mass. That Uncle Mud video shows a Gamera working with an L shaped single pipe filled in bench, and I think it says in the video the piping is a bit over 5 meters. I don't think he is working with a bypass, but not sure, and it is a flue system, so not certain that can just be straight applied to a hollow bench.

I'd be happy with a filled in piped bench (if I could water proof it against wet paws and fur), but I just worry 320 cm of single pipe will not utilise the same amount of heat storage as a hollow bench could, but maybe I am wrong?

My suggestion was based on the height shown in your drawing so to check if I was misunderstanding I looked up the dimensions.  I see that there are 3 sizes even the largest would fit but a smaller one may be more appropriate for the size of your home.
The solution for the wood on both sides and above which worked well for my neighbor was to make a brick arch inside the wood so the stove sits in an alcove.  This absorbs the radiant heat from the stove and stores it like the bench to keep heating after the fire is out.   The heated air and radiant heat are both directed out into the room  and not just going up to the ceiling.   This also keeps the dogs from getting to close to the hot barrel. The flue pipe would com down as it does now and have an elbow going into the bottom of the bench.  to reduce extension into the room the feed could be to the side. If I am reading the dimensions correctly that should fit in the width of the bench.  The small size heats 4o meters square, would you need more than that?

Hans Quistorff wrote:/snip

I love the idea of the arch, but the space between the beams is only 127 cm width by 130 cm height. I need the biggest Gamera as I am looking at heating about 70 sqm. I can and will reduce that floor space by closing doors, especially after the stove has gone out, but the thick walls also need some time to warm up, so more heat is important.

Also, I have my bedroom in the loft, so some rising warmth also matters, plus the Gamera 7 can be used to cook, so I will use it to boil water, which then adds more space needed above the stove.

Thank you so much for thinking about the dogs! That is lovely :D :D and I have considered that as well, and the stove will have a small wall going up next to it on the right, just for protection, so dogs can't accidentally get burned (and maybe to catch some more heat for storage).

I am extremely grateful for all the info and the ideas I was given here. It has provided me with much needed additional insight into the subject. Time to set upon building, hoping it will work out as planned! ^_^

Aine,

I have run the Gamera for a few seasons in my own house and installed several with different mass bench configurations. I highly recommend the Gamera. Tell Zhivko that Uncle Mud says Hi when you order it. When you decide where you are putting the Gamera I strongly recommend you order yours with a side exit rather than a rear exit to keep your space open.

If you have any idea how many KWH or BTUs it takes to heat your house on the coldest days I can give you a better idea of which of the three models of Gamera to use. If not then go with the & though it takes up more space. I really like for you this Gamera and bench configuration I did for a small space in a 250 year old farmhouse.



The bench is a solid core of cob wrapped around the 6" chimney pipe (do not use 8" it will make your draw worse on the Gamera) and supported by bricks to allow air to circulate under and up behind the bench. It was designed to keep the wooden floor AND WOOD WALL STUDS cool while not overloading the weight capacity of the wood joist floor. It would work well keeping those beams cool and if you removed the doors of the cupboard you could still use shelves in that corner given the extra air circulation. Here are some more videos of that build

Uncle Mud Farmhouse Gamera Build

and links to my other Gamera builds

Uncle Mud Gamera

and Liberator builds

Uncle Mud Liberator

and bench builds that you might find handy

Uncle Mud Bench Builds

Although your stone and brick mass will be sexy, for a bench bell I usually cut an open top 50 gallon drum in half lengthwise and connect the halves to make a vault to support the cob and brick mass bell. Corners are tricky but manageable if you can cut a barrel half in half again at a 45 degree angle and connect the two bits to make a corner.

A single bell--even one that goes around a corner--is so effective at providing even heat that you don't need your exhaust feed from the stove to go far into the bell like the drawings, just place your pickup tube going to the final chimney going up two inches from the floor of the bell as far from the input as possible.

If you take the advice to put the Gamera on the existing hearth a long exhaust tube going from the Gamera into the bench bell about 2/3 of the way to the far corner will ensure even heat throughout the bell. The Gamera on the hearth would look more "natural" and it would work well with a corner bench or straight bench (bell or pipe in cob) along the wall where the electric heater is now. A double pass of pipe will fit in a 2' wide cob bench  (topped with stone if you like for durability) for a lot more storage mass than a bell would have.

I strongly recommend a tee and cap at the base of your final chimney for cleanout and priming as has been recommended.

I have also sworn never to build another bench without cup holders and USB ports and a spot I could sit where I could feed the fire without getting up to reach the dedicated wood storage. Those are my personal requirements. My wife won't sit on a hard bench but she insists we have one so she can put her feet on it.

Best wishes
--Uncle Mud

Chris McClellan wrote:Aine,

I have run the Gamera for a few seasons in my own house and installed several with different mass bench configurations. /snipp

Ah, thank you so much for the reply! And in fact it was your video, which had me stumble upon the Gamera in the first place :D :D For how long do you run your Gamera per session/per day?

