Results of the 8" batch box thingy at the Innovators Gathering

Big Al,
Not sure how you mean your last sentence. Can you clarify please.

Just to clarify a "peter channel" in my mind. It's a thin air inlet to add oxygen to a J tube just prior to entering the riser tube? I saw one pic someplace that kinda illustrated this and it almost makes sense as a way to regenerate the burn, perhaps it should be closed before you get some draw? Either that or I just can't see where it belongs.

Rick Howd wrote:Just to clarify a "peter channel" in my mind. It's a thin air inlet to add oxygen to a J tube just prior to entering the riser tube? I saw one pic someplace that kinda illustrated this and it almost makes sense as a way to regenerate the burn, perhaps it should be closed before you get some draw? Either that or I just can't see where it belongs.

Well, the Peter channel, in the case of the J tube, is at the entrance of the burn tunnel, air being injected at the ceiling. In that case, it usualy consist of just a metal plate in the feed.

In the batch box, it is just before the port at the top, overhanging on three sides, exept on the port side, to create suction. Usualy made with a tube going to the front of the stove. For both cases it's about 5% csa.

Thanks for your reply, it's been driving me crazy. If it's at the front of the burn tunnel why don't we modify the feed tunnel for more air? Maybe a 1" diameter pipe that stops at the top of the burn tube or a groove to prevent wood entering the burn tube at that spot but still allowing additional air. Wouldn't it be better to allow the air in from the rear as low as possible to bring in the coldest possible air and draw it into the chamber?

Rick Edwards wrote:A side note about the box. Per Peter's notes, wood never goes inside the vertical port to the riser, not above the P-tube and not within 2" of the front door. So there is always 3-4" of free space above the full batch of wood and always a 2" gap between the batch and the front loading door.

Very, very cool. I duly regret I was sleeping my jetlag off at the time.
First amendment about the box notes: The space above the fuel load can be smaller, 2"would be adequate. So the complete notes would be:

No piece of fuel should ever goes inside the vertical port to the riser, not within 2" above the fuel load and not within 2" of the front door. So there is always 2" of free space above the full batch of wood and always a 2" gap between the batch and the front loading door. Lighting the batch box: small kindling fire just in front of the port, when that catches on two or three moderately sized pieces of fuel on top of that. When that is burning healthy, stack the required load only lengthwise front-to-back, to a maximum of 2" under the ceiling of the box.

I'll leave it to a native speaker to correct any mistakes in the wording.

Rick Edwards wrote:It has been pointed out that the transition from barrel to duct is important and needs to be larger than the duct itself.

The design here has a short 8" duct between the bottom of the first barrel and top of the third. Would it have been better to have that larger on the first barrel side or is there a reason that it works in this system? Or is it or should it be at the output of the third barrel?

Yes, there is a reason why it works in this system.
I'll try to make the long story shorter. The gases which are streaming to the exit in the side of the first barrel are coming from above and the sides, less from the bottom. When the exhaust opening is as low as possible, no stream can get past via the bottom, due to the gap between the barrel and the riser, the "side gap". The fact that the gases are turning there around a 90 degree corner could slow those down as well. One thing you could do is make room under the exhaust opening in order to allow the gases to stream from below also. Another way is to widen the side gap, or enlarging the opening. In order to calculate whether you have a restriction down there take the exhaust opening's circumference and multiply that by the side gap. When the resulting figure is smaller than 150% of the exhaust cross sectional area you almost certainly will have friction at that spot.

OK, now the solution in the auditorium: the exhaust opening is about 2" from the bottom of the barrel which is not enough but it helps. If possible, I would rise the opening a distance of about half the diameter above the barrel floor. Furthermore, the gap between the barrel and the ceramic fiber riser is a little more than 5". Multiplied by the circumference of the 8" pipe we'll get 125.66 sq in. The csa of the pipe is 50 sq in, so the stream profile is as large as 250% of the pipe csa. Plenty of space, no problem at all.

Minimum requirements for that spot in this design would be: elevated 4" above the barrel floor and a side gap of 3" at least. That will give us a 150% stream profile, which isn't posing a restriction at all. I know, it looks like there isn't such a thing as a manifold (which is true by the way) so that leaves people puzzled how this in heaven's name could work.

