Project:RMH,horizontal feed Batchbox model 6",

[dvawolk]

Attached is link of my review of the stove (PDF), and some brainstorming... I would be very happy to hear from you...


www.dropbox.com/s/la4edt9tzmmh65e/review01.pdf?dl=0

[esbjornaneer]

Hello Klemen,

Thank you for your thread donkey32.proboards.com/thread/691/project-horizontal-feed-batchbox-model and the link to your review of your (batch) BRMH.



I have read through the 15 pages of it now, what a good read. I had made plans to replace the old radiant mass heater I built several years ago with a J-tube RMH (the only type I knew of). But after building a mock-up of the J-tube outside yesterday my partner said she would not be happy with it and that she would not see enough flames from it. I found your thread and you seem to have built close to what we want. We have a 150mm round flue liner already installed from previous stove.



The main differences are that we have a hob/plate that we will put 100mm over the heat riser and incorporate an oven in the flue passage to a bell that is on the side of these. And no bench is needed for us.



I have some questions I would love you to answer, and if you prefer I could post them on the forum if you think others might see them and have more to say about them:



You say that you would use 5.5m^2 ISA for a new build, how much less would you recommend when the hot gasses have passed a 250x500mm metal plate and an oven?



In the formula that you offered in the beginning about the fire box dimensions: is the height (=3*sqrt((SCSA)*2/3)) from the bottom of the 'V' shaped floor or from the top of the 'V' where the sides are parallel?



When calculating the ISA for the bell, if one of the 4 sides is insulated with 50mm rock wool and another side is connected to the flue passages that heat the oven for the bottom 700mm of the bell, would these areas be included in the ISA?



Have you ever considered stacking bricks as walls with holes on them in a bell so it makes the volume of the bell partially filled with mass? (To more describe what I mean: stand bricks up on the longest&thinnest edge with a 3/4length gab between them, then stack next layer over the gaps, etc.) Would these bricks be added to the ISA? Or are they a way of adding mass in the bell if ISA=inner surface area of the walls?



There was talk about SCSA needing to be 1/4 of Bell CSA (BCSA), does it matter how the shape of the BCSA is achieved? BCSA = 200*200 = 20*2000 = 2000*20 would all create the bell effect? I offer the two last as distinct shapes as in one the SCSA flue would enter and run across a short distance in the bell and the other it would run a long distance before exiting the bell.



Is there of any importance how the entrance and exit of the flues to the bell? I know the exit must be as low as possible to heat more of the bell, but I mean should they be in opposite corners of the bell or does it not matter? And along these lines: I can not remember if you needed to do a 'fix' of your exit flue from the bench to increase the draft? If I have a 150mm rigid stove pipe coming vertically down to about 200mm from the floor of the bell, in one corner, would that be a restriction for the draft? What length off the floor would be recommended?



When you had redesigned & rebuilt the outdoor stove you talked about the port size (I guess that is the hole from the Fire box to the Heat riser?) being 220x56mm to be 70% of SCSA... Were those dimensions from bottom of 'V' to top of Fire box or to P-channel? The dimensions you mention do not seem to fit with the 70% of SCSA to me...



How does the air get to the P-channel? Do I need to have access to change the mild steel plate that I will use for the channel? How far does it hang from the bottom of the 'V'? Does the first horizontal fire brick of the heat riser start 5mm up from the bottom of the P-channel like it does in the J-tube RMH?



Wow that is a lot of questions... I did not realise that I had so many still. My worst problem is that I need to have my stove up and running this winter, which means I have to get it built in the next 2 weeks as I will go away for a month after that and then will be needing to heat the house when I get back in December.



Please let me know if you will be able to answer any of these questions and please answer them in what you feel is the order of priority for what I need to know to complete my build. (As I assume you will not be able to toss off answers to all of them in just a couple of minutes



Many thanks for any answers, I will start building asap.

Great read as I said and good that you are enjoying the heat from your stove.

Esbjorn

PS would your daft problems have been effected if your heat riser had been made higher? I would not be able to do such a fix as wanting to reach the cooking plate over it but you have lots of space inside your vertical bell.
PPS I can not supply SketchUp but would be able to scan some plan and section drawings if you need more info about what I am wanting to do.

