Bricks for the box of my cob bench

Bacon Lee wrote:
Hello

I had such a hard time upload the video from my smartphone. I finally decide to use my ipad to re-record. My ipad is out of battery so now I have to charging it. Not thing break but I saw pieces of computer paper already burn but still intact which is big pieces of ashes. Many of them at bottom of heat riser. It's didn't burn good isn't it?

I forgot to ask you what do you mean by enlarge the manifold? What does that mean?

The manifold is the area that transitions from the barrel into the duct work system. If it gets too tight and too constricted, it can have a negative effect upon the air flow throughout the system. Peterberg has some calculations for it, I suspect I read that on Donkey's forum. You can try looking over there for detail. But basically, bigger is better. You want air to move easily from the barrel into the duct work. This is also one of the largest areas of error first-time builders make, according to the experience of the Wisner's.

This is where your duct work connects to your barrel. You'll come across this term as you read the Evan's book.

If you disconnect that ductwork, you will be able to build a square or rectangle or really any smooth shaped space, immediately out of the barrel, and then at the end of that you narrow down to a connection to the duct work, just like you already have done now. Many people also add a clean out here, so they can get at the ashes that collect here, as it is supposed to be on the more likely places for ash to accumulate. Especially if you also make the bottom of it a little deeper than the bottom of the duct work into which it feeds.
The purpose, other than a convenient place for ash collection and clean out, is to avoid causing a "damming" effect in the duct work, as the hot (expanded) air tried to move into a much smaller area, of the duct work. You would, however, also be advised to make a much larger opening in the barrel, where you are currently hooking up the duct work. A 12" round hole, or a rectangle something like 10 or 12 inches tall and 16 or 18" wide, and with the very bottom of that new opening something like 2 or 3 inches above the very bottom of the barrel. This is all to make the flow of air easy. This is what Peterberg discusses in his posts (on the Donkey forum).

You can also look up YouTube videos done by the Ernie and Erica Wisner, they often mention this. And you can look up the series of YouTube videos Paul did on his portable RMH, and that is of special interest, because he did identify this as one of the problems he re-worked from one build to the next.

So that's the manifold. Is it mandatory? I don't know; I doubt it. Will it make the system more effective? Yes, in theory; and it certainly won't hurt anything.

I would add a manifold. What I would not wish to hear, after having cobbed in 5,000 pounds of clay, is that I really ought to dig a bunch out and cut a bigger hole in the (bottom) barrel, and add a manifold. And while I'm doing that, I might as well add a clean out.

I say cut a bigger hole in the *bottom* barrel, right where you are currently connecting the duct work to the barrel, because in my opinion adding a second barrel on top, and making your fire riser is super important - I think I'll go so far as to say mandatory. If you do not, the system just is not going to work well, and everyone who tries to help you figure out what is wrong, is going to say "your fire riser needs to be taller - a lot taller" and they really will not be able to give you the best advice to fix your system, until you fix and giant glaring error that exists

OK, moving on...

No bricks fallen into the fire riser. Good news! I thought that was unlikely, but now you know for sure.

Big pieces of ash (former computer paper) laying at the bottom of the fire riser.

This suggest maybe a couple issues. The most obvious, is that you are not getting hot enough. Most likely, in my mind, is because the fire riser is half as tall as it needs to be, and that is not allowing the optimal temperatures to be reached.

Second, you need to clean the ashes out girl! heheh

Get a bent piece of whatever, kind of like a small 3 or 4 inch wide hoe, and reach to the back wall of the fire riser, going through the feed tube, and pull those ashes and debris out to the bottom of the feed tube, and then scoop them out and put them in a metal bucket, or metal trash can. (Try to keep water from getting into the wood ask, as that tends to make lye; OK for making soap later, but not ideal to have just laying around, waiting to spill, heheh.)


QUESTION: What are the dimensions of your burn chamber?

Your burn chamber, is the part of the stove that connects the feed tube to the fire riser. I believe you said that is three fire brick long, so that's 27 inches, and your inside dimension will measure a little less than that (27 - feed tube wall - fire riser wall).

But how tall is it? And how wide?

I forgot to ask you what do you mean by enlarge the manifold? What does that mean?

Bacon, you see here your tube at the bottom, sticking out inside the barrel, that's not very good.

https://permies.com/t/43419/a/24857/thumb-20150123_130746_resized.jpg

Well, normaly we consider that the transition area or plenum had to be 3 times the CSA of he system to work well. So may be a 10"x10" square reducing on a short lengh to your 6 or 8 pipe would be better. And one thing i notice, you haven't insulated the heat riser nor burn tunnel! That's plain wrong if you want a proper "rocket mass heater" Just find a sheet of metal, wrap it around your riser, rivet it and fill with either perlite, vermiculite or rockwool. Let say 4 inches all around is good. Leave a 3 inch gap, i would say. between insulation and barrel. If more at the back, where your transition area is, it doesn't matter, actualy it would help.

OK, then, a suggested "to do" list:

Get second barrel (same size as first)
Remove existing barrel
Remove the paint from both barrels

Add manifold
I had a thought here. If you have an angle grinder, put on a cutting blade and just cut the big rectangle, all the way around the duct work right where it is right now. That way you may be able to keep the duct attached to the side of the barrel, and use that and the cut out piece of barrel, as the back wall of the manifold.