I was planning to come back and update, when everything is finally finished. It has taken a while, and we are still not fully done, as in the final touches are in the process right now. Painted the wall and under the cupboard yesterday (2nd coat planned today :P). Under the cupboard will be for wood storage. We will be hunting for paint behind the stove next. First thought had been to instal fireboard, but that wall is a solid very thick rock wall with plaster over it, and it has proven to be perfect as is. The heat from the camera warms the rock wall, with the kitchen on the other side, so not an outside wall. This way the wall itself stores some heat too, but I want fire resistant paint, and I want a terracotta colour to match the bench and floor tiles, which we still need to get hold of. It will look so nice once all is finished! ^______^



The building has taken time, also as we had to rebuild to some degree (my poor friend has been a fantastic sport!). As I could not find slabs to fit the measurements I wanted, we decided to pour concrete slabs for it. That was not a good idea... Nothing exploded, but when I fired the Gamera up, I heard a loud pop. I had done so much research, but typically the info that concrete can explode, had evaded me. When in my worry I searched specifically for concrete exploding - there the info was, and we decided to redo. As the bench was built already and we did not want to knock everything down, we went for a half barrel. Obviously the measurements were specific, so we had a half barrel made to fit the space. Was a bit more expensive, but it is really good strong sheet metal, which is nice. Then we filled the rest up with cob and a layer of pebbles imbedded in the cob. Think we got about 8 inches of cob. We put thin black limestone slabs over it (2.5 cm), which do not fit the bench fully, but we will finish the back with some wood still, probably, it's not so important as it's hidden under the cosy covering.




Of course, going from a full bell to a half barrel meant the plunger pipe had to come out. I tried it with the plunger pipe still in place, but it affected the draw badly. I had so much heat extraction, the pipe leading into the chimney never even got warm. Had the same issue actually, while it was still a full bell. The pipe would not get warm at all, and the whole system did not pull too well.

Now it all draws like a charm. We took the plunger pipe out, and the system works perfect. I bought the Gamera 7, and while it is rocketing along, I open all doors and let the warmth travel through the cottage. I run the Gamera for 2.5 to 3 hours usually. Once the stove has gone out, I start closing doors, according to how I feel the temperature dropping. The Gamera itself keeps radiating warmth for about 2 to 3 hours after it has gone out. Once the Gamera has stopped giving warmth - the bench kicks in. It takes about 5 to 6 hours from first starting the stove to feeling actual warmth in the slabs. They never get hot like the concrete slabs did when it was still a full bell, but it's actually faaaaaaar nicer this way. The heat is gentle - and constant. Currently I only need to have the Gamera running for those 3 hours a day - and have warmth in my main room (and bedroom above in the loft) for 24 hours +. I assume once outside temps will drop further and the cob has dried out fully, I will probably need to run the Gamera twice a day, 5 hours in all per day, is my current estimate, during the harder winter time (Ireland not having extreme winters, just around 0 degrees to -5 Celsius).

It's a bit of learning how to best start the Gamera, as I would think same goes for all rocket stoves, but I am now pretty good at getting it going with no smoke entering into the room (phew!) and once it's going, it works brilliantly. I can run it with 10 degrees C outside, no problem.

I always burn a bit of paper in the 'mini fireplace' we built, to warm the chimney pipe up, before starting the Gamera, just to help the system. That little mini fireplace does not get hot when the stove operates, most energy seems to be left in the bench, but it's a good place to put the kettle after boiling ^_^ (the little enclosure for the dog water will still get tiles on top)




It has been an adventurous process, which has provided me with unexpected concrete slabs for the garden :P but I am totally in love with the outcome. I only have one small shovel full of ash, only need about 4 to 5 logs, split, to currently have warmth for over 24 hours. The stove needs tending, so one must have the time to keep feeding, think that's the same for all rockets, but I do not mind that, for me that's grand. The Gamera does heat the whole cottage, but the bench does not, yet again, for my situation it works very well. If I'd want the whole cottage warm all day, I'd have to run the Gamera all day, so that would not be a great set-up, then I'd say I'd have to rather go for a different system. For next winter we do want to see how we can get something with thermal mass storage going for my daughter as well. I think a batch box will be more suited to her life style, so we got another adventure ahead, more learning, but is has been huge fun, and the outcome is just so rewarding!!

Thank you to everyone for advice and encouragement. It has helped me out heaps, and my friend has done such a great job building it all, so grateful to him. He has shown pictures to others and it has sparked a lot of interest in the area, but he says he'd not do it for anyone else, lol

Again thank you to everyone here, and also thank you to the guys from Gamera, they have been wonderful to deal with. One happy rocket stove owner here, and goodness, all my dogs are fighting over the bench, from the smallets (on the photo) to my 100 pound giant hehe :D :D :D