[dvawolk]

Hello, Esbjorn.

I will start with answers right away.

Oct 21, 2015 22:54:35 GMT -8 esbjornaneer said:

Hello Klemen,
You say that you would use 5.5m^2 ISA for a new build, how much less would you recommend when the hot gasses have passed a 250x500mm metal plate and an oven?

As for metal ISA versus brick ISA you would need twice less ISA with metal surfaces. This was Peterberg's educated guess and as far as i know it worked quite okay. But i would also say that it depends of the thickness of the plate.

So to say: 250x500mm is 1/8 of sq.meters for metal. That would be 2/8=1/4 sq. meters /500x500mm for brick ISA. But i would say that it would be too close to heat riser (it would become red-hot) and secondly (as i know) the gap between the top of heat riser and the top of the first bell should be at least 30 cm (1 feet) - this is also info from Peterberg.

The same is with the oven (in the beginning i wanted to install a metal oven but later i decided not to - i preffered longer, cosy bench :-)

In the formula that you offered in the beginning about the fire box dimensions: is the height (=3*sqrt((SCSA)*2/3)) from the bottom of the 'V' shaped floor or from the top of the 'V' where the sides are parallel?

This is the height from the bottom of V shaped floor.

When calculating the ISA for the bell, if one of the 4 sides is insulated with 50mm rock wool and another side is connected to the flue passages that heat the oven for the bottom 700mm of the bell, would these areas be included in the ISA?

As a rule each(!) area that takes away the heat from the gasses should be included into consideration. But sometimes you have to be carefull: if you have a thin brickwall and then insulation behind it, then at the begining of heating it would take away the heat. But when it is charged (*1) (that would be much quicker as compared to ordinary brick wall) it would not take away any more heat and consequentially stack temperature will go up and the stove will become faster... The same is with oven... It is a difference already if it is closed or openned, if it is empty or full...

In my thread i took out of ISA the surface of batchbox burner and all the surfaces that are not touched by gases... Please - do chek the .skp sketch. It is quite easy to move and to measure dimensions and you will understand the thread (mine and other's) so much faster - this is also the answer to the dimensons that you are asking...

Have you ever considered stacking bricks as walls with holes on them in a bell so it makes the volume of the bell partially filled with mass? (To more describe what I mean: stand bricks up on the longest&thinnest edge with a 3/4length gab between them, then stack next layer over the gaps, etc.) Would these bricks be added to the ISA? Or are they a way of adding mass in the bell if ISA=inner surface area of the walls?

Yes i did consider it (but to late). It would be very easy job to start with 5.5 isa at the begining and then fine tune with those stacked bricks... BUT if you put them inside, do them in a way that the thickness of thoses's brick gob is twice as thick as ordinari brickwork in your stove - or they will be charged way too fast. This is connected with *1 some rows behind...

There was talk about SCSA needing to be 1/4 of Bell CSA (BCSA), does it matter how the shape of the BCSA is achieved? BCSA = 200*200 = 20*2000 = 2000*20 would all create the bell effect? I offer the two last as distinct shapes as in one the SCSA flue would enter and run across a short distance in the bell and the other it would run a long distance before exiting the bell.

The effect of the bell appears whenever the flue in the bench widens at least 4 times. The gasses should slow down, hot goes up and in the way to exit they cool..... If you can find some simulations (member karl) you will see that that is really not so slow process and the mixing of gasses is quite obvious.

In the Peterberg's thread
donkey32.proboards.com/thread/40
and
donkey32.proboards.com/thread/113

You have loooots of knowledge...

Is there of any importance how the entrance and exit of the flues to the bell? I know the exit must be as low as possible to heat more of the bell, but I mean should they be in opposite corners of the bell or does it not matter? And along these lines: I can not remember if you needed to do a 'fix' of your exit flue from the bench to increase the draft? If I have a 150mm rigid stove pipe coming vertically down to about 200mm from the floor of the bell, in one corner, would that be a restriction for the draft? What length off the floor would be recommended?

they don't need to be in the opposite direction.. My bench has a long "dead end" but it warms well to the end... Also my first try at the balcony had even longer " dead end" and it worked fine... The hot gasses are pushed by cold gasses upways.and when they reach a new bell they "spill" to the top of the bell.