EDIT:
Insulate the fire riser and burn chamber.
Now that I can see the pics, yes, insulate the fire riser and burn chamber. I insulate the feed tube, at least a bit, so as to not get burned, but that is not as important more of a user-friendliness point. But the fire riser and burn chamber should be insulated. Your perlite-clay will do well for that (obviously, first install something around the fire riser to hold in the perlite-clay -- some have used two or more pieces of duct, and instead of snapping them onto themselves, you snap one onto the next, until you have a circle of the required diameter (which will not be a really nice looking circle, and will benefit from some extra bending and shaping into a near-circle, but it will work well enough)).

Goodness a log to big job to do.

1) Protect the floor with 2 more inches of perlite and Porland cement, right?
2) Remove the paint
3) Add more high to the heat riser
4) Add a manifold
5) Insulate the heat riser? I saw the one Erica and Ernie did, same as mine, they didn't insulate the heat riser as it is already in fire brick

My burn tunnel is only 2 bricks, which make it 9". So the dimension is 9" long, 6.5" wide, and 4.5" high

Here today in CA, the outside temperature is 70 degree. In CA, days with high temperature we can't burn the wood stove. Those day call Spare The Air-day. Violate will be a $500 fine, but I just burned any way so I can report the number to you. Here are the numbers:

I burn from 2.10PM to 2.40PM, so I burned for half an hour, and then I took measurements:

Lid: 385
Burn tunnel: 496
Feed: 134
Top layer of barrel: 236
Second layer of Barrel: 208
Last layer of barrel: 139

Duct:
Where connected to barrel: 88
At the U-turn: 87
After U-turn: 77
Verticle duct up the roof: 71

Today when I burned I heard the rocket effect again, and I think I know what happen yesterday: Yesterday when I started the fire, it took long and I had a hard time, I put a lot of computer papers in. But non of them I put all the way to the heat riser. Somehow they stuck there and made the burn very poorly. Today I had a hard time at first, so I stopped and get a stick to get all the ashes papers out, then I redo it. This time, the fist ball of paper, I put it all the way to the heat rise, then a next one follow, it then burned very well. I think last time I didn't put the papers all the way to the heat riser. I just sticked them under the burn tunnel, somehow it made it burn very poorly

Now, about protect my floor, I think I will add 2 more inches and I am thinking of embeded copper coil in there to help cool down the temperature and to provide hot water for my fish pond. I have been thinking of running copper coil to get hot water for my pond. That's what I did last time with the conventional heater. I threw a coil to copper tube in the stove, make 2 holes on top to run water in and to release water out into the pond. Now if I embeded copper coil into the 2 inches layer of cement/perlite on the floor, what I am worry is what if the copper coil damage, then I have to undo everything to fix the copper. Copper tube is very fragile and soft easy to be damage. Never mind then, maybe i stick with my first plan which is have the copper coil on the lid to get hot water, this is safer, right?
Here is the copper coil I am talking about:

http://www.lowes.com/pd_43729-76063-6362408799806_0__?productId=3134493&Ntt=copper+coil&pl=1¤tURL=%3FNtt%3Dcopper%2Bcoil&facetInfo=

Oh my! Don't get a fine on *my* account! I'm not going to help pay it! heheh ....we can wait... ...if you can, heheh...

Bacon Lee wrote:

1) Protect the floor with 2 more inches of perlite and Porland cement, right?

No, do not use any portland cement. Just use your perlite and clay mix. I was using anywhere from a 1:3 to a 1:9 mixture of fire clay to perlite. I think I'd ball park a 1:6 to a 1:9 ratio of clay to perlite. I think that'll be fine. If you add an air gap, it will almost certainly work very well. Air moves best when it is at least 1-inch space. More on that suggestion later.

Bacon Lee wrote:

5) Insulate the heat riser? I saw the one Erica and Ernie did, same as mine, they didn't insulate the heat riser as it is already in fire brick

Was it the one using kiln brick? If so, kiln brick is very different than fire brick. Both take extreme temperatures, but kiln brick really *is* insulation, whereas fire brick is *not* insulating.

But I am quite certain they do *not* recommend using fire brick all by itself. I saw one, where I too thought that at first, and got excited. Then discovered I was mistaken, and something else was going on (I no longer what).

Bacon Lee wrote:

My burn tunnel is only 2 bricks, which make it 9". So the dimension is 9" long, 6.5" wide, and 4.5" high

That will be just fine. Pretty close to a nominal 6-inch system. Almost the same as mine, actually, although my burn chamber is a little longer, at 13.5-inches. If you can fit 9" into your space, as you have, that is even better. Good going.

Cross Sectional Area CSA = 4.5 x 6.5 = 29.25 square inches. That will be a good number for you to remember And also remember the 4.5 x 6.5 inche dimensions.