As for the exit of the third barrel: this is completely open inside apart from the stacked bricks around the wall, plenty of room in front of that exhaust opening, a little elevated from the floor, no problem at all.

It has been a delight and a real pleasure to meet all you people. Thank you Rick, specifically for the help with the p-channel and the glass dimensions.

Rick Edwards wrote:Ask for wood stove door glass or boro-silicate glass I think (someone correct me please). Our glass shop called it neo-ceram, a brand name I assume.

Borosilicate glass isn't up to the job and quite different from Neoceram. This last one is a brand name indeed, see this link. It is extremely heat resistant up to 1272 F continuously. Up to 1000 F it's quasi-non-expanding.

The only alternative is Schott Robax as far as I am aware of. It's hard to tell the difference between the two, the only way I know is this: Robax is coloured purple when you look at the thickness edge and Neoceram is amber coloured. Borosilicate like Pirex is clear, normal glas is green.

Peter Berg wrote:
This is one of the fundamentals: the port (or gate) is 70% of the riser diameter, so according to Bernoulli's theorem, in the opening itself the speed is higher and the pressure comparatively lower. The secondary air channel is right in front of the port so this lower pressure will feed air in automatically. Behind the port both the pressure and the speed do go back to normal which in turn causing a lot of turbulence. The flames inside the riser are forming a double ram's horn pattern, coming back onto itself and spiralling up, thus lengthening the time in the riser.

Your explanation is clear and that video is awesome, explains everything perfectly. Thank you.

Peter, I believe when I heard you and Matt talking that it also seemed important that the secondary air is heated for good combustion, performance, etc.

Thus our P-channel being inside the batch.

You might want to expand on this a little. I've seen others in this forum ducting secondary air inlets completely from the outside of the burn box/tunnel.

Three more pics of mockup.
Still waiting on new burn pics and vid of the installed version.
Soon.

Rick Edwards wrote:Peter, I believe when I heard you and Matt talking that it also seemed important that the secondary air is heated for good combustion, performance, etc. Thus our P-channel being inside the batch.
You might want to expand on this a little. I've seen others in this forum ducting secondary air inlets completely from the outside of the burn box/tunnel.

In general, the hotter the supplemental air, the less cooling of the fire. I've measured the temperature of secundary air in a couple of experiments. When the Testo results were best the secundary air tended to be around 300 C (572 F). Self-ignition temperatures of most wood species are between 250 and 350 C. So I would think it is safe to say when the combustible gases are slightly too cold, these will ignite nevertheless when mixed with the hot air.

This advantage isn't there when the air is at room temperature. Rather the other way around, the air will cool the flammabe gases well below the temperature needed for spontaneous combustion. So, adding comparatively cold air isn't a positive act regarding combustion quality, period.

Later that night.

In the process of writing the article about the big batch box and answering all the questions after that I've omitted the acknowledgements. Lots of people do that, same thing happened with Tim Barker's water heater and Geoff Lawton presenting it.

So here goes: the original idea to use a letterbox opening on its side is of Lasse Holmes from Homer, Alaska. What I did is taking the concept further, finding out the best ratio of firebox, port and riser. The idea to use a riser behind a more or less normal firebox is mine, however. This is a lame excuse I know that, I'll try to do the recognition of other people's work earlier on in the process.
There is a long development story about this type of horizontal feed over at Donkey's forum, see this thread.

Finally had the parts and time to finish the chimney properly. We also had a reason to fire it up. An earlier attempt had a little smoke back (warm day) and another with smoke leaking out of seams (not priming system long enough to get chimney pulling as well as the rocket pushing). This evening was a successful start up and prime built into a full load with clean combustion and no smoke into the building. It ran just like designed and is such a crazy radiating beast at full batch load.

I'll get video of the full cycle from fresh start to full load all the way down to coals on a cold start and a warm start soon.

For now here is some candy.
This batch has about 8-10" underneath it that is mostly hollow and ready to collapse. The speed with which this burns down is hard to get used to.