Very usefull skill is to imagine how it works if you turn upside down your stove and then you start to pump cold water through your heat riser... In this imagination you are trying to cool the stove with water and it works similarly to the hot gases in the stove (that is not upside down :-)

I wouldn't say that would be a restriction - it has even more space compared to L elbow if you put it there... But i would say that it would perform better if you put this elbow on it so that coming gasses do not have to find a way to the top (competing with incoming gasses just behind them) If the gasses are coming directly down, they want to go directly up if possible and that's where is your enter to the bell - they are somehow contradicting themseves.. But if the gasses are led via elbov to come to the bell horizontally, then they have a free path to go directly up... - this is my thinking, by all means i am not an expert :-) It would be interesting if some other guy replies here...

No, i didn't need to fix my exit flue... What i did (sketches with green bricks in the last few pages) was blocking off some of the bell's ISA to consequetially achieve a better draft (higher stack temperature) - the exit is okay. The problem is too large ISA of my stove (and probably not that great chimney - where two other residents are connected. And also, not that good option is to be connected with upper part of your house (stairways can work like chimneys).

When you had redesigned & rebuilt the outdoor stove you talked about the port size (I guess that is the hole from the Fire box to the Heat riser?) being 220x56mm to be 70% of SCSA... Were those dimensions from bottom of 'V' to top of Fire box or to P-channel? The dimensions you mention do not seem to fit with the 70% of SCSA to me...

The dimensions are correct. Measured from the bottom of the batchbox without V shape. And two bricks (220mm) in height. The total height is 330mm. The calculations are correct - backcalculation gives 149,7mm diameter of the ROUND heat riser.

How does the air get to the P-channel? Do I need to have access to change the mild steel plate that I will use for the channel? How far does it hang from the bottom of the 'V'? Does the first horizontal fire brick of the heat riser start 5mm up from the bottom of the P-channel like it does in the J-tube RMH?

Please, do look .skp files move thoruhg first few sketches (just bachbox burner) and you will understand these things perfectly - it is really easier to see that and measure on the sketch( you have a meter icon there and you just measure whatever you want, scroll for zoom...)
My P-chanel is INOX and it is still fine (it is cooled with coming secondary air). The exit from p-channel to the port is underpressurized when burning. It is really interesting to bring a smoke to the intake of p-channel - it is quite obviously sucking the air in.. But of course, only when burning...

PS would your daft problems have been effected if your heat riser had been made higher? I would not be able to do such a fix as wanting to reach the cooking plate over it but you have lots of space inside your vertical bell.
PPS I can not supply SketchUp but would be able to scan some plan and section drawings if you need more info about what I am wanting to do.

I would be quite sure that that would solve my problems...higher heat riser would add speed to the burner and consequetially it would make for higner stack temperatures. But trying to higten it now is just impossible without a large hammer :-)

I would say your best bet is to have abit smaller ISA and then you try to broaden it with techniques mentioned in one of my last reply...

Best regards, Klemen
Do post your sketcehs!

[esbjornaneer]

Thank you for the reply! If anyone else has anything to add it will be greatly appreciated. 
I will take some time to incorporate this info in my sketches and get them scanned/photographed tomorrow to post them.
Thanks again, Esbjorn

[satamax]

Carefull with ISA, Peter has refined his calculations. donkey32.proboards.com/post/18796/thread

[esbjornaneer]

Hello Klemen,
These answers are great! and attached is a link to the drawings (https://www.dropbox.com/sh/lps6qipg9m3fuoq/AAB4caIiby1mvEfDZBsU1eEqa?dl=0). It is all better than I hoped apart from the first question that I am not sure I gave enough information about the stove for it to make sense.