If I recall correctly, you said your fire riser was 6.5 x 6.5 inches. So that opens up a little (larger CSA than the burn chamber). I think you'll be fine in that regard. It is not perfect, but a great many builds are not "perfect" according to the geometry in the book. Mine, for example, has a fire riser opening in the fire brick of 4.5 x 6.5 inches, but sitting on top of that is the 7-inch diameter duct (insulated with about 2.5 inches of perlite-clay), so mine too opens up after the first 5-inches or so, and it draw and burns well enough.

But your "system size" is the smallest dimension in the feed tube, burn chamber, or fire riser. And it is better if the smallest CSA is in the burn chamber. The other two can be a little bit larger without causing harm. Therefore, you have that part right. Good deal.

Bacon Lee wrote:
I burn from 2.10PM to 2.40PM, so I burned for half an hour, and then I took measurements:

Lid: 385
Burn tunnel: 496
Feed: 134
Top layer of barrel: 236
Second layer of Barrel: 208
Last layer of barrel: 139

Duct:
Where connected to barrel: 88
At the U-turn: 87
After U-turn: 77
Verticle duct up the roof: 71

Today when I burned I heard the rocket effect again, and I think I know what happen yesterday: Yesterday when I started the fire, it took long and I had a hard time, I put a lot of computer papers in. But non of them I put all the way to the heat riser. Somehow they stuck there and made the burn very poorly. Today I had a hard time at first, so I stopped and get a stick to get all the ashes papers out, then I redo it. This time, the fist ball of paper, I put it all the way to the heat rise, then a next one follow, it then burned very well. I think last time I didn't put the papers all the way to the heat riser. I just sticked them under the burn tunnel, somehow it made it burn very poorly

I'd say you are right about the paper causing the air flow to get cut down too much. Just be careful when lighting the paper and let it get going well before laying it down. I just put mine in the throat of the burn chamber, like you did before. I don't try to push it back under the fire riser. I figure if it is in the throat of the burn chamber I can watch it. But if you have nice strong draft, it will just suck those flames sideways, and it may pull some of that burning paper deeper into the fire box, and I think it is possible it will draft so hard it puts the flames out (sometimes).

Temperatures, these seem a little on the low side to me. My guess is going to be because the fire riser is too short. That height really drives the "fire engine" of the rocket stove. It will let things get hotter, and push the draft harder. Both good things. But you are not way, way off. I seem to recall many people talking about temperatures at the bottom of the barrel (manifold area) being in the 200-300 F range.

I'm guessing your burn tunnel measurement of almost 500 F is on the top surface. That seems about right. It should be much, much hotter inside, of course. On the sides and bottom I have measured almost 600 F through split fire brick (1.25" thick), so 500 F is not all that different.

Perhaps others can comment too, but I think your duct work should be warmer than that. Again, it goes back to the tiny fire riser. It should really be at least 40 inches tall, if not 48 or 50 inches tall (and insulated). After you get your second barrel, figure out how tall you can make the fire riser, while leaving a gap somewhere about 2 to 4 inches between the top of the fire riser and the top of the barrel. That includes making an angled "lip" or "top edge" on the fire riser.

You make a top edge or lip on the very top of the fire riser so that fly ash doesn't tend to accumulate there. It can angle either out toward the barrel, or inward toward the center of the fire riser. Of the two, more folks seem to favour inwards toward the center of the fire riser, so that ash tends to fall back into the fire riser, where you can clean it out along with the rest of the ashes; otherwise, it accumulates around the bottom of the barrel, and in the manifold. Not a real big deal, but it mean you have to clean that more often that otherwise.

EDIT:

You may also notice higher temperatures simply by burning for an hour or so.

(But the fire riser still needs to be tall -- or the all the brick ought to be rebuilt, to make it a smaller system size, and I'd not want to do that, much smaller than you are building is said to be more difficult to get to run right.)

Bacon Lee wrote:

Now, about protect my floor, I think I will add 2 more inches and I am thinking of embeded copper coil in there to help cool down the temperature and to provide hot water for my fish pond. I have been thinking of running copper coil to get hot water for my pond. That's what I did last time with the conventional heater. I threw a coil to copper tube in the stove, make 2 holes on top to run water in and to release water out into the pond. Now if I embeded copper coil into the 2 inches layer of cement/perlite on the floor, what I am worry is what if the copper coil damage, then I have to undo everything to fix the copper. Copper tube is very fragile and soft easy to be damage. Never mind then, maybe i stick with my first plan which is have the copper coil on the lid to get hot water, this is safer, right?
Here is the copper coil I am talking about:

http://www.lowes.com/pd_43729-76063-6362408799806_0__?productId=3134493&Ntt=copper+coil&pl=1¤tURL=%3FNtt%3Dcopper%2Bcoil&facetInfo=

This is more complicated, and has more options, a number of which should work. So there is very much room here for choosing between several options.

To reinforce the point, do *not* use portland cement under your fire box, or anywhere within several feet of it. The cement will not take the heat, and it will come apart.

You could do the copper like you suggest. You've done it before which is a plus. The one super important point, is that the water is open to the air in the room at some point - like the fish tank! But, if at any point the water system is NOT open to the air, do not heat that water. Folks call it "boom squish" because it if turns to steam, it can blow up, and that is super, super bad. Like blow the house flat bad. If the heater water *is* open to the air in the room, there is not a problem. So be super clear on that point.