Been running it all day to dry out a tipi we have hanging in the auditorium. This thing works so crazy good with the radiation side of things, also the mass feels like it's warming up.

More candy.

Looks very good, I like your comments. Since you kept it running all day, are there any unexpected effects to mention?
Provided the decision has already been made to keep this heater, maybe it's time to fabricate a proper door.

The door is waiting for time during the winter. I am pondering options of glass use in the door. Window up top, A piece of glass with the rectangle cut out for the primary air intake or a large piece for most of the door.

Also thinking of splitting the door down the middle thus having smaller doors on each side instead of one larger door on either side.

Need a little more time to organize our wood storage and loading habits to see what I think about that.

Rick : eye candy indeed, keep them coming ! Big AL !

What do you think about two doors top and bottom?
The lower one with the air intake that would usually only be opened when the fire isn't operating to clean out the ash, and an upper one (maybe with a window in it) that you'd normally use for loading or re-loading an active fire?

I like the idea of the doors being a little smaller, changing the air flow less when you open a door to re-load (and less chance for smoke to escape), yet being big enough to handle the wood without problems. I like the idea of a window in the door.
Most woodstoves keep soot off the window with an air-wash or air-curtain effect over the glass, which might need to be considered in the design of the air intake size.

[]888888888888[]
[].|----------~|.[]
[].||./\.../\./\||.[]
[].||(/ ),(/\)')||.[]
[].||----------||.[]
[].|----------~|.[]
[].|. . UUU . .|.[]
[].|_________|.[]

UUU is the air intake,
the ~ are door handles (could be centered along the side of each door, so you can open both and get into the whole front of the firebox if you really need to work on something)
. . . these fill in areas that would likely be steel outside, refractory facing on the inside
and these represent the top ---- and bottom ___ of each door.

I think of the top of the opening being 2" below the ceiling of the burn box, so that it is difficult to accidentally load wood too high. If you can slide it in through the door without scraping on the top, it's good.
I think that it's hard to build anything in to make sure you have the fuel 2" away from the doors, but perhaps there can be a color difference inside or something, maybe we paint the no-load zones white with a refractory paint or clay. Or perhaps the operator is trained and sensible about such things.

I think of the fuel-loading door being bigger, easy to carefully handle the wood, or even to reach in with tongs or a stick to adjust something.

I think of the air-feed door being smaller, maybe something to protect the air feed so coals can't easily drop and obstruct it.


I can see where doors split down the middle would be easier on the hinges, but I think a top-bottom split is more useful for re-loading with less chance of room-air-to-smoke exchange eddies.

I would love to hear what Peter thinks about the best door. He has said that he would love to see what these skilled metal workers can do with a door, but I wonder if Peter has some ideas about how best to manage the fuel and air access by the choice of doors, sizes, viewing windows, etc.

If there was one bottom door for the air feed, and then the top door was split into 2 for easier swinging weights, and each one had a window in it, then it might look like a jack-o-lantern:

[]888888888888[]
[].|---- .T. ----|.[]
[].||'/\'|||'/\'||.[]
[].||('')|||('')||.[]
[].||----JL----||.[]
[].|----------~|.[]
[].|. . UUU . .|.[]
[].|_________|.[]



Now I want a "halloween mask" for woodstoves.

Erica, I use a door like you describe on my Walker Stove...




This one the primary air inlet is too small, it's been adjusted and covered with a spark screen since, but I don't have a good photo of that iteration handy. Anyway, it works well, but the frame between doors limits fuel size, which is one of the big benefits of the batch style. There are ways around that, but that was a downside to this particular configuration. You are right though, keeping the opening smaller when the door is open means higher intake velocity and better smoke retention. I like the jack-o-lantern idea!

Erica Wisner wrote:I would love to hear what Peter thinks about the best door. He has said that he would love to see what these skilled metal workers can do with a door, but I wonder if Peter has some ideas about how best to manage the fuel and air access by the choice of doors, sizes, viewing windows, etc.