Fortunately satamax I have only got room for 1.9m^2 ISA in the part I call the bell (far right in drawings) But I have no idea how much bell equivalent the hob, oven and walls leading from heat riser to bell should count as...? I have not designed this part of the stove intending it to be a bell but a channel/flue that leads gasses past hob & oven to the bell. Would it be better to incorporate it all into one bell or if we can manage to cook on a hob 1m high increase the height of the hob to get the 30cm clearance above the heat riser?

In the pictures 'w flow' I have drawn in the exit flue that is a thin stove pipe liner from previous stoves that I will terminate vertically inside the bell 15cm from the floor.
The red arrows are gas-flow indicators to make the drawings more easily understood. 'x' is away and 'o' with dot in is coming towards you. Dimensions are a bit incorrect as it is free-hand drawing but each square is 5x5cm.
Height of bell from top of platform is 130cm.
The bell is the cavity on far right.
At the top of the bell & over oven I will put a thinner metal plate with loose stacked fire bricks so I have easy access to inspect internal areas.

Pics do not show access pits 1, right of fire box under oven; 2, in bell

A friend I talked with today said I did not need as big a gap around the pillar as 10cm but that 5cm should be enough... I'd love your comments on that please!

The hob I will be using is and old cast iron hob from a 'Rayburn Royal' (solid fuel range) that is ~10mm thick and has 'fins'/'heat absorbers' ~10-15mm thick hanging down (that I would have over the heat riser). 

Any comments most welcome. Have to go on a 3-4hour roundtrip tomorrow to get rockwool, can't get it locally.
All the best and keep warm,
Esbjorn

[esbjornaneer]

Hey Klemen,
This video of yours is too good and useful not to be posted in your thread!
Thank you and it has improved my burns enormously to load the wood for the next burn into the FB 8 hrs after the last, but I do remove it all to light the next fire right close to the port rather than at the front.



What is the reason for the horizontal bar and pipe that you put inside the door?
Great work!
Esbjorn

[dvawolk]

Thanks Esbjorn for pasting the link to my video. It was really stupid that i haven't posted it here in the first place .

There are two horizontal bars one in the front (about 2cm above floor) and one in the back (about 4cm above the floor). Their task is to hold the main fuel above the already burned kindling. When kindling burns out, the main fuel shifts down without bars and when this happens, the air paths are to narrow for a sufficient draft below the kindling, so primary air must go above the main fuel. At the begining of the burn that is not good for a rockety burn because the air "misses" the first burning coals.
The piece of pipe also serves the same purpose - to (at least slightly) direct primary air to the place where first fire is burning...

I would say that there are some similarities with first tries of walker's channel... But my need for that arose from not very optimal draft and slightly too large ISA...


Practcally, my fire also starts in front of the port, because there is such a small ammount of kindling at the door, that it only serves to transport flames to the right place... But this should be only used when you can see the draft towards the port in the flame of the match... At my place, this is the case when burning it daily or not more than two days apart...

But i am sure that you can set the kindling and wood that way so that you can light a fire (with a long match) just in front of port... But you would at least need the front horizontal bar so that main fuel is slightly lifted up...

[mudder]

sounds like you got it figured out good! great video, thanks for sharing it.

[gugaiz]

Hi dvawolk, thanks for all the info you and everybody have shared on this thread.

Would you mind to post the updated sketchup file of your stove? Looking at your review file (pdf), the drawings do not match the sketchup file I found on this thread.

[dvawolk]

Hi, people.

I will just add a small photo of the stove that is right now.


I added local brown colored clay plaster on places where abrasion is more severe (bottom edge, around the door) and at some places to make it more special... I will be adding it to the top also, because i put there the wooden drier that i made last year and it works perfectly - putting it to the regular clay plaster abrades it, so i will put another brown layer and painted it with linseed+tung oil... This oil really makes a difference...The surface becomes scratch proof :-)

Also i glued a brushed cypress plank to the wall to be more comfy to the back...


There is another thing i would like to share with you, some kind of unconvenient anomaly of brick moving...But this will be available in a separate post - here is the link

Have a nice weekend,
Klemen

[dvawolk]

Oh, boy, what a photo :-) Next time i will tidy it up before :-)