Now, having said that, if I were going to embed the copper like you are talking about, and wanted to protect it from crushing, the first thing that comes to mind is to frame it with split fire brick. That will make a supporting "wall" for the copper pipe, and my *hope* would be it would save the copper from getting crushed. I say "hope" because I have not done anything like that, so I am just guessing and throwing an idea out there.

But all the same, having the soft copper pipe on top ... I like that idea!

But I would add an air gap right on the perlite-clay you already have laid down, and then I'd lay the new 2-inches of perlite-clay on top of that air gap. I feel very confident that'll protect your floor. I'll try to upload some pics to show what I did; we'll find out if I do it right! heheh

I used fire brick to make a 4-inch wide channel, 1.25-inches deep (the height of a split fire brick) that runs from the back wall of my fire riser, all the way to the front of my feed tube, opening to the room air at the front of the feed tube (but *not* under the fire riser, which is under the barrel). Then, I spaced the brick so there are two side gaps, about 2-inches wide, roughly below the throat of the burn chamber.

This would require some holes to be drilled in your existing brick, or to in some other way make some openings for air to move. A sledge hammer can go a longs ways heheh All you really need is at least two openings in the brick wall surrounding your build. To make the air channels, you could use fire brick like I did, or steel tubing. Hot air rises, and if there is a minimum of an inch, the air flows well. So that's 1x1 tubing, either square or round. And if one end is lower than the other, so much the better. If both ends are higher than the middle, that's not so good.

Is all that required? Do you really *need* to have air gaps?

I don't think so. I am just certain it will work really well, if properly built. But just by adding 2 more inches of perlite, you may be doing enough. That is a total of 4 inches of perlite-clay insulation, and that is getting into the range I have often heard recommended as safe. I'd really like to hear what others have done in this regard, and what temperatures they have measured in that perlite-clay insulation at various levels.

If there was one thing I'd skip doing, that I have spoken of, what would it be? Most likely skipping adding the air gaps. They are a great idea, I think, but they do require swinging a sledge hammer and knocking out a two or three bricks (or drilling some holes) and then laying the air pathways, whether those are made of fire brick or steel tubing.

heheh, I forgot to try to upload the images.... ( and you are taking advice from this guy! )

If this works, the first images shows the laying of the air channel. The second pic, shows the 2-inch wide hole that runs all the way across to the other side of the fire box. And the third shows the 4-inch wide hole in the front, below the front of the feed tube....

...OK, it worked.

The floor of the fire box (the floor of the feed tube and burn chamber) spans across the flat fire brick splits you see in the first picture. This results in a long air channel under the center of the fire box along the long axis, and opening to the front, with two additional smaller openings, one per side, roughly under the spot where the feed tube changes into the burn chamber (which I call the "throat" of the burn chamber).

Previously, I have measured temperatures in excess of 500 F (nearly 600 F) under the place where the coals pile up. In my first test burn, which I did this afternoon to make sure I didn't have any smoke leaks, the maximum temperature I measured in the air gap under that spot, was 129.3 F; meanwhile, the maximum temperature I measured in the living fire itself, at the throat of the burn chamber, was 1,924.7 F.

"cut the big rectangle, all the way around the duct work right where it is right now."

An even better way might be to cut out an "X" in the barrel from the duct hole to a 10" square or something like that, then bend the tabs out at about 45 degrees. This will give an automatic smooth shape to the manifold transition area. You will need to cut a few extra slices in the top part of the X so the curved metal can bend out without warping the barrel shape.

In regard to "fire brick" and "kiln brick", they are really interchangeable terms depending on what area of the country you are in. For clarity, manufacturers and online sellers often say "fire brick" as a generic term or for dense brick, and "insulating fire brick" for the lightweight ones. If not specified as "insulating", don't expect it to be so, as that is generally more expensive.

Glenn Herbert wrote:

In regard to "fire brick" and "kiln brick", they are really interchangeable terms depending on what area of the country you are in. For clarity, manufacturers and online sellers often say "fire brick" as a generic term or for dense brick, and "insulating fire brick" for the lightweight ones. If not specified as "insulating", don't expect it to be so, as that is generally more expensive.

I've not used kiln (insulating) brick yet. I've read that it can be easily cut with a hack saw. Certainly not fire brick! heheh So that, and the large weight difference (insulating "kiln" brick being much lighter) would be another clue

Glen,

So I will not actually cut off the rectangle from on the barrel, right? I just make the shape of the rectangle with the metal bend outside and still intact to the barrel ?

I need to go buy the manifold ahead of time to know what side it would be so I can cut the barrel, right?

Erik: I went on home depot to search "manifold" and there is not thing. Would you please send me a photo of the manifold

already broke the thing apart, tomorrow will start the "to do" list. Because I put most of the burn chamber inside the barrel only the feed tube is outside with no insulation and I don't have the cob in yet, breaking apart is easier and didn't take that long either. But this is what I concern: Now I think I will add 3 more layers to my heat riser, so 27+13.5=40.5, that's good enough yet?