Yes, there are some doors I would like. Not the ones in the shop but along the lines of a jack o'lantern. The lower door with the hinges at the bottom and the double access door above that. Glass in the access door left and right, the lower door with a contra weight to keep it closed. The whole thing looks like a quite old-fashioned door setup like the Finnish quality doors by UPO of 25 years ago. The doors itself are made of a T-profile with the vertical leg of the T pointing inwards the stove. Let's see whether I can find an old picture...



This stove has been in use for 19 years when something went wrong with it in 2010. Luckily I was able to fix it.

How did you attach the 2 barrels to one another?

We used two open top barrels and at first I tried to fix the two top ends together with a barrel lid clamp. That didn't work because those top rims are too thick. Ernie's advice was to cut out the bottoms of both barrels and fix those together with a lid clamp. This did work because the bottom rims are thinner and both did fit inside one clamp. So there's one lid on the top of the tower and the other at the bottom. Somewhere in this thread there's a picture how we fitted the lid around the riser.

The bottom barrel is upside down, the top barrel is right side up. The solid bottom (when upright) of the first (bottom) barrel was mostly cut out. I heard they left a 2"ish ring around the edge for stability and so it would keep its' proper round shape. Then that barrel was turned upside down and lowered over the heat riser and onto the top of the brick work and the duraboard where it sits now. Then the second (top) barrel had the same hole cut out of its' bottom and lowered right side up on top of the bottom barrel. These two barrels were then sealed with high temp silicone tape and i think also graphite braid tape for wood stove doors and clamped together with a standard barrel clamp ring. (they hold the lids on the barrells.) The high temp silicone tape has melted off and a little smoke can leak out, but that is only if not properly primed (warmed) up before a full batch goes in. Both the bottom of the bottom barrel and the top of the top barrel have lids attached by a barrel clamp ring. The bottom one has a hole cut into the middle for the heat riser and the edge of that hole was expertly formed into a half inch lip perpendicular to the lid for strength by Peter using our newly formed ball / claw hammer.

I think this answers the question. If you want any more clarification or more detailed close up pics, ask away.

On another note, I'm considering cutting a circle out of the top of the top barrel's lid and putting a piece of neo-ceram up there sealed with the graphite braid tape and a metal clamp ring for no leakiness. Of course this is pretty tall so... wait for it... then mount a piece of mirror or reflective glass above it so looky loos can see straight down to the bottom of the heat riser and be oohed and ahed by the double rams horn.

On this note i was thinking a one foot square piece, but now just thought the whole lid could be replaced with neo-ceram of correct diameter for a lot more cost I'm sure. Any pros or cons to either?

Big AL. Time for you to cut and paste that PM to me here. I think it is worth discussion in this thread.

Also I like all the door ideas. Couple of things. I want the doors to be full height so it is not hard to load that top wood layer and also it can be done quicker. The shorter the door is open the better all things are with this batch box. As far as the clearances go, that is just part of system knowledge and loading / firing experience. I want proper loading to be done easier and quicker for system performance and for safer operating / loading. I'm not worried about safe guarding improper loading with physical barriers and inconvenient designs when that won't work anyway. People will be taught how to load it properly and then they can load it.

Also, the full open approach is handy when reloading from scratch but the system (bricks) are still hot. The coals need to be spread even and the heat radiating from the coals and the bricks is so hot that after about 5-10 seconds just inside or near the door, you can't have your hand near the door any more. So a long stick and a shallow angle are needed to perform this task. I do like the look of the three door side by side top and single bottom third. as long as there isnt a division between them so when all three are open the entire front of the box is barrier free. I think it is more clever than functional after running this over ten loads now, but I still like the look and style. It wont hamper reloading as long as there is still wood to the top of the angled bricks and is still full open when bottom door is open (would be held shut by top doors overlapping.)

Does anybody know if this neo-ceram (what is the not brand name) can have the rectangle cut out of it for the primary air intake?

Also Peter, if much of the front becomes glass, will that have any negative effects on the system by allowing that much more radiation?

Peter and I just responded at the same time, not trying to steal his thunder.