Look at this clip: Erica and Ernie also added around the same size as I will add. In the system, you see the whole barrel, right, so what is added is the high of the bench (pretty much) so it is around 14 inches ( eyeball around that). I will add the same 13.5 inches. That's good enough right?

https://www.youtube.com/watch?v=4usXIAoy9us

But the thing is: Since I will add more bricks to the heat riser which means more mass for the barrel to bare. I am afraid the bottom of the barrel would not hold up to it? What I think is: If we turn the barrel up side down, we will see that the barrel has circular leg kind off. What I mean is there is a hollow space from the bottom of the barrel and the floor. I am afraid more mass made that bottom bends or damage. I want to turn the barrel up side down and fill up that empty space also with fire clay and perlite to make it solid and attached to the floor, do you think it will help make it stronger?

Bacon Lee wrote:


Erik: I went on home depot to search "manifold" and there is not thing. Would you please send me a photo of the manifold

Well, these are transitional duct work pieces, usually called plenums. They serve to assist when changing direction of air flow in HVAC systems. And they are usually expensive.

I'm under the impression most people just brick or cob something together for use in their RMH.

I can't find an online image I like. But you have the book by Evans, "Rocket Mass Heaters" right? In the 3rd edidition, look at the drawings/pictures on the following pages:

28 (also has the summary of all the basic geometry), 55, and 66. Now, compare those with page 67, where is says "Too tight" and "Too much ash..." and "No clean-out." The first pages (28, 55, and 66) show you what you want; page 67 shows what you do not want (and what you have right now).

When you have a little over an hour, this may be a useful YouTube video to watch. It is one of Ernie and Erica's classes:

http://youtu.be/3mZQdu2wNi4

Now, let's see if I can upload some images of mine. I am a little uncertain I should. You are building a full RMH, whereas I have just built my second test rocket stove, and this winter I am not going to add the thermal mass, so it will *not* look like what you are trying to do -- if you look at these pictures, you have to keep that in mind. I am not doing what you are trying to do. I will build the full RMH this summer, on my concrete floored porch, after taking down the wall behind where I am building this test stove. This entire stove is going to be un-built, torn down to nothing, and then I am going to rebuild the entire thing about 10 to 20 feet from where it is now.

And right now I am on a wooden floor, which is not designed to take the weight of a massive thermal bench. So I am very conscious of the weight. This is why I just cobbed in a small manifold on this rocket stove. When I build the rocket mass heater, and I have no concerns about weight, I will make it larger, include a clean out, and I will most likely build it out of bricks, and then cob all over it. So keep all this in mind as you look at the following pictures....

A view standing back a ways, during the first test-firing of build #2...

...and this is the complete build# 2, which I remind you, is only the rocket stove portion of the project, so that I may take temperature readings and generally get used to it, and see what I think, before building the full masonry heater later in the year....

...the strange looking things above the stove are experiments to diminish the heat flowing up onto the ceiling.

While, we're here, typical temperatures while burning have been in the 450 F to maybe as high as 550 or 600 F on the top of the black barrel; 200-220 F on top of the 7-inch partial barrel above that (that I call the "top hat"); and above that, is a piece of foil-faced 1/2-inch insulation board, just there to push the heat out, and to give it time to cool before hitting the ceiling; temperatures on the foil side run up to the area of 160-170 F, and temperatures on the other side of the foil insulating board have not yet run up above 95 F or so (I've not yet measured 100 F there).

That foil-faced 1/2-inch insulation board is the same thing that is lining the walls. There is an inch or more gap behind them, a couple inch gap at the floor and and also at the ceiling. That's what makes a heat shield -- metal with at least an inch of air space. Somewhere I read that the gap at the top should be at least 3-inches, at least according to that particular set of codes I was reading (I don't know where they were for, I have forgotten).

Ok, I know what's a manifold is. Saw it in the video of Ernie and Erica. Now the rock wool, is it the soft fiber like material people usually wrap them around smoke pipes right? I should find it at Homedepot right? How come I went on home depot search for rockwool I didn't see any thing.

how come Eria said we can use wire mess to hold rockwool into the the heat riser, wouldn't that material cat on with the flame and burn too? May be I don't know what is rock wook, would you please give me a picture of rockwool

Bacon Lee wrote:
already broke the thing apart, tomorrow will start the "to do" list. Because I put most of the burn chamber inside the barrel only the feed tube is outside with no insulation and I don't have the cob in yet, breaking apart is easier and didn't take that long either. But this is what I concern: Now I think I will add 3 more layers to my heat riser, so 27+13.5=40.5, that's good enough yet?

40.5 inches, was I believe the suggested minimum height for your geometry. So that's OK, but there is another consideration, you also want the top of the fire riser to be within between 2 and 4 inches (some folks say 2-3 inches) of the top of the barrel (the one you will add).

So, grab a yard stick and measure up from the rim of your bottom barrel, 34 inches. That is the height the second barrel will be at. So you want your fire riser to stop somewhere between 2 and 4 inches lower.

Of course, there is one more factor, and that is if you will be changing anything that effects the height of the bottom barrel.

Bacon Lee wrote:

Look at this clip: Erica and Ernie also added around the same size as I will add. In the system, you see the whole barrel, right, so what is added is the high of the bench (pretty much) so it is around 14 inches ( eyeball around that). I will add the same 13.5 inches. That's good enough right?

https://www.youtube.com/watch?v=4usXIAoy9us

Yep, interesting clip.