Both answers were awesome! Thank- You, Jay

Rick Edwards wrote:On another note, I'm considering cutting a circle out of the top of the top barrel's lid and putting a piece of neo-ceram up there sealed with the graphite braid tape and a metal clamp ring for no leakiness. Of course this is pretty tall so... wait for it... then mount a piece of mirror or reflective glass above it so looky loos can see straight down to the bottom of the heat riser and be oohed and ahed by the double rams horn.

On this note i was thinking a one foot square piece, but now just thought the whole lid could be replaced with neo-ceram of correct diameter for a lot more cost I'm sure. Any pros or cons to either?

Rick,
Yes, there is downside, the glass will collect soot when the stove is started cold. It will burn clean after about 15 minutes and after that the sight will be pretty awesome, I assure you.

Probably, leakage will occur when the top lid buckle up or down. This could be alleviated by making a relative small window right in the middle and a welded frame around that opening. An upright flange around that could contain the glass and strips of superwool. The glass need to be away from touching any steel and allowed to move freely.

Rick Edwards wrote:I want the doors to be full height so it is not hard to load that top wood layer and also it can be done quicker. The shorter the door is open the better all things are with this batch box. As far as the clearances go, that is just part of system knowledge and loading / firing experience. I want proper loading to be done easier and quicker for system performance and for safer operating / loading.

Let's see where the playful idea of the Jack o' Lantern would lead to.
A hole in the glass will make it very difficult to close the primary intake. Maybe a small bottom steel door with the mouth of the Jack o' Lantern cut out of the right intake size with a 1.5" deep spark arrestor behind it. This way it's easier to make a closing valve or slider for it at the outside, the opening doesn't need to be a rectangle as long as it is at the borrom middle of the firebox. The double door above it doesn't need to have a lot of glass because that's on the top already. So that could be made with the eyes of the J o' L cut out with small pieces of glass set behind it.

The amount of glass in the doors doesn't lead to negative effects by the way. Keep in mind that the firebox doesn't need to hold the highest temperatures, that function is nicely executed by the afterburner/riser thingy behind it. That's the only part which is insulated, the firebox isn't.

Oh, the coals don't need to be spread much when doing a refill. Wait 5 minutes longer when there's only coals in the rear half of the firebox in front of the port. When reloaded on top of that, the situation is quite similar to a cold start procedure. When the stove is hot, the roar will commence immediatly upon closing the door or even at loading the pieces of fuel.

All these features won't make it a simple door to fabricate but the result will be an fantastic eye catcher, even an icon which will be remembered.

Thanks Peter. What you said about the glass on top is pretty much exactly what I thought for mounting. Still curious about a full glass lid. The edge could be wrapped in braided ribbon and carefully clamped. Never mind, just thought it will expand and contract too differently from the metal around it to seal that way without having the potential of cracking. Also not sure if I could get it in a circle and if so, how expensive that would be.

I do like the jack o lantern style, but I also really like the idea of being to able show off the heart of the fire and the coals. Kind of at a crossroads here. What do people think on this one? Or other ideas?

Just got one. Maybe a wide toothy smiling mouth with the port in the center. I'm not worried about closing the port. Like permaculture, the more complicated the system, the easier the design elements. I already have a couple ideas for closing a glass lined port. Or the port can have a rim of metal with glass around it. This might be the better solution. Then I can have a piece of metal with a handle that sets in a groove of the rim and seals the port. I see what's in my head and I like it. Anyway, still open to suggestions.

Also, I used to carve prize winning pumpkins in relief and scared most children with them. It wasn't my intention just a side effect. Hind sight and all, they were pretty scary.

On my smart phone with finger. So don't judge.

Chimney stuff finally finished. I hate these sheet metal roofs. Way to much sealant. Shingle roofs much easier to flash.

Need feedback on some things.

1. For the temps on the door, can this all be made out of mild angle and plate?

2. Peter, how strong is the bond of the outer brick work? Not the fire brick. Can I attach to the front of these for my "jams"? Or, should I wrap a long sided angle around the sides and attach to two bricks deep? I'm also considering putting the angle between the two brick types where the thin duraboard is so you could still see the front of the outer brick wall. This would be harder to pull off and I'm not sure if possible until further investigation.