But I didn't understand your question.

Bacon Lee wrote:

But the thing is: Since I will add more bricks to the heat riser which means more mass for the barrel to bare. I am afraid the bottom of the barrel would not hold up to it? What I think is: If we turn the barrel up side down, we will see that the barrel has circular leg kind off. What I mean is there is a hollow space from the bottom of the barrel and the floor. I am afraid more mass made that bottom bends or damage. I want to turn the barrel up side down and fill up that empty space also with fire clay and perlite to make it solid and attached to the floor, do you think it will help make it stronger?

It would not hurt anything to add support under the barrel, as you are suggesting. I think that is a good idea. I'd either use sand, or better, perlite and clay mix.

Now it is complicated. The manifold is a hard piece square or rectangular then turn into circle at the other end, how could I attached a hard piece of rectangular around my barrel which is curve?

Can I just use cob to mold into some shape of the manifold? That would make cob is the only barrier, would that be dangerous if the cob crack and the CO go into the room, right?

If you buy it, it will be a "reducer" or reducing transition... there are several possible names. Floor register boot might be another thing to look for.

http://www.ebay.com/itm/Imperial-Mfg-Group-GV0708-Galvanized-Register-Boot-6X12X6-REGISTER-BOOT-/111568494927?pt=LH_DefaultDomain_0&hash=item19fa00214f

Bacon Lee wrote:
Ok, I know what's a manifold is. Saw it in the video of Ernie and Erica. Now the rock wool, is it the soft fiber like material people usually wrap them around smoke pipes right? I should find it at Homedepot right? How come I went on home depot search for rockwool I didn't see any thing.

how come Eria said we can use wire mess to hold rockwool into the the heat riser, wouldn't that material cat on with the flame and burn too? May be I don't know what is rock wook, would you please give me a picture of rockwool

Yes, it sounds to me like you are describing rock wool. It can also be called mineral wool. And some people call it by manufacturer trade names instead. But rock wool is not made from wool. I believe it is some kind of mineral, which would explain why it is sometimes called mineral wool.

But I don't have any rock wool, so no picture. They call it something else at Home Depot and Lowe's. Roxul or something like that. Just make sure to check the heat rating, which should be at least 1,000 F I would expect. The top of that barrel can and will get that hot. But it also cools down rapidly as it falls to the bottom of the barrel. Kind of neat!

This is why you can just use wire to wrap that rock wool onto the fire brick. Inside that fire riser it gets super, super hot. But outside of it, not so much. Maybe 1,000 F or so at the top, and then all the way down to a few hundred degrees at the bottom of the barrel.

Erik: In your photo, you also cob the manifold, and wrap around with wire mess, you didn't buy the manifold, right? I don't think there is a manifold which curve around the barrel. And would you please give me a photo of rockwool or a link. I went on homedepot, didn't find it. Homedepot should have rockwool, right?

I started writing my previous post an hour ago and got distracted. You could take that cheap 10" x 6" register boot and cut its corners so you can bend it from a rectangle to a circle, then trim it to fit a matching large circle cut out of the barrel (with little tabs you can bend out and rivet to the barrel).


I know Lowe's has Roxul brand rockwool, not sure if Home Despot does...

Should I buy this one, and have it lay on the floor of the barrel and stick the circle out the hole on the barrel right now, then around this rectangular opening I will cob so it will be the only hole on the floor for the hot air to fall into. I saw other people do it that way.

http://www.ebay.com/itm/Imperial-Mfg-Group-GV0627-C-Galvanized-Register-Boot-4X12X6-90D-BOOT/301494165592?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D28794%26meid%3D19b49a894e59400880fca5126d7aae3a%26pid%3D100005%26rk%3D3%26rkt%3D6%26sd%3D111568494927&rt=nc

Bacon, if you buy anything, it's this

http://www.ebay.com/itm/Imperial-Mfg-Group-GV0705-C-Galvanized-Register-Boot-4X12X6-REGISTER-BOOT/111574474542?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D28794%26meid%3De1d875adb7dd462d9c8a68910de1b5a8%26pid%3D100005%26rk%3D3%26rkt%3D6%26sd%3D301494165592&rt=nc#ht_1572wt_1092


But there's other ways!

Use a half barrel with the barrel cobbed over.



http://s65.photobucket.com/user/mremine/library/NYC%20Rocket%20Stove%20Build?sort=3&page=1#/user/mremine/library/NYC%20Rocket%20Stove%20Build?sort=3&page=1&_suid=142208174735906173896451329552

This is from Matt Walker's New york heater restaurant bench.

Bacon Lee wrote:
Erik: In your photo, you also cob the manifold, and wrap around with wire mess, you didn't buy the manifold, right? I don't think there is a manifold which curve around the barrel. And would you please give me a photo of rockwool or a link. I went on homedepot, didn't find it. Homedepot should have rockwool, right?