3.The batches seem to run cleaner and "better" when I don't load fuel completely against the back wall. If I leave just a half inch gap things seem much better. Some of this might be other factors and coincidence. As I get more practice I'll try more loads both ways and see if the pattern continues. Wanted to see what other batchers had to say about this. It seems the fire likes a little room to slide across the back wall sideways until it can shoot into the slot. But maybe this is unnecessary.

Rick Edwards wrote:Chimney stuff finally finished. I hate these sheet metal roofs. Way to much sealant. Shingle roofs much easier to flash.

Rick, proper way to do it!

Rick, the proper way to do it, overlapping from the top, underlapping from the bottom

Rick, nice job on the first step of sealing around the rubber boot.

Have you given thought to the final step? I.e. placing two pieces of metal roofing over the boot, both with U-shaped notch cutouts, bottom sheet placed first with the "legs" of the cutout extending just above the boot. Second sheet of roofing placed over the first piece with its U-shaped cutout overlapping and extending below the rubber boot. Obviously, the top/second sheet will extend to the top of the roof with its edge positioned under the existing ridge cap.

Make the U-shaped cutout fit tightly around the rubber boot. The idea, beyond additional water proofing, is to shade the boot from eventual UV damage over the years and etc.

Rick Edwards wrote:1. For the temps on the door, can this all be made out of mild angle and plate?

Yes, that's possible. Be careful with possibly buckling of larger stretches of plate though.

Rick Edwards wrote:2. Peter, how strong is the bond of the outer brick work? Not the fire brick. Can I attach to the front of these for my "jams"? Or, should I wrap a long sided angle around the sides and attach to two bricks deep? I'm also considering putting the angle between the two brick types where the thin duraboard is so you could still see the front of the outer brick wall. This would be harder to pull off and I'm not sure if possible until further investigation.

Bond isn't strong at all, it's done with local clay and sand. Best to use at least two metal strips on each side and attach those several bricks deep, maybe even around the back to be sure. The thin duraboard is a small vertical strip of only 3" deep. Not easy to attach steel strips in the narrow space between firebrick and clay brick.

Rick Edwards wrote:3.The batches seem to run cleaner and "better" when I don't load fuel completely against the back wall. If I leave just a half inch gap things seem much better. Some of this might be other factors and coincidence. As I get more practice I'll try more loads both ways and see if the pattern continues. Wanted to see what other batchers had to say about this. It seems the fire likes a little room to slide across the back wall sideways until it can shoot into the slot. But maybe this is unnecessary.

Your observation is correct, it looks like some of the stream need space between the back wall and the fuel. It isn't really necessary according to the Testo but the burn appears to be smoother. The specific circumstances differs greatly between burns which is far more important.
The way I load a batch box is as follows: I stick in the fuel piece until I feel it's touching the end, and then pull it a little back. Don't ever throw in the fuel, the back wall and the port will get damaged. Use welding gloves when reloading the stove?

Warm start up. pt 1



Pictures are not associated with this video, Just more candy!

Having that glass on top, to see what the flame it doing, is great.

In one of the lab videos someone was talking about seeing the flame going both ways...what was that about?

The rams horn effect at the back of the riser after traveling through the slot.

The fire hits the back wall and is helped upwards by a ramp at the bottom of the riser floor. Then the fire has to spread out, like hitting a T-intersection and having to go both ways.So now it is spinning right and left of back center and curling full circle but only to the middle of the riser while traveling upwards at the same time.


Thus a rams horn is seen from above. Or figure eight kind of or infinity symbol.

The video above from Satamax shows
the effect in a square riser.

IN the video, when looking through the slot, you can see the flames curling around both directions from the back wall.

Sorry got my threads mixed up.

Satamax posted his video on page 2 of the emergency batch box wofati thread.

Rick Edwards wrote:Sorry got my threads mixed up.

Satamax posted his video on page 2 of the emergency batch box wofati thread.

Rick, stop boozing

It's on page one! And here too now!

http://www.youtube.com/watch?feature=player_embedded&v=tjzQyNXBKAA