Here's link to the stuff at Lowe's:
http://www.lowes.com/pd_305816-1278-RXSS31525_0__?productId=3394032

Note the part of the description that reads "Non-combustible, fire-resistant up to 2150 F"

Home Depot may not carry that brand, but they should have something like it. Although, I did find a link for that same brand at Home Depot:
http://www.homedepot.ca/product/roxul-safensound-for-wood-studs-16-in-on-centre/972187
"can withstand intense temperatures of up to 1177C" which is 2150.6 degrees Fahrenheit. Same stuff.

If you show the workers at Home Depot these links, they should be able to show what they carry in your nearest store. I can't say they *do* carry it, but I would expect so.

Bacon, to answer your question, yes, I just cobbed over the 1/4-inch hardware wire. I only used hardware wire (that metal screen looking stuff) because I need to keep my weight low. If I was doing it on a nice concrete floor like yours, I would just build up the walls with brick and lay something over the top, which could be all kinds of things to make a "roof" for the brick walls. That could be paving stones, which often come in 16x16 inch squares, or it could be metal cut from a barrel, or you could lay down some pieces of rebar, then lay hardware cloth over than, and cob it in when you cob over the brick walls.

In my opinion that is much easier than making the hardware wire manifold screen like I did. It works, but is a little bit of a pain to do.

Hi bacon ; Thought I would show you some pics of my transition area,maybe they will help. Very little $ needed. I created a brick box with a cleanout door and an ash pit. One large flat rock covers this box and I stack my split wood there to preheat it. I did use 1/4" hardware cloth to form up to the barrel, then a thick layer of cob to seal.

Some extra pics

@ Thomas:

Did you use anything to seal the clean-out cap against the cob? (Rockwool, etc) Or did you just pack the cob tight and give the cap a twist every now and then so it would not stick to the cob, as it dried?

What you have done is essentially what I plan to do for my permanent build.

Hello everyone

I tried to insulate the floor with 1 clay and 6 perlite as per your instruction. Are you sure you are right, how come the mixture is not sticky at all, they are like sands seperated I wonder will they stick together when they dry off?

My first experiment with perlite/clay (with only just enough clay to cover the surfaces of the perlite granules) was that it didn't want to stick together much, but when dry, it did make a weak rigid structure. In a contained area with nothing moving, it should be fine. Firing the test brick of perlite/clay made it actually able to take some stress.

Bacon Lee wrote:
Hello everyone

I tried to insulate the floor with 1 clay and 6 perlite as per your instruction. Are you sure you are right, how come the mixture is not sticky at all, they are like sands seperated I wonder will they stick together when they dry off?

Working with cob, and clay, is a very touch-feel, kind of thing. There are a lot of variables. Recipes are only general guidelines. When you actually do it, you have to go by feel. And I'll say, this is one area that I for one cannot get by reading or watching videos (although both help). For me it boils down to feeling it in my hands.

Not being there, I'm just going to make some wild guesses, and try to remember difficulties I have had, and suggest what I have done. I'm not where you are, so I may be mistaken, or overlooking something I'd see if I were there. That said, here goes...

First, I'd try adding more water. Not too much. Just enough. How much is that? Well, you just "feel" when it is right. Sorry.

If that didn't work, I'd add more clay. Depending upon the mix of the clay you are using, it may be different from what I'm using, or what someone else is using. This is really evident when digging clay out of your back yard! heheh.

Here's the deal, clay acts as a binder, or a glue. It will also get hard as the water dries out of it, and that helps it hold its shape. And if it is good clay, and I think you're using Lincoln 8, which others said was a good clay, so you should be good there, anyway, if it is good clay for this purpose it will hold up to the high heat just fine.

The perlite is the insulator. It also has rough surfaces and will grab some of the water. So it tends to suck up or dry out the mixture as you are mixing it. I assume you have felt this when adding perlite to your mixture. But, perlite will do nothing to make the mix more sticky. It will have the opposite effect.

So, if too dry and powdery, add clay and, or water. If too wet and too sticky, add more perlite. And if the stickiness feels right, but it is too wet, then try to remember the ratios you have used and add more of the dry ingredients (clay and perlite) in the same ratio. Then adjust as needed.

Another point, if I remember your images correctly, there is going to be nowhere for even loose-poured perlite from spilling out anywhere, right? The only chance of that is if the wall falls over (and I have no reason to believe it will, so don't worry about that). So, if that is true, then the purpose of the clay in this application is more for the structural component -- you want the clay to help hold everything together and support the barrel and brick on top of it. With that being the case, I would go for a slightly clayish feeling to the mix. Not much, just a little.

So how can we try to figure out what these touchy-feely words mean? It will be difficult, because the best way to learn this is with someone right there, sharing the cob and clay mix with you, getting their hands as dirty as yours. But we can't do that online, so we'll have to try with less useful words...

I'd suggest getting a small mixing bowl and put a cup or so of clay in there. Slowly add water, and pay attention to the changes in texture. It'll be dry, become clumpy. get really sticky and thick, get like pudding, and then get progressively more and more watery. Watch how the clay sticks to your skin. At some point you can get a lot of clay to stay in the bowl but there is a film on your skin. As more and more water goes into the mix, less and less clay sticks to your skin. That is one of the ways I use to "feel" how "clayish" my mix is.

Now do the same thing with the perlite (different bowl, or after washing the first one out). It start out bone dry and powdery, then clumpy, then easy to swish around, and then very loose feeling, then wet, and then more and more watery.

So when mixing these, you want a combination of clay, perlite, and water that clumps together, like a snowball if you have ever made one, but still leaves a layer of clay on your skin. Also, when you press into it with your fingers, it "pops" apart, as opposed to just squishing like Play-Dough, or a good bread dough.

Erik; You guessed it , pack the cob tight and keep twisting. I did put some wax on the cap to help. I also poured a castable refractory inside the cap too help hold the heat in the manifold. When I fired it off for the first time ,I got a few leaks along the top edge but a little cob smeared along that edge sealed it up . I haven't had too remove that cap since the original build. Last season I was burning a cast core using matt walkers design and it was so efficient that I had less than 2 gal of ash at the end of season! I replaced my cast core with a brick one this spring & I used a shop vac thru the barrel access to suck up an amazingly small amount of ash ! This season my efficiency is down due in part to a heavy firebrick core vs perlite & fireclay core. I also increased my burn tunnel length a little too much... So I expect to be opening that cleanout this spring.

I finished the 4" protection for the floor. When it dries off then I can start building my burn chamber, right? How long would it take to dry?

I changed my mine, I think I will throw away the current barrels, and do it the way others with half of the burn chamber below the cob, and the top part is in the barrel. I thought if I put the burn chamber in the barrel, then I don't have to insulate the burn tunnel and the heat riser, but I was wrong. According to you experienced people, then I still need to insulate it or it wouldn't be that effective. If I still have to insulate it, then it is easier to have them outside the barrel, in the cob like many people do it.

Now please give me tips for the type of burn chamber with half of the burn chamber in the cob.

What's about the manifold now? Which one should I buy. Should i buy the same manifold which I saw in the clip of Erica and Ernie did, with the opening open up from the bottom of the barrel ?

I try to understand the photos of Thomas about ashes pit, but I don't get it yet. Maybe I have to read the book to understand it.

I finished the 4" protection for the floor. When it dries off then I can start building my burn chamber, right? How long would it take to dry?

I changed my mine, I think I will throw away the current barrels, and do it the way others with half of the burn chamber below the cob, and the top part is in the barrel. I thought if I put the burn chamber in the barrel, then I don't have to insulate the burn tunnel and the heat riser, but I was wrong. According to you experienced people, then I still need to insulate it or it wouldn't be that effective. If I still have to insulate it, then it is easier to have them outside the barrel, in the cob like many people do it.

Now please give me tips for the type of burn chamber with half of the burn chamber in the cob.

What's about the manifold now? Which one should I buy. Should i buy the same manifold which I saw in the clip of Erica and Ernie did, with the opening open up from the bottom of the barrel ?

I try to understand the photos of Thomas about ashes pit, but I don't get it yet. Maybe I have to read the book to understand it.

Yes, read the book. Most of these questions are answered in there.

I built on top of my perlite-clay base the next day. So I'd say tomorrow is fine. Or waiting longer, won't hurt anything.

With regard to the burn chamber and barrel, you do it just like you did, the only difference is the barrel sits back farther. And you cob over the burn chamber with perlite-clay insulation, of course.

And if you decide not use a bottom barrel, then you build up the walls with fire brick, where the bottom barrel would be, and cob over that to seal it (both sides, making the inside smooth, and sloping toward the manifold outlet into the duct work). Then you set the top barrel on top of that brick work, which has been cobbed over. I'd then suggest making the top barrel one with a removable lid. Then you can cob the bottom right into the cob on the supporting bricks.

How high is all that? Well, you want the fire riser to be a minimum of 40.5 inches tall, and taller if you can, up to 45 or 48 inches or so as a very effective height. After you know how high the fire riser is, you decide if you want a 2, 3, or 4 inch gap between the top of the fire riser and the bottom of the barrel. I personally recommend 3 or 4 inches. Then, you subtract 34 inches (the height of the top barrel) and that is the height you need the brick (cobbed over) wall to reach.

The pics Thomas showed is the way I'd make the manifold, so I suggest you do what he did. I think it is the easier and cheapest solution, provided you have a good floor that can take the weight (like you have).

I really suggest reading the book and see if all this doesn't make sense after you read it. I was under the impression you were going to do so as soon as you got it. It is not a very long book, only a little over 100 pages, and with a lot of pictures. It will really help you understand a great deal of this. It is really a very good idea to read it two or three times before you start building. So, go a head and read it at least once, making that #1 on your new "to do" list.

That's my two-cents, anyway.

Maybe I have to read the book to understand it

you have to read the book anyway.
better to do it now then after erik will be need to write more 10 pages for you

Hey bacon; Thought you might like a few pictures from my rebuild. I used about 3" of perlite/clay below my burn tunnel. Brick surround supports the 55 gal barrel. You asked about the (ash pit) in my earlier post , it is the round metal circle at the very bottom of my manifold. It is the deepest spot in the manifold , lower than my 8" outgoing horizontal pipe. Any ash will settle down to this point and not clog up the horizontal pipes! It is also directly below my cleanout door making cleaning out the ash pit an easy job! That metal circle in the picture was a form while cobbing, it was removed before firing.

